摘要
本文对北大别片麻岩锆石中矿物包体及年代学进行了研究,首次发现了北大别片麻岩的超高压变质作用证据。结合阴极发光图像和同位素定年,片麻岩锆石中矿物包体组合至少可分出三期:(1)原岩岩浆矿物组合,即斜长石、黑云母、石英和磷灰石;(2)超高压变质矿物组合,即金刚石、石榴子石和金红石等;(3)麻粒岩相退变质矿物组合,如透辉石等。其中,金刚石和石榴子石主要以包体形式被包裹于透辉石中,而透辉石是北大别麻粒岩相退变质阶段形成的代表性矿物。锆石SHRIMP U-Pb定年结果表明,北大别片麻岩的峰期变质时代和麻粒岩相退变质时代分别为218±3Ma和199±10Ma。这些证明北大别片麻岩,如同其中的榴辉岩一样,经过了印支期超高压变质作用。
Micro-inclusions and the U-Pb age of zircons were investigated from the banded gneiss in the northern Dahie complex, central China. Mineral inclusions in zircon from the gneiss ,combined with cathodoluminescene images and isotopic dating, can be divided into three generations, i.e. primary magma assemblage of feldspar ＋ biotite ＋ quartz ＋ apatite, ultrahigh-pressure （ UHP ） metamorphic assemblage of diamond ＋ garnet ＋ rutile, and granulite-facies retrograde assemblage such as diopside. Diamond and garnet occurred as inclusion in diopside, which is representative retrograde mineral of granulite-facies in the northern Dabie complex. The zircons from the studied gneiss, analyzed by SHRIMP U-Pb, yielded peak metamorphic age of 218 ± 3Ma and granulite-facies retrograde age of 199 ± 10Ma. The evidences for UHP metamorphism were firstly discovered on the gneiss from the northern Dahie complex, indicating the banded gneiss of northern Dahie complex suffered Triassic UHP metamorphism as well as the enclosed eclogites.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第7期1827-1832,共6页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40572035)
国家"973"专项项目(2003CB716500)的联合资助成果.
关键词
超高压变质作用
金刚石
锆石
片麻岩
北大别
Ultrahigh-pressure metamorphism, Diamond, Zircon, Gneiss, Northern Dabie complex
