地学前缘 ›› 2011, Vol. 18 ›› Issue (2): 79-84.

• 论文 • 上一篇    下一篇

全吉地块花岗片麻岩中镁铁质岩包体的矿物演化和锆石定年与古元古代区域变质作用

张璐，廖梵汐，巴金，徐利盼，王勤燕，陈能松   

  1. 1. 中国地质大学（武汉） 地球科学学院， 湖北 武汉  430074
    2. 中国地质大学（武汉） 研究生院， 湖北 武汉 430074
    3. 中国地质大学 地质过程与矿产资源国家重点实验室， 湖北 武汉 430074
  • 收稿日期:2011-02-01 修回日期:2011-03-01 出版日期:2011-03-15 发布日期:2011-04-15
  • 作者简介:张璐(1987—)，女，硕士研究生，岩石学专业，研究方向为前寒武纪变质作用与构造演化。E-mail:zhanglu20060616@163.com
  • 基金资助:

    国家自然科学基金项目（41072044，40972042)

Mineral evolution and zircon geochronology of mafic enclave in granitic gneiss of the Quanji Block and implications for Paleoproterozoic regional metamorphism.

  1. 1. Faculty of Earth Sciences, China University of Geosciences(Wuhan), Wuhan 430074, China
    2. Graduate School, China University of Geosciences(Wuhan), Wuhan 430074, China
    3. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
  • Received:2011-02-01 Revised:2011-03-01 Online:2011-03-15 Published:2011-04-15

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摘要：

全吉地块中段古元古代早期的德令哈二长花岗片麻岩中发育一个来自围岩的变质镁铁质岩包体。该包体的岩性从核部到边缘依次为角闪斜长辉石岩、斜长角闪岩和石榴石角闪片岩。角闪斜长辉石岩的显微结构指示三个世代的矿物演化，世代Ⅰ为单斜辉石+棕绿色普通角闪石+斜长石+石英+钛铁矿，世代Ⅱ为蓝绿色普通角闪石+斜长石+石榴子石，世代Ⅲ为阳起石+钠长石+黝帘石。世代Ⅰ指示其峰期变质达高角闪岩相条件。角闪斜长辉石岩的锆石全部为浑圆状多晶面晶体，其CL图像具高温变质结晶特征。LAICPMS技术测定获得上交点UPb年龄为（1 913±38） Ma（MSWD=015），指示峰期变质发生在古元古代末。研究表明，全吉地块中区域性分布的古元古代早期的二长花岗片麻岩与达肯大坂岩群在响应全球Columbia超大陆汇聚事件中一起发生了区域变质作用。

关键词: 镁铁质岩包体, 区域变质作用, 锆石UPb定年, 超大陆汇聚事件, 全吉地块

Abstract:

A wallrockderived metamafic enclave was discovered in the EarlyPaleoproterozoic Delingha monzogranitic gneiss in the middle part of the Quanji Block. The enclave includes three rocks, from the margin to the center, being hornblende plagioclase pyroxenite, amphibolite, and garnethornblende schist. Three generations of mineral assemblages have been identified from petrological evidence and microtextural relationship in the hornblende plagioclase pyroxenite. The generation I is of clinopyroxene+brownish greenhornblende+plagioclase+quartz+ilmenite, the generation II is of bluish greenhornblende+plagioclase+garnet and the generation III is of actinolite+albite+zoisite. The generation I assemblage indicates the peak metamorphic condition of upper amphibolitefacies. Zircons from the hornblende plagioclasepyroxenite all display multifaced crystals; their CL images are characterized by hightemperature recrystallization. LAICPMS dating of the zircons yielded an upper intercept age of 1 913±38 Ma (MSWD=0.15), suggesting peak metamorphism in the Late Paleoproterozoic. It is suggested that all regionally developed monzogranitic gneisses in the Quanji Block underwent regional metamorphism with the Dakendaban Group, in response to the global assembly event of the Columbia supercontinent.

Key words: mafic enclave, regional metamorphism, zircon UPb dating, assembly event of the Columbia supercontinent, Quanji Block

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