内蒙古喀喇沁地区早中生代闪长岩中麻粒岩捕虏体矿物化学及变质温压条件

MINERAL CHEMISTRY AND METAMORPHIC p-t CONDITIONS OF GRANULITE XENOLITHS IN EARLY MESOZOIC DIORITE IN HARKIN REGION, EASTERN INNER MONGOLIA AUTONOMOUS REGION, CHINA

在内蒙古东部喀喇沁地区早中生代大营子闪长岩中首次发现基性麻粒岩捕虏体 .初步研究表明它们不同于华北克拉通地表出露的前寒武纪麻粒岩 .根据其主要造岩矿物斜方辉石、单斜辉石、黑云母及斜长石的电子探针分析结果 ,重点研究了各主要造岩矿物的化学成分特点 ,并讨论了麻粒岩捕虏体的变质作用温压条件 .研究结果表明 ,捕虏体岩石的变质作用已达麻粒岩相 ,其变质作用条件约为 85 0～ 90 0℃ ,0 .6～ 1.0GPa .这些麻粒岩捕虏体反映了研究区早中生代下地壳的组成特点 ,为恢复该区早中生代深部地壳结构提供了依据 .

The mafic granulite xenolith was first reported to have occurred in Early Mesozoic diorite in Harkin region, Eastern Inner Mongolia Autonomous Region, China. The preliminary research indicates that the basic granulite xenoliths are different from the Precambrian granulite exposed on the earth surface of the North China craton. The electron microprobe analysis was performed of the four main rock_forming minerals: orthopyroxene, clinopyroxene, biotite and plagioclase, in comparison with those of Precambrian granulite terrain. The major focus is on the research into the chemical composition of various major rock_forming minerals. In addition, the metamorphic p_t conditions for the granulite xenoliths are discussed. The research results show that the metamorphism of the xenoliths had reached the granulite facies at the metamorphic temperatures ranging from 850?℃ to 900?℃ and at the metamorphic pressures ranging from 0.6?GPa to 1.0?GPa. These mafic granulite xenoliths reflect the component features of the Early Mesozoic continental lower crust of the research region, providing some evidence for the reconstruction of the Early Mesozoic deep crustal structure.