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为探讨三塘湖盆地牛东区块晚石炭世—二叠纪火山岩类型、成因特点及区域构造背景,系统研究了其岩石学和地球化学特征,结果显示,火山岩属中-基性岩类.玄武岩主要组成斑晶矿物是斜长石、辉石和少量橄榄石,为钠质碱性系列.安山岩主要组成矿物是斜长石、少量辉石,为低钾-中钾钙碱系列.火山岩稀土元素含量较高,w(EREE)在104.60×10~(-6)～203.28×10~(-6),w(LREE/HREE)比值为6.92～18.75,La_N/Yb_N比值为7.07～35.18,属轻稀土元素富集型.稀土元素分布模式为右倾曲线,无Eu负异常,δEu为0.88～1.05.δCe为0.91～1.04.火山岩富含LILE(特别是Ba,K)和LREE,强烈亏损HFSE(Nb,Ta),具很高的LREE/HREE比值.判别图解表明,研究区晚石炭世—二叠纪岩浆活动既显示板内演化特征,又有陆缘弧火山岩地球化学痕迹.综合区域地质资料和前人研究成果,推断研究区晚石炭世—二叠纪火山岩可能是弧火山岩浆在造山后期伸展裂陷环境中的喷发产物.
In order to discuss the Late Carboniferous-Permian volcanic rock types, genetic characteristics and regional tectonic setting in Niudong block, Santanghu Basin, the petrological and geochemical characteristics of the Late Carboniferous-Permian volcanic rocks were systematically studied. The results show that the volcanic rocks are medium- The main components of plagiocrystalline minerals are plagioclase, pyroxene and a small amount of olivine, sodium alkaline series.Andanic rocks are mainly composed of plagioclase, a small amount of pyroxene, for the low-potassium-calcium-alkali series.Role of rockThe content of rare earth elements (EREE) ranged from 104.60 × 10-6 to 203.28 × 10-6 and the ratio of LREE / HREE was 6.92-18.75, and the La_N / Yb_N ratio was 7.07-35.18. Elemental enrichment.The pattern of REE is a right-angled curve with no Eu anomaly, with δEu ranging from 0.88 to 1.05.δCe ranging from 0.91 to 1.04.The volcanic rocks are rich in LILE (especially Ba, K) and LREE and strongly depleted in HFSE (Nb, Ta) with a high LREE / HREE ratio.The results show that the Late Carboniferous-Permian magmatism in the study area not only shows intraplate evolution characteristics but also shows geochemical traces of continental arc volcanic rocks.Comprehensive regional geological data and the former According to the results of the research, it is inferred that Late Carboniferous-Permian volcanic rocks in the study area may be caused by arc volcanic magma Post-stretching rift eruption product environment.