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柴北缘宗务隆构造带蓄集地区闪长岩的发现及其地质意义
Discovery and geological significance of Xuji diorite in Zongwulong tectonic belt on the northern margin of Qaidam Basin
投稿时间:2020-02-14  修订日期:2020-05-28
中文关键词:蓄集闪长岩  锆石U-Pb测年  Lu-Hf同位素  宗务隆构造带
英文关键词:Xuji diorite  zircon U-Pb dating  Lu-Hf isotopes  Zongwulong tectonic belt
基金项目:青海省科技重点研发项目(2018-SF-109);青海省财政专项(41250103);青海省自然科学基金项目(2019-ZJ-964Q)
作者单位E-mail
陈敏 中国地质大学(北京) 地球科学与资源学院, 北京 100083
青海大学 地质工程系, 青海 西宁 810016 
 
薛春纪 中国地质大学(北京) 地球科学与资源学院, 北京 100083 chunji.xue@cugb.edu.cn 
薛万文 青藏高原北部地质过程与矿产资源青海省重点实验室, 青海 西宁 810000  
赵文涛 青海大学 地质工程系, 青海 西宁 810016  
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中文摘要:
      宗务隆构造带是柴达木北缘一个重要构造单元,但其构造属性长期存在争议。本次在宗务隆构造带中西部蓄集地区发现了闪长岩体,对其开展了岩相学、地球化学、锆石U-Pb年代学及Lu-Hf同位素等研究。结果表明,岩体侵入时代为258±1 Ma,富集轻稀土元素而亏损重稀土元素,具弱的负Eu异常,相对富集Rb、K、Sr等大离子亲石元素,而强烈亏损P、Ti、Nb等高场强元素,Cr和Ni含量分别为38.0×10-6~92.8×10-6和6.7×10-6~14.1×10-6,Mg#值为50~56,Rb/Sr值为0.32~0.34,Ti/Zr值为23.26~32.30,Ti/Y值为145.29~163.97,Nb/Ta值为10.45~11.45,Th/La值为0.39~ 0.51,Ba/La值为15.04~16.60,207Pb/204Pb(i)值为15.602~15.611,锆石εHf(t)值为-8.52~-3.00,二阶段模式年龄值(tDM2)值存在1 563~1 478 Ma[εHf(t)=-4.37~-3.00]和1 827~1 790 Ma[εHf(t)=-8.52~-7.98]两组,指示蓄集闪长岩岩浆是壳幔混合的产物,其中古老地壳物质占主导。结合区域地质调查结果,推测宗务隆构造带中西部地区的边缘裂陷应晚于东部。
英文摘要:
      Zongwulong tectonic belt is an important tectonic unit on the northern margin of Qaidam Basin, but its tectonic properties remain controversial. In this study, a diorite intrusion was recognized in central Xuji area of the Zongwulong tectonic belt, and its petrography, geochemistry, zircon U-Pb chronology and Lu-Hf isotopes were studied. The intrusion time of the diorite is 258±1 Ma;light rare-earth elements are enriched while heavy rare-earth elements are depleted, with weak negative Eu anomaly; it is relatively enriched in large ionic lithophile elements such as Rb, K and Sr, but strongly depleted in high field strength elements such as P, Ti and Nb. The content of Cr and Ni are 38.0×10-6~92.8×10-6 and 6.7×10-6~14.1×10-6 respectively, Mg# values are 50~56, Rb/Sr ratios are 0.32~0.34, Ti/Zr ratios are 23.26~32.30, Ti/Y ratios are 145.29~163.97, Nb/Ta ratios are 10.45~11.45, Th/La ratios are 0.39~0.51, Ba/La ratios are 15.04~16.60, 207Pb/204Pb(i) ratios are 15.602~15.611, zircon εHf(t) values are -8.52~-3.00, and the two-stage Hf model ages are 1 563~1 478 Ma[εHf(t)=-4.37~-3.00] and 1 827~1 790 Ma[εHf(t)=-8.52~-7.98]. It can thus be concluded that the magma was derived from mixture of the crust and the mantle, where the ancient crustal material was dominant. Combined with regional geological studies, it is suggested that the marginal rifting in the central and western regions of the Zongwulong tectonic belt should be later than that in the east.
陈敏,薛春纪,薛万文,赵文涛,2020,柴北缘宗务隆构造带蓄集地区闪长岩的发现及其地质意义[J].岩石矿物学杂志,(5):552~568.
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