黑龙江东部完达山地体蛇绿岩形成时代及其构造意义

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摘要：对出露于完达山造山带的饶河蛇绿岩和跃进山蛇绿岩进行了岩石地球化学以及锆石UPb年代学的研究，以便了解其成因、形成时代以及它们所揭示的区域构造背景。饶河蛇绿岩TiO2含量高，高场强元素Nb、Ta、Hf、Zr等富集，大离子亲石元素Rb、Sr、Ba等相对富集，岩石样品球粒陨石标准化稀土元素配分模式及原始地幔标准化微量元素蛛网图与典型的洋岛玄武岩一致，总体表现出洋岛玄武岩的特征。跃进山蛇绿岩的微量元素特征兼具洋中脊拉斑玄武岩与岛弧拉斑玄武岩的属性，富集大离子亲石元素Rb、Ba、K、Sr等，亏损高场强元素Zr、Hf、Nb、Ta等，无负Eu异常，轻微富集轻稀土元素，形成于弧后环境。测年结果表明：饶河蛇绿岩的年龄为（219.0±2.4）Ma，跃进山蛇绿岩的年龄为（311±11）Ma。结合二者形成的构造环境，在晚石炭世—晚三叠世，黑龙江东部地区在古太平洋板块向西俯冲的背景下经历了洋岛或海山的剥落与拼贴以及“弧盆”体系演化等复杂的地球动力学过程。

关键词：蛇绿岩；地球化学；锆石UPb定年；洋岛；弧后盆地；构造演化；完达山地体；黑龙江

中图分类号：P548；P581；P595文献标志码：A

Formation Ages and Tectonic Significance of Ophiolites in Wandashan Terrane of the Eastern Heilongjiang

WANG Jiyao1， YANG Yanchen1， HUANG Yongwei2， HOU Yushu2， TAN Yan1， ZHANG Guobin1

（1. College of Earth Sciences， Jilin University， Changchun 130061， Jilin， China； 2. The First Institute of Geology

Exploration of Heilongjiang Province， Mudanjiang 157000， Heilongjiang， China）

Abstract： Rock geochemistry and zircon UPb dating are reported for Raohe and Yuejinshan ophiolites in Wandashan orogenic belt in order to understand its origin and age， and reveal their regional tectonic setting. Content of TiO2 is high， high field strength elements （Nb， Ta， Hf， Zr， etc.） are eiched， large ion lithophile elements （Rb， Sr， Ba， etc.） are relative eiched for Raohe ophiolite； chondritenormalized REE patterns and primitive mantlenormalized trace element spider diagrams of rock are consistent with that of the typical oceanic island basalt （OIB）， showing the characteristics of OIB. The characteristics of trace elements of Yuejinshan ophiolite are both midocean ridge tholeiite and island arc tholeiite， large ion lithophile elements （Rb， Ba， K， Sr， etc.） are eiched， high field strength elements （Zr， Hf， Nb， Ta， etc.） are depleted， Eu anomaly is not negative， LREE is eiched lightly， and Yuejinshan ophiolite is formed in backarc environment. Dating results show the ages of Raohe and Yuejinshan ophiolites are （219.0±2.4）Ma and （311±11）Ma， respectively. Combined with the formation of tectonic environment， the eastern Heilongjiang in Late PaleozoicLate Triassic experiences a series of complicated geodynamic processes in the background of the westward subduction of PaleoPacific Plate， including the scaling and combining of oceanic island or seamount and “arcbasin” system evolution.

Key words： ophiolite； geochemistry； zircon UPb dating； oceanic island； back arc basin； tectonic evolution； Wandashan terrane； Heilongjiang

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