辽西兰家沟钼矿床花岗岩SHRIMP锆石U-Pb年龄及岩石化学特征
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Zircon SHRIMP U-Pb age and petrogeochemical features of Lianjiagou granite in western Liaoning province
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    摘要:

    兰家沟钼矿床位于辽宁西部,矿体主要赋存于兰家沟细粒花岗岩岩体内,少部分赋存在细粒花岗岩与粗粒花岗岩的接触部位。岩石学和地球化学分析表明,兰家沟花岗岩具高硅(ω(SiO2)=73.65%~77.88%)、富碱(ω(K2O)+ω(Na2O)=5.92%~9.14%)、准铝质(A/CNK=0.99~1.07)特征。P2O5随SiO2含量的增高呈现出降低趋势。REE配分模式图和原始地幔多元素蜘蛛网图显示Th、La、Ce、Nd、Zr、Hf、Y、Yb、Lu和LREE相对富集,而Nb、Ta、Ti、Ba和Sr亏损,Eu为中等负异常(δEu=0.52~0.66)。这些特征表明兰家沟花岗岩在演化的过程中经历了一定程度的分离结晶作用,属于分异的I型花岗岩,细粒花岗岩和粗粒花岗岩属于同源演化系列。SHRIMP锆石U-Pb测年表明,兰家沟细粒花岗岩锆石U-Pb年龄为(184.7~196.4)Ma,加权平均年龄为(188.9±1.2)Ma(MSWD=1.03)。花岗岩侵位于早侏罗世,与钼矿化的时间相当。结合区域资料分析认为,兰家沟花岗岩的侵位和钼矿化形成于早侏罗世燕辽地区的挤压变形过程中。

    Abstract:

    Lanjiagou molybdenum deposit is located in western Liaoning province and associated temporal–spatially with Lanjiagou granite which is composed of fine-grained and coarse-grained granite. The orebodies occurred at the inner of the fine-grained granite or the contact zone between the fine-grained granite and the coarse-grained granite. Main elements analysis of Lanjiagou granites shows that they are rich in Si (ω(SiO2)=73.65%~77.88%), alkalis (ω(K2O)+ω(Na2O)=5.92%~9.14%), metaluminous (A/CNK=0.99~1.07). The chondrite-normalized REE patterns are characterized by LREE enrichment with variable of middle negative Eu anomalous (δEu=0.52~0.66). The primitive mantle-normalized spidergrams show that they are depleted in Ba, Sr, P, Ti and Nb. In the SiO2-P2O5 diagram, the P2O5 contents show a decrease trend with increasing SiO2 contents. These geochemical characteristics suggest that Lanjiagou granite underwent less fractional crystallization processes and belong to differential I-type composite granite. The fine-grained granite and coarse-grained granite belong to the same evolutional series in source. They Zircon SHRIMP U-Pb dating for the fine-grained granite yields concordant ages from 184.7 to196.4 Ma, with a weighted mean age of (188.9±1.2) Ma. The U-Pb ages are almost identicalness with Re-Os age ((186.5±0.7) Ma), suggesting that the granite emplacement and Mo mineralization occurred in Early Jurassic and the mineralization is probably genetically associated with the granite. Base on regional geology data, we draw a conclusion that the emplacement of Lanjiagou granite and the mineralization timing of the molybdenum deposit occurred in Early Jurassic during the compression deformation period in Yan-liao area.

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代军治.2008.辽西兰家沟钼矿床花岗岩SHRIMP锆石U-Pb年龄及岩石化学特征[J].地质学报,82(11):1555-1564.
Dai Junzhi.2008. Zircon SHRIMP U-Pb age and petrogeochemical features of Lianjiagou granite in western Liaoning province[J]. Acta Geologica Sinica,82(11):1555-1564.

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  • 收稿日期:2008-07-24
  • 最后修改日期:2008-07-24
  • 录用日期:2008-11-24
  • 在线发布日期: 2008-11-24