内蒙兴和黄土窑石墨矿地区古元古代高温高压泥质麻粒岩与含石榴石花岗岩的成因及其地质意义

The Paleoproterozoic high temperature and high pressure metamorphism in North China Craton (NCC) is an important key to understand the early crustal evolution. The detailed metamorphic history of the pelitic granulite and its related melting process are effective points to make deeper researches. The Huangtuyao graphite deposit, in the Inner Mongolia, is a typical area of exposing the intact pelitic granulite and high pressure mafic granulite simultaneously. There are some geological evidences to show that the generation of garnet bearing S-type granite should relate to the high grade metamorphism in previous studies. This project would choose the pelitic granulite occurring as the host rock of the S-type granite, garnet bearing S-type granite and granulite enclave of the S-type granite as the major objects to uncover the relationship between the high temperature - high pressure metamorphism and anatexis and to construct the detailed process of the metamorphic-magmatic process through several studies including metamorphic reactions of minerals and inclusions, genesis of different types of garnets in different kinds of rocks, geochemistry of whole rock or minerals, in-situ geochronology and pseudosection modelling. This project aims at providing evidence to constrain the history of peak-stage, anatexis and retrograde-stage and to determine a reasonable and fine P-T-t-D path. Finally, this project ultimately aims at providing clues to deeply understand the character and process of the high temperature-high pressure metamorphic events in North China Craton and to reasonably discuss the Paleoproterozoic tectonic mechanism of the North China Craton and its geological evolution history.

华北克拉通古元古代高温高压变质作用在早期陆壳演化中具有重大意义。其中泥质麻粒岩（孔兹岩）的变质精细过程以及与高级变质作用相关的熔融作用产物-含石榴石花岗岩的成因与演化历史研究，是深入进行有关研究的切入点之一。内蒙黄土窑石墨矿是泥质麻粒岩完整出露并与高压基性麻粒岩共生的典型地区，前期认为含石榴石S型花岗岩与高级变质作用密切相关。本课题以围岩产出的泥质麻粒岩、含石榴石S型花岗岩及其麻粒岩包体为研究对象，将高温高压变质作用与深熔作用的成因联系和精细变质-岩浆过程作为主攻目标，通过对这几类岩石的变质矿物和包裹体及其变质反应研究（关注不同岩石中不同类型石榴石的成因）、全岩和单矿物地球化学、原位微区年代学、变质作用模拟，限定高温高压麻粒岩相变质事件的峰期变质、熔融作用及退变历史，建立精细P-T-t-D路径，为深刻理解华北克拉通高温高压变质作用的性质、过程及探讨华北古元古代构造机制和地质演化史提供依据。

华北克拉通古元古代高温高压变质作用在早期陆壳演化中具有重大意义。其中泥质麻粒岩（孔兹岩）的变质精细过程以及与高级变质作用相关的熔融作用产物-含石榴石花岗岩的成因与演化历史研究，是深入进行有关研究的切入点之一。内蒙黄土窑石墨矿是泥质麻粒岩完整出露并与高压基性麻粒岩共生的典型地区，前期认为含石榴石S型花岗岩与高级变质作用密切相关。本课题以围岩产出的泥质麻粒岩、含石榴石S型花岗岩及其麻粒岩包体为研究对象，将高温高压变质作用与深熔作用的成因联系和精细变质-岩浆过程作为主攻目标，通过变质作用分析及原位地球化学分析方法，从而尝试限定高温高压麻粒岩相变质事件的峰期变质、熔融作用及退变历史，为深刻理解华北克拉通高温高压变质作用的性质、过程及探讨华北古元古代构造机制和地质演化史提供依据。. 课题对来自兴和黄土窑地区泥质麻粒岩中石榴矽线黑云片麻岩开展了详细的变质作用研究、基于副矿物金红石、锆石、独居石的原位变质年代学研究，对黄土窑地区的石榴石花岗岩中的锆石、独居石开展了原位年代学研究及矿物的原位微量元素地球化学研究。基于年代学、微量元素在锆石与石榴石、金红石与石榴石之间的分配关系，以及锆石、金红石的产状信息，对锆石、金红石的年代学结果进行了准确的限定，为解读华北北缘重要的两组变质年龄~1.95Ga与1.85Ga的意义提供了重要依据。基于变质作用模拟及石榴石的微量元素产出特征，对石榴石花岗岩的石榴石的成因进行了初步限定，为进一步探讨石榴石花岗岩与泥质麻粒岩的成因提供了依据。