The Recognition of Shengliqiao Rock Mass of Saliyakedaban, West Kunlun
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摘要: 胜利桥岩体是西昆仑库地—麻扎地区出露的面积较大的"浆混"花岗岩,岩性复杂,岩石类型较多.岩石地球化学特征显示,该岩体SiO2含量较高,主要属酸性岩类;里特曼指数σ=2.13~2.89;强不相容元素K、U、Ba、Rb、Th具有明显的富集特征,高场Nb、Ta、P、Ti元素明显亏损,Nb-Ta呈槽状,Sr元素亏损明显;稀土元素总量较低,属轻稀土富集、重稀土亏损型.根据锆石U-Pb法同位素测年,2个U-Pb年龄平均值分别为(229.7 ±1.4)Ma与(204.65±0.59)Ma,时代确定为晚三叠世.综合分析,认为胜利桥岩体属于过铝高钾钙碱性花岗岩类,属I型花岗岩类,其物质来源主要来自地幔,并有一定地壳物质的加入,是壳幔共同作用的结果.胜利桥单元为陆内俯冲作用的产物,其呈现的火山弧花岗岩特征主要受地壳物质物源影响所致.Abstract: With complex lithology and rock types, Shengliqiao rock mass is a large outcrop of mixed granite in Kudi-Mazha area of West Kunlun. Geochemical characteristics of high SiO2 content indicates that the rock mass is mainly acid rock. The value of Rittmann index(σ) is between 2.13 and 2.89; strong incompatible elements including K, U, Ba, Rb, Th have obvious enrichment features; high field elements such as Nb, Ta, P, Ti are apparently depleted; the distribution of Nb-Ta is in a groove shape, and Sr element is also in an obvious deficit; the total of rare earth element is fairly low, with LREE enriched while HREE depleted. According to the zircon U-Pb isotopic dating analysis, the average ages are (229.7±1.4)Ma and (204.65±0.59)Ma, indicating that Shengliqiao rock mass occurred in the Late Triassic age. In summary, the rock is I-type granite of high aluminum potassium calcium alkaline, a result of interaction between crust and mantle. The material resource came mainly from the mantle with a certain amount of crustal material. Combined with the features of regional tectonic position and magmatic evolution of the analysis, it is concluded that Shengliqiao rock unit is a product of intracontinental subduction. The displayed feature of island arc granite is induced by the influence of crustal material resources.
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Keywords:
- petrochemistry /
- petrogenesis /
- tectonic environment /
- Shengliqiao rock mass /
- West Kunlun
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