Ultrahigh‐pressure metamorphism and decompressional P‐T paths of eclogites and country rocks from Weihai, eastern China

• DOI: 10.1111/j.1440-1738.1995.tb00151.x
• Publication Date: 2006-04-05T09:45:47Z
• Authors: R. Y. Zhang; J. G. Liou; W. G. Ernst
• Keywords: Hornblende; Omphacite; Coesite; Grossular

Abstract Altered quartz‐rich and nearly quartz‐free eclogitic rocks completely retrograde garnet amphibolites occur as blocks or lenses in gneisses at Weihai, northeastern tip of the Sulu ultrahigh‐P belt. Eclogitic with assemblage ± clinopyroxene coesite + rutile have experienced three‐stage metamorphic events including ultrahigh‐pressure eclogite, granulite amphibolite facies. Granulite event is characterized by formation hypersthene salite plagioclase hornblende corona between quartz clinopyroxene. P‐T conditions for recrystallization sequence are 840 50°C, >28 kbar, about 760±50°C, 9 ~650°C, <8 kbar respectively. Most country rock contain dominant amphibolite‐facies assemblages; some garnet‐bearing recrystallized under granulite‐facies 740±50°C 8.5 kbar; similar to metamorphism enclosed blocks. Minor cale‐silicate within containing an grossular titanite secondary zoisite may formed a large pressure range 14‐35 kbar. boudins quartzo‐feldspathic coeval situ UHP subsequent metamorphism. The established isothermal decompression path suggests that this area represent interior portion relatively subducted sialic block. recognized terrane extend eastward across Yellow Sea Korean Peninsula.