江西广丰铜山中酸性岩体锆石U Pb年代学、地球化学特征及成因研究
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Geochronology, Geochemistry and Petrogenesis of the Tongshan Intermediate Felsic Rocks in Guangfeng County, Jiangxi Province
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    摘要:

    广丰铜山中酸性岩体侵位于华夏地块和扬子地块的结合部位——钦杭结合带东段。岩性为花岗闪长斑岩和石英闪长玢岩,与之伴生有中型矽卡岩型铜矿床。花岗闪长斑岩的锆石环带结构明显,Th/U值较大(0.40~1.07),为典型的岩浆锆石,LA ICP MS锆石U Pb成岩年龄为171.0±1.6 Ma(n=15,MSWD=0.16)。主微量元素特征表明该套中酸性侵入岩属于高钾过铝—偏铝质I型花岗岩类,轻重稀土分异明显(La N/YbN=10.53~38.37),无明显Eu异常(δEu平均值1.05),富集大离子亲石元素(Rb、Ba、Th、U、K),亏损Nb、Ta、Ti,低Y(<10.4×10-6)、Yb(<0.93×10-6),高Sr/Y比值(>26),具有弧型岩石和埃达克质岩石的双重地球化学特征。综合研究表明,铜山矿区的中酸性岩石形成压力大于1.5 GPa,熔体起源深度大于50 km,源区为富含金红石的角闪榴辉岩,形成于古太平洋板块斜向俯冲的挤压后松弛阶段,由新元古代洋壳俯冲形成的增厚下地壳部分熔融形成。其埃达克质特性使其易于萃取、聚集铜金等成矿物质,因此具有扩大找矿的潜力。

    Abstract:

    The Tongshan intermediate felsic rocks emplaced in conjunction area between Yangtze block and Cathaysian block, i.e. in the eastern part of the Qinhang conjunction areas. Tongshan intermediate felsic rocks consist of granite diorite porphyry and quartz diorite porphyrite, accompanied with medium sized skarn copper deposits. The zircons from granite diorite porphyry show distinct zonation structure with high Th/U ratios(0.40~1.07), suggesting that zircons are typical magmatic in origin. LA ICP MS zircon U Pb dating yields an age of 171.0±1.6 Ma(n=15, MSWD=0.16).Major element and trace element characteristics indicate that the intermediate acid intrusive rocks are high K peraluminous aluminous I type granitoid, with strong LREE/HREE fractionation (LaN/YbN=10.53~38.37) and no significant negative Eu anomalies (δEu average of 1.05). Enrichment of large ion lithophile elements (Rb, Ba, Th, U and K) and depletion of Nb, Ta and Ti, low contents of Y (<10.4×10-6) and Yb (<0.93×10-6), high Sr/Y ratio(>26), suggest the rocks are of double geochemical characteristics of arc volcanic rock and adakite. Comprehensive study shows that the intermediate felsic rocks formed at the pressure greater than 1.5 GPa, magmatic source depth was more than 50 km, and the source region composition was rutile rich amphibole eclogite facice rocks, which resulted from partial melting of thickening lower crust with relaxation environment after extension caused by the oblique subduction tectonic of the Paleo Pacific Plate. The ore forming materials were easily extracted and accumulated to form Cu Au deposits from the magmatic melts with adakitic characteristics. Therefore, the Tongshan area has the potential of mineralization and is worth broadening exploration.

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吕劲松,张雪辉,孙建东,骆学全,康丛轩,简崟峰,唐正.2016.江西广丰铜山中酸性岩体锆石U Pb年代学、地球化学特征及成因研究[J].地质学报,90(6):1253-1267.
LV Jinsong, ZHANG Xuehui, SUN Jiandong, LUO Xuequan, KANG Congxuan, JIAN Yinfeng, TANG Zheng.2016. Geochronology, Geochemistry and Petrogenesis of the Tongshan Intermediate Felsic Rocks in Guangfeng County, Jiangxi Province[J]. Acta Geologica Sinica,90(6):1253-1267.

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  • 收稿日期:2015-10-09
  • 最后修改日期:2016-02-04
  • 录用日期:2016-02-05
  • 在线发布日期: 2016-06-28
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