新疆阿舍勒铜锌矿区英云闪长岩年代学及地球化学

摘要

LA-ICP-MS U-Pb zircon ages and whole rock geochemical data are reported for tonalites from the Ashele Cu-Zn deposit on the southern margin of Altay. The zircons from tonalite samples yielded mean 206Pb/238U ages of 375.3 ± 2.1 Ma and 386.2 ± 3.8 Ma, suggesting that the intrusion took placed between Early Devonian and Middle Devonian. These tonalites have high SiO2 (74.72% to 77.72%), moderate A12O3( 12.06% to 13.5%) and total alkali (Na2O + K2O) (5.84% to 6.59%), and low P2O5(<0.04%) and CaO (0.34% to 1.65%). In addition, they are enriched in Na (Na2O/K2O = 3.3 to 10.9) with high A/CNK values (1.10 to 1.18), implying low-K peraluminious granites. They display negative anomalies of Nb, Ta, Ti, Sr, Ba and P and obvious enrichment of LREE and LILEs (Th, U and Pb) with significant Eu (0.47 - 0.81) negative anomalies. Combined with the tectonic evolution of the southern margin of the Altay, the authors hold that these tonalities were generated from the melting of continental crust in an island arc tectonic setting.%对新疆阿尔泰南缘阿舍勒铜矿区英云闪长岩进行了锆石LA-ICP-MS U-Pb年龄测定,获得了375.3±2.1Ma和386.2±3.8 Ma的加权平均年龄,表明英云闪长岩形成于早泥盆世晚期一中泥盆世早期.岩石地球化学分析结果表明:所有岩石具有高SiO2(74.72％～77.72％)和中等的A12O3(12.06％～13.5％)含量,低的P2O5(＜0.04％)和CaO(0.34％～1.65％)含量,且具有贫碱(K2O+ Na2O=5.84％ ～6.59％)、富钠(Na2O/K2O=3.3～ 10.9)、过铝质(A/CNK=1.10～1.18)特点；富集LREE和Th、U、Pb元素,贫P、Sr、Nb、Ta、Ti元素,呈现明显的Eu负异常(δEu=0.47～0.81),属低钾过铝质岩石.综合阿尔泰造山带南缘的区域地质资料及英云闪长岩的地球化学特征,认为阿舍勒铜锌矿区英云闪长岩是早中泥盆世的活动大陆边缘环境陆壳岩石部分熔融的产物.