ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    甘肃北山地区花牛山群变英安岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义

    LA-ICP-MS Zircon U-Pb Age, Geochemistry and Tectonic Implications of Metamorphic Dacite from Huaniushan Group in Beishan Area, Gansu, China

    • 摘要: 采用锆石U-Pb方法在甘肃北山地区花牛山群中变英安岩中获得LA-ICP-MS U-Pb年龄为(454.7±0.87)Ma(MSWD=0.28),属晚奥陶世早期的产物,该年龄可为准确厘定花牛山群的沉积时代提供新的依据,从而将其修订为上奥陶统。同时岩石地球化学具高碱、高铝,富集Rb、Th、U、K、Pb,亏损Nb、Ta、Ti,无明显δEu异常,显示出明显的火山弧岩浆特征。结合区域地质资料表明,岩体形成于活动大陆边缘,其形成与俯冲流体交代或俯冲沉积物的加入有关,与花牛山铅锌矿的喷流(气)沉积型块状硫化物矿床形成环境不同,因此,认为花牛山群并非花牛山铅锌矿的赋矿层位。

       

      Abstract: By using the zircon LA-ICP-MS U-Pb dating, the obtained ages of metamorphic dacite from Huaniushan Group are (454.7 ±0.87)Ma (MSWD=0.28), which belong to the early stage of Late Ordovician.This age can provide a new basis for accurately determining the depositional age of Hunshan Group, thus the age of Hunshan Group has been revised as Upper Ordovician.This metamorphic dacite have high alkali and high Al, obvious enrichment of Rb, Th, U, K, Pb, negative anomalies of Nb, Ta, Ti, no obvious δEu anomaly, showing the typical volcanic magma characteristics.According to the regional geological data, the metamorphic dacite is formed in the active continental margin,which is related to the addition of subduction fluid or subduction sediments and is different from the formation of massive sulfide deposits in the Huaniushan Pb-Zn deposit.Therefore, it is considered that the Huaniushan Group is not the ore-bearing strata of Huaniushan Pb-Zn deposit.

       

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