桂东南大村和古龙岩体的成因:地球化学、锆石U-Pb年龄及Hf同位素制约

发布时间：2018-02-28 13:48

本文关键词： 加里东期桂东南大村岩体古龙岩体 LA-ICP-MS锆石U-Pb定年 Hf同位素地球化学　出处：《地质通报》2017年Z1期 　论文类型：期刊论文

【摘要】：大村和古龙岩体产于扬子地块与华夏地块拼合带的西南段,对剖析华南区域构造演化具有重要的地质意义。对大村和古龙岩体的石英闪长岩样品进行LA-ICP-MS锆石U-Pb测年,获得~(206)Pb/~(238)U年龄加权平均值分别为438±1Ma和435±2Ma,说明2个岩体均形成于加里东期。大村和古龙岩体具有钙碱性、准铝质-过铝质特征的I型花岗岩。锆石的ε_(Hf)(t)值主要集中在0~+4之间,二阶段模式年龄(T_(DM2))主要集中在1.15~1.45Ga之间,指示物源主要来自中元古代新生的基性下地壳物质。根据大村和古龙岩体的地球化学、Hf同位素组成、岩体发育暗色微粒包体等特征,结合区域地质情况,认为其是在陆内碰撞造山期后伴随岩石圈局部伸展-减薄,软流圈高温地幔物质上涌,导致中元古代新生的基性下地壳部分熔融形成的酸性岩浆和幔源岩浆在源区不同程度的混合形成母岩浆,随后又经历了一定程度的分异演化最终固结成岩。
[Abstract]:The Dacun and Gulong pluton occurred in the southwestern section of the Yangtze and Huaxia assemblage zones, which are of great geological significance for the analysis of the regional tectonic evolution in South China. LA-ICP-MS zircon U-Pb dating of quartz diorite samples from the Dacun and Gulong pluton is carried out. The weighted average values of Pb / P / T 238U were 438 卤1Ma and 435 卤2Marespectively, indicating that the two intrusions were formed in Caledonian. Dacun and Gulong granites have calc-alkaline and quasi-alumina-peraluminous characteristics. The 蔚 ~ (-1) of zircon is mainly between 0 ~ 4. The main source of indicator material is from the Mesoproterozoic basic lower crustal material. According to the geochemical HF isotopic composition of the Dacun and Gulong rock bodies and the development of dark particle inclusions in the rock mass, and so on, the two-stage model age is mainly between 1.15and 1.45Ga, and the source of the indicator material is mainly from the Mesoproterozoic material of the basic lower crust. Combined with the regional geological conditions, it is considered that it is associated with the local extension and thinning of lithosphere after the intracontinental collision orogenic period, and the high temperature mantle material upwelling in the asthenosphere. The acidic magma and mantle-derived magma formed by partial melting of the Mesoproterozoic basic lower crust formed the mother magma in different degrees in the source region and then underwent a certain degree of differentiation and evolution and finally consolidated diagenesis.
【作者单位】：广西壮族自治区地质调查院;中化地质矿山总局广西地质勘查院;广西遥感中心;
【基金】：中国地质调查局项目《桂东-粤西成矿带地质矿产调查》(编号:D20160035)
【分类号】：P597;P581

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