塔里木东北缘库鲁克塔格地块西段新元古代花岗闪长岩成因及其地质意义

Genesis and Geological Significance of the Neoproterozoic Granodiorite in the Western Quruqtagh Section,Northeast Margin of the Tarim Craton

库鲁克塔格地块位于塔里木克拉通东北缘,其中发育有大量新元古代岩浆岩,为进一步明确这些岩浆岩的成因,探讨区域地质演化过程,本文对库鲁克塔格地块西段的卡乌留克花岗闪长岩进行了岩相学、年代学及地球化学研究。结果表明,花岗闪长岩形成于新元古代早期(823~810 Ma),为准铝质-过铝质Ⅰ型花岗岩类;显示高硅、钠、铝,低钙、铁、钾的岩石地球化学特征;其Sr高(1690×10^(-6)~2060×10^(-6))、Y低(7.5×10^(-6)~13.1×10^(-6)),Sr/Y(140.84~274.67)及LaN/YbN(1.98~65.23)值较高,与埃达克质岩石类似;岩石富集LREE、LILE,亏损HREE、HFSE,具有弱的Eu正异常(δEu为1.02~1.20);锆石饱和温度(tZr)为747~762℃(平均755℃)。综合区域地质资料,本文推断该花岗闪长岩可能形成于与俯冲有关的大陆弧环境,是流体参与下加厚下地壳部分熔融的产物。

The Quruqtagh massif is located in the northeast margin of the Tarim Craton. A large amount of Neoproterozoic magmatic rocks are developed in the massif. In order to further clarify the origin of the magmatic rocks in this area and to discuss the regional geological evolution, in this paper, we have studied petrography, chronology and geochemistry of the Kavulyuk granodiorite in the western part of Quruqtagh massif. The results show that the granodiorites were formed in the early Neoproterozoic(823-810 Ma). They belong to meta-aluminum-peraluminum I-type granite. They have petrochemical characteristics of high contents of SiO2, Na2O and Al2O3, low contents of CaO, TFe2O3 and K2O. Meanwhile, their high Sr contents(1690×10^(-6)-2060×10^(-6)), low Y(7.5×10^(-6)-13.1×10^(-6)) contents, relatively high Sr/Y(140.84-274.67) and LaN/YbN(1.98-65.23) ratios are similar to those of the adakitic rocks. They are enriched in LREE, LILE, but depleted in HREE and HFSE, with weakly positive Eu anomalies(δEu is 1.02-1.20) and zircon saturation temperatures(tZr) varying from 747 ℃ to 762 ℃(average of 755 ℃). Based on the regional geological data, it is suggested that the granodiorite could be formed in the subduction-related continental arc environment and was the product of partial melting of the thickened lower crust under the participation of fluid.