投稿时间：2012-04-11
修订日期：2012-05-11
中文摘要:金川铜镍硫化物矿床及其与附近的镁铁-超镁铁质岩体的成因关系对成岩成矿理论研究及找矿具有重要意义。通过对镁铁-超镁铁质岩体的岩石学、年代学、岩石地球化学、同位素地球化学研究,获得金川附近的茅草泉镁铁-超镁铁质岩体中单颗粒锆石U-Pb年龄为(832.5±1.5) Ma,与金川超镁铁质岩体中锆石U-Pb年龄(831.8±0.6) Ma在误差范围内一致。岩石地球化学数据显示,金川岩体与茅草泉岩体都属于亚碱性拉斑玄武岩系列,微量及稀土元素配分曲线平行,变化趋势相似,属于右倾型,具有Nb、Ta负异常;Cu/Zr比值显示过渡变化特征,Cu/Ni比值都小于1,原始地幔标准化的铂族元素配分曲线平行过渡。同位素地球化学数据显示,样品具有高正εSr(t)值,低的εNd(t)值,较低的206Pb/204Pb值,指示岩浆源区为EMⅠ型富集岩石圈地幔。多种方法证明了金川、茅草泉岩体具有同期同源岩浆演化特征,茅草泉小岩体群可能是金川母岩浆先期侵入岩相,为金川矿床的形成贡献了亲铁元素与橄榄石成分。
Abstract:The genetic relationship between the Jinchuan Cu-Ni sulfide deposit and the near-by mafic-ultramafic intrusions is important for further exploration. The zircon U-Pb age (832.5±1.5) Ma of the Maocaoqun mafic intrusion is consistent with the zircon U-Pb age (831.8±0.6) Ma of the Jinchuan ultramafic intrusion. Petrogeochemical compositions indicate that both intrusions belong to sub-alkaline tholeiitic basalts, and chondrite-normalized REE and primitive-mantle normalized micro-elements diagrams show parallel patterns, displaying LREE enrichment and Nb, Ta negative anomalies. Primitive-mantle normalized PGE patterns show parallel distribution between Maocaoqun and Jinchuan ultramafic intrusions. Isotopic geochemical data display high εSr(t), low εNd(t) and fairly low 206Pb/204Pb values for both intrusions, which implies that the magma forming the intrusions came from the enrichment mantle source like EMⅠ-type mantle. The above features suggest that the Jinchuan and Maocaoquan intrusions were derived from the same magma source with the same age. Maocaoquan mafic-ultramafic intrusions were possibly formed by earlier stage magma from the Jinchuan magma chamber, which contributed siderophile elements and olivine for later stage magma, thus forming the Jinchuan Cu-Ni sulfide deposit.
keywords:geochemistry zircon U-Pb dating mass balance of magma mafic-ultramafic intrusions Maocaoquan Jinchuan
文章编号：
中图分类号：P618.41;P618.63
文献标志码：
基金项目:本文得到国家自然科学基金项目"甘肃龙首山地区与铜镍成矿有关的幔源岩浆事件重建"(编号:41072058)、公益性行业科研专项(编号:200911007,201011058)与长安大学科技创新研究项目(编号:CHD2010ZD005,CHD2011TD007)的联合资助
引用文本：
焦建刚,汤中立,闫海卿,刘民武,孙涛,徐刚,段俊.2012.金川铜镍硫化物矿床的岩浆质量平衡与成矿过程[J].矿床地质,31(6):1135~1148JIAO JianGang,TANG ZhongLi,YAN HaiQing,LIU MinWu,SUN Tao,XU Gang,DUAN Jun.2012.Magmatic mass balance and metallogenic process of Jinchuan Cu-Ni sulfide deposit[J].Mineral Deposits31(6):1135~1148
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