湖南塔山、阳明山花岗岩的岩石成因:来自锆石U-Pb年龄、地球化学及Sr-Nd同位素证据

发布时间：2018-06-12 20:40

本文选题：锆石U-Pb年龄 + 地球化学　；参考：《地质学报》2016年02期

【摘要】：湖南塔山、阳明山岩体位于扬子地块和华夏地块的结合部位,主要由不同粒度的斑状二长花岗岩构成,其中塔山岩体的粗中粒、中细粒、中粒斑状二长花岗岩的锆石La-ICP-MS定年结果分别为221.3±0.9Ma、221.5±1.9Ma、213.4±1.1Ma,阳明山中细粒斑状二长花岗岩的年龄为213.7±1.0Ma,均属印支晚期花岗岩。花岗岩富SiO_2(70.43%~74.06%)、Al_2O_3(13.25%~15.37%)、高A/CNK(1.03~1.24)、高分异指数DI(85.25~93.0)、富集Rb、Th、U、Ta,亏损Ba、Sr、Nb、Ti,具明显的负Eu异常(δEu=0.15~0.45),为高分异的过铝花岗岩。高(~(86)Sr/~(87)Sr)_i(0.72993~0.77391)、低ε_(Nd)(t)(-9.9~-12.11)、Nd的t_(DM2)(1801~1978Ma)较大等特征,表明塔山、阳明山花岗岩为壳源S型花岗岩。结合其形成年龄和区域构造背景,认为塔山、阳明山岩体是在印支运动晚期挤压作用向伸展作用转换形成的局部伸展-减薄的机制下,由加厚地壳中的中元古代变质砂屑岩、变质泥岩部分熔融形成,并经历了分离结晶作用。年龄为3523Ma的继承锆石核显示本区可能存在古太古代的古老基底。
[Abstract]:Tashan, Yangmingshan, Hunan Province, is located in the combination of Yangtze block and Huaxia block. It is mainly composed of porphyry monzonitic granite of different granularity, in which the coarse medium grain and medium fine grain of the Tashan rock body. The zircon La-ICP-MS dating results of the mesomorphic porphyry monzonitic granites are 221.3 卤0.9MaA 221.5 卤1.9MaU 213.4 卤1.1 Ma.The age of the meso-fine-grained porphyry monzomorphic granites is 213.7 卤1.0Ma. they all belong to the late Indosinian granites. The granite is rich in SiO2C 70.43, and 74.06%, and Al2OT has a negative EU anomaly (未 EU (0.15 ~ 0.45) 0.45). It has a negative EU anomaly (未 EU _ (0.15) ~ 0.45). It is a kind of peraluminous granite with high A- / CNK _ (1.03N) ~ (1.24), a high score index (DI85.25 ~ 93.0), rich in RbTU _ (T), and depleted in BaSrNbTi.It has a negative EU anomaly (未 -EU _ (0.15) ~ 0.45), which is a peraluminous granite with high grade. It is shown that the Taishan and Yangmingshan granites are of crust-origin S-type granites, which are characterized by the relatively large T / M ~ (2 +) M _ (2) ~ (2) ~ (2) ~ (-1) T _ (T) D _ (2) ~ (2) ~ (1) ~ (18) ~ (18) 1 ~ (78) Ma, respectively, which indicate that the Tashan and Yangmingshan granites are of crust-origin S-type granites. Combined with its age of formation and regional tectonic background, it is considered that the Tashan and Yangmingshan rock bodies were formed by the mechanism of local extensional thinning formed by the late Indosinian compressional process to extensional process, and the Mesoproterozoic metamorphic sandstones in the thickened crust were formed from the Mesoproterozoic metamorphic sandstones in the thickened crust. Metamorphic mudstone formed by partial melting and underwent separation and crystallization. The inherited zircon core at 3523 Ma indicates that the paleoArchean basement may exist in this area.
【作者单位】：中国地质调查局武汉地质调查中心;中国地质调查局花岗岩成岩成矿地质研究中心;湖南省地质矿产勘查开发局405队;
【基金】：中国地质调查项目(12120114020701) 地质矿产调查评价项目(1212011120804)资助的成果
【分类号】：P597.3;P588.121

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