Journal of Petrology Advance Access originally published online on January 18, 2008
Journal of Petrology 2008 49(2):353-391; doi:10.1093/petrology/egm085
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mafic and Felsic Magma Interaction in Granites: the Hercynian Karkonosze Pluton (Sudetes, Bohemian Massif)
aby1,*
1Institute of Geochemistry, Mineralogy and Petrology, Faculty of Geology, University of Warsaw, AL. 
wirki I Wigury 93, 02-089 Warszawa, Poland
2Laboratoire Magmas ET Volcans; Opgc, Cnrs, Université Blaise Pascal, 5, Rue Kessler, 63038 Clermont-Ferrand, France
RECEIVED JANUARY 23, 2007; ACCEPTED DECEMBER 12, 2007
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
The Hercynian, post-collisional Karkonosze pluton contains several lithologies: equigranular and porphyritic granites, hybrid quartz diorites and granodiorites, microgranular magmatic enclaves, and composite and lamprophyre dykes. Field relationships, mineralogy and major- and trace-element geochemistry show that: (1) the equigranular granite is differentiated and evolved by small degrees of fractional crystallization and that it is free of contamination by mafic magma; (2) all other components are affected by mixing. The end-members of the mixing process were a porphyritic granite and a mafic lamprophyre. The degree of mixing varied widely depending on both place and time. All of the processes involved are assessed quantitatively with the following conclusions. Most of the pluton was affected by mixing, implying that huge volumes (>75 km3) of mafic magma were available. This mafic magma probably supplied the additional heat necessary to initiate crustal melting; part of this heat could have also been released as latent heat of crystallization. Only a very small part of the Karkonosze granite escaped interaction with mafic magma, specifically the equigranular granite and a subordinate part of the porphyritic granite. Minerals from these facies are compositionally homogeneous and/or normally zoned, which, together with geochemical modelling, indicates that they evolved by small degrees of fractional crystallization (<20%). Accessory minerals played an important role during magmatic differentiation and, thus, the fractional crystallization history is better recorded by trace rather than by major elements. The interactions between mafic and felsic magmas reflect their viscosity contrast. With increasing viscosity contrast, the magmatic relationships change from homogeneous, hybrid quartz diorites–granodiorites, to rounded magmatic enclaves, to composite dykes and finally to dykes with chilled margins. These relationships indicate that injection of mafic magma into the granite took place over the whole crystallization history. Consequently, a long-lived mafic source coexisted together with the granite magma. Mafic magmas were derived either directly from the mantle or via one or more crustal storage reservoirs. Compatible element abundances (e.g. Ni) show that the mafic magmas that interacted with the granite were progressively poorer in Ni in the order hybrid quartz diorites—granodiorites—enclaves—composite dykes. This indicates that the felsic and mafic magmas evolved independently, which, in the case of the Karkonosze granite, favours a deep-seated magma chamber rather than a continuous flux from mantle. Two magma sources (mantle and crust) coexisted, and melted almost contemporaneously; the two reservoirs evolved independently by fractional crystallization. However, mafic magma was continuously being intruded into the crystallizing granite, with more or less complete mixing. Several lines of evidence (e.g. magmatic flux structures, incorporation of granite feldspars into mafic magma, feldspar zoning with fluctuating trace element patterns reflecting rapid changes in magma composition) indicate that, during its emplacement and crystallization, the granite body was affected by strong internal movements. These would favour more complete and efficient mixing. The systematic spatial–temporal association of lamprophyres with crustal magmas is interpreted as indicating that their mantle source is a fertile peridotite, possibly enriched (metasomatized) by earlier subduction processes.
KEY WORDS: Bohemian Massif; fractional crystallization; geochemical modelling; hybridization; Karkonosze
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
It has long been recognized that granitic bodies result from a complex interplay of several petrogenetic processes. The present-day composition of any granite has been determined by processes that cannot always be easily separated, determined and quantified. Many granite masses contain hybrid rocks; pointing to the coexistence of two or more compositionally contrasting magmas (Didier, 1973
; Didier & Barbarin, 1991; Bateman, 1995; Wiebe, 1996; Barbarin, 1999, 2005; Barnes et al., 2001; Wiebe et al., 2002; Bonin, 2004, 2007; Janou
ek et al., 2004; Kerim, 2006). As summarized by Barbarin (2005), these hybrid rocks provide evidence of the important role played by mafic magmas in the generation and evolution of calc-alkaline granitoid magmas. Thus understanding their origin is of fundamental significance in interpreting the history of granitic batholiths.
It is now well established that hybrid rocks represent different stages of interaction between mafic and felsic magmas (see Janouek et al., 2004; Barbarin, 2005, for review). However, the conditions and detailed mechanisms of these interactions remain hotly debated. Unfortunately, until now, most research strategies, based on only one tool, have seemed inadequate to resolve the problem; rather, a multi-faceted approach is required. For instance, a whole-rock geochemical approach alone does not provide an unequivocal petrogenetic model because the linear trends in binary diagrams can result not only from mixing but also from small degrees of fractional crystallization. Similarly, small, hybrid magma bodies could have chemically re-equilibrated with their host magma and consequently their composition no longer reflects their initial magmatic chemistry (Watson, 1982; Wall et al., 1987; Castro et al., 1990; Fourcade et al., 1992; Elburg, 1996; Waight et al., 2000).
There are numerous processes that can make it difficult to establish clear chronologies for magma mixing events. For instance, many magmatic structures indicate that granitic magmas experience dynamic flow during emplacement and/or during internal convection (Barrière, 1981). Similarly, as granite crystallization can span long time periods (Annen et al., 2006), there is ample opportunity for the injection of multiple discrete pulses of mafic magma. Some studies (Zorpi et al., 1989, 1991; Bouchet, 1992) have demonstrated that the compositions of interacting granitic and mafic magmas may both evolve over time. Indeed, during cooling, fractional crystallization may take place in tandem with mixing, thus increasing the ultimate complexity of the pluton. Depending on the degree of crystallization, the mode of interaction between a cooling granite and an injected mafic magma can vary—for example, as expressed in thorough mixing (blending), or the presence of rounded enclaves, composite dykes and intrusive dykes (Hallot et al., 1994, 1996; Barbarin, 2005)—such that it is often difficult to establish an accurate chronology of mafic magma emplacement.
Consequently, the aim of this paper is to address the question of magma interactions during the course of granite crystallization and to determine their effects on the overall compositions. The work is based on field observations, petrography and geochemistry. The processes identified are modelled and their relative importance is assessed. The well-exposed Karkonosze granite in the Hercynian Sudetes (Bohemian Massif) has been chosen as a suitable case study. Earlier studies (Berg, 1923; Cloos, 1925; Borkowska, 1966; Klominsky, 1969) have documented the abundance of rounded mafic microgranular magmatic enclaves (MME) and dykes in the granite. A detailed mineralogical investigation of the granite and its magmatic enclaves, using cathodoluminescence and mineral chemistry, has already demonstrated that the minerals of the granite reveal a complex growth history (Saby & Galbarczyk-G
siorowska, 2002; Saby & Götze, 2004; Saby et al., 2007a, 2007b). These results are used here, together with whole-rock geochemistry data, further to elucidate the history of mafic and felsic magma interaction in the Karkonosze intrusion.
|
ANALYTICAL METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
Minerals were analysed at the Inter-Institute Analytical Complex for Minerals and Synthetic Substances, Warsaw University, using a Cameca SX-100 electron microprobe (10 s counting times; 15 kV acceleration voltage and 20 nA beam current for major elements and 20 kV and 50 nA for trace elements; beam diameter 5 µm). Applying a Monte Carlo simulation (Robert & Casella, 2004
), the interaction depth of the electron beam with the sample was less than 5 µm. Feldspar and biotite analyses were recalculated on the basis of eight and 22 oxygens, respectively. Amphibole formulae were calculated following Droop's (1987) schema No. 6 (assuming 13 cations and excluding Ca, Na, K)
Major elements (SiO2, TiO2, Al2O3, Fe2O3t, MnO, MgO, CaO, Na2O, K2O, P2O5) and some trace elements (Ba, Sr, Zr) were determined at the Institute of Geological Sciences UAM, Pozna
, using an XRF S4 Explorer. Glass beads were made from a mixture of lithium tetraborate and sample powder in the proportion 1:5. The accuracy for major elements is <2%, and for trace elements <10%. The remaining trace elements [Ni, Nb, Rb, Th, rare earth elements (REE)] were analysed at the ACME Analytical Laboratories, Vancouver (Canada), by inductively coupled plasma mass spectrometry (ICP-MS) (REE and refractory elements by lithium tetraborate fusion and base metals by aqua regia digestion). All analyses were recalculated on an anhydrous basis, with iron expressed as Fe2O3t = Fe2O3 + 1·111 FeO (see Tables 8–12).
Nd isotope analyses were performed on 100 mg powdered samples at the Institute of Geological Sciences of the Polish Academy of Sciences, Warsaw, using a VG Sector 54 mass spectrometer in multi-collector dynamic mode. 143Nd/144Nd ratios were normalized to 146Nd/144Nd = 0·7219. Time-related calculations use values of 143Nd/144Nd = 0·512638 and 147Sm/144Nd = 0·1967 for the present-day depleted mantle following a radiogenic linear growth for the mantle with 
Nd = 0 at 4·568 Ga.
|
GEOLOGICAL SETTING |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
The Carboniferous Karkonosze pluton is a part of the mid-European segment of the Hercynian orogenic belt that reflects the convergence of Gondwana and Laurasia during Palaeozoic times (Matte, 1986
; Ziegler, 1986; Finger & Steyrer, 1990; Matte et al., 1990; Dallmeyer et al., 1995; Franke, 2000; Franke et al., 2005). In this orogenic belt, convergence and subsequent continent–continent collision led to the emplacement of many granite bodies (Finger et al., 1997). The greatest magmatic activity took place during the Late Carboniferous and was related to transpressional–transtensional tectonics (Finger & Steyrer, 1990; Diot et al., 1995; Mazur & Aleksandrowski, 2001). The Karkonosze pluton (the Krkonoe–Jizera Plutonic Complex, the Krkonoe–Jizera pluton, Krkonoe–Jizera massif in the Czech literature and the Riesengebirge in German literature) intruded into the Saxothuringian zone of the Hercynian belt (Fig. 1a).
|
The pluton is located in the Western Sudetes on the northern extremity of the Bohemian Massif. The Sudetes resulted from the accretion of four major terranes during the Hercynian (Aleksandrowski & Mazur, 2002
). The pluton and its metamorphic envelope have been studied geologically for more than a century. The different models for its genesis and emplacement have been reviewed by Mierzejewski & Oberc (1990). Karkonosze is surrounded by several structural units (Izera–Kowary, South Karkonosze Metamorphic Complex) of contrasting lithostratigraphic and metamorphic evolution. These units are interpreted as being a Late Devonian–Early Carboniferous nappe pile (Mazur & Aleksandrowski, 2001; Aleksandrowski & Mazur, 2002) intruded by the late to post-collisional Karkonosze granite (Duthou et al., 1991; Diot et al., 1995; Mazur, 1995; Wilamowski, 1998) during the extensional collapse of the chain (Matte, 1998).
The Karkonosze pluton is an east–west elongate body extending for c. 70 km with a minimum width of 20 km. Following the nomenclature of Barbarin (1999), the granite is a typical K-rich calc-alkaline granite (KCG). Pin et al. (1987) and Duthou et al. (1991) obtained whole-rock Rb–Sr isochron ages of 328 ± 12 Ma and 329 ± 17 Ma for the porphyritic granite. For the same facies Kröner et al. (1994) determined an age of 304 ± 14 Ma by Pb–Pb zircon evaporation and Marheine et al. (2002) an age of 320 ± 2 Ma by the 40Ar–39Ar method on biotite. The equigranular granite has been dated at 310 ± 14 Ma by the Rb–Sr whole-rock method (Duthou et al., 1991), whereas 40Ar–39Ar on biotite yielded an age of 315 ± 2 Ma (Marheine et al., 2002).
The Karkonosze mass consists mainly of biotite-bearing porphyritic to equigranular granite, small volumes of two-mica granite and subordinate granodiorite (Berg, 1923; Borkowska, 1966; Klominsky, 1969). The granite is cut by lamprophyre and aplite dykes (Berg, 1923; Borkowska, 1966; Awdankiewicz et al., 2005a, 2005b). A two-mica granite occurs at the south and SW margins of the pluton. Both its mineral and chemical composition are drastically different from the rest of the Karkonosze pluton. Klominsky (1969) and 
ak et al. (2006) considered this to be an independent early magma pulse. It is not discussed further in this paper.
Recently, it has been proposed that the Karkonosze intrusion is of mixed mantle–crustal origin (Saby & Götze, 2004; Saby & Martin, 2005). Granodiorites, occurring as large irregular zones, microgranular magmatic enclaves and ductile stretched dykes, were considered hybrid facies by Saby & Martin (2005; see also below). The hybrid zones vary in scale from several tens of metres to several kilometres. Larger hybrid screens <12 km in length delineate contacts between separate injections of granitic magma (ak & Klominsky, 2007). Magmatic structures recognized in the porphyritic granite by ak & Klominski (2007) indicate highly localized magma flow after chamber-wide mixing. Magma movement was coupled with magma segregation (biotite schlieren), compaction, filter pressing, gravitational differentiation and other processes taking place in crystal-rich mushes. The present study is focused on the evolution of magmatic liquids and we avoided sampling these places. Geochemical data prove the non-cumulative character of the collected samples.
Lamprophyre dykes ranging up to few metres in width occur in the eastern part of the Karkonosze intrusion to the SE of Jelenia Góra and above the inferred feeder conduit of the pluton (Mierzejewski & Oberc, 1990; Awdankiewicz et al., 2005a, 2005b). Sharp contacts with the granite are accentuated by occasional chilled margins. The genetic relationships with the granite are not clear; some lamprophyres are arguably related to late porphyritic granites, others are mafic dykes younger than the porphyritic granite (see details below). Aplite dykes are comagmatic with the granite and in many places can be viewed as melt expelled as a result of filter pressing.
|
PETROLOGY |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
During the last 85 years, the Karkonosze pluton has been the subject of a number of petrological studies (e.g. Berg, 1923
; Cloos, 1925; Borkowska, 1966; Klominsky, 1969). Below we give a brief summary of previously published and new data on the most important features of the Kakonosze rocks. Sample localities are given in Fig. 1b and in Table 1.
|
Granite
Equigranular granite (EQU)
This granite facies is a fine- to medium-grained, equigranular, biotite granite—the ‘ridge’ granite of Borkowska (1966
) and the ‘crestal’ and ‘Harrachov’ granite of ak & Klominsky (2007). It crops out in the central and eastern parts of the pluton and as small scattered bodies in the porphyritic facies (Fig. 1b). The grain size varies from 5 to 1 mm (Fig. 2a) with the progressive transition from medium- to fine-grained rock. Pockets of biotite granite with granophyric texture are occasionally found (Fig. 2b). The equigranular granite contains K-feldspar (36–18 vol. %), plagioclase (35–25 vol. %), quartz (42–30 vol. %), biotite (6–1 vol. %), small amounts of muscovite (<0·1%) and accessory apatite, zircon, allanite, titanite, epidote, magnetite, ilmenite and monazite (Borkowska, 1966). Apart from occasional larger quartz crystals (Fig. 2a), the granite is very homogeneous without megacrysts, microgranular magmatic enclaves (MME) or mafic schlieren. In a few places it is cut by composite dykes.
|
Porphyritic granite (POR)
The porphyritic granite—the ‘central granite’ of Borkowska (1966
) and the ‘Liberec and Jizera’ granite of ak & Klominsky (2007)—is the most widespread facies of the Karkonosze pluton (Figs 1b and 2c–f). This granite contains anhedral–subhedral K-feldspar (13–35 vol. %), subhedral–euhedral plagioclase (25–48 vol. %), anhedral quartz (21–40 vol. %), biotite (4–21 vol. %), occasional subhedral amphibole (0–3 vol. %) and accessory apatite, zircon, allanite, titanite, magnetite, ilmenite and monazite. The medium- to coarse-grained matrix has the same texture as the equigranular granite whereas the K-feldspar megacrysts can be 5 cm long and 3 cm wide (Fig. 2d and e). Plagioclase megacrysts are rare. In some places, where K-feldspar megacryst accumulations occur, the matrix is almost absent from what appears to be a megacryst-rich mush. The porphyritic granite is rich in various types of hybrid, mostly MME (Fig. 2f), and in small isolated bodies of hybrid quartz diorite and granodiorite. In most places, elongated enclaves and megacrysts define a magmatic foliation. Interactions between the hybrids and the host granite involve the introduction of K-feldspar megacrysts into MME and of quartz ocelli into hybrid quartz diorites and granodiorites (Fig. 2c). Locally, biotite schlieren are abundant (Fig. 2g).
Hybrid rocks
Hybrid quartz diorite–granodiorite (HYB)
These mesocratic–melanocratic rocks represent zones of mafic–felsic magma mixing; Klominsky (1969) called them the ‘Fojtka granodiorite’ whereas Borkowska (1966) described them as ‘lamprophyre and granite porphyry’. Hybrid quartz diorite–monzodiorite–granodiorite are exclusive to the porphyritic granite. Their texture is porphyritic to equigranular (Fig. 2g–i) and their minerals show growth textures compatible with magma mixing and variable, oval to almost subhedral–euhedral habits. The mineral assemblage is plagioclase, quartz, K-feldspar, amphibole and biotite and subordinate amounts of apatite, zircon, titanite, magnetite and ilmenite. Because of the abundance of biotite and amphibole these rocks are dark in colour. However, they often contain large pink K-feldspar crystals mantled with white plagioclase rims (Fig. 2g). Feldspar megacrysts commonly lie across the border between hybrid and porphyritic granite; together with the rapakivi texture, this is indicative of the mechanical introduction of granite megacrysts into a hybrid magma. Hornblende- and biotite-mantled quartz ocelli are abundant (Fig. 2i).
Microgranular magmatic enclaves (MME)
Centimetre- to metre-sized MME consist mainly of a fine- to medium-grained assemblage of subhedral plagioclase and biotite, variable amounts of euhedral–subhedral hornblende and accessory titanite, apatite, ilmenite, magnetite and zircon. Single plagioclase megacrysts or glomerophyric plagioclase clusters, commonly with syneusis texture, occur in or adjacent to the enclaves. They display boxy-cellular texture and an inner spiky zone (Wnorowska, 2006; Saby et al., 2007a). All plagioclase megacrysts show a narrow, marginal reaction rim; similarly, all alkali-feldspar megacrysts have a narrow rapakivi rim (Fig. 2f). Biotite and hornblende occasionally form mafic clots. Plagioclase–hornblende intergrowths are common, as are quartz ocelli. Enclaves are always rounded or lobate, which, together with the mineral-growth textures, strongly suggests the coexistence and mixing of two magmas.
Composite dykes (COM)
Many dykes (2–3 m thick) intrude both the porphyritic and equigranular granites. They consist of broken and ductilely deformed mafic bodies (Fig. 2j) ranging from monzodiorite to granodiorite in composition. They are medium-grained (2–3 mm) and show a bimodal crystal distribution with subhedral hornblende, biotite, plagioclase and slightly larger anhedral quartz and alkali feldspar. Accessory apatite, zircon, allanite and ilmenite are very abundant. The composite dykes contain mafic clots of biotite and hornblende surrounded by quartzo-feldspathic rims. Plagioclase crystals mantled by alkali feldspar (anti-rapakivi) and alkali feldspar mantled by plagioclase (rapakivi) are common.
Lamprophyres (LAM)
Lamprophyres form dyke swarms cutting the porphyritic granite. They are mainly fine-grained (<1 mm) kersantites and malchites (Borkowska, 1966) containing euhedral plagioclase (oligoclase), amphibole, biotite and magnetite together with sporadic, interstitial quartz and alkali feldspar. Pyroxene, olivine, titanite and apatite are subordinate.
|
MINERAL COMPOSITION |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
All the facies of the Karkonosze pluton have similar mineral assemblages; they differ in the relative abundances of the minerals, growth textures and compositions. The two latter aspects are the focus of the following discussion.
Alkali feldspar
Megacrysts
Alkali megacrysts are restricted to the porphyritic granite and hybrids. All show growth zoning that irregularly and recurrently evolves from relatively Ab-rich cores (Or60–65Ab40–34An0–1) to Or-rich rims (Or83–97Ab17–3An0) (Table 2). The zones are outlined by plagioclase–biotite lath trails and frequently show dissolution–regrowth textures. Many megacrysts reveal a complex polyphase (plagioclase and quartz) mantled rapakivi texture. Their trace-element patterns, in particular, indicate that the alkali feldspar grew in a heterogeneous magma composed of coherent and active regions in the sense of Perugini et al. (2003). Based on Ba, light REE (LREE) and Pb isotope characteristics, Saby et al. (2007a, 2007b) concluded that the megacrysts formed in a magma-mixing regime involving two end-members, rich and poor respectively in large ion lithophile elements (LILE). Cathodoluminescence studies of megacrysts in the hybrids revealed an additional type of zoning interpreted as reflecting changes in the density of structural defects (Saby & Götze, 2004). Zones with high structural defect densities are correlated with growth within active (poorly mixed) magma regions.
|
Matrix
Alkali feldspar is present in the matrix of all the granite facies. The feldspars in the matrices of the hybrid diorite–granodiorite, the MME and the composite dykes are characterized by growth zoning differing in structural defect densities (S
aby & Götze, 2004) and in trace-element characteristics. In contrast, matrix alkali feldspars in both the porphyritic and equigranular granites are homogeneous; compared with the megacrysts, they are richer in Or (Table 2) and poorer in Ba and LREE.
Plagioclase
Megacrysts
In both porphyritic granite and hybrids, plagioclase megacrysts are less common than those of alkali feldspar and are typically strongly altered. Although some display concordant zoning, most show a complex zoning pattern with a patchy core (An52) surrounded by discordant and truncated zones of andesine–oligoclase. Commonly, discordances are separated by simple zoning. Thin marginal rims of almost pure albite (Ab95–97) are interpreted as due to subsolidus reaction (Table 3). Resorption–regrowth textures are common within the complex zoning. Cathodoluminescence study (Saby & Götze, 2004; Wnorowska, 2006) shows that during their crystallization, the plagioclase crystals migrated between variably mixed mafic and felsic environments.
|
Matrix
Plagioclase crystals in the matrices of hybrid quartz diorite–granodiorite, MME and composite dykes, or included in alkali feldspar megacrysts, have exactly the same growth morphologies and compositions as the plagioclase megacrysts (S
aby & Götze, 2004; Wnorowska, 2006). Some crystals from hybrid quartz diorite–granodiorite and MME unequivocally have ternary feldspar compositions (Table 3, MME-2). The plagioclase in the matrices of the porphyritic and equigranular granites is, in contrast, oligoclase (An27–17) occasionally showing limited, continuous and concordant zoning. Thin marginal rims of almost pure albite match the similar megacryst rims.
Quartz
Anhedral interstitial quartz is abundant in hybrids and in porphyritic and equigranular granites. In all hybrids, occasional quartz megacrysts have a hornblende-mantled ocellar texture. Cathodoluminescence reveals that the hybrid megacrysts exhibit simple and complex zoning patterns (Saby & Götze, 2004), whereas quartz from the granites is homogeneous. Myrmekite is widespread in all facies.
Biotite
Biotite is the most abundant ferromagnesian mineral in all granite and hybrid facies and in some lamprophyres. It occurs as euhedral–anhedral, strongly pleochroic, zoned (hybrids) or homogeneous (equigranular granite) flakes characterized by low AlVI contents (
0·05–0·31 a.p.f.u.), almost constant AlIV and variable Fe/(Mg + Fe) of 0·71–0·58 (Table 4). They plot in the annite–phlogopite field in the annite–siderophyllite–phlogopite–eastonite quadrilateral. Lamprophyres contain biotites with Fe/(Mg + Fe) as low as 0·19 (Awdankiewicz et al., 2005b).
|
Changes in biotite Alt, Ti, Fe and Mg concentrations record magmatic evolution. Biotite Alt (a.p.f.u.) is almost constant in the hybrid facies and porphyritic granite, but increases in the equigranular granite (Table 4); this could be interpreted to be the result of an increasing contribution from aluminous crustal material (Shabani et al., 2003
). Biotite compositions evolve from Ti-rich (0·65 a.p.f.u.) and low Fe/(Fe + Mg) (0·2–0·35 a.p.f.u.) in lamprophyres, to Ti-poor (0·3 a.p.f.u.) and higher Fe/(Fe + Mg) (0·7 a.p.f.u.) in equigranular granites (Fig. 3).
|
Amphibole
Amphibole is present only in the more mafic rock types—lamprophyres, hybrid quartz diorites–granodiorites, composite dykes and some porphyritic granites. Based on the Leake et al. (1997
) classification, are all calcic amphiboles (CaB >1·5), but they differ significantly in their SiT, (Na + K)A and Mg/(Mg + Fe). Amphibole in lamprophyres is a magnesio-hastingsite [silica- and iron-poor, Mg/(Mg + Fe) = 0·78–0·87 a.p.f.u.]. Because of variable Mg/(Mg + Fe) values (0·46–0·53 a.p.f.u.), amphiboles in hybrid quartz diorites–granodiorites range from magnesio- to ferro-hornblende (Table 5). Composite dykes contain hastingsite (silica-poor, and iron-rich). As for biotite, amphibole Ti contents and Mg/(Mg + Fe) decreased during magma differentiation (Fig. 3).
|
As the Karkonosze rocks contain eight solid phases (quartz, K-feldspar, plagioclase, biotite, amphibole, titanite, ilmenite, magnetite) plus melt and vapour (Hammastrom & Zen, 1986
; Hollister et al., 1987), amphibole Alt can be used as a geobarometer. Estimated pressures using various calibrations (Hammastrom & Zen, 1986; Hollister et al., 1987; Johnson & Rutherford, 1989; Schmidt, 1992; Anderson & Smith, 1995) are in the range of 7–5 kbar for lamprophyres, 3–1 kbar for hybrid quartz diorites–granodiorites and 6–4 kbar for the composite dyke. However, the estimated composite-dyke pressures may be questionable as their amphiboles are iron-rich and the barometers are calibrated for Mg/(Fe + Mg) >0·35 (Anderson & Smith, 1995).
Accessory minerals
Apatite, zircon, allanite, titanite, magnetite, ilmenite and monazite are the most common accessory minerals, and occur in all facies. The growth textures and composition of apatite, zircon and allanite shed light on the evolution of the host magmas.
Apatite
Long prismatic–acicular apatites and stubby apatites occur in the porphyritic granite, hybrid rocks and lamprophyres. Equant crystals occur only in the equigranular granite. In both cases, crystals are zoned mostly in LREE, Y and Mn contents (Table 6) (Saby & Götze, 2004).
|
In the equigranular granite, apatite is regularly zoned (oscillatory) with Y contents increasing from core (7900 ppm) to rim (11540 ppm) whereas the LREE contents remain relatively low. In the hybrid quartz diorites–granodiorites and in the porphyritic granite, the zoning is mostly irregular and discontinuous with multiple resorptions. Zones are alternately REE-rich and REE-poor. These apatite crystals are richer in LREE than those in the equigranular granite, but significantly poorer in Y (
1200 ppm). In composite dykes, stubby crystals have irregular shapes with deep dissolution embayments. Some crystals display sieve textures. All have high (<15 000 ppm) Y contents, and a contrasting, bimodal LREE distribution. The apatite growth textures and zone compositions reflect growth in a magma mixing regime during formation of the porphyritic and hybrid rocks (Saby & Götze, 2004), as well as progressive closed-system behaviour in the equigranular granite (Przywóski, 2006; Saby et al., 2007b).
Zircon
Zircon occurs as single grains in the equigranular and porphyritic granites and in the hybrids. In composite dykes, zircon forms complex clusters of crystals with skeletal morphology. Cathodoluminescence and BSE images reveal flame-like magmatic zoning and point to the lack of any inherited cores, although these have been previously reported in the Karkonosze granite (Kryza et al., 1979). Zircons from the composite dykes and from the more silicic equigranular granites are zoned, with strong rimward enrichments in Y, Th and heavy REE (HREE) (Table 7).
|
|
|
|
|
|
Allanite
Zoned allanite crystals occur in the granite and composite dykes. Zoning patterns are complex with, in some cases, discordant sector zoning repeatedly separated by oscillatory zoning. All crystals are allanite-(Ce), with LREE-rich and Th-, Fe-, Ti-poor cores and with rims relatively poor in LREE and rich in Th, Fe and Ti (Table 8). Y contents are low in both cores and rims.
|
WHOLE-ROCK GEOCHEMISTRY |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
Whole-rock major- and trace-element compositions for the various rock types are given in Tables 9–13
.
|
Equigranular and porphyritic granites
The very homogeneous equigranular granite is SiO2-rich (73·01–77·87 wt %) with low Mg-number [atomic Mg/(Mg + Fe)] values of 0·11–0·38 (Table 9). In the (Na2O + K2O) vs SiO2 diagram (Fig. 4a), it plots in the upper part of the sub-alkaline field of Rickwood (1989
). The Na2O/K2O ratio is low (<1), a result of the K2O-rich (4·33–6·10%) character of rocks that plot in the high-K calc-alkaline field of the K2O vs SiO2 diagram (Fig. 4b). The equigranular granite is mostly peraluminous, with A/CNK [Al2O3/(CaO + Na2O + K2O)] ranging from 0·98 to 1·14 (Fig. 4c, Table 9). The porphyritic granite has the same characteristics except that it ranges towards lower SiO2 contents (69·27%) and higher Mg-number (0·47) (Tables 10 and 11). Some samples are significantly poorer in K2O than the equigranular granite and plot in the medium-K calc-alkaline field (Fig. 4b).
|
In the CIPW normative An–Ab–Or classification diagram, the equigranular granite plots in the granitic field, whereas the porphyritic types may extend towards the granodiorite field (Fig. 5a). The Q–Ab–Or triangular diagram (Fig. 5b) shows that the equigranular granite has a composition close to the minima on the quartz–feldspar cotectics in the ‘hydrous granitic system’ for pressures ranging between 1 and 2 kbar (Fig. 5b). This is consistent with the pressure deduced from the amphibole compositions. Some of the porphyritic rocks plot together with the equigranular rocks, whereas others plot below the cotectic and do not display eutectic-like compositions.
|
On Harker diagrams (Fig. 6), all elements except for K2O correlate negatively with SiO2. In most cases the data for both equigranular and porphyritic facies plot on more or less the same trend. However, in (Na2O + K2O) /CaO vs Al2O3 and (MgO/Fe2O3) vs SiO2 plots (Fig. 7), the equigranular granite follows a differentiation trend, whereas the porphyritic granite (particularly SiO2-poor samples) deviates markedly.
|
|
The equigranular granite REE patterns (Fig. 8a) show variable LREE (115 > LaN > 19), high and variable HREE (25 > YbN > 12) and strong Eu anomalies (0·38 > Eu/Eu* > 0·11); Eu/Eu* = EuN/[(SmN + GdN)/2)]. The porphyritic granite (Fig. 8b) shows similar REE patterns, although the LREE (196 > LaN > 31) are somewhat higher than in the equigranular granite; Eu anomalies are also strongly negative (0·69 > Eu/Eu* > 0·18). The LaN vs SiO2 diagram (Fig. 9a) shows that these two elements are strongly anti-correlated in the equigranular granite—and also in the more silicic (SiO2>
71%) porphyritic granites; such a correlation is absent in the less silicic porphyritic granites. The decrease in La (and other LREE) with progressive differentiation points to the fractionation of mineral phase(s) with 
. In contrast, Yb is not correlated with SiO2 (Fig. 9b), indicating that the crystallizing phases had a bulk partition coefficient D 1 and, thus, that the mineral phase with had significantly lower 
.
|
|
Primitive mantle-normalized, multi-element diagrams (Sun & McDonough, 1989
; Fig. 10) show that both equigranular and porphyritic granites are strongly enriched in LILE. Both show negative anomalies (Ba, Nb, Sr, P, Eu, Ti), which are clearly more pronounced in the equigranular granite.
|
The significance of these anomalies can be investigated using element ratio vs SiO2 diagrams (Fig. 11). The (Ba/Rb)N diagram (Fig. 11a) shows that the negative Ba anomaly increases during the course of differentiation—implying the fractionation of phases such as K-feldspar and biotite with
. However the fractionation of these minerals should also deplete the melt in both K and Rb (behaving as a compatible element in Karkonosze alkali feldspars; E. Saby, unpublished data), which is obviously not the case in the Karkonosze granite (Fig. 6). It must be noted that 
has been reported for natural rhyolites (Nash & Crecraft, 1985) as well as for experimental leucosomes (Bea et al., 1994). Streck & Grunder (1997) obtained 
ranging between 6 and 19 in high-Si rhyolites and Icenhower & London (1996) measured 
between 1·1 and 18 in experimental granitic melts. These results show that in melts such as those from which the equigranular granite crystallized, not only K-feldspar and biotite are able to significantly fractionate Ba, but plagioclase also.
|
Both (Sr/Ce)N (Fig. 11c) and (Eu/Gd)N (Fig. 11f) show that the Sr and Eu negative anomalies also increase with differentiation, although some porphyritic granites deviate from the trend defined by the rest of the data. On the other hand, the strong correlation of Sr with Eu (Fig. 11h) may be interpreted as demonstrating control by a single phase. In granitic magmas, only feldspars have both
and 
>1, but as K and Rb increase during differentiation, this phase must have been plagioclase. The good correlation between Ba and Sr (Fig. 11i) also favours plagioclase fractionation controlling Sr, Eu and Ba.
The (P/Nd)N plot (Fig. 11d) reveals the role of a P-bearing phase that could have been apatite. However, a correlation between this ratio and SiO2 exists only for rocks with SiO2 > 74% (mainly equigranular granite). Early apatite evidently attained only localized saturation (Hoskin et al., 2000) rather than late saturation appearing during the last stages of differentiation. Similarly, the (Ti/Gd)N diagram (Fig. 11g) points to the fractionation of a Ti-rich phase that could be ilmenite and/or Ti-rich magnetite or biotite.
(Zr/Sm)N behaviour (Fig. 11e) is slightly different. (Zr/Sm)N is correlated with SiO2; in the less differentiated rocks it is >1 (positive anomaly) whereas it is <1 (negative anomaly) in the more differentiated rocks (Fig. 11e). The rather good correlation shows that zircon fractionated, but the values >1 in less differentiated rocks show that the parental magma already had a small positive Zr anomaly that turned negative during fractionation.
Unlike other element ratios, (Nb/K)N (Fig. 11b) is not correlated with SiO2 even though a pronounced Nb anomaly is evident in the primitive mantle multi-element diagrams (Fig. 10). The lack of correlation with SiO2 indicates that the negative Nb anomaly was inherited from source melting and does not reflect later differentiation.
Geochemical modelling of granite differentiation
Several lines of evidence, presented above, indicate that fractional crystallization occurred in both porphyritic and equigranular granites. The schlieren, and internal feldspar segregation, for example, could reflect fractional crystallization in a dynamic flow regime. Although crystal separation was not perfect, multiphase flow resulted in zones enriched in cumulus phases and differentiated liquid, respectively. Mass-balance calculations allow the total amount of cumulate removed to be determined, irrespective of the exact physical process invoked. Initially, the process is modelled using mass-balance calculations based only on major elements (Störmer & Nicholls, 1978) to yield the modal and chemical compositions of the cumulate and the degree of fractional crystallization. In the second step, these computed values are entered into trace-element models using the equations of Rayleigh (1896).
Both major and trace elements define linear differentiation trends for the equigranular granites and the more silicic porphyritic granites (SiO2 > 72%). Consequently, modelling of the fractional crystallization process was performed to try to explain the differentiation of high-Si melts (78%) from those with lower Si contents (72%). The compositions used in the mass-balance calculations were computed from the correlation lines in the Harker diagrams (Fig. 6); these, and the mineral compositions used in modelling, are given in Table 14, where the results are also shown. The cumulate assemblage that best fits the data comprises 62·46% plagioclase + 30·46% biotite + 4·66% magnetite + 2·3% apatite + 0·12% ilmenite. The low (0·07) sum of squared residuals testifies to the goodness of fit. The amount of fractional crystallization is low (18%). There is a very good correlation between the size of the negative Ti anomaly and the degree of differentiation (Fig. 11g). The amount of ilmenite in the cumulate is very low (0·12%), probably because in the Karkonosze granite both biotite and magnetite are Ti-rich (TiO2 4·3% and 8·13%, respectively); consequently, Ti fractionation was almost totally controlled by these phases. All the computed models preclude fractionation of significant K-feldspar (always <2%). The best fit between model and data is obtained with K-feldspar-free cumulates. If K-feldspars crystallized, they were not removed from the magma.
|
Trace-element modelling was based on mineral/liquid partition coefficients (Kdm/l) for rhyolites and high-silica rhyolites; the chosen values are given in Table 15. Sample POR-1 (SiO2 72·63%) was chosen as representative of the parental magma and sample EQU-12 (SiO2 77·37%) as representative of the daughter magma. When the cumulate composition and the degree of fractionation calculated from the major-element data are used in trace-element modelling, the models do not appear to fit the analytical data at all. This is particularly obvious for LREE where the modelled magma has 40 ppm La whereas sample EQU-12 has only 9·9 ppm La (Fig. 12a). Similarly, modelling predicts the incompatible behaviour of Zr (Fig. 13a) whereas in the Karkonosze granite, Zr decreases from 204 ppm in POR-1 to 54 ppm in EQU-12, indicating strongly compatible behaviour (Fig. 11e). These differences are easily resolved. Only a small amount (0·12%) of zircon is needed to explain Zr abundances in the evolved magma. Both allanite and monazite can strongly fractionate the LREE without significantly modifying the HREE. As monazite also fractionates P, significantly reducing the amount of cumulative apatite, REE and P behaviour could reflect either monazite or allanite + apatite fractionation. The latter seems more likely. First, unlike monazite, allanite is abundant in the Karkonosze granite. Second, the slight impoverishment of middle REE (MREE) relative to LREE and HREE in the differentiated magma is consistent with apatite fractionation with
> 
. Also, the calculated amount of allanite is low (0·27%). The introduction of these two accessory phases into the modelling allows perfect agreement between the computed composition and the composition of EQU-12 for both REE and other trace elements (Figs 12b and 13b).
|
|
|
The models do not predict any significant modification of the negative Nb anomaly in the Karkonosze rocks (Fig. 11b). Only Eu does not fit the analytical data. The models predict the development of a less pronounced negative Eu anomaly than that characterizing the rocks. Plagioclase is the main phase capable of inducing a negative Eu anomaly in melts. Low fO2 would strongly favour high
. However, ilmenite + magnetite in the mineral association in the Karkonosze granite and in the computed cumulate would rather argue for a high fO2. A very high (9) in rhyolitic magmas has been already reported by Nash & Crecraft (1985).
In conclusion, modelling, based on both major and trace elements, shows that the composition of the more silicic equigranular granites in Karkonosze can reasonably be accounted for by about 18% fractional crystallization of a plagioclase + biotite + accessories (apatite, magnetite, ilmenite, zircon, allanite) cumulate from a parental magma with 72% SiO2.
Hybrid rocks and lamprophyre
Hybrid quartz diorites–granodiorites and lamprophyre dykes
The SiO2 contents of the hybrid quartz diorites–granodiorites, mostly from Fojtka and Rudolfov near Liberec, Czech Republic (Fig. 1b), range between 53 and 71% and Mg-number varies in the narrow range 0·37–0·48 (Table 12). They are K2O-rich (2·69–4·47%) with Na2O/K2O ranging from 1·45 to 0·75, anti-correlated with SiO2 content. They are metaluminous with A/CNK ranging from 0·83 to 1·01 (Fig. 14a, Table 12).
|
Lamprophyres occur as syn-kinematic dykes. They are commonly weathered, which could explain the relative scatter in their chemical composition, although the analysed samples showed no visible effects of alteration in the field or in thin section. The least differentiated types have SiO2 of 49·65% (Table 11). Mg-number ranges from 0·59 to 0·47, K2O is >3·7% and Na2O/K2O
1 except for LAM-3 (K2O 2·34% and Na2O/K2O = 1·7). A/CNK varies in the range 0·75–0·95 as in the hybrid quartz diorites–granodiorites (Fig. 14a, Table 11). The hybrid quartz diorites–granodiorites define a linear trend linking the equigranular granite and the lamprophyres (Fig. 14a). The lamprophyre and hybrid fields overlap extensively with the more mafic porphyritic granites, showing a similar, if less pronounced, link with the lamprophyres. The same observation can be drawn from Fig. 14b: if the equigranular granite has a composition close to the minimum on the cotectics of the ‘hydrous granitic system’ for pressures between 1 and 2 kbar, all hybrids and some of the porphyritic rocks plotting far below the cotectics define a linear trend towards the lamprophyres. This trend cannot be accounted for by melting or crystallization processes. Mixing is indicated. Similar correlations are seen in major element Harker diagrams (Fig. 15). Even in the K2O vs SiO2 plot where the granite data scatter, the hybrid quartz diorites–granodiorites define a coherent trend. The hybrid rocks, in systematically falling between the equigranular granite and the lamprophyre compositions (Fig. 15), reinforce the hypothesis that they resulted from mixing between magmas with compositions similar to those of the equigranular granite and the lamprophyres. The hybrid quartz diorites–granodiorites define a continuous trend indicating that end-member mixing occurred in all proportions. The low-SiO2 porphyritic granites display the same trend towards the lamprophyre composition but, in this case, mixed compositions are restricted to a field close to that of the equigranular granites; the lamprophyre volumes involved were low. At the present level of exposure, the granite is several orders of magnitude more voluminous than the lamprophyre in the dykes.
|
The REE patterns for hybrid quartz diorites–granodiorites (Fig. 16a) are relatively homogeneous; they are characterized by high LREE (155 > LaN > 71) and high HREE (24 > YbN > 13). The LREE are fractionated whereas the HREE are almost flat. In addition, all patterns display a significant negative Eu anomaly (0·64 > Eu/Eu* > 0·36). In contrast, the lamprophyres are richer in REE (Fig. 16b); LaN can be as high as 300; Awdankiewicz et al. (2005b
) reported LaN = 230 in the Bukoviec lamprophyre near Jelenia Góra. Both LREE and HREE are similarly fractionated with no or insignificant negative Eu anomalies (0·90 > Eu/Eu* > 0·72) at most. The primitive mantle-normalized multi-element diagrams (Sun & McDonough, 1989; Fig. 17a) corroborate the relatively restricted variability of the hybrid quartz diorites–granodiorites. They show negative Ba, Nb, Sr, P, Eu and Ti anomalies as in the granite but they are less marked. Two exceptional samples display significant positive Zr anomalies (Fig. 18e). The lamprophyres show regularly fractionated patterns (LILE-richer and HREE-poorer) and, except for Nb, do not show any significant anomalies. The Nb anomaly characterizes only two samples and is totally absent in the least differentiated variety.
|
|
|
In all trace-element ratio vs SiO2 diagrams (Fig. 18a–i) the hybrids plot on a trend connecting equigranular granites and lamprophyres. Comparison with the similar relationships shown by the major elements reinforces the hypothesis of lamprophyre- and granite-magma mixing. Figure 18a–g records element ratios that indicate the importance of the anomalies observed in multi-element plots (Fig. 17); the magnitude of Sr, P, Eu and Ti anomalies (Fig. 18c, d, f and g) correlates with SiO2. Anomalies in Nb and Zr remain constant. Thus, if mixing occurred, the prospective lamprophyre end-member might most probably be lamprophyre characterized by a negative Nb anomaly (Fig. 18b). Plotted against SiO2 (Fig. 18a), the Ba anomaly shows no definable correlation.
Mixing in hybrid quartz diorites–granodiorites
In terms of both major- and trace-element compositions (Figs 14 and 18), the hybrid quartz diorites–granodiorites plot systematically between the lamprophyres and the equigranular granites. For most elements, they also define reasonable correlation lines, the only exceptions being LILE (e.g. Rb, Sr and Ba). There is a clear possibility that the latter elements were affected by other processes; for example, local selective assimilation or segregation of feldspars rich in Rb, Sr and Ba (Saby et al., 2007a). In addition, in both hybrid quartz diorites and granodiorites and the porphyritic granite, mineral compositions and growth morphologies point to crystallization coeval with magma mixing (Saby & Götze, 2004; Saby et al., 2007a). Saby et al. (2007a, 2007b) used mineral–magma equilibria to calculate magma compositions. In the Karkonosze hybrid quartz diorites–granodiorites these compositions systematically fall between those of lamprophyre and equigranular granite.
A first attempt to test the hypothesis that the hybrid quartz diorites–granodiorites resulted from the mixing of lamprophyre and equigranular granite magmas is based on major elements. The calculation uses an average lamprophyre and the parental magma composition used for the fractional crystallization modelling (Table 14). The results for an average hybrid are given in a C(hybrid quartz diorite–granodiorite) – C(parental magma) vs C(lamprophyre) – C(parental magma) diagram (Fig. 19a; Fourcade & Allègre, 1981), where C represents the concentration of an oxide. In a case of mixing, all of the points on such a diagram would plot on a straight line passing through the origin and with a slope that represents the degree of mixing. The line (R2 = 0·989) for the Karkonosze hybrid quartz diorites–granodiorites, going exactly through the origin, supports the mixing hypothesis and shows that an average hybrid can be explained by the mixing of 44% lamprophyre and 56% granitic magma. For the less silicic porphyritic granite (sample POR-1), the line (R2 = 0·949) in Fig. 19b indicates about 15% contamination of the porphyritic granite by lamprophyre.
|
The trace-element data, despite the relative scatter in Rb, Sr and Ba, also strongly support mixing. The entire range of compositions obtained by mixing between an average lamprophyre and a slightly differentiated equigranular granite (sample EQU-5) define the grey-shaded field in Fig. 20. That all the hybrid quartz diorites–granodiorites plot in this field is perfectly consistent with Fig. 18, which shows the size of trace-element anomalies in hybrids increasing from mafic to felsic compositions.
|
Accepting that the hybrid quartz diorites–granodiorites formed by mixing between lamprophyric and granitic magmas, it would be interesting to know when this event took place in the crystallization history of the granite. In (Na2O + K2O)/CaO vs Al2O3 and (MgO/Fe2O3) vs SiO2 plots (Fig. 21) and in all Harker diagrams, the hybrids plot along straight lines linking equigranular granite and lamprophyre. These diagrams efficiently discriminate between fractional crystallization (dotted line, Fig. 21) and mixing (continuous line) trends. The mixing and crystallization trends intersect at SiO2 contents and (Na2O + K2O)/CaO ratios characterizing the less differentiated equigranular granites. This indicates that mixing occurred early in the magmatic history during the first stages of fractional crystallization. This conclusion is reinforced by the fact that, in the same diagrams, the less differentiated porphyritic granites are the more mixed (Fig. 21). Field relationships also favour early emplacement of the hybrid quartz diorites–granodiorites (
ak & Klominsky, 2007).
|
Microgranular magmatic enclaves (MME) and composite dykes
The MME and composite dykes were emplaced at a late stage into the granite; indeed, some dykes cut the more differentiated facies of the equigranular granite. In the MME, SiO2 contents range between 68·24 and 69·77% except for one sample (MME-1, with 64·33% SiO2). They have Mg-number between 0·42 and 0·31 and are Na2O-rich with Na2O/K2O typically >2 (in hybrid quartz diorites–granodiorites this ratio is
1); A/CNK is in the range 1–1·1 (Table 13). The composite dykes form a rather homogeneous group (67·42% < SiO2 < 69·46%, except for COM-1 with 62·33% SiO2; Table 13). Mg-number is low (0·30–0·25) with Na2O/K2O typically <1 and A/CNK 1 as for enclaves (Fig. 14a, Table 13). The composite dyke (Na2O + K2O)/CaO (4·35–5·55) and MgO/Fe2O3 (0·14–0·22) values both differ from their equivalents in the hybrid quartz diorites–granodiorites (1·7–3·8 and 0·30–0·46) and in MME (1·88–3·08 and 0·32–0·36) (Fig. 21). Consequently, in most Harker diagrams (Fig. 15), the composite dykes plot on different trends from the mixing trend of the hybrid quartz diorites–granodiorites. These trends point towards a more mafic, silica-poor end-member that is not lamprophyre in composition. Consequently, if the dykes originated by the same process as the hybrids, at least the mafic component was different. A (CaO/Na2O) vs Al2O3 diagram (Fig. 22) clearly discriminates between the trends followed by the hybrid quartz diorites–granodiorites, enclaves and dykes. Whereas all the enclaves and dykes point towards a granite composition, only the hybrid quartz diorites–granodiorites appear directly related to lamprophyres.
|
The enclave REE patterns (Fig. 23a) differ from those of the composite dykes (Fig. 23b). They show distinctly different LREE contents; in the composite dykes, LaN is >100 and typically less in the MME. In both, some samples (MME-4, COM-3, COM-4 and COM-6; black symbols in Fig. 23) have low HREE contents and small negative Eu anomalies very similar to those of some lamprophyres (e.g. LAM-3). Others have high HREE contents associated with pronounced negative Eu anomalies.
|
In primitive mantle-normalized multi-element diagrams (Sun & McDonough, 1989
; Fig. 24), negative anomalies are generally more prominent in the composite dykes than in the MME. Composite dykes show a slightly positive Zr anomaly, which is more marked in the MME. However, the main difference between these two rock types is a significant positive Y anomaly in the MME, which is not seen in the granites, lamprophyres or hybrid quartz diorites and granodiorites. Only two composite-dyke samples (COM-1 and COM-5) show a slight Y positive anomaly. The origin of the Y anomaly and the contrasted geochemical behaviour of Y and HREE await explanation.
|
Mixing in microgranular magmatic enclaves (MME) and composite dykes
As with the hybrid quartz diorites–granodiorites, field and petrographic evidence indicates that both the MME and the composite dykes were hybridized. However, their compositional range is narrower than in the hybrid quartz diorites–granodiorites, which span the whole range from equigranular granite to lamprophyre (Fig. 15). As compositional trends defined by both MME and composite dykes converge on equigranular or silicic porphyritic granite (Figs 15, 20 and 21), the latter can be considered one end-member involved in the mixing. Unfortunately, the other end-member has not yet been identified. The evolutionary trends defined for the composite dykes and MME do not point towards lamprophyric compositions (Figs 21 and 22); lamprophyre is unlikely to have been the other end-member. However, some MME (MME-4) and composite dykes (COM-3, COM-4 and COM-6) have trace-element patterns similar to those of the lamprophyres, thus a genetic link with lamprophyres is considered possible.
For these rocks, the mafic, mixing end-member was lamprophyre and another mafic magma linked to lamprophyre. A genetic link may reflect partial melting of a single source or fractional crystallization of a unique parental magma. As lamprophyres are generated by melting of enriched mantle (Awdankiewicz et al., 2005a), the mafic end-member for the MME and the composite dykes could also have the same source. However, mantle melting would produce magmas with relatively high Mg-number and high Ni contents (Mg-number = 0·47–0·59 and Ni 100 ppm in lamprophyres; Table 11), which is not the case for the dykes (Mg-number = 0·25–0·30 and Ni 4 ppm). The remelting of residual mantle would result in even higher values.
Enclave and granite Ni contents (Fig. 25) may provide some insight. Ni contents in the composite dykes are lower than in all porphyritic and most equigranular granites; this argues against their efficient contamination by granitic material. Consequently, the basic end-member in mixing was already strongly depleted in Ni. During mantle partial melting or fractional crystallization of lamprophyric magma, Ni will always have 
and behave as a strongly compatible element. The contrasting behaviour of compatible elements during fractional crystallization and partial melting allows a distinction between these two processes. Whereas partial melting cannot efficiently decrease the compatible element content in magmatic liquids, on the contrary fractional crystallization strongly impoverishes magmas in these elements (i.e. Hanson, 1980). Thus, it seems that the very low Ni contents in the basic end-member involved in composite-dyke mixing could have been achieved only by fractional crystallization. In addition, the pronounced negative Sr, Eu, P and Ti anomalies (Fig. 24) characterizing both the composite dykes and the MME indicate fractionation of plagioclase-, apatite- and Ti-bearing phases. In contrast, the positive Zr anomaly points to a lack of zircon fractionation.
|
As noted above, the composite-dyke compositional trends also point to an equigranular granite composition. However, in contrast to the hybrid quartz diorite and granodiorite trends, the dyke trend points towards the most evolved and differentiated equigranular granite (Figs 15, 20 and 24). This indicates that this mixing event took place late in the differentiation history of the Karkonosze granite, a conclusion supported by field and petrographic observation.
Magmatic evolution
The above discussion shows that limited fractional crystallization (F < 20%) occurred in the Karkonosze granite. Mixing also occurred between a felsic and a more mafic lamprophyric magma. Hybrid quartz diorites–granodiorites reveal that lamprophyre interacted with granitic magma at an early stage, before much of the crystallization took place. In contrast, the composite dykes were emplaced into, and interacted with, an already differentiated granitic magma. MME compositions fall between those of the hybrid quartz diorites–granodiorites and those of the composite dykes (Figs 21 and 24), suggesting that they could have interacted with granite after the hybrid quartz diorites–granodiorites had formed but before the dykes had done so. This relative chronology is consistent with the experimental work of Hallot et al. (1994, 1996), who showed that the shape of a mafic magma injection into a felsic magma depends on the relative viscosity of both magmas. A small difference in viscosity favours more complete mixing, a higher viscosity contrast leads to spheroidal microgranular magmatic enclaves and, where the contrast is very high, emplacement of the mafic magma as dykes. As magma viscosity correlates with degree of differentiation (increasing polymerization and crystal load), continuous injection of mafic magma into a crystallizing granitic pluton would result in mixed hybrid granodiorites, MME and dykes in that order (see also Barbarin, 2005). The sequence seen in the Karkonosze pluton indicates that mafic (lamprophyric) magma was injected into the granite throughout the granite crystallization history of the granite.
The composition of the mafic end-member also became increasingly more differentiated. Thus, the history of the Karkonosze pluton involved the parallel evolution of two reservoirs, one granitic, the other lamprophyric. Interactions between these two reservoirs continued as the differentiation of both progressed—as summarized in Fig. 26.
|
Nd–Sr isotopic data
143Nd/144Nd ratios were measured in 16 samples and
Nd(T) recalculated for an age of 320 Ma, the 40Ar–39Ar age determined for the Karkonosze granite (Marheine et al., 2002) (Table 16). In a plot of Nd(T) vs SiO2 (Fig. 27), the negative correlation of most of the data clearly corroborates the magma mixing hypothesis indicated by the major- and trace-element patterns. The higher Nd(T) of the lamprophyres could be consistent with a mantle origin. However, to date, no positive Nd(T) values have been reported from this massif—suggesting that even the more primitive mafic magmas had already reacted with crustal rocks. It is also possible that the lamprophyres originated by partial melting of an enriched mantle with a relatively low Nd(T).
|
|
In contrast, the low
Nd(T) (< –7) of the equigranular granites is consistent with a crustal origin. Porphyritic-facies rocks are characterized by a slightly less negative Nd(T), indicating that they could have interacted with more primitive magmas. Earlier studies (Mierzejewski et al., 1994) reported Nd(T) –3·5 for the porphyritic granite, which is in the same range as those analysed in this work. Hybrid rocks have Nd(T) intermediate between lamprophyres and granites.
Duthou et al. (1991) also proposed a crustal origin for the granite, based on Sr isotope data, considering the protolith to be mostly mafic. The conclusion that the Karkonosze granite originated predominantly by melting of a crustal source is supported by major element evidence for its weakly peraluminous character (Fig. 4). It is also consistent with the observation that the equigranular granites plot close to the minima on the cotectics of the ‘hydrous granitic system’ of pressures ranging between 1 and 2 kbar (Fig. 5b).
In conclusion, the Nd isotope data confirm that the composition of the Karkonosze granite resulted from long-term interactions between two evolving magmas, one being of mantle (possibly enriched) origin, the other the result of crustal melting. This also indicates that the granite does not have a single global isotopic initial ratio, but rather one varying from place to place that depends on the degree of mixing between the mafic and felsic end-members, thus making highly disputable the interpretation of data alignment in isochron plots in terms of age.
|
DISCUSSION AND CONCLUSIONS |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
The Karkonosze pluton largely comprises equigranular granite and porphyritic granite. The entire pluton, except for the equigranular granite component, was affected by mixing processes. The porphyritic granite, representing a volume of >500 km3 (Cwojdziñski et al., 1991
), had its original magmatic composition totally modified by interaction with contemporaneous mafic magmas. This implies that huge volumes of mafic magma were available. Given a degree of mixing of 15%, as calculated for the least silicic porphyritic granite (Fig. 19b), the volume of mafic lamprophyric magma can be estimated at 75 km3. The role played by mafic magma, therefore, was not negligible or subordinate. Indeed, hot mafic magma might well have supplied much of the heat necessary to start and maintain crustal melting; part of this heat could have been released by latent heat of crystallization. Only a very small part of the Karkonosze granite escaped mixing with mafic magmas. This includes the equigranular granite and a subordinate part of the porphyritic granite, which represent relatively small volumes of differentiated magmas (SiO2 > 70 wt %). The equigranular granite does not contain enclaves or bodies of hybrid quartz diorite or hybrid granodiorite; it is cut only by lamprophyre dykes or some late composite dykes. Feldspars from the equigranular granite are homogeneous or, in some cases, show a faint continuous normal zoning. They are devoid of mantled structures or resorption features. The zoning, together with geochemical modelling, indicates that the evolution of this granite involved small (<20%) degrees of fractional crystallization. The equigranular granite has a composition close to the minima on cotectics in the Q–Ab–Or–H2O system at water pressure of 1–2 kbar; protracted fractional crystallization was not possible. Accessory minerals, abundant in this granite type, played an important role during magma differentiation. Small degrees of crystallization of major minerals (biotite + plagioclase + magnetite) would not have significantly modified the major-element composition of the magma. In contrast, the fractionation of small amounts of accessory phases such as allanite, zircon and apatite was able to significantly modify the budget of some trace elements (Figs 11 and 12). Thus, the history of fractional crystallization is more clearly recorded by trace than by major elements.
Interaction between mafic and felsic magmas took different forms: (1) homogeneous hybrid quartz diorites and granodiorites reflecting two magmas that have been relatively intimately mixed; (2) rounded and lobate MME–mafic magmas coexisting with large volumes of granite melt; (3) composite ductile stretched dykes with rare chilled margins; (4) late intrusive lamprophyre dykes with chilled margins. As shown by several workers (Furman & Spera, 1985; Sparks & Marshall, 1986; Frost & Mahood, 1987; Hallot et al., 1994, 1996; Barbarin, 2005) all of these features result from differing degrees of inter-magma viscosity contrast; with increasing contrast, homogeneous hybridization gives way to rounded mafic enclaves, composite dykes and, finally, late mafic dykes. As a result of cooling and increasing crystal contents during granitic magma crystallization, the felsic magma viscosities increase strongly. Thus, it is possible to link each type of magmatic interaction with a stage of granite differentiation. Early injection of mafic magma into a low-viscosity, melt-rich granitic mass allowed relatively homogeneous mixing to produce hybrid quartz diorites–granodiorites. Later injections into more fully crystallized granite produced MME and, later, composite dykes. Finally, injection into almost totally crystallized granite resulted in dykes with sharp contacts and chilled margins. The recognition of all of these interaction styles in Karkonosze indicates that injections of mafic magma took place throughout the granite crystallization history; the mafic magma source was long-lived and the conditions for mantle melting were realized during at least the period of the granite crystallization. Alternatively, the mafic magma could have been stored in a deeper magma chamber and injected episodically into the granitic pluton.
The episodic emplacement of mafic magmas at different stages of granite crystallization is fairly common. Very often, two or more compositional types of magmatic enclaves are reported; for example, in the Mont Blanc granite, where Mg-rich and Fe-rich enclaves led Bussy (1987, 1990) to conclude that two melts of mafic to intermediate composition had coexisted with the granite magma. The parallel evolution of granite and mafic magmas, and their recurring interaction throughout granite crystallization, has been described from the Bono granodiorite in Sardinia (Zorpi et al., 1989, 1991; Bouchet, 1992). Bouchet (1992) demonstrated that these mafic and felsic magmas interacted from the beginning until the end of granite crystallization. In the course of time the mafic magma also crystallized and differentiated; hence the composition of late mafic inputs is more evolved than that of early injections. In Karkonosze, compatible elements such as Ni reveal that the mafic magma interacting with the granite became progressively impoverished in Ni with time from hybrids to enclaves and finally to composite dyke. Unlike partial melting, fractional crystallization is a highly efficient process to impoverish the magma in compatible elements. Consequently, the Ni content decrease in the mafic component can be logically interpreted in terms of fractional crystallization. The data indicate that both felsic and mafic magmas evolved independently by fractional crystallization, which, in the case of the Karkonosze granite, argues for a deep-seated magma chamber rather than for continuous mantle melting. In summary, in Karkonosze, two magma sources (mantle and crust) melted almost contemporaneously. Then the two magma reservoirs evolved independently by fractional crystallization. However, episodically the mafic magma intruded into crystallizing granite, with attendant various degrees of interaction.
In the Karkonosze granite, several lines of evidence indicate dynamic magma movement. Parallel alignments of both megacrysts and enclaves point to magma flow. Zones almost exclusively composed of feldspar megacrysts and little matrix suggest, regardless of the exact process of feldspar accumulation (crystal settling, filter pressing, etc.), relative movement of crystals and liquid. The rapakivi textures characterizing the alkali-feldspar megacrysts in the hybrid rocks show that the feldspars were mechanically introduced from the granite into the mafic magma (Saby & Götze, 2004). Feldspar megacrysts astride contacts between hybrid and porphyritic granite demonstrate the capture of granite-derived feldspar by the mafic magma. In addition, feldspar crystals show evidence of repeated episodes of resorption and regrowth as a result of rapid changes in magma composition (Saby & Götze, 2004; Saby et al., 2007a, 2007b). This zoning is interpreted as a result of mineral crystallization and transfer within a heterogeneous magmatic flow field caused by mafic–felsic magma interaction. Similar feldspar migrations have been reported in numerous magma-chamber systems (Vernon, 1986; Cox et al., 1996; Tepley et al., 1999; Davidson et al., 2001; Troll & Schmincke, 2002; Perini et al., 2003; Troll et al., 2004). Obviously, a well-stirred magma would favour more efficient mixing and mingling. Emplacement would have been the most obvious cause of granite magma movement but convection induced by the introduction of hot mafic magma batches may have contributed (Wiebe, 1996; Janouek et al., 2004).
Since Archaean times, the association of lamprophyres with crustal magmas has been fairly common; for example, in the late Archaean Closepet granite (Jayananda et al., 1995; Moyen et al., 2001, 2003a, 2003b). Most of the Archaean sanukitoids are also spatially and genetically associated with lamprophyre-like rocks (Shirey & Hanson, 1984; Stern & Hanson, 1991; Halla, 2005; Lobach-Zhuchenko et al., 2005; Samsonov et al., 2005). The association of lamprophyre with granite and/or monzodiorite is common in Hercynian granites, e.g. in Spain (Bea et al., 1999), Brittany (Barrière, 1977; Albarède et al., 1980), Mont Blanc (Bussy, 1990), the French Central Massif (Lameyre et al., 1980; Barbarin, 1983; Solgadi et al., 2007), Corsica and Sardinia (Zorpi et al., 1989, 1991; Bouchet, 1992), the Vosges (Pagel & Leterrier, 1980) and in Bohemia (Förster et al., 1999; Janouek et al., 2000). In all these cases a mixed origin is invoked, implying both mantle and crust magmatic inputs. The assumed mantle source is, in many cases, a fertile peridotite possibly enriched by earlier subduction (Jayananda et al., 2000; Moyen et al., 2001). Most of these granites correspond to the KCG (K-rich and K-feldspar porphyritic calc-alkaline granitoids) as defined by Barbarin (1999). The Karkonosze granite is not an exception.
|
ACKNOWLEDGEMENTS |
|---|
We are deeply grateful to B. Bonin and V. Janou
ek for their very constructive and thorough reviews, and to Marjorie Wilson for efficient editorial oversight and very helpful comments. We appreciate very much friendly assistance by R. Macdonald and P. Kennan, who substantially improved the scientific content and who, in addition, corrected both English style and grammar. We are also indebted to B. Bonin, B. Barbarin, M. 
temprok, J. ák, M. Mierzejewski and A. Wilamowski for stimulating and fruitful discussions on the field in the Polish and Czech part of the Karkonosze. We acknowledge R. Bachliski for assistance in the isotope laboratory, as well as P. Dzier
anowski and L. Jeak in the microprobe laboratory. The work has been funded by KBN grant 307/1766/B/PO1/2007/33, BW 1642 and BW 1761/13.
*Corresponding author. Telephone: +48 22 55400308. Fax: +48 22 5540001. E-mail: e.slaby{at}uw.edu.pl
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONANALYTICAL METHODSGEOLOGICAL SETTINGPETROLOGYMINERAL COMPOSITIONWHOLE-ROCK GEOCHEMISTRYDISCUSSION AND CONCLUSIONSREFERENCES |
|---|
Albarède F, Dupuis C, Taylor HP. 18O/16O evidence for non-cogenetic magmas associated in a 300 Ma old concentric pluton at Ploumanac'h (Brittany, France). Journal of the Geological Society, London (1980) 137:641–647.
Aleksandrowski P, Mazur S. Collage tectonics in the northeasternmost part of the Variscan Belt; the Sudetes, Bohemian Massif. In: Palaeozoic Amalgamation of Central Europe—Winchester JA, Pharaoh TC, Verniers J, eds. (2002) 201. Geological Society, London: Special Publications. 237–277.
Anderson JL, Smith DR. The effects of temperature and fO2 on the Al-in-hornblende barometer. American Mineralogist (1995) 80:549–559.[Abstract]
Annen C, Scaillet B, Sparks RSJ. Thermal constraints on the emplacement rate of a large intrusive complex: the Manaslu leucogranite, Nepal Himalaya. Journal of Petrology (2006) 47:71–95.
Awdankiewicz M, Awdankiewicz H, Kryza R. Petrology of mafic and felsic dykes from the eastern part of the Karkonosze massif. Polish Mineralogical Society, Special Papers (2005a) 26:111–114.
Awdankiewicz M, Awdankiewicz H, Kryza R. The richterite minette from Bukowiec (Karkonosze–Izera block): Petrological characteristics. Polish Mineralogical Society, Special Papers (2005b) 26:115–118.
Bacon CR, Druitt TH. Compositional evolution of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon. Contributions to Mineralogy and Petrology (1988) 98:224–256.[CrossRef][Web of Science]
Barbarin B. Les granites carbonifères du Forez septentrional (Massif Central français). In: Typologie et relations entre différents massifs (1983) Thesis, Univ. 177. Clermont-Ferrand II.
Barbarin B. A review of the relatioships between granitoid types, their origins and their geodynamic environments. Lithos (1999) 46:605–626.[CrossRef][Web of Science]
Barbarin B. Mafic magmatic enclaves and mafic rocks associated with some granitoids of the central Sierra Nevada batholith, California: nature, origin, and relations with the hosts. Lithos (2005) 80:155–177.[CrossRef][Web of Science]
Barker F. Trondhjemites: definition, environment and hypothesis of origin. In: Trondhjemites, Dacites and Related Rocks—Barker F, ed. (1979) Amsterdam: Elsevier. 1–12.
Barnes CG, Burton BR, Burling TC, Wright JE, Karlsson HR. Petrology and geochemistry of the Late Eocene Harrison Pass Pluton, Ruby Mountains Core Complex, northeastern Nevada. Journal of Petrology (2001) 42:901–929.
Barrière M. Le complexe de Ploumanac'h, massif armoricain, Essai sur la mise en place et l’évolution pétrologique d'une association plutonique subalcaline tardi-orogénique. In: Thesis, Univ. Brest (1977) 290.
Barrière M. On curved laminae, graded layers, convection currents and dynamic crystal sorting in the Ploumanac'h (Brittany) subalkaline granite. Contributions to Mineralogy and Petrology (1981) 77:214–224.[CrossRef][Web of Science]
Bateman R. The interplay between crystallization, replenishment and hybridization in large felsic magma chambers. Earth-Science Reviews (1995) 39:91–106.
Bea F, Pereira MD, Stroh A. Mineral/leucosome trace-element partitioning in a peraluminous migmatite (a laser ablation-ICP-MS study). Chemical Geology (1994) 117:291–312.[CrossRef][Web of Science]
Bea F, Montero P, Molina J. Mafic precursors, peraluminous granitoids, and late lamprophyres in the Avila batholith: a model for the generation of Variscan batholiths in Iberia. Journal of Geology (1999) 107:399–419.[CrossRef][Web of Science]
Berg G. Der Granit des Riesengebirges und seine Ganggesteine (petrographische Studien). In: Abhandlungen der Preussischen Geologischen Landesanstalt (1923) 94.
Blundy J, Cashman K. Ascent-driven crystallisation of dacite magmas at Mount St Helens, 1980–1986. Contributions to Mineralogy and Petrology (2001) 140:631–650.[Web of Science]
Bonin B. Do coeval mafic and felsic magmas in post-collisional to within-plate regimes necessarily imply two contrasting, mantle and crustal, sources? A review. Lithos (2004) 78:1–24.[CrossRef][Web of Science]
Bonin B. A-type granites and related rocks: Evolution of a concept, problems and prospects. Lithos (2007) 97:1–29.[CrossRef][Web of Science]
Borkowska M. Petrography of Karkonosze granite. Geologia Sudetica (1966) 2:7–119.
Bouchet G. Mélanges magmatiques et genèse des granitoïdes calco-alcalins: l'exemple du complexe tonalo-granodioritique de Bono (Sardaigne septentrionale). Etude pétrologique et géochimique. In: Thesis, Univ. Saint-Etienne (1992) 310.
Brenan JM, Neroda E, Lundstrom C, Shaw HF, Ryerson FJ, Phinney DL. Behaviour of boron, beryllium, and lithium during melting and crystallization: Constraints from mineral–melt partitioning experiments. Geochimica et Cosmochimica Acta (1998) 62:2129–2141.[CrossRef][Web of Science]
Bussy F. Interactions physico-chimiques entre le granite du Mont-Blanc et ses enclaves. Schweizeriche Mineralogische und Petrographische Mitteilungen (1987) 67:380–384.
Bussy F. Pétrogenèse des enclaves microgrenues associées aux granitoides calco-alcalins: exemple des massifs varisques du Mont Blanc (Alpes occidentales) et miocène du Monte Capanne (Ile d'elbe, Italie). Memoires de Geologie (Lausanne) (1990) 7:309.
Castro A, Moreno-Ventas I, De la Rosa JD. Microgranular enclaves as indicators of hybridisation processes in granitoid rocks, Hercynian belt, Spain. Geological Journal (1990) 25:391–404.[CrossRef][Web of Science]
Cloos H. Einführung in die tektonische Behandlung magmatischer Erscheinungen (Granittektonik). I Spezial Teil. Das Riesengebirge in Schlesien (1925) Berlin: Gebrüder Borntraeger.
Cox RA, Dempster TJ, Bell BR, Rogers G. Crystallization of the Shap granite: evidence from zoned K-feldspar megacrysts. Journal of the Geological Society, London (1996) 153:625–635.
Cwojdziñski Z, Cymerman Z, Jerzmañski J, Królikowski L, Sawicki L. Geologiczna interpretacja wynikow zastosowania metody strippingu dla poznania budowy wglebnej obszaru dolnoslaskiego (1991) Wrocaw: Polish Geological Institute.
Dallmeyer RD, Franke W, Weber KEB. Pre-Permian Geology of Central and Eastern Europe (1995) Springer: Berlin.
Davidson JP, Tepley FJ, Palacz Z, Main S. Magma recharge, contamination and residence time revealed by in situ laser ablation isotopic analysis of feldspar in volcanic rocks. Earth and Planetary Science Letters (2001) 182:427–442.
Didier J. Granites and their Enclaves. The Bearing of Enclave on the Origin of Granites (1973) Amsterdam: Elsevier.
Didier J, Barbarin B. Enclaves and Granite Petrology (1991) Amsterdam: Elsevier.
Diot H, Masur S, Pin C. Karkonosze batholith (NE Bohemian Massif): The evidence for pluton emplacement during transtensional–extensional collapse. Journal of the Czech Geological Society (1995) 40:62.
Droop GTR. A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides using stoichiometric criteria. Mineralogical Magazine (1987) 51:431–435.[Web of Science]
Duthou JL, Couturié JP, Mierzejewski MP, Pin C. Rb/Sr age of the Karkonosze granite on the base of the whole rock method. Przegld Geologiczny (1991) 2:75–79.[Medline]
Elburg MA. Evidence of isotopic equilibration between microgranitoid enclaves and host granodiorite, Warburton Granodiorite, Lachlan Fold Belt, Australia. Lithos (1996) 38:1–22.[CrossRef][Web of Science]
Ewart A, Griffin WL. Application of proton-microprobe data to trace-element partitioning in volcanic rocks. Chemical Geology (1994) 117:251–284.[CrossRef][Web of Science]
Finger F, Steyrer HP. I-type granitoids as indicators of a late Paleozoic convergent ocean–continent margin along the southern flank of the central European Variscan Orogen. Geology (1990) 18:1207–1210.
Finger F, Roberts MP, Haunschmid B, Schermaier A, Steyrer HP. Variscan granitoids of Central Europe; their typology, potential sources and tectonothermal relations. Mineralogy and Petrology (1997) 61:67–96.[CrossRef][Web of Science]
Förster HJ, Tischendorf G, Trumbull RB, Gottesmann B. Late collisional granites in the Variscan Erzgebirge, Germany. Journal of Petrology (1999) 40:1613–1645.[CrossRef][Web of Science]
Fourcade S, Allègre CJ. Trace element behavior in granite genesis: a case study. The calc-alkaline plutonic association from Querigut complex (Pyrénées, France). Contributions to Mineralogy and Petrology (1981) 76:177–195.[CrossRef][Web of Science]
Fourcade S, Martin H, de Bremond d’Ars J. Chemical exchange in migmatites during cooling. Lithos (1992) 128:43–53.
Franke W. The mid-European segment of the Variscides: tectonostratigraphic units, terrane boundaries and plate tectonic evolution. In: Orogenic Processes: Quantification and Modelling in the Variscan Belt—Franke W, Haak V, Oncken O, Tanner D, eds. (2000) 179. Geological Society, London: Special Publications. 35–61.
Franke W, Matte P, Tait J. Europe; Variscan Orogeny. In: Encyclopedia of Geology; Volume 2 (2005) Elsevier: Oxford. 75–86.
Frost TP, Mahood GA. Field, chemical, and physical constraints on mafic–felsic magma interaction in the Lamarck Granodiorite, Sierra Nevada, California. Geological Society of America Bulletin (1987) 99:272–291.
Furman T, Spera T. Co-mingling of acid and basic magma with implications for the origin of mafic I-type xenoliths, field and petrochemical relations of an unusual dike complex at Eagle Peak Lake, Sequoia National Park, California, U.S.A. Journal of Volcanology and Geothermal Research (1985) 24:151–178.[CrossRef][Web of Science]
Halla J. Late Archean high-Mg granitoids (sanukitoids) in the southern Karelian domain, eastern Finland: Pb and Nd isotopic constraints on crust–mantle interactions. Lithos (2005) 79:161–178.[CrossRef][Web of Science]
Hallot E, Auvray B, de Bremond d’Ars J, Davy P, Martin H. New injection experiments in non-Newtonian fluids. Terra Nova (1994) 6:274–281.[CrossRef][Web of Science]
Hallot E, Davy P, de Bremond d’Ars J, Auvray B, Martin H, van Damme H. Non-Newtonian effects during injection in partially crystallised magmas. Journal of Volcanology and Geothermal Research (1996) 71:31–44.[CrossRef][Web of Science]
Hammastrom JM, Zen E. Aluminium in hornblende: an empirical igneous geobarometer. American Mineralogist (1986) 71:1297–1313.[Abstract]
Hanson GN. Rare earth elements in petrogenetic studies of igneous systems. Annual Review of Earth and Planetary Sciences (1980) 8:371–406.[CrossRef][Web of Science]
Hollister LS, Grissom GC, Peters EK, Stowell HH, Sisson VB. Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calc-alkaline plutons. American Mineralogist (1987) 72:231–239.[Abstract]
Hoskin P, Kinny P, Wyborn D, Chappell B. Identifying accessory mineral saturation during differentiation in granitoid magmas: an integrated approach. Journal of Petrology (2000) 41:1365–1396.
Icenhower JP, London D. Experimental partitioning of Rb, Cs, Sr, and Ba between alkali feldspar and peraluminous melt. American Mineralogist (1996) 81:719–734.[Abstract]
Irvine TN, Baragar WRA. A guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences (1971) 8:523–548.
Janouek V, Bowes DR, Braithwaite CJR, Rogers G. Microstructural and mineralogical evidence for limited involvement of magma mixing in the petrogenesis of Hercynian high-K calc-alkaline intrusion; the Kozarovice Granodiorite, Central Bohemian Pluton, Czech Republic. Transactions of the Royal Society of Edinburgh, Earth Sciences (2000) 91:15–26.[Web of Science]
Janouek V, Braithwaite CJR, Bowes DR, Gerdes A. Magma-mixing in the genesis of Hercynian calc-alkaline granitoids: an integrated petrographic and geochemical study of the Sazava intrusion, Central Bohemian Pluton, Czech Republic. Lithos (2004) 78:67–99.[CrossRef][Web of Science]
Jayananda M, Martin H, Peucat J.-J, Mahabaleswar B. Late Archaean crust–mantle interactions in the Closepet granite, Southern India: evidence from Sr–Nd isotopes, major and trace element geochemistry. Contributions to Mineralogy and Petrology (1995) 119:314–329.[Web of Science]
Jayananda M, Moyen J.-F, Martin H, Peucat J.-J, Auvray B, Mahabaleswar B. Late Archaean (2550–2520 Ma) juvenile magmatism in the Eastern Dharwar craton, southern India: constraints from geochronology, Nd–Sr isotopes and whole rock geochemistry. Precambrian Research (2000) 99:225–254.[CrossRef][Web of Science]
Johnson MC, Rutherford M. Experimental calibration of the aluminium-in-hornblende geobarometer with application to Long Valley caldera (California) volcanic rocks. Geology (1989) 17:837–841.
Kerim K. Hybridization of mafic microgranular enclaves: mineral and whole-rock chemistry evidence from the Karamadazi Granitoid, Central Turkey. International Journal of Earth Sciences (2006) 95:587–607.[CrossRef][Web of Science]
Klominsky J. Krkonossko-jizersky granitoid massif. Sbornik Geologickich Ved, Geologie (1969) 15:7–132.
Kröner A, Hegner E, Hammer J, Haase G, Bielicki KH, Krauss M, Eidam J. Geochronology and Nd–Sr systematics of Lusatian granitoids—significance for the evolution of the Variscan orogen in East–Central Europe. Geologische Rundschau (1994) 83:357–376.
Kryza G, Kusnierz A, Majerowicz A. Cyrkony z granitoidow Karkonoszy oraz wschodniej czesci krystaliniku izerskiego. Acta Universitatis Wratislaviensis, Prace Geologiczno Mineralogiczn (1979) 7:107–150.
Kuno H. Lateral variation of basalt magma types across continental margins and island arcs. Bulletin of Volcanology (1966) 29:195–222.
Lameyre J, Autran A, Barrière M, Bonin B, Didier J, Fluck P, Fourcade S, Giraud P, Jonin M, Orsini J-B. Les granitoides de France. In: Evolutions géologiques de la France. Mémoires du BRGM—Autran A, Dercourt J, eds. (1980) 107:51–97.
Leake BE, Woolley AR, Arps CES, et al. Nomenclature of amphiboles: report of the subcommittee on amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names. Mineralogical Magazine (1997) 61:295–321.[Abstract]
Lobach-Zhuchenko SB, Rollinson HR, Chekulaev VP, Arestova NA, Kovalenko AV, Ivanikov VV, Guseva NS, Sergeev SA, Matukov DI, Jarvis KE. The Archaean sanukitoid series of the Baltic Shield: geological setting, geochemical characteristics and implications for their origin. Lithos (2005) 79:107–128.[CrossRef][Web of Science]
Mahood GA, Hildreth EW. Large partition coefficients for trace elements in high-silica rhyolites. Geochimica et Cosmochimica Acta (1983) 47:11–30.[CrossRef][Web of Science]
Marheine D, Kachlik V, Maluski H, Patocka F. The 40Ar/39Ar ages from the West Sudetes (NE Bohemian Massif): constraints on the Variscan polyphase tectonothermal development. In: Palaezoic Amalgamation of Central Europe—Winchester JA, Pharaoh T, Verniers J, eds. (2002) 201. Geological Society, London: Special Publications. 133–155.
Masuda A, Nakamura N, Tanaka T. Fine structures of mutually normalized rare-earth patterns of chondrites. Geochimica et Cosmochimica Acta (1973) 37:239–244.[CrossRef][Web of Science]
Matte P. Tectonics and plate tectonics model for the Variscan Belt of Europe. Tectonophysics (1986) 126:329–374.[CrossRef][Web of Science]
Matte P. Continental subduction and exhumation of HP rocks in Paleozoic belts; Uralides and Variscides. Linnemann U, Heuse T, Bankwitz P, Falka O, eds. (1998) 120:209–222. GFF.
Matte P, Maluski H, Rajlich P, Franke W. Terrane boundaries in the Bohemian Massif; result of large-scale Variscan shearing. Tectonophysics. (1990) 177:151–170.
Mazur S. Structural and metamorphic evolution of the country rocks at the eastern contact of the Karkonosze granite in the southern Rudawy Janowickie Mts and Lasocki Ridge. Geologia Sudetica (1995) 29:31–98.
Mazur S, Aleksandrowski P. The Tepla(?)/Saxothuringian suture in the Karkonosze–Izera Massif, western Sudetes, Central European Variscides. International Journal of Earth Sciences (2001) 90:341–360.[CrossRef][Web of Science]
Mierzejewski MP, Oberc DT. The Izera–Karkonosze Block and its tectonic development (Sudetes, Poland). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen (1990) 179:197–222.
Mierzejewski MP, Pin C, Duthou JL, Couturié JP. Sr–Nd isotopic study of the Karkonosze granite (Western Sudetes). In: Igneous Activity and Metamorphic Evolution of the Sudetes Area—Kryza R, ed. (1994) 82(1). Wroclaw: Universytet Wroclawski.
Moyen J-F, Martin H, Jayananda M. Multi-element geochemical modelling of crust–mantle interactions during late-Archaean crustal growth: the Closepet granite (South India). Precambrian Research (2001) 112:87–105.[CrossRef][Web of Science]
Moyen J-F, Jayananda M, Nédelec A, Martin H, Mahabaleswar B, Auvray B. From the roots to the roof of a granite: the Closepet granite of South India. Journal of the Geological Society of India (2003a) 62:753–758.
Moyen J-F, Martin H, Jayananda M, Auvray B. Late Archaean granites: a typology based on the Dharwar Craton (India). Precambrian Research (2003b) 127:103–123.[CrossRef][Web of Science]
Nash WP, Crecraft HR. Partition coefficients for trace elements in silicic magmas. Geochimica et Cosmochimica Acta (1985) 49:2309–2322.[CrossRef][Web of Science]
O’Connor JT. A classification for quartz-rich igneous rocks based on feldspar ratios. US Geological Survey, Professional Papers (1965) 525-B:79–84.
Pagel M, Leterrier J. The subalkaline potassic magmatism ot the Ballons massif (Southern Vosges, France). Shoshonitic affinity. Lithos (1980) 13:1–10.[CrossRef][Web of Science]
Pearce JA, Norry MJ. Petrogenetic implications of Ti, Zr, Y and Nb variations in the volcanic rocks. Contributions to Mineralogy and Petrology (1979) 69:33–47.[CrossRef][Web of Science]
Perini G, Tepley F. J. III, Davidson JP, Conticelli S. The origin of K-feldspar megacrysts hosted in alkaline potassic rocks from central Italy: a track for low-pressure processes in mafic magmas. Lithos (2003) 66:223–240.[CrossRef][Web of Science]
Perugini D, Poli G, Mazzuoli R. Chaotic advection, fractals and diffusion during mixing of magmas: evidence from lava flows. Volcanology and Geothermal Research (2003) 124:255–279.[CrossRef]
Pin C, Mierzejewski PM, Duthou JL. Isochronous age Rb/Sr of Karkonosze granite from the quarry Szklarska Porêba Huta and significance of initial ratio 87Sr/86Sr in this granite. Przegld Geologiczny (1987) 35:512–516.
Przywóski 
. Chemical and CL study on apatite as an indicator of Karkonosze granite petrogenesis. (2006) University of Warsaw. MSc thesis.
Rayleigh J. Theoretical considerations respecting the separation of gases by diffusion and similar processes. Philosophical Magazine (1896) 42:77–107.
Rickwood PC. Boundary lines within petrologic diagrams which use oxides of major and minor elements. Lithos (1989) 22:247–263.[CrossRef][Web of Science]
Robert CP, Casella G. Monte Carlo Statistical Methods (2004) Springer: New York.
Samsonov AV, Bogina MM, Bibikova EV, Petrova AY, Shchipansky AA. The relationship between adakitic, calc-alkaline volcanic rocks and TTGs: implications for the tectonic setting of the Karelian greenstone belts, Baltic Shield. Lithos (2005) 79:83–106.[CrossRef][Web of Science]
Schmidt MW. Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al in hornblende barometer. Contributions to Mineralogy and Petrology (1992) 110:304–310.[CrossRef][Web of Science]
Shabani AAT, Lalonde AE, Whalen JB. Composition of biotite from granitic rocks of the Canadian Appalachian orogen: a potential tectonomagmatic indicator? Canadian Mineralogist (2003) 41:1381–1396.[CrossRef][Web of Science]
Shand SJ. Eruptive Rocks. Their Genesis, Composition, Classification and their Relations to Ore-deposits (1943) Hafner Publishing Co.: New York.
Shirey SB, Hanson GN. Mantle derived Archaean monzodiorites and trachyandesites. Nature (1984) 310:222–224.[CrossRef]
Saby E, Galbarczyk-Gsiorowska L. Barium in alkali feldspar megacrysts from Szklarska Poreba Huta porphyritic granite: possibly indicator of magma mixing. Mineralogical Society of Poland, Special Papers (2002) 20:198–200.
Saby E, Götze J. Feldspar crystallization under magma-mixing conditions shown by cathodoluminescence and geochemical modelling—a case study from the Karkonosze pluton (SW Poland). Mineralogical Magazine (2004) 68:541–557.
Saby E, Martin H. Mechanisms of differentiation of the Karkonosze granite. Polish Mineralogical Society, Special Papers (2005) 26:264–267.
Saby E, Galbarczyk-Gasiorowska L, Seltmann R, Müller A. Alkali feldspar megacryst growth: geochemical modelling. Mineralogy and Petrology (2007a) 89:1–29.[CrossRef][Web of Science]
Saby E, Seltmann R, Kober B, Müller A, Galbarczyk-Gsiorowska L, Jeffries T. LREE distribution patterns in zoned alkali feldspar megacrysts—implication for parental melt composition. Mineralogical Magazine (2007b) 71:193–217.
Solgadi F, Vanderhaeghe O, Moyen J-F, Sawyer E. Generation of synorogenic Hercynian granites in the Livradois area, French Massif Central: The relative roles of crustal anatexis and mantle derived magmas. Canadian Mineralogist (2007) 45:581–606.[CrossRef][Web of Science]
Sparks RSJ, Marshall LA. Thermal and mechanical constraints on mixing between mafic and silicic magmas. Journal of Volcanology and Geothermal Research (1986) 29:99–124.[CrossRef][Web of Science]
Stern RA, Hanson GN. Archaean high-Mg granodiorite: a derivative of light rare earth enriched monzodiorite of mantle origin. Journal of Petrology (1991) 32:201–238.
Störmer JC, Nicholls J. XLFRAC: a program for interactive testing of magmatic differentiation models. Computers and Geosciences (1978) 87:51–64.
Streck MJ, Grunder AL. Compositional gradients and gaps in high-silica rhyolites of the Rattlesnake Tuff, Oregon. Journal of Petrology (1997) 38:133–163.[CrossRef][Web of Science]
Sun SS, McDonough WF. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Magmatism in the Ocean Basins—Saunders AD, Norry MJ, eds. (1989) 42. Geological Society, London: Special Publications. 313–345.
Tepley FJ, Davidson JP, Clynne MA. Magmatic interactions as recorded in plagioclase phenocrysts of Chaos Crags, Lassen volcanic center, California. Journal of Petrology (1999) 40:787–806.[CrossRef][Web of Science]
Troll VR, Schmincke HU. Magma mixing and crustal recycling recorded in Tertiary feldspar from compositionally zoned peralkaline ignimbrite ‘A’, Gran Canaria, Canary Islands. Journal of Petrology (2002) 43:243–270.
Troll VR, Donalson CH, Emeleus H. Pre-eruptive magma mixing in ash-flow deposits of the Tertiary Rum igneous centre, Scotland. Contributions to Mineralogy and Petrology (2004) 147:722–739.[Web of Science]
Vernon RH. K-feldspar megacrysts in granites—phenocrysts, not porphyroblasts. Earth-Science Reviews (1986) 23:1–63.
Waight TE, Dean AA, Maas R, Nicholls IA. Sr and Nd isotopic investigations towards the origin of feldspar megacrysts in microgranular enclaves in two I-type plutons of the Lachlan Fold Belt, southeast Australia. Australian Journal of Earth Science (2000) 47:1105–1112.[CrossRef]
Wall VJ, Clemens JD, Clarke B. Models for granitoid evolution and source compositions. Journal of Geology (1987) 95:731–749.[Web of Science]
Watson EB. Basalt contamination by continental crust: some experiments and models. Contributions to Mineralogy and Petrology (1982) 80:73–87.[CrossRef][Web of Science]
Wiebe RA. Mafic–silicic layered intrusions: the role of basaltic injections on magmatic processes and the evolution of silicic magma chambers. Transactions of the Royal Society of Edinburgh, Earth Sciences (1996) 87:233–242.[Web of Science]
Wiebe RA, Blair KD, Hawkins DP, Sabine CP. Mafic injections, in situ hybridization, and crystal accumulation in the Pyramid Peak granite, California. Geological Society of America Bulletin (2002) 114:909–920.
Wilamowski A. Srodowisko geotektoniczne intruzji granitowych Tatr i Karkonoszy w swietle danych geochemicznych. Archiwum Mineralogiczne (1998) 52:261–271.
Wnorowska U. Enclaves from Karkonosze granite as an example of magma mixing processes—evidence from CL, Nomarski DIC microscopy, combined with local chemical analyses of feldspars. (2006) TU Bergakademie, Freiberg. MSc thesis.
ak J, Klominsky J. Magmatic structures in the Krkonoe–Jizera Plutonic Complex, Bohemian Massif: evidence for localized multiphase flow and small-scale thermal–mechanical instabilities in a granitic magma chamber. Journal of Volcanology and Geothermal Research (2007) 164:254–267.[CrossRef][Web of Science]
ak J, Vyhnalek B, Kabele P. Is there a relationship between magmatic fabrics and brittle fractures in plutons? A view based on structural analysis, anisotropy of magnetic susceptibility and thermo-mechanical modelling of the Tanvald pluton (Bohemian Massif). Physics of the Earth and Planetary Interiors (2006) 157:286–310.[CrossRef][Web of Science]
Ziegler P. Geodynamic model for the Paleozoic crustal consolidation of western and central Europe. Tectonophysics (1986) 126:303–328.[CrossRef][Web of Science]
Zorpi MJ, Coulon C, Orsini J.-B, Corcita C. Magma mingling, zoning and emplacement in calc-alkaline granitoid plutons. Tectonophysics (1989) 157:315–329.[CrossRef][Web of Science]
Zorpi MJ, Coulon C, Orsini J.-B. Hybridization between felsic and mafic magmas in calc-alkaline granitoids—a case study in Northern Sardinia, Italy. Chemical Geology (1991) 92:45–86.[CrossRef][Web of Science]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. Pieczka, B. Golebiowska, and J. Parafiniuk CONDITIONS OF FORMATION OF POLYMETALLIC MINERALIZATION IN THE EASTERN ENVELOPE OF THE KARKONOSZE GRANITE: THE CASE OF REDZINY, SOUTHWESTERN POLAND Can Mineral, August 1, 2009; 47(4): 765 - 786. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||