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    张家口高家庄多金属矿床成矿时代厘定及其地质意义

    The metallogenic age of the Gaojiazhuang polymetallic deposit in Zhangjiakou area and its geological implications

    • 摘要: 太行山北东向构造-岩浆岩带中发育有多个燕山期酸性岩体,目前已发现的多金属及贵金属矿床与燕山期岩体有着密切的成因联系。本文对分布于大河南岩体北西侧的高家庄多金属矿床采用硫化物Rb-Sr法进行了同位素定年,(144.5±1.4)Ma等时线测年结果与采用锆石U-Pb法确定的大河南岩体形成时代接近;此外,矿床硫化物的初始锶同位素比值为0.7122~0.7123,显示成矿物质来源以壳源为主。这与大河南岩体主要为陆壳物质部分熔融形成的认识相一致,即高家庄多金属矿床在成矿物质来源上与大河南岩体的形成与演化之间具有密切的成因联系。大河南岩体的形成时限与区内多金属矿床形成时限与中国东部第二次大规模成矿期一致,此时区内地球动力学环境正处于主应力场由近南北向转换到近东西向的构造体制大转折时期。在此独特的成矿背景下,深熔作用形成的花岗质岩浆沿NNE向与原EW向断裂交汇处侵位。花岗质岩浆高侵位但未发生喷发作用,使挥发组分和成矿元素得以保存,从而为大规模成矿作用提供了必须的热、流体、挥发组分和成矿元素。

       

      Abstract: There are many Yanshanian acid intrusive bodies located in the northeast structural-magmatic belt of Taihang Mountain. The currently discovered polymetallic deposits and precious metal ore deposits are genetically related to the acid rocks of Yanshanian epoch. This study provides the metallogenic age of the Gaojiazhuang polymetallic deposit by means of Rb-Sr isotopic dating. The deposit is located on the northwestern margin of the Dahenan rock mass. Isochron age of (144.5±1.4)Ma is close to the formation age of Dahenan rock mass shown by zircon (U-Pb). Initial Sr isotope ratios (0.7122-0.7123), suggesting that the ore materials of the deposit were derived from the rock mass mainly formed by partial melting magma of crust-derived materials. It is shown that the evolution of Dahenan rock mass controlled the formation of polymetallic deposits in the study area. The metallogenic age of the Gaojiazhuang polymetallic deposit is consistent with the age of the second large-scale mineralization epoch in eastern China, with the geodynamic setting belonging to the tectonic regime transition period. In this unique metallogenic background, the emplacement of granitic magma took place along the intersection of NNE-striking and EW-trending faults. This process provided the necessary heat, fluid, volatile components and metallogenic elements for large-scale metallogeny.

       

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