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上木水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。针对上木水岩体的花岗闪长岩样品进行LA-ICP-MS锆石UPb测年,获得~(206)Pb/~(238) U年龄加权平均值为444 Ma±4 Ma(MSWD=0.027),说明岩体均形成于加里东期。上木水岩体具有钙碱性-高钾钙碱性、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_(2DM))主要集中在1.2Ga~1.4Ga之间,指示其物源主要来自中元古代新生的基性下地壳物质。综合地球化学、锆石Hf同位素组成特征、岩体发育暗色微粒包体等特征及区域地质资料,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,从而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并最终固结成岩。
It is of great geological significance to dissect the tectonic evolution of the South China area in the southwestern segment of the upper Mushui granodior that is produced by the combination of the Yangtze block and the Huaxia block. The LA-ICP-MS zircon UPb dating of the granodiorite samples collected from the Shangmu water rock mass obtained a weighted average of ~ (206) Pb / ~ (238) U ages of 444 Ma ± 4 Ma (MSWD = 0.027), indicating that the rock mass was formed in Caledonian. The Shangmushui granite is characterized by type I granite with calc-alkaline-high-K calc-alkaline and quasi-aluminum-peridotite characteristics. The ε_ (Hf) (t) values for zircons mainly range from 0 to +4, and the T_ (2DM) ages for the two phases mainly range from 1.2Ga to 1.4Ga, indicating that the source of these zircons mainly come from the Zhongyuan The ancient basement of the lower crustal material. Synthetic geochemistry, Hf isotopic compositions of zircons, dark-colored granulite inclusions and other geological characteristics of the rock mass and their regional geological data suggest that they are associated with lithospheric extension and thinning after intracontinental collision orogeny, high-temperature mantle material in asthenosphere Upwelling, resulting in the formation of parent magma in different degrees of mixed magmatic magma and mantle magma formed by the melting of the underlying Lower Proterozoic Neoproterozoic reefs, followed by a certain degree of differentiation and evolution and eventually consolidation into diagenesis .