赣东北弋阳早古生代麻粒岩的发现及其地质意义  

The geological significance of a Paleozoic mafic granulite found in the Yiyang area of northeastern Jiangxi Province

作　　者：于津海[1] 楼法生[2] 王丽娟[1,3] 沈林伟[1] 周雪瑶[1] 张春晖[1] 黄志忠[2] 

机构地区：[1]南京大学地球科学与工程学院内生金属矿床成矿机制研究国家重点实验室,南京210046 [2]江西省地质调查研究院,南昌330201 [3]江苏省地质调查研究院,南京210018

出　　处：《科学通报》2014年第35期3508-3516,共9页Chinese Science Bulletin

基　　金：国家重点基础研究发展计划(2012CB416701);国家自然科学基金(41330208,41272085)资助

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.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.

关 键 词：赣东北 高级变质作用早古生代 碰撞造山作用 

分 类 号：P588.3[天文地球—岩石学]