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    辽西建平烧锅营子金矿花岗岩的锆石U-Pb年代学、地球化学特征及地质意义

    Zircon U-Pb geochronology, geochemical characteristics and geological significance of the pluton in the Shaoguoyingzi gold ore deposit in Jianping, western Liaoning

    • 摘要: 辽西建平烧锅营子花岗岩岩体位于华北地台北缘朝阳-赤峰金矿成矿带,岩体周围分布着烧锅营子、撰山子等金矿床或金矿点。与金矿同源关系的岩体主要为二长花岗岩。3个不同粒度的二长花岗岩LA-ICP-MS锆石UPb测年结果分别为(159.1±1.5)Ma、(160.2±4.4)Ma、(160.1±1.1)Ma,表明烧锅营子岩体形成晚侏罗世早期;其周边金矿床也形成于此时期或稍晚。结合前人资料总结认为160Ma左右是朝阳-赤峰地区一个重要的金矿成矿时期。烧锅营子花岗岩体主量元素以富Si、低Al、中偏低碱、高钾和低Mg、低Ca为特点;微量元素表现出富集Th、Zr、Nd、Rb、K和亏损Ba、Sr、P、Ti的特点,具有强烈的负Eu(δEu=0.08~0.60)、Sr异常。岩石总体上属于经历了高度结晶分异的高钾钙碱性I型花岗岩,Sr-Yb-Y元素特征显示其源区深度为30km。晚侏罗世整个中国东部处于构造域转折期,结合区域上构造环境分析,烧锅营子岩体是太平洋板块俯冲背景下的弧后伸展环境的产物。

       

      Abstract: The Shaoguoyingzi intrusion is located in the Chifeng-Chaoyang gold concentration area on the northern margin of the North China Craton, surrounded by Shaoguoyingzi and Zhuanshanzi gold deposits or gold ore spots. The lithology of the intrusion is monzogranite which shares the same source with the gold deposits. The zircon U-Pb age data obtained by using laser ablation ICPMS technique are 159.1±1.5 Ma, 160.2±4.4 Ma and 160.1±1.1 Ma, which indicate that the Shaoguoyingzi intrusion was formed in Late Jurassic and the gold deposits were formed at the same time or a little later. The major and rare elements are characterized by high Si, low Al, medium alkali, poor Mg and Ca, rich Th, Zr, Nd, Rb and K and comparatively low Ba, Sr, P and Ti, with obvious negative Eu(δ Eu=0.08-0.60)and Sr anomalies; which indicates that the Shaoguoyingzi intrution is a high-K calc-alkaline I-type granite that has experienced a high degree of crystallization and differentiation. The depth of the source is about 30km, as shown by the characteristics of Sr-Yb-Y. This area was a tectonic transition period in late Jurassic, and the intrusion was formed by back-arc extension in the Pacific plate subduction environment, as shown by an analysis of the regional tectonic environment.

       

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