新疆东准噶尔拉伊克勒克斑岩铜(钼)矿床成岩成矿年龄、地球化学特征及其意义

Rock-forming and ore-forming ages and geochemistry of the Layikeleke porphyry Cu(Mo) deposit in East Junggar of Xinjiang and their geological significance

拉伊克勒克矿床是在第四系覆盖区新发现的隐伏斑岩铜(钼)矿床。采用LA-ICP-MS技术,对赋矿岩体英云闪长岩中的锆石和矿石中的辉钼矿分别进行锆石U-Pb同位素、Re-Os同位素和锆石Hf同位素测定及相应的研究。测得锆石U-Pb年龄为421.8±2.5Ma,辉钼矿Re-Os模式年龄为409.1±2.6Ma,表明拉伊克勒克斑岩铜(钼)矿床形成于晚志留世—早泥盆世,与琼河坝地区主要斑岩矿床大规模成矿时间一致。英云闪长岩属过铝质-钙碱性系列花岗岩类,岩体具有较高的铝钙含量,K_2O/Na_2O值普遍偏低,介于0.16~0.29之间;稀土元素配分曲线呈现右倾特征,稀土元素总量较低,轻稀土元素相对富集,负Eu异常不明显。在微量元素原始地幔标准化蛛网图上,高场强元素Th、Nb、Ta、P、Ti等相对亏损,大离子亲石元素Rb、Ba、U、K、Sr等相对富集。同时岩体具有高的正ε_(Hf)(t)值(10.98~15.01)和年轻的模式年龄(451~708Ma),暗示英云闪长岩体是大陆边缘弧环境下大洋板片熔融的产物,对进一步明确琼河坝地区斑岩型矿床的成矿环境和找矿方向具有重要意义。

The Layikeleke deposit is a concealed porphyry deposit newly discovered by comprehensive geoprehensive exploration in Quaternary coverage area. In this paper, U-Pb dating of LA-ICP-MS zircon and dating of Re-Os isotope and Hf isotopes were conducted to investigate the petrology, isotope geochemistry and the age of mineralized tonalities. U-Pb dating of LA-ICP-MS zir-con was conducted to investigate the age of the sample, which is 421.8±2.5Ma, and the Re-Os weighted mean age for five molybde-nite samples is 409.1±2.6Ma, suggesting that, from the Late Silurian to the Early Devonian, the Layikeleke porphyry copper （molyb-denum） deposit was formed here, similar to things of the porphyry in Qiongheba area. The tonalities are of peraluminous and calc-al-kaline series with high AI2O 3, CaO and low K 2O/Na 2O ratios. The pluton has low total REE content w i th relative enrichment o f LREE and obscure Eu negative anomaly. The primitive mantle normalized trace element patterns are characterized by the depletion of the HFSE （Th, Nb, Ta, P, Ti） and enrichment of the LILE （Rb, Ba, U, K, Sr）. The testing results of Hf isotope show that tonalitie plutons have high and positive snr（t） and younger model age,indicating that they were formed in a continental margin arc setting and were related to partial melting of subducted oceanic crust. The results obtained by the authors have important significance for deepen-ing the understanding of magmatic hydrothermal metallogenesis in this area.