【摘要】 新发现于赣东北弋阳县南的麻粒岩是一个基性麻粒岩,具有石榴子石+斜长石+紫苏辉石+黑云母+磁铁矿的矿物组合,根据矿物成分变化和矿物的包含关系确定了峰前变质(M1)和峰期变质(M2).成岩格子和地质温压计计算限定了麻粒岩峰前变质的温压是830~870℃和~1.0 GPa,而峰期的变质条件是850~900℃和0.7~0.8 GPa,显示了一个近于等温降压的顺时针P-T-t轨迹.LA-ICPMS锆石U-Pb定年表明麻粒岩相变质作用发生在436 Ma,而其原岩可能形成于新元古代早期.结合已有的发现,本文指出华夏地块内发生的早古生代(加里东期)高级变质作用与碰撞造山带作用有关,很可能是扬子地块与东冈瓦纳大陆挤压碰撞的结果.更多还原

【Abstract】 A mafic granulite has been found in southern Yiyang county in northeastern Jiangxi Province. This granulite has a mineral assemblage of garnet+plagioclase+hypersthene+biotite+magnetite. Based on the composition variation of minerals and relationships among them, pre-peak metamorphism(M1) and peak metamorphism(M2) are recognized. A petrogenetic grid and geothermobarometry measurements yield pre-peak metamorphic conditions of 830–870°C and ~1.0 GPa, and peak metamorphic conditions of 850–900°C and 0.7–0.8 GPa, suggesting a near isothermal decompression clockwise P-T-t path. LA ICPMS zircon U-Pb dating indicates that granulite facies metamorphism occurred about 436 Ma, and its protolith was possibly formed in the early Neoproterozoic. Coupled with available data, we suggest that early Paleozoic(Caledonian) high-grade metamorphism in the Cathaysia Block is related to collisional orogeny, which probably results from the collision-compression between the Yangtze Block and Eastern Gondwana.更多还原