地学前缘 ›› 2010, Vol. 17 ›› Issue (4): 218-226.

• 论文 • 上一篇    下一篇

四川拉拉铜矿床赋矿层位变质沉积岩地球化学特征

何德锋,钟宏,朱维光,肖芳   

  1. 中国科学院 地球化学研究所 矿床地球化学国家重点实验室, 贵州 贵阳 550002
  • 收稿日期:2009-11-26 修回日期:2009-12-03 出版日期:2010-07-01 发布日期:2010-07-01
  • 作者简介:何德锋(1981—), 男, 博士, 助理研究员, 矿床地球化学专业, 主要从事岩浆活动与成矿作用研究。Email: hedf04@mails.gucas.ac.cn
  • 基金资助:

    中国科学院知识创新工程重要方向项目(KZCX2-YW-136, KZCX2-YW-111); 中国科学院地球化学研究所领域前沿项目

 Geochemical characteristics of the orebearing strata metasedimentary host rocks in the Lala copper deposit, Sichuan Province.

 HE  De-Feng, ZHONG  Hong, SHU  Wei-Guang, XIAO  Fang   

  1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
  • Received:2009-11-26 Revised:2009-12-03 Online:2010-07-01 Published:2010-07-01

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摘要：

拉拉铜矿区赋矿层位变质沉积岩的主量元素(ICV(av)=304,K2O/Al2O3(av)=022,CIA(av)=531)及Cs、Rb显著亏损特征,表明其物源区岩石只含有较少的粘土矿物和碱性长石,为中—低化学风化程度,且处于较不稳定的构造环境;多数样品的微量元素表现为显著富集高场强元素、亏损过渡族元素及Cr/Zr(av)=015、Th/Sc(av)=058,且具轻稀土富集、重稀土平坦((La/Yb)n(av)=257)的稀土元素配分模式,表明物源区以长英质组分为主;Sm、Nd同位素组成特征也显示其物源区以长英质组分为主,且沉积于大陆岛弧的弧后拉张环境。同时,结合矿区赋矿层位变钠质火山岩的构造判别结果,认为拉拉铜矿床也形成于该构造背景下。

关键词: 拉拉铜矿床, 变质沉积岩, 物源区, 风化条件, 构造背景

Abstract:

 Geochemical study of metasedimentary rocks in the Lala copper deposit was conducted to better constrain their provenance, chemical weathering condition and tectonic environment. These rocks have relatively low CIA values (4465) and K2O/Al2O3 values (002043) with high ICV values (144511), suggesting that they underwent relatively weak chemical weathering and were derived from an immature source with minor clay minerals and alkali feldspar. Compared to PAAS, the samples mostly have relatively lower large ion lithophile element (LILE) contents (Cs, Rb), lower transitional element contents (V, Cr, Zn) and relatively higher high field strength elements (HFSE) contents (Y, U, Zr, Hf, Nb, Sc). The rightslope REE ((La/Yb)n(av)=257) pattern, low Cr/Zr (001042) and Th/Sc (037114) ratios, and Sm and Nd isotopic characteristics, indicate that these rocks were deposited in a continental back arc environment and derived from a felsicdominated provenance. Furthermore, in combination with the results of tectonic setting discrimination of sodic metavolcanic rocks, we conclude that the Lala copper deposit may also have been formed in a continental back arc environment.

Key words: Lala copper deposit, metasedimentary rocks, provenance, weathering condition, tectonic setting

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