High-Pressure Granulites (Retrograded Eclogites) from the Hengshan Complex, North China Craton: Petrology and Tectonic Implications |
| |
| Authors: | ZHAO GUOCHUN; CAWOOD PETER A; WILDE SIMON A; LU LIANGZHAO |
| |
| Institution: | 1TECTONICS SPECIAL RESEARCH CENTRE, SCHOOL OF APPLIED GEOLOGY, CURTIN UNIVERSITY OF TECHNOLOGY, GPO BOX U1987, PERTH, W.A. 6845, AUSTRALIA
2DEPARTMENT OF GEOLOGY, COLLEGE OF EARTH SCIENCES, CHANGCHUN UNIVERSITY OF SCIENCE AND TECHNOLOGY, CHANGCHUN, 130026, P.R. CHINA |
| |
| Abstract: | Both high- and medium-pressure granulites have been found asenclaves and boudins in tonalitic–trondhjemitic–granodioriticgneisses in the Hengshan Complex. Petrological evidence fromthese rocks indicates four distinct metamorphic assemblages.The early prograde assemblage (M1) is preserved only in thehigh-pressure granulites and represented by quartz and rutileinclusions within the cores of garnet porphyroblasts, and omphacitepseudomorphs that are indicated by clinopyroxene + sodic plagioclasesymplectic intergrowths. The peak assemblage (M2) consists ofclinopyroxene + garnet + sodic plagioclase + quartz ±hornblende in the high-pressure granulites and orthopyroxene+ clinopyroxene + garnet + plagioclase + quartz in the medium-pressuregranulites. Peak metamorphism was followed by near-isothermaldecompression (M3), which resulted in the development of orthopyroxene+ clinopyroxene + plagioclase symplectites and coronas surroundingembayed garnet grains, and decompression-cooling (M4), representedby hornblende + plagioclase symplectites on garnet. The THERMOCALCprogram yielded peak (M2) P–T conditions of 13·4–15·5kbar and 770–840°C for the high-pressure granulitesand 9–11 kbar and 820–870°C for the medium-pressuregranulites, based on the core compositions of garnet, matrixpyroxene and plagioclase. The P–T conditions of pyroxene+ plagioclase symplectite and corona (M3) were estimated at |
| |
| Keywords: | |
| 本文献已被 Oxford 等数据库收录！ |
|
