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通过LA-ICP-MS锆石U-Pb定年法,获得甘肃北山牛圈子地区辉绿岩中锆石加权平均年龄为(313.6±3.3)Ma(MSWD=0.61),为晚石炭世,代表岩墙侵位年龄。岩石地球化学特征具高Mg、贫K,P和Ti,富集不相容元素,亏损相容元素,Nb,Ta明显亏损等特点,具亚碱性拉斑玄武岩特征。构造环境判别图解显示其形成于陆内裂谷环境。结合前人研究成果认为,晚石炭世牛圈子地区处于伸展拉张的构造背景。通过对比天山和本地区岩体的主微量和稀土元素认为,其可能是晚石炭世天山大火成岩省的组成部分,为晚石炭世塔里木地幔柱作用的产物。
By zircon LA-ICP-MS zircon U-Pb dating, the weighted average age of diabase in the diabase of Beishan Niushanzi area is (313.6 ± 3.3) Ma (MSWD = 0.61), which is Late Carboniferous, Age of invasion. The geochemical characteristics of rocks are characterized by high Mg, poor K, P and Ti, rich incompatible elements, depleted compatible elements, obvious depletion of Nb and Ta, etc, and are characterized by subbase alkaline tholeiites. Tectonic environment discrimination diagram shows that it is formed in the continental rift environment. According to the previous research results, the Late Carboniferous Cattle Circle is in a tectonic setting with stretching and stretching. By comparing the main trace and rare earth elements of the Tianshan and the local rock mass, it is considered that it may be a component of the Late Carboniferous Tianshan Igneous Province and is the product of the Late Carboniferous Tarim plume effect.