阿尔泰小土尔根铜矿区岩体LA-ICP-MS锆石U-Pb定年及地质意义

小土尔根是近年来阿尔泰诺尔特盆地发现的首例斑岩铜矿床,其成岩成矿年代学的研究可以对矿床模型构建、区域成矿规律的总结提供制约。矿区侵入岩发育,矿化受花岗闪长斑岩控制,少部分赋存在地层中。文章利用LA-ICP-MS锆石U-Pb测年法对矿区岩体进行了成岩年代学研究。含矿花岗闪长斑岩、黑云二长花岗岩和花岗斑岩中锆石的206Pb/238U年龄的加权平均值分别为(401.0±2.9)Ma、(398.1±2.2)Ma和(400.5±2.0)Ma,为早泥盆世同一岩浆侵入活动形成的不同侵入岩。侵入岩年龄结合凝灰岩年龄,将矿区地层划归早泥盆世诺尔特组。含矿花岗闪长斑岩锆石U-Pb年龄限定小土尔根斑岩铜矿床成矿时代略晚于401 Ma,即矿床形成于早泥盆世。

Zircon LA-ICP-MS U-Pb age of intrusion from Xiaotuergen copper deposit in Alta y, Xinjiang, and its geological significance

The Xiaotuergen deposit is the first porphyry copper deposit discovered in Nuoerte Basin of Altay in recent years. The study of its geochronology will help further set up metallogenic model and summarize regional ore-forming pattern. Intrusive rocks are widely developed in the Xiaotuergen ore district, the mineralization is controlled by the granodiorite porphyry, and a small number of ores are hosted in the strata. In this paper, the authors studied geochronology of intrusive rocks and mineralization using zircon LA-ICP-MS U-Pb method. The zircon ²⁰⁶Pb/²³⁸U-weighted average ages of ore-bearing granodiorite porphyry, biotite monzonite granite and granite porphyry are(401.0±2.9) Ma,(398.1±2.2) Ma and(400.5±2.0) Ma, respectively, suggesting that they were different intrusive rocks from the same magmatism in the Early Devonian. Combining the ages of intrusive rocks and the tuff, the authors hold that the strata of the Xiaotuergen ore district belong to Early Devonian Nuoerte Formation. The zircon U-Pb age of ore-bearing granodiorite porphyry suggests that the Xiaotuergen porphyry copper deposit was formed later than 401Ma, indicating that this deposit was formed in the Early Devonian.