| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Petrology | Volume 44 | Number 9 | Pages 1681-1701 | 2003
© Oxford University Press 2003
Petrogenesis of the Post-kinematic Magmatism of the Central Finland Granitoid Complex II; Sources and Magmatic Evolution
DEPARTMENT OF PHYSICS AND EARTH SCIENCE, UNIVERSITY OF NORTH ALABAMA, FLORENCE, AL 35632-0001, USA
* Telephone: (256) 765-4482. Fax: (256) 765-4795. E-mail: baelliott{at}una.edu
RECEIVED OCTOBER 25, 2000; ACCEPTED MARCH 9, 2003
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
The 1·88–1·87 Ga post-kinematic granitoids of the Central Finland Granitoid Complex (CFGC) provide a key geochemical link to understanding granite formation in Paleoproterozoic orogenic and post-orogenic terrains. Thickness of the crust and intra-crustal differentiation processes played an important role in the formation of three granitoid types that shortly followed the peak of the Svecofennian orogeny. In the eastern CFGC, pyroxene-bearing plutons with C-type geochemical affinities predominate. These were formed from a mixture of low- to moderate-degree partial melts (
30%) of mafic mantle-derived (basaltic, 49% SiO2) source rocks and partial melts of pre-existing mafic granulite lower crust at depth. In the western CFGC, high-silica, iron-rich, fluorite-bearing plutons with A-type granite characteristics predominate. A higher thermal gradient, thinner upper and lower crust, and significantly more shallow Moho depth resulted in higher proportions of crustal melts (0·3–0·4 vs 0·1–0·2 in the eastern CFGC) incorporated into the partial melts of a mafic mantle-derived source. A geochemical model focusing on the Jämsä and Honkajoki plutons of the post-kinematic suite is presented, constraining the nature of the source rock(s), the degree of partial melting, proportions of partial melts and fractionation processes involved. KEY WORDS: magmatic evolution; geochemistry; Proterozoic; granite; Finland
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
The central part of the Fennoscandian Shield in Finland is dominated by the Central Finland Granitoid Complex (CFGC; Fig. 1). The CFGC encompasses an area of
40 000 km2 and consists mainly of granodiorite and granite; gabbroic, ultramafic, metavolcanic, and metasedimentary rocks are uncommon (Nironen et al., 2000). The synkinematic CFGC granitoids (see Fig. 1) have generally yielded U–Pb zircon ages around 1·89–1·88 Ga, which is the main crust-forming event of the Finnish Svecofennian orogeny (Huhma, 1986; Vaasjoki, 1996). Crosscutting the synkinematic granitoids, numerous 1·88–1·87 Ga post-kinematic intrusions constrain the time when the crust was stabilized in central Finland. These granitoids exhibit a transition in age and geochemical evolution from NE to SSW, intruding anomalously thick lithosphere shortly (15 Myr) after the peak of the orogeny (see Korsman et al., 1999; Rämö et al., 2001).
|
|
A comparison of whole-rock major and trace element geochemistry between the Honkajoki pluton (1867 ± 6 Ma), with A-type granite characteristics, in the western CFGC and the Jämsä pluton (1878·5 ± 1·5 Ma), with C-type geochemical characteristics [high K2O, TiO2, P2O5, large ion lithophile elements (LILE), and low CaO at a given SiO2 compared with I-, S- and A-type rocks; see Kilpatrick & Ellis, 1992], in the eastern CFGC has provided insights into the petrogenesis of this late-stage granitic magmatism (see Nironen et al., 2000). The aim of this study is to use whole-rock major and trace element geochemistry, combined with Sr–Nd–Pb isotope geochemistry presented in a companion paper (Rämö et al., 2001), to develop a detailed petrogenetic model constraining the source(s) and processes that were involved in the formation of the 1·88–1·87 Ga post-kinematic plutons of the CFGC.
|
GEOLOGIC SETTING |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
The Fennoscandian Shield comprises an Archean domain in the NE and a 2·5–1·6 Ga Paleoproterozoic (Svecofennian) domain in the SW. A considerable part of the Svecofennian domain in Finland is occupied by the CFGC (Fig. 1), and its formation has been modeled as the result of accretion of an arc complex (volcanic arc assemblages plus an older Paleoproterozoic nuclei), to the Archean continental margin at 1·91 Ga (Lahtinen, 1994), and subsequent collision of another arc complex against the accreted one at 1·89 Ga (Nironen, 1997). The emplacement of the 1·89– 1·88 Ga rocks of the CFGC was coeval with regional metamorphism in central Finland (Korsman et al., 1984) and is thus considered as synkinematic with respect to lithospheric convergence, which continued in southern Finland until 1·80 Ga (see Lindroos et al., 1996). The peak of metamorphism in southern Finland (south of the CFGC) occurred at 1·82–1·84 Ga (Väisänen & Hölttä, 1999), before the emplacement of post-orogenic shoshonitic intrusions at
1·80 Ga (Eklund et al., 1998; Väisänen et al., 2000). The 1·88–1·87 Ga granites were emplaced after major contractional movements related to collision and, thus, are considered post-kinematic. The post-kinematic granites are found as at least 25 stocks and small (<500 km2) batholiths (Fig. 1). They are weakly to non-foliated and medium to coarse grained, generally comprising more than one geochemical composition and are, on average, more potassium rich and higher in Fe/(Fe + Mg) than the synkinematic granitoids (Nironen & Rämö, 1995; Lahtinen, 1996). The post-kinematic granites have been divided into three groups based on petrography, mineralogy, outcrop characteristics, mineral chemical and geochemical variation (Elliott et al., 1998; Rämö et al., 1999; Nironen et al., 2000).
Honkajoki pluton
The 750 km2 Honkajoki pluton, located in the western part of the CFGC, is one of the largest post-kinematic intrusions (Fig. 1). It is associated with mafic rocks and is a multi-phase intrusion representing all the typical characteristics of the Type 2 post-kinematic plutons [high Fe/(Fe + Mg), fluorite-bearing, elevated Rb and F, tholeiitic affinity; see Nironen et al., 2000]. The main rock type is red, porphyritic, coarse-grained biotite granite that encompasses over 80% of the pluton area (Fig. 2a). A minor biotite–hornblende granite in the SE margin of the pluton is porphyritic and coarse to medium grained. The main mineral modes and accessory minerals of the Honkajoki granites are summarized in Table 1.
|
Mafic rocks associated with the Honkajoki pluton range from gabbro to diorite and quartz diorite, and are found along the eastern flank of the granites in at least three separate bodies (Fig. 2a). The largest of these is the Perämaa layered mafic intrusion, which contains both leucocratic and ultramafic rocks ranging from quartz diorite to wehrlite; cumulate textures and rhythmic layering (occasional <1 m thick, Fe–Ti oxide layers) are locally well developed (Rämö, 1986; Nironen et al., 2000). U–Pb data indicate that the Honkajoki granites and associated mafic intrusions are coeval at
1·87 Ga (Rämö et al., 2001).
Jämsä pluton
The 50 km2 Type 3 Jämsä pluton consists of a 0·5–1 km wide margin of dark brown, slightly porphyritic, pyroxene-bearing quartz monzonite and a white to pink, porphyritic, pyroxene-free biotite– hornblende granite that forms the bulk of the pluton (Fig. 2b). The east–central part of the pluton is relatively evolved, white to pink, coarse-grained, quartz-rich granite. The modal mineralogy of the three Jämsä granitoid types is summarized in Table 1. Fine-grained, nearly vertical microgranite dikes cut the Jämsä pluton in several locations. These microgranite dikes are strongly discordant, striking NE, perpendicular to the regional foliation, but parallel to numerous major shear zones (see Nironen et al., 2000). The dikes show little to no interaction with the granitoids in the Jämsä pluton, and do not appear to intrude the rocks outside the pluton.
Large areas and bands or layers of mafic silicate mineral aggregates are common throughout the quartz-rich granite. These bands are largely composed of amphibole and biotite (>70%), occasionally contain alkali feldspar megacrysts (10–30%), and have more zircon, apatite and Fe–Ti oxides than the quartz-rich granite. In many cases, the areas immediately around the mafic aggregates are depleted in mafic minerals, leaving little doubt as to the cumulus nature of the segregation.
Structure of the crust below the CFGC
Geophysical studies across central Finland provide a three-dimensional perspective of the structure of the crust and mantle below the CFGC and allow characterization of crustal and mantle lithologies that provide model constraints on source rock composition, genesis, and physical emplacement of the post-kinematic granitoid suite. The deep seismic sounding study Global Geoscience Transect SVEKA (GGT/SVEKA) indicates the presence of anomalously thick, fairly heterogeneous lower crust under the CFGC (Korsman et al., 1999). The profile shows the depths to the Moho and the top of the lowermost high-velocity lower crust and is extrapolated into a three-dimensional perspective in Fig. 3. The depth to the lower crust in the western CFGC near Honkajoki is 21 km, and 23 km in the eastern CFGC near Jämsä. The depth to the Moho in the western CFGC is 54 km near Honkajoki, and 58 km in the eastern CFGC near Jämsä. Korsman et al. (1999) used thermal modeling based on velocity models to characterize the lower-crustal lithology of the Svecofennian terrane. The probable rock types present include anorthosite, mafic granulite, metapelite, and, at the higher-velocity end, pyroxenite (Holbrook et al., 1992; Christensen & Mooney, 1995; Rudnick & Fountain, 1995). Kukkonen (1998) also used thermal modeling to estimate the relative proportions of metapelite and mafic granulite, and concluded that in the lowermost Svecofennian crust (depths >39 km) mafic granulites appear to be dominant (>90%). The GGT/SVEKA geophysical profile across the CFGC did not include a model of deep-crustal magnetic properties. However, high-altitude aeromagnetic data obtained as part of the European Geotraverse (EGT) and the magnetic modeling (Henkel et al., 1991) along the FENNLORA profile in Sweden suggest the presence of a more magnetized lower crust in the Svecofennian domain (Korsman et al., 1999). The degree of magnetization corresponds to a magnetite content of 4% (Henkel et al., 1991), which might result from intra- and underplating of the Svecofennian crust by mafic magmas (Korsman et al., 1999). Moreover, irregular crustal reflectivity data recorded by the BABEL experiment (BABEL Working Group, 1993a, 1993b), supported by near-transparent refraction seismic data (e.g. Korhonen et al., 1990; BABEL Working Group, 1993a, 1993b), indicate that prominent lithological layering in the lower crust becomes less pronounced in the deepest parts, consistent with the proposed mafic intra- and under-plate. Mafic granulite xenoliths in exhumed kimberlite pipes from east–central Finland are the only known samples of the lower crust in the Finnish part of the Svecofennian (Hölttä et al., 2000). The mafic granulites range from hornblende-dominant to plagioclase–pyroxene-dominant types (Appendix B).
|
|
GEOCHEMISTRY |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
Analytical methods
Samples from the Honkajoki and Jämsä plutons were analyzed at the Geological Survey of Finland (GTK). Samples of
20 kg from each locality were broken into smaller pieces, and pieces with unweathered surfaces were recombined into a single sample of 10 kg (except the mafic segregate sample from Jämsä, which weighed 3 kg). Samples were jaw crushed, and splits pulverized in a tungsten-carbide ball-mill for X-ray fluorescence (XRF) analysis, and in a carbon steel ball-mill for inductively coupled plasma mass spectroscopy (ICP-MS). Major elements and Rb, Sr, Zr, and Ba were determined by XRF. Rare earth elements were analyzed by ICP-MS, and F by ion-selective electrode. Detection limits for the minor and trace elements are 0·01% for F, 20 ppm for Ba, 10 ppm for Zr, 5 ppm for Rb and Sr, 0·25 ppm for Nd, 0·2 ppm for Sm, 0·15 ppm for Ce, Gd, Dy, Er and Yb, 0·1 ppm for La, Pr and Lu, and 0·05 ppm for Eu, Tb, Ho and Tm. The estimated uncertainty is 1–5% for major elements and 3–10% for trace elements.
Honkajoki pluton
The biotite–hornblende granite and the biotite granite have distinct geochemical characteristics (Table 2; Fig. 4). The biotite–hornblende granite SiO2 ranges from 67% to 72%, compared with 72–75% in the biotite granite. The biotite–hornblende granite has slightly higher FeOT, MgO, TiO2, CaO and Al2O3, and lower K2O than the biotite granite (Fig. 4). Both compositions are peraluminous and show no significant difference in molecular Al2O3/(CaO + Na2O + K2O) (A/CNK) values, which range from 0·98 to 1·07 for the biotite–hornblende granite and from 0·96 to 1·07 for the biotite granite (Table 2).
|
|
The trace element concentrations in the Honkajoki granites are typical of high-silica granites. In general, Ba and Sr decrease and Rb increases with increasing SiO2, suggestive of feldspar fractionation processes (Fig. 4g–i). Zr concentrations are similar in the two granite types, despite the differences in major element compositions (Table 2). Rare earth element (REE) patterns are very similar in the two granite types (Fig. 5), with a distinct negative Eu anomaly. The samples show relatively flat heavy REE (HREE) patterns from Dy to Lu, but marked light rare earth element (LREE) enrichment. Normalized abundances of the HREE are higher in the biotite granite; (La/Yb)N ratios are between 8·58 and 19·85 in the biotite– hornblende granite compared with 8·62–13·53 in the biotite granite (Table 2; Fig. 5). The negative Eu anomaly is also slightly less pronounced in the biotite–hornblende granite than in the biotite granite; Eu/Eu* ratios average 0·39 and 0·28, respectively.
|
Jämsä pluton
The marginal quartz monzonite and the biotite– hornblende granite of Jämsä form two distinct geochemical groups that slightly overlap (Fig. 4). The pyroxene-bearing rocks have higher TiO2, FeOT, MgO and CaO, and slightly higher Al2O3 contents than the other compositions within the pluton, and grade into the main granite of the pluton at
60% SiO2 (Fig. 4). The main granite of the pluton ranges in SiO2 from 60% to 70%, and the late-stage quartz-rich granite displays a small compositional range at SiO2 values above 73% (Fig. 4; Table 3).
|
Rb increases and Ba decreases slightly between the marginal quartz monzonite and biotite–hornblende granite, and more dramatically at higher SiO2 contents (Fig. 4g and i). This suggests very little feldspar fractionation during early stages of crystallization and relatively more leading up to the crystallization of the quartz-rich granite. REE patterns of all three granitoid compositions in the Jämsä pluton are similar (Fig. 6). The marginal quartz monzonite, however, lacks a distinct Eu anomaly (average Eu/Eu* = 1·03) and is less LREE enriched in character [average (La/Yb)N = 8·50] (Table 3; Fig. 6). The biotite–hornblende granite has slightly more enriched LREE [average (La/Yb)N = 11·61], and the Eu anomaly becomes slightly negative away from the marginal assemblage (average Eu/Eu* = 0·77). The quartz-rich granite has significantly lower abundances of the HREE, and slightly higher LREE than the biotite–hornblende granite. The mafic segregate has a slightly flatter LREE slope and significantly higher HREE compared with the quartz-rich granite [(La/Yb)N = 9·55]. The Eu anomalies in the quartz-rich granite and the mafic segregate are more negative than in the biotite– hornblende granite (average Eu/Eu* = 0·45 and 0·24, respectively; Table 3). The microgranite dike lacks an Eu anomaly, has a similar LREE slope to the quartz-rich granite, and has lower REE abundances overall (Fig. 6).
|
|
PETROGENESIS OF THE POST-KINEMATIC GRANITOIDS |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
Source rock constraints
In the absence of direct source rock indicators (cognate xenoliths, autoliths, etc.), determination of magma source compositions has to be largely based on indirect geochemical and isotopic constraints, and trial and error geochemical modeling of probable mantle and lower-crustal rock types. The similar Nd and Sr isotopic compositions of granitoids throughout the CFGC (Rämö et al., 2001) suggest that the source for the post-kinematic plutons was very homogeneous. This source was characterized by
Nd of 0 and very low overall Rb/Sr; initial 87Sr/86Sr ratios for the Jämsä pluton and the Perämaa mafic intrusion are 0·7030 and 0·7029, respectively (Rämö et al., 2001). It has been suggested that the granites of the 1·88–1·87 Ga post-kinematic suite were produced by partial melting of relatively anhydrous mafic to intermediate granulites in the lower to middle crust and mafic, mantle-derived, magmatic rocks intra- and under-plated during the Svecofennian orogeny (Nironen et al., 2000). The differences in composition of the post-kinematic granitoids, particularly their C-type and A-type characteristics, have been attributed to variation in the anhydrous mineral assemblages that remained in the lower crust after a previous episode of I-type granitoid magmatism (Landenberger & Collins, 1996). Considering the mineralogical and geochemical similarities of the post-kinematic granitoids and many anorogenic granitoids (e.g. the Wolf River batholith, Anderson & Cullers, 1978; the Sherman batholith, Frost et al., 1999; the Pikes Peak batholith, Smith et al., 1999), a similar type of source material may be likely for the Jämsä and Honkajoki plutons. Studies on possible origins for various A-type and C-type granites disagree on source composition or protolith, but share many common characteristics that influence petrogenesis. Kilpatrick & Ellis (1992) proposed the vapor-absent melting of hornblende-free or hornblende-poor granulite, whereas Frost et al. (2000) suggested that any rock type can produce C-type magmas as long as the water activity is low enough. Many A-type granites are thought to form through vapor-absent melting of a lower-crustal protolith and involve interaction with mafic mantle-derived magma directly as a source component, or indirectly as a heat source. Possible protolith compositions include partially melted, mantle-derived, mafic rocks derived from tholeiitic basalt (Frost et al., 1999), partially melted tonalitic to granodioritic rocks from the middle to lower crust (Creaser et al., 1991), and a combination of both fractionation of mantle-derived basaltic magmas and crustal anatexis of granodiorite or tonalite sources (Smith et al., 1999).
Melting mafic rocks in the lower crust
Experimental studies on melting of metabasalt compositions at 16 kbar (Rapp & Watson, 1995), the estimated depth at which the magmas of the post-kinematic granitoids of the CFGC are thought to have been formed, produced 33% partial melt with major element compositions similar to that of the post-kinematic granitoids. Similar studies at 15 kbar involving dehydration melting of meta-volcaniclastic rocks with abundant hydrous minerals (Skjerlie & Johnston, 1996) produced considerably more evolved melt compositions (SiO2>70, A/CNK>1·10) and, thus, are less likely to be a suitable source.
Basaltic intra- and under-plating plays an important role in crustal growth and differentiation, and is probably the cause for the anomalously thick crust in east–central Finland (Korja et al., 1993; Korja & Heikkinen, 1995). Intrusion of basaltic magma clearly provides a heat source to melt granulitic lower crust. The basaltic magmas may intrude both the upper and lower crust, fractionating to produce mafic and ultramafic cumulates plus more evolved magmas that could subsequently partially melt to produce more silicic magmas (Rudnick, 1992). As a result of its iron-enriched nature and relatively reduced redox state, gabbro and ferrodiorite derived from differentiated tholeiitic basalt have been suggested as a possible protolith for reduced rapakivi granites (Frost & Frost, 1997). Geochemical similarities between the CFGC post-kinematic granitoids [e.g. high Zr, FeOT/(FeOT + MgO), and K2O] and high-K fayalite rhyolites derived from differentiation of parental tholeiitic basalt (Hildreth et al., 1991) suggest that a similar petrogenesis might occur for the post-kinematic suite. Similarly, Lahtinen (1994) suggested that the pyroxene-bearing granitoids in the eastern CFGC might have been derived from differentiation of within-plate basalts, possibly incorporating crustal material during ascent.
Frost & Frost (1997) suggested that ferrodiorite is probably a more likely protolith for the petrogenesis of granitoids by crustal melting than basalt because it has a lower melting point than basalt, and ferrobasalts are found in many extensional settings. Scoates et al. (1996) have shown experimentally that monzonitic rocks with >4·0% K2O at intermediate SiO2 contents (60%) can be formed from ferrodioritic source compositions (45% SiO2; Mitchell et al., 1996), but only at very low degrees of partial melting (10%). These intermediate major element melt compositions are very similar to the compositions of the Type 3, pyroxene-bearing, post-kinematic plutons in the CFGC.
The model described below involves: (1) the crystallization of under-plated and intra-plated tholeiitic basaltic magma, and differentiates thereof, at the base of the lower crust; (2) subsequent under-plating by mafic magmas (mantle derived), which produced partial melts of these earlier mafic intrusions and associated differentiates, as well as partial melts of granulite-facies lower crust in variable proportions; (3) local mixing of these partial melts in the lower crust; (4) fractionation processes during ascent and emplacement, which account for the variable composition of the 1·88–1·87 Ga post-kinematic granitoids.
Major element modeling
A semi-quantitative least-squares approximation approach to major element modeling was used to constrain the source compositions for the post-kinematic granitoids. This mass balance approach can be used for both partial melting and fractional crystallization. Isotopic constraints suggest a dominant mafic component (initial 87Sr/86Sr = 0·702–0·704), based on contemporaneous mafic rocks associated with type 2 plutons, and the relatively low Th/U (2·0 in Type 3 and 2·3 in Type 2 plutons) is indicative of Th retention in the source, mostly in plagioclase, during partial melting (Rämö et al., 2001). The major element composition of the Jämsä magma, before emplacement, was estimated by multiplying the proportion (by area) of each granite type by its average geochemical composition. The fractionation of an evolved tholeiitic basalt (SiO2 49%, K2O 0·5%, Mg-number 46), leaving behind a residue of predominantly clinopyroxene and plagioclase, produces a 25–30% melt fraction that grossly resembles the initial Jämsä magma composition (
r2 = 1·35; Table 4). Amphibole- and plagioclase-dominant mafic granulite compositions also produce semi-quantitative compositions similar to the initial Jämsä magma (r2 = 1·81; Table 4). The residual mineral assemblage is similar to that fractionated by basalt, mainly pyroxene and plagioclase, but the estimated melt fraction is considerably lower, only 10–15%.
|
REE and trace element modeling
Fractional crystallization and AFC
Fractionation crystallization (FC) modeling incorporates Rayleigh fractionation of a parental tholeiitic basalt and an assimilation–fractional crystallization (AFC) model combining the assimilation of mafic granulite. Element concentrations in the fractionating and assimilating magma are derived using the AFC equations of DePaolo (1981). The comparison between FC and AFC models is illustrated so that the likelihood of assimilation processes during fractionation can be assessed.
Fractional crystallization of a tholeiitic basalt, alone, will not form a parental magma compatible with the predicted Honkajoki and Jämsä parental magmas (see Fig. 7). However, AFC modeling shows that a parental magma composition similar to the post-kinematic granitoids could be formed through AFC processes. Tholeiitic basalt, assimilating mafic granulite in the lower crust at a fairly high rate compared with the rate of fractionation (r = 0·7), could produce a parental Jämsä magma after 30–40% crystallization (Fig. 7). Lower, more realistic, r values provide less compatible values (e.g. r = 0·4), shifting the trends toward higher Ba and Sr concentrations (Fig. 7).
|
Crustal melting
REE and trace element compositions were modeled using the batch melting equations of Shaw (1970). Under fluid-absent conditions, reaction of hornblende and quartz to produce pyroxene, plagioclase and melt could occur (Rushmer, 1991). Therefore, in addition to the batch melting model, incongruent batch partial melting of mafic granulite was also modeled, where, in the most extreme case, all hornblende is consumed, resulting in the production of clinopyroxene (see Benito-García & López-Ruiz, 1992; Zou, 2000; Zou & Reid, 2001).
The partial melt modeling incorporates a linear variation in mineral/melt distribution coefficients (see Zou, 2000; Zou & Reid, 2001) to account for changes in melt composition for variable melt proportions during the partial melting of tholeiitic basalt. Thus, bulk mineral/melt partition coefficients range between those for basalt (high degrees of partial melting), and those for rhyolitic to dacitic liquids (low degrees of partial melting; see Appendix A).
Batch melting (BM) and incongruent batch melting (IBM; where all hornblende is consumed to produce clinopyroxene), of three mafic granulite compositions are shown in Fig. 8a–c. Small degrees of batch melting (10%), in general, produce LREE-enriched patterns with variable depletion of middle REE (MREE) to HREE. For hornblende-rich mafic granulites, REE abundances are increased with the production of congruent clinopyroxene during IBM. Figure 8a shows that 10% partial melting of a pyroxene-rich source produced through IBM processes (hornblende reacted to pyroxene) exhibits an REE pattern very similar to that of the quartz monzonite and biotite–hornblende granite from Jämsä and Honkajoki, respectively. Partial melting (BM) of tholeiitic basalt (30–50%) produces REE patterns similar to those of the Jämsä and Honkajoki granitoids, but with lower LREE concentrations. If we presume that the magma compositions are the result of partial melting of lower-crustal source rocks, predominantly a basalt or crystal cumulate derived from a basaltic parent and mafic granulite, a mixing model involving variable degrees of melting and proportion of basalt and mafic granulite may best approximate the magma composition from which the post-kinematic granitoids crystallized.
|
The best approximation of modeled REE concentrations for the ‘average’ Jämsä granitoid magma is between 0·8 x 30% BM of basalt + 0·2 x 30% IBM of mafic granulite and 0·9 x 30% BM of basalt + 0·1 x 10% IBM of mafic granulite (Fig. 9). Similarly, but with higher proportions of mafic granulite, the mixing proportions for the Honkajoki magma are 0·65 x 30% BM of basalt + 0·35 x 10% BM of mafic granulite and 0·65 x 30% BM of basalt + 0·35 x 10% IBM of mafic granulite (Fig. 10). Using these mixing proportions and degrees of partial melting, the range of partially melted basalt (BM) and mafic granulite (both BM and IBM) compositions are shown for Ba and Sr in Fig. 11. Modeled Sr and Ba concentrations are in good agreement with the REE predicted proportions and partial melt values for the parental magmas of the post-kinematic granitoids. Major element modeling is also in good agreement with the REE and trace element modeling, suggesting the partial melt proportion is between 10% and 30% for the most and least evolved post-kinematic granite compositions, respectively.
|
|
|
, the mafic segregate.Fractional crystallization
Modeling the effects of individual mineral fractionation on the trace element characteristics of the Jämsä and Honkajoki plutons shows which minerals were important in controlling magmatic differentiation. Trace element concentrations for residual melts during fractionation were modeled using the equation for Rayleigh fractional crystallization.
A plot of Ba vs Sr shows trends consistent with major fractionation of feldspars (Fig. 11). The fractionation trend for biotite–hornblende granite in the Jämsä and Honkajoki plutons from a parental magma, represented by the average of REE model predicted values, closely resembles the range of Ba and Sr concentrations. The Jämsä pluton shows fractionation of feldspar, predominantly alkali feldspar in minor proportions (<10%) from the quartz monzonite to the biotite–hornblende granite. Further fractionation (>40%) produces the quartz-rich granite. This is consistent with field observations, as the biotite– hornblende granite covers 70% of the total pluton area and the quartz-rich granite and quartz monzonite only about 17% and 13%, respectively. The mafic segregate from the quartz-rich granite shows fractionation in the direction of biotite and hornblende (increasing Sr and decreasing Ba concentrations) in minor proportions (<30%). The Honkajoki pluton shows similar fractionation trends, but extends to include more evolved compositions. The biotite– hornblende granite is similar to the biotite–hornblende granite of Jämsä, and the biotite granite is similar to the quartz-rich granite at Jämsä.
The average Jämsä magma at the present emplacement level was calculated from a reintegration of the geochemical compositions by area distribution (13% average quartz monzonite + 70% average biotite–hornblende granite + 17% average quartz-rich granite compositions). From the BM and IBM modeled parental magma composition (Fig. 9a), fractional crystallization of 10–30% of the marginal quartz monzonite mineral assemblage (see Table 1; Stage 1 fractionation) produces an REE pattern similar to the approximated residual liquid composition (84% average biotite–hornblende granite + 16% average quartz-rich granite compositions by area; Fig. 9b). The fractionation of the biotite–hornblende granite from the post-Stage 1 liquid at 70% produces a close approximation to the quartz-rich granite and mafic segregate residual liquid (15% mafic segregation + 85% average quartz-rich granite compositions by area; Fig. 9c). The quartz-rich granite is host to numerous glomerocrystic ferromagnesian mineral masses that separated from the felsic liquid and can be modeled as a third and final stage of fractionation (Stage 3), involving 10–30% of the minerals and in the same proportions as mafic segregates (Fig. 9d). The Honkajoki granites may have been derived from similar source rocks to the Jämsä pluton. However, the REE model (BM and IBM) suggests a larger proportion of mafic granulite partial melt (0·35; Fig. 10a). This parental magma, fractionating 30–50% of a biotite–hornblende assemblage, produces REE patterns closely resembling the biotite granite (Fig. 10b). Major element modeling of the same sources for both Honkajoki and Jämsä, undergoing similar partial melting and crystal fractionation processes (although in different proportions), is in good agreement with REE and trace element models.
|
CONCLUSIONS |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
The isotopic compositions of Pb and Nd in the post-kinematic granitoids are remarkably uniform. Characterized by Bulk-Earth-type Nd isotopic compositions and low Rb/Sr, the protolith of the post-kinematic granitoids was relatively mafic deep crust. On the basis of these radiogenic isotope constraints presented in a companion paper (see Rämö et al., 2001) and the geochemical model presented here, the following conclusions on the protolith composition and magmatic evolution of the post-kinematic granites of the CFGC may be reached:
- the 1·88–1·87 Ga post-kinematic plutons were emplaced over a relatively large area and can be discriminated by differences in their mineralogy and geochemical composition. The Jämsä and Honkajoki plutons could have been derived by partial melting of similar crustal source rocks and may have shared a rather similar magmatic evolution, despite differences in their mineralogy and geochemistry.
- Geochemical modeling and isotopic constraints suggest that the parental magma of the 1·88–1·87 Ga granitoids formed by partial melting of recently emplaced, mantle-derived, mafic rocks (tholeiitic basalt, or crystal cumulate from a basaltic parent, emplaced in the lower crust during mafic intra- and under-plating), mixed with variable proportions of anatectic melts of mafic granulite.
- Fractionation processes during the formation and following the emplacement of the parental magmas were similar in post-kinematic plutons in the eastern and western CFGC. Fractionation of the observed mineral assemblages from the calculated initial and residual magma compositions closely approximates the observed REE patterns in the Jämsä and Honkajoki plutons.
- The thickness of the crust probably played an important role in controlling the different types of post-kinematic granites. The post-kinematic magmas in the eastern CFGC formed from lower-degree partial melts at deeper levels in the lower crust, where the Mohorovi
i discontinuity is also relatively deeper. These parental magmas may also have formed at higher pressures with less mantle–crust interaction. In the western CFGC, the thinner upper and lower crust resulted in more effective partial melting and greater mixing between melt proportions at lower pressures.
|
APPENDIX A: MINERAL/MELT PARTITION COEFFICIENTS |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
In the REE and trace element modeling, rhyolitic and dacitic melt Kd values were used to better represent the range of observed geochemical variation. For example, more primitive monzonitic post-kinematic granitoids (
59% SiO2) have compositions similar to dacite and the more evolved post-kinematic granites (72–75% SiO2) are similar to rhyolite. Partition coefficient references are as follows. Garnet data are from Arth (1976) for dacite and Irving & Frey (1978) for dacite and rhyolite with 62·89–70·15% SiO2. Kd values of La in amphibole are from Henderson (1984), and for other REEs from Arth (1976) for dacitic melts. Clinopyroxene values are from Fujimaki et al. (1984). Plagioclase coefficients for La are after Nash & Crecraft (1985) and for other REE after Arth (1976) for dacitic melts. K-feldspar and biotite coefficients for La from high-silica rhyolites are from Mahood & Hildreth (1988) and for other REE from Arth (1976) for rhyolitic melts. Orthopyroxene data are from Fujimaki et al. (1984) for dacite. REE partition coefficient data for basaltic melts are from Fujimaki et al. (1984). Ba and Sr partition coefficients are from Arth (1976).
|
|
APPENDIX B: GEOCHEMICAL COMPOSITIONS AND MINERAL MODES OF POSSIBLE SOURCE COMPONENTS USED IN THE PETROGENESIS FOR THE JÄMSÄ AND HONKAJOKI PLUTONS |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
|
|
APPENDIX C: FRACTIONATION MODELING FOR RARE EARTH ELEMENTS |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
|
|
ACKNOWLEDGEMENTS |
|---|
I would like to give my personal thanks to I. Haapala, O. T. Rämö and M. Nironen for their assistance and guidance in developing the ‘Petrogenesis of the post-kinematic granitoids of the CFGC’ project, and their comments and suggestions on the early versions of the manuscript. I would like to thank O. T. Rämö for valuable discussion and comments. I am grateful to M. Nironen and the Chemical Laboratory at the Geological Survey of Finland (GTK) for providing the high-quality geochemical data. The University of Helsinki and the Academy of Finland provided funding for this project (project 40674), with co-operation and support from the Geological Survey of Finland. This study is a contribution to IGCP-426 ‘Granite Systems and Proterozoic Lithospheric Processes’. Thorough and thoughtful editorial handling by M. Wilson and constructive reviews from M. Wilson, J. Patchett, T. Andersen, and an anonymous reviewer improved the manuscript significantly.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONGEOLOGIC SETTINGGEOCHEMISTRYPETROGENESIS OF THE POST...CONCLUSIONSAPPENDIX A: MINERAL/MELT...APPENDIX B: GEOCHEMICAL...APPENDIX C: FRACTIONATION...REFERENCES |
|---|
Anderson, J. L. & Cullers, R. L. (1978). Geochemistry and evolution of the Wolf River batholith, a late Precambrian rapakivi massif in north Wisconsin, U.S.A. Precambrian Research 7, 287–324.[CrossRef][Web of Science]
Arth, J. G. (1976). Behavior of trace elements during magmatic processes: a summary of theoretical models and their applications. Journal of Research of the US Geological Survey 4(1), 41–47.[Web of Science]
BABEL Working Group (1993a). Integrated seismic studies of the Baltic Shield using data in the Gulf of Bothnia region. Geophysical Journal International 112, 305–324.[Web of Science]
BABEL Working Group (1993b). Deep seismic reflection/refraction interpretation of crustal structure along BABEL profiles A and B in the southern Baltic Sea. Geophysical Journal International 112, 325–343.[Web of Science]
Benito-García, R. & López-Ruiz, J. (1992). Mineralogical changes of the residual solid and trace-element fractionation during partial incongruent melting. Geochimica et Cosmochimica Acta 56, 3705–3710.[CrossRef][Web of Science]
Boynton, W. V. (1984). Geochemistry of the rare earth elements: meteorite studies. In: Henderson, P. (ed.) Rare Earth Element Geochemistry. Amsterdam: Elsevier, pp. 63–114.
Christensen, N. L. & Mooney, W. D. (1995). Seismic velocity structure and composition of the continental crust: a global view. Journal of Geophysical Research 100(B7), 9761–9788.[CrossRef]
Creaser, R. A., Price, R. C. & Wormald, R. J. (1991). A-type granites revisited: assessment of residual-source model. Geology 19, 163–166.
DePaolo, D. J. (1981). Trace element and isotopic effects of combined wallrock assimilation and fractional crystallization. Earth and Planetary Science Letters 53, 189–202.[CrossRef][Web of Science]
Eklund, O., Konopelko, D., Rutanen, H., Fröjdö, S. & Shebanov, A. D. (1998). 1·8 Ga Svecofennian post-collisional shoshonitic magmatism in the Fennoscandian shield. Lithos 45, 87–108.[CrossRef][Web of Science]
Elliott, B. A., Rämö, O. T. & Nironen, M. (1998). Mineral chemistry constraints on the evolution of the 1·88–1·87 Ga post-kinematic plutons in the Central Finland Granitoid Complex. Lithos 45, 109–129.[CrossRef][Web of Science]
Frost, C. D. & Frost, B. R. (1997). Reduced rapakivi-type granites: the tholeiite connection. Geology 25, 647–650.
Frost, C. D., Frost, B. R., Chamberlain, K. R. & Edwards, B. R. (1999). Petrogenesis of the 1·43 Ga Sherman batholith, SE Wyoming, USA: a reduced, rapakivi-type anorogenic granite. Journal of Petrology 40, 1771–1802.[CrossRef][Web of Science]
Frost, B. R., Frost, C. D., Hulsebosch, T. P. & Swapp, S. M. (2000). Origin of the charnockites of the Louis Lake Batholith, Wind River Range, Wyoming. Journal of Petrology 41, 1739–1776.
Fujimaki, H., Tatsumoto, M. & Aoki, K. (1984). Partition coefficients of Hf, Zr, and REE between phenocrysts and groundmasses. Journal of Geophysical Research 89(Supplement), B662–B672.[CrossRef]
Henderson, P. (1984). Rare Earth Element Geochemistry. Amsterdam: Elsevier.
Henkel, H., Lee, M. K., Lund, C.-E. & Rasmussen, T. M. (1991). An integrated geophysical interpretation of the 2000 km FENNLORA section of the Baltic Shield. In: Freeman, R., Geise, P. & Mueller, S. (eds) The European Geotraverse: Integrative Studies, Results from the Fifth Earth Science Study Centre, Rauischholzhausen, Germany, March 26–April 7, 1990. Strasbourg: European Science Foundation, pp. 1–48.
Hildreth, W., Haliday, A. N. & Christiansen, R. L. (1991). Isotopic and chemical evidence concerning the genesis and contamination of basaltic and rhyolitic magma beneath the Yellowstone plateau volcanic field. Journal of Petrology 32, 63–138.
Holbrook, W. S., Mooney, W. D. & Christensen, N. L. (1992). The seismic velocity structure of the deep continental crust. In: Fountain, D. M., Arculus, R. & Kay, R. W. (eds) Continental Lower Crust. Amsterdam: Elsevier, pp. 1–43.
Hölttä, P., Huhma, H., Mänttäri, I., Peltonen, P. & Juhanoja, J. (2000). Petrology and geochemistry of mafic granulite xenoliths from the Lahtojoki kimberlite pipe, eastern Finland. Lithos 51, 109–133.[CrossRef][Web of Science]
Huhma, H. (1986). Sm–Nd, U–Pb, and Pb–Pb isotopic evidence for the origin of the Early Proterozoic Svecokarelian crust in Finland. Geological Survey of Finland Bulletin 337, 48 pp.
Irving, A. J. & Frey, F. A. (1978). Distribution of trace elements between garnet megacrysts and host volcanic liquids of kimberlitic to rhyolitic composition. Geochimica et Cosmochimica Acta 42, 771–787.[CrossRef][Web of Science]
Kilpatrick, J. A. & Ellis, D. J. (1992). C-type magmas: igneous charnockites and their extrusive equivalents. Transactions of the Royal Society of Edinburgh, Earth Sciences 83, 155–164.[Web of Science]
Korhonen, H., Kosminskaya, I. P., Azbel, I., Sharov, N., Zagorodny, V. & Luosto, U. (1990). Comparison of crustal structure along DSS profiles in SE Fennoscandia. Geophysical Journal International 103, 157–162.[Web of Science]
Korja, A. & Heikkinen, P. (1995). Proterozoic extensional tectonics of the central Fennoscandian Shield: results from the Baltic and Bothnian echos from the Lithosphere experiment. Tectonophysics 14, 504–517.
Korja, A., Korja, T., Luosto, U. & Heikkinen, P. (1993). Seismic and geoelectric evidence for collisional and extensional events in the Fennoscandian Shield—implications for Precambrian crustal evolution. Tectonophysics 219, 129–152.[CrossRef][Web of Science]
Korsman, K., Hölttä, P., Hautala, T. & Wasenius, P. (1984). Metamorphism as an indicator of evolution and structure of the crust in eastern Finland. Geological Survey of Finland Bulletin 328, 40 pp.
Korsman, K., Korja, T., Pajunen, M., Virransalo, P. & GGT/SVEKA Working Group (1999). The GGT/SVEKA transect: structure and evolution of the continental crust in the Paleoproterozoic Svecofennian orogen in Finland. International Geology Review 41, 287–333.[Web of Science]
Kukkonen, I. T. (1998). Temperature and heat-flow density in a thick cratonic lithosphere: the SVEKA transect, central Fennoscandian Shield. Journal of Geodynamics 26, 111–136.[CrossRef][Web of Science]
Lahtinen, R. (1994). Crustal evolution of the Svecofennian and Karelian domains during 2·1–1·79 Ga, with special emphasis on the geochemistry and origin of 1·93–1·91 Ga gneissic tonalites and associated supracrustal rocks in the Rautalampi area, central Finland. Geological Survey of Finland Bulletin 378, 128 pp.
Lahtinen, R. (1996). Geochemistry of the Paleoproterozoic supracrustal and plutonic rocks in the Tampere–Hämeenlinna area, southern Finland. Geological Survey of Finland Bulletin 389, 113 pp.
Landenberger, B. & Collins, W. J. (1996). Derivation of A-type granites from the dehydrated charnockitic lower crust: evidence from the Chaelundi Complex, eastern Australia. Journal of Petrology 37, 145–170.
Lindroos, A., Romer, R. L., Ehlers, C. & Alviola, R. (1996). Late-orogenic Svecofennian deformation in SW Finland constrained by pegmatite emplacement ages. Terra Nova 8, 567–574.[CrossRef][Web of Science]
Mahood, G. A. & Hildreth, E. W. (1988). Large partition coefficients for trace elements in high-silica rhyolites. Geochimica et Cosmochimica Acta 47, 11–30.
McKenzie, D. & O'Nions, R. K. (1991). Partial melt distributions from inversion of rare earth element concentrations. Journal of Petrology 32, 1021–1091.
Michael, P. J. (1988). Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: the importance of accessory mineral inclusions. Geochimica et Cosmochimica Acta 52, 275–282.[CrossRef][Web of Science]
Mitchell, J. N., Scoates, J. S., Frost, C. D. & Kolker, A. (1996). The geochemical evolution of anorthosite residual magmas in the Laramie anorthosite complex, Wyoming. Journal of Petrology 37, 637–660.
Nash, W. P. & Crecraft, H. R. (1985). Partition coefficients for trace elements in silicic magmas. Geochimica et Cosmochimica Acta 49, 2309–2322.[CrossRef][Web of Science]
Nironen, M. (1997). The Svecofennian orogen: a tectonic model. Precambrian Research 86, 21–44.[CrossRef][Web of Science]
Nironen, M. & Rämö, O. T. (1995). Petrogenesis of a 1·87 Ga post-tectonic granite suite in the Svecofennian of Finland: general and Nd isotope geochemistry. In: Brown, M. & Piccoli, P. M. (eds) The Origin of Granites and Related Rocks, Third Hutton Symposium Abstracts. US Geological Survey Circular 1129, 109.
Nironen, M., Elliott, B. A. & Rämö, O. T. (2000). 1·88–1·87 Ga post-kinematic intrusions of the Central Finland Granitoid Complex: a shift from C-type to A-type magmatism during lithospheric convergence. Lithos 53, 37–58.[CrossRef][Web of Science]
Rämö, T. (1986). The petrography, mineralogy, and petrology of the Perämaa mafic intrusion with special reference to the gabbroic rocks, Honkajoki. M.Sc. thesis, University of Helsinki, 161 pp. (in Finnish).
Rämö, O. T., Nironen, M., Kosunen, P. & Elliott, B. A. (1999). Proterozoic Granites of South–Central Finland—Traverse across a Paleoproterozoic Terrane Boundary. IGCP Project 426 Field Trip to Southern and Central Finland, September 13–18, 1999, Field Trip Guide. Helsinki: Helsinki University Press, 106 pp.
Rämö, O. T., Vaasjoki, M., Mänttäri, I., Elliott, B. A. & Nironen, M. (2001). Petrogenesis of the post-kinematic magmatism of the Central Finland Granitoid Complex I; radiogenic isotope constraints and implications for crustal extension. Journal of Petrology 42, 1971–1993.
Rapp, R. P. & Watson, B. W. (1995). Dehydration melting of metabasalt at 8–32 kbar: implications for continental growth and crust–mantle recycling. Journal of Petrology 36, 891–931.
Rickwood, P. C. (1989). Boundary lines within petrologic diagrams which use oxides of major and minor elements. Lithos 22, 247–263.[CrossRef][Web of Science]
Rudnick, R. (1992). Restites, Eu anomalies, and the lower continental crust. Geochimica et Cosmochimica Acta 56, 963–970.[CrossRef][Web of Science]
Rudnick, R. L. & Fountain, D. M. (1995). Nature and composition of the continental crust: a lower crustal perspective. Reviews of Geophysics 33, 267–309.[CrossRef][Web of Science]
Rushmer, T. (1991). Partial melting of two amphibolites: contrasting experimental results under fluid-absent conditions. Contributions to Mineralogy and Petrology 107, 41–59.[CrossRef][Web of Science]
Scoates, J. S., Frost, C. D., Mitchell, J. N., Lindsley, D. H. & Frost, B. R. (1996). Residual liquid origin for a monzonitic intrusion in a mid-Proterozoic anorthosite complex: the Sybille intrusion, Laramie Anorthosite Complex, Wyoming. Geological Society of America Bulletin 108, 1357–1371.
Shaw, D. M. (1970). Trace element fractionation during anatexis. Geochimica et Cosmochimica Acta 34, 237–243.[CrossRef][Web of Science]
Skjerlie, K. P. & Johnston, D. (1996). Vapour-absent melting from 10 to 20 kbar of crustal rocks that contain multiple hydrous phases: implications for anatexis in the deep to very deep continental margins. Journal of Petrology 37, 661–691.
Smith, D. R., Noblett, J., Wobus, R. A., Unruh, D., Douglass, J., Beane, R., Davis, C., Goldman, S., Kay, G., Gustavson, B., Saltoun, B. & Stewart, J. (1999). Petrology and geochemistry of late-stage intrusions of the A-type, mid-Proterozoic Pikes Peak batholith (central Colorado, USA): implications for petrogenetic models. Precambrian Research 98, 271–305.[CrossRef][Web of Science]
Vaasjoki, M. (1996). Explanation to the geochronological map of southern Finland: the development of the continental crust with special reference to the Svecofennian orogeny. Geological Survey of Finland Report of Investigation 135, 30 pp.
Väisänen, M. & Hölttä, P. (1999). Structural and metamorphic evolution of the Turku migmatite complex, southwestern Finland. Bulletin of the Geological Society of Finland 71(Part 1), 177–218.
Väisänen, M., Mänttäri, I., Kriegsman, L. M. & Hölttä, P. (2000). Tectonic setting of post-collisional magmatism in the Paleoproterozoic Svecofennian orogen, SW Finland. Lithos 45, 87–108.
Wood, B. J. & Trigila, R. (2001). Experimental determination of aluminous clinopyroxene–melt partition coefficients for potassic liquids, with application to the evolution of the Roman province potassic magmas. Chemical Geology 172, 213–223.[CrossRef][Web of Science]
Zou, H. (2000). Modeling of trace element fractionation during non-modal dynamic melting with linear variations in mineral/melt distribution coefficients. Geochimica et Cosmochimica Acta 64, 1095–1102.[CrossRef][Web of Science]
Zou, H. & Reid, M. R. (2001). Quantitative modeling of trace element fractionation during incongruent dynamic melting. Geochimica et Cosmochimica Acta 65, 153–162.[CrossRef][Web of Science]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  H. K. Brueckner Subduction of continental crust, the origin of post-orogenic granitoids (and anorthosites?) and the evolution of Fennoscandia Journal of the Geological Society, July 1, 2009; 166(4): 753 - 762. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||