Journal of Petrology Volume 43 Number 2 Pages 291-314 2002
© Oxford University Press 2002
The Fluid-absent Partial Melting of a Zoisite-bearing Quartz Eclogite from 1·0 to 3·2 GPa; Implications for Melting in Thickened Continental Crust and for Subduction-zone Processes
1DEPARTMENT OF GEOLOGY, UNIVERSITY OF TROMSØ, 9037 TROMSØ, NORWAY
2DEPARTMENT OF GEOLOGY, UNIVERSITY OF GEORGIA, ATHENS, GA 30602, USA
Fluid-absent melting experiments on a zoisite- and phengite-bearing eclogite (omphacite, garnet, quartz, kyanite, zoisite, phengite and rutile) were performed to constrain the melting relations of these hydrous phases in natural assemblages, as well as the melt and mineral compositions produced by their breakdown. From 1·0 to 3·2 GPa the solidus slopes positively from 1·5 GPa at 850°C to 2·7 GPa at 1025°C, but bends back at higher pressures to 975°C at 3·2 GPa. The melt fraction is always low and the melt compositions always felsic and become increasingly so with increasing pressure. The normative Ab–An–Or compositions of the initial melts vary from tonalites at 1·0 GPa to tonalite–trondhjemites at 1·5 GPa, adamellites at 2·1 and 2·7 GPa, and to true granites at 3·2 GPa. At pressures <
2·5 GPa zoisite and phengite break down more or less simultaneously. At 3·2 GPa and 1000°C zoisite is unreacted whereas phengite is absent, so that the first formed melt at these conditions is granitic. Our experiments show that if sufficiently high temperatures (of the order of 1000°C) are attained, zoisite- and phengite-bearing eclogites can produce small fractions of silicic melts of a wide range of compositions. These melts are rich in water and, probably, in Sr and other incompatible elements, so that they can act as metasomatic agents in the mantle wedge.
KEY WORDS: zoisite; dehydration-melting; orogenic thickening; subduction; felsic melt; metasomatism
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S. LIU, R.-Z. HU, C.-X. FENG, H.-B. ZOU, C. LI, X.-G. CHI, J.-T. PENG, H. ZHONG, L. QI, Y.-Q. QI, et al. Cenozoic high Sr/Y volcanic rocks in the Qiangtang terrane, northern Tibet: geochemical and isotopic evidence for the origin of delaminated lower continental melts Geological Magazine, July 1, 2008; 145(4): 463 - 474. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Bali, Z. Zajacz, I. Kovacs, CS. Szabo, W. Halter, O. Vaselli, K. Torok, and R. J. Bodnar A Quartz-bearing Orthopyroxene-rich Websterite Xenolith from the Pannonian Basin, Western Hungary: Evidence for Release of Quartz-saturated Melts from a Subducted Slab J. Petrology, March 1, 2008; 49(3): 421 - 439. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. D. Putirka Thermometers and Barometers for Volcanic Systems Reviews in Mineralogy and Geochemistry, January 1, 2008; 69(1): 61 - 120. [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Hiroi, Y. Motoyoshi, N. Ishikawa, T. Hokada, and K. Shiraishi Origin of xenocrystic garnet and kyanite in clinopyroxene-hornblende-bearing adakitic meta-tonalites from Cape Hinode, Prince Olav Coast, East Antarctica Geological Society, London, Special Publications, January 1, 2008; 308(1): 333 - 350. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Liebscher, G. Franz, D. Frei, and P. Dulski High-Pressure Melting of Eclogite and the P-T-X History of Tonalitic to Trondhjemitic Zoisite-Pegmatites, Munchberg Massif, Germany J. Petrology, May 1, 2007; 48(5): 1001 - 1019. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Q. WANG, J.-F. XU, P. JIAN, Z.-W. BAO, Z.-H. ZHAO, C.-F. LI, X.-L. XIONG, and J.-L. MA Petrogenesis of Adakitic Porphyries in an Extensional Tectonic Setting, Dexing, South China: Implications for the Genesis of Porphyry Copper Mineralization J. Petrology, January 1, 2006; 47(1): 119 - 144. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. E. PATINO DOUCE Vapor-Absent Melting of Tonalite at 15-32 kbar J. Petrology, February 1, 2005; 46(2): 275 - 290. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. W. Schmidt and S. Poli Magmatic Epidote Reviews in Mineralogy and Geochemistry, January 1, 2004; 56(1): 399 - 430. [Full Text] [PDF]
|
|
|
|
|
|
D. Frei, A. Liebscher, G. Franz, and P. Dulski Trace Element Geochemistry of Epidote Minerals Reviews in Mineralogy and Geochemistry, January 1, 2004; 56(1): 553 - 605. [Full Text] [PDF]
|
|