High-Pressure Granulites (Retrograded Eclogites) from the Hengshan Complex, North China Craton: Petrology and Tectonic Implications

Abstract

Both highand medium-pressure granulites have been found as because of the absence of modal minerals. The combination of petrographic textures, mineral compositions, metamorphic reaction enclaves and boudins in tonalitic–trondhjemitic–granodioritic gneisses in the Hengshan Complex. Petrological evidence from these history, petrogenetic grids and thermobarometric data defines a nearrocks indicates four distinct metamorphic assemblages. The early isothermal decompressional clockwise P–T path for the Hengshan prograde assemblage (M1) is preserved only in the high-pressure granulites, suggesting that the Hengshan Complex underwent initial granulites and represented by quartz and rutile inclusions within crustal thickening, subsequent exhumation, and cooling and retrothe cores of garnet porphyroblasts, and omphacite pseudomorphs gression. This tectonothermal path is considered to record a major that are indicated by clinopyroxene + sodic plagioclase symplectic phase of collision between two continental blocks, which resulted in intergrowths. The peak assemblage (M2) consists of clinopyroxene the final assembly of the North China Craton at >1·8 Ga. + garnet + sodic plagioclase + quartz ± hornblende in the high-pressure granulites and orthopyroxene + clinopyroxene + garnet + plagioclase + quartz in the medium-pressure granulites.