新疆东天山觉罗塔格地区自然铜矿化玄武岩的成岩年代及其地质意义

Geochronology and geological indication of the native copper mineralized basalt formation in Jueluotage area,Eastern Tianshan,Xinjiang

新疆觉罗塔格地区自然铜矿化玄武岩沿着阿齐库都克深大断裂北侧分布,前人对其成岩年代一直存在争议。本文测得玄武岩条带中部的黑尖山玄武岩同岩浆期锆石SHRIMPU-Pb年龄为306.2±4.0Ma;测得东部东尖峰玄武岩的同岩浆期锆石LA-ICPMSU-Pb年龄为308.9±5.8Ma,确定了玄武岩是晚石炭世的岩浆作用,且归属于晚石炭世马头滩组。与觉罗塔格地区著名的晚石炭世-早二叠世铜镍矿化基性-超基性岩成因对比表明,该晚石炭世玄武岩与之具有共同岩浆源区特征,它们都是觉罗塔格地区晚石炭世-早二叠世岩石圈地幔深部受热熔融而形成岩浆作用。马头滩组玄武岩层是自然铜矿化的重要矿源层。

The native copper mineralized basalt （NCMB） distributes north side along with the Aqikuduke deep fault, Jueluotage area, Eastern Tianshan, Xinjiang. As the basaltic magmatism erupted epoch hasn＇t been acknowledged yet, this study focuses on the geology and geochronology of the NCMB strata. The authors got the in-situ SHRIMP U-Pb age of basalts sampled from Heijianshan Cu- Fe mineralized occurrence （ middle study area） is 306. 2 ± 4. 0Ma; and the in-situ La-ICPMS U-Pb age of basalt sampled from Dongjianfeng native copper mineralized occurrence （ east study area） is 308. 9 ± 5.8Ma. These two confident and coherent ages can be used for confirming that the basalt bearing in Lower Matoutan Formation is the product of Late Carboniferous magmatism. After compared geochemical characters and genesis with the C2-P1 Cu-Ni sulfide mineralized mafic-ultramafic intrusions in Jueluotage area, It shows that the NCMB shared the same magmatic source with the younger one, and both NCMB and mafic-ultramafic intrusions were the products of the mafic magma, which were derived from the same vulnerable lithosphere mantle through some geodynamic heat abnormalities in Jueluotage area. The basaltic stratum is an important metal source of the Cu mineralized occurrence bearing in the Matoutan Formation.