内蒙古锡林格勒杂岩的地球化学研究：从Rodinia聚合到古亚洲洋闭合后碰撞造山的历史记录

内蒙古锡林格勒杂岩的地球化学研究：从Rodinia聚合到古亚洲洋闭合后碰撞造山的历史记录

朱永峰1, 孙世华2, 毛骞2, 赵光1

1. 造山带与地壳演化教育部重点实验室，北京大学地球与空间科学学院北京 100871; 2. 中国科学院地质与地球物理研究所矿产资源重点研究室北京 100029

收稿日期:2004-09-20 修回日期:2004-09-20 出版日期:2004-09-20 发布日期:2004-09-20

Geochemistry of the Xilingele Complex,Inner Mongolia: A Historic Record from Rodinia Accretion to Continental Collision after Closure of the Paleo-Asian Ocean

ZHU Yong-Feng1, SUN Shi-hua2, MAO Qian2, ZHAO Guang1

1. The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, China, School of Earth and Space Sciences, Peking University, Beijing 100871; 2. Institute of Geophysics and Geology, Chinese Academy of Sciences, Beijing 100029, China

Received:2004-09-20 Revised:2004-09-20 Online:2004-09-20 Published:2004-09-20

摘要/Abstract

摘要： 内蒙古东部出露的锡林格勒杂岩主要由中元古代原岩为火成岩的黑云母片麻岩和斜长角闪岩透镜体组成。片麻岩显示轻稀土元素富集的中等分异特征，具明显的Eu负异常，其不相容元素特征与平均地壳类似但相对亏损Ba和Sr。斜长角闪岩构成一条Sm-Nd等时线，其年龄值为1202±65Ma，εNd(1．20Ga)值为6．8。角闪岩的亏损地幔模式年龄(tDM，1．26～1．32Ga)与其Sm-Nd同位素等时线年龄接近。角闪岩的Rb-Sr同位素等时线年龄为393±14Ma，其^87Sr／^86Sr初始比值为0．70379±0．00007，此Rb-Sr等时线年龄与本区出露的篮片岩Ar-Ar年龄(～383Ma)一致，记录了中亚造山带东南部洋壳俯冲结束后由大陆碰撞造山引起的变质作用事件。黑云母片麻岩的Rb-Sr同位素等时线年龄为279．5±6．4Ma，^87Sr／^86Sr初始比值为0．70851±0．00010，此Rb-Sr等时线年龄与本区广泛分布的早二叠世火山岩的Rb—sr等时线年龄(～277±15Ma)一致，因此可能是由大规模岩浆活动诱发的变质作用的记录。锡林格勒杂岩因此不仅记录了Rodinia超大陆聚合的地质事件，并且通过对比研究本地区蛇绿岩和晚古生代岩浆岩的演化历史，可以恢复从Rodinia超大陆聚合(～1．20Ga)到古亚洲洋关闭(～430Ma)、大陆碰撞造山(～393Ma)以及碰撞后大规模岩浆活动(～280Ma)的全过程。

Abstract: The metamorphic rocks in Xilingele complex mainly consist of biotite gneisses with plagioclase amphibolite lenses.The gneisses show medium fractionated LREE-enriched pattern with obvious negative Eu anomalies.Their incompatible trace element concentrations are similar to the average continental crust but with depletions of Ba and Sr.One Sm-Nd isochron for amphibolites yields an age of 1 202±64 Ma with εNd(t)value of+6.8.The Rb-Sr isochron for amphibolites yields an isochron age of 393±14 Ma with an initial 87Sr／86Sr ratio of 0.703 79.This Rb-Sr isochron age is consistent with the Ar-Ar age(～383 Ma)of the blueschists in this region,and is～40 Ma younger than the Rb-Sr isochron age of Hegenshan ophiolite.It probably recorded the metamorphism caused by the continental collision after the closure of the Paleo-Asian Ocean ,which finally led to the continental collision of the north China craton with the Siberian craton.The Rb-Sr isoehmn for the gneisses yields an age of 279±6.4 Ma with an initial 87Sr／S86Sr ratio of 0.708 51.which is consistent with the age of volcanic rocks(～277 Ma)most-widely distributed in this region.Such coincidence probably implies that the metamorphism recorded in the studied gneisses was caused by magmatic processes during Early Permian.The geochemistry of the Xilingele complex thus recorded not only the Rodinia accretion processes,but also the closure event of the Paleo-Asian Ocean (～430 Ma),continental collision(～390 Ma)and post-collisional magmatism(～280 Ma)by comparing the ophiolites and magmatic rocks in this region.

朱永峰, 孙世华, 毛骞, 赵光. 内蒙古锡林格勒杂岩的地球化学研究：从Rodinia聚合到古亚洲洋闭合后碰撞造山的历史记录[J]. J4.

ZHU Yong-Feng1, SUN Shi-hua2, MAO Qian2, ZHAO Guang1. Geochemistry of the Xilingele Complex,Inner Mongolia: A Historic Record from Rodinia Accretion to Continental Collision after Closure of the Paleo-Asian Ocean[J]. J4.