新疆准噶尔东北缘玉依塔斯斑岩Cu-Au-Mo矿床成岩成矿时代及成矿潜力

Geochronology and metallogenic potential of Yuyitasi porphyry Cu-Au-Mo deposit in northeastern Junggar, Xinjiang, China

中文关键词:斑岩Cu-Au-Mo矿化  LA-ICP-MS锆石U-Pb定年  辉钼矿Re-Os定年  埃达克岩  新疆

keywords:porphyry Cu-Au-Mo mineralization  LA-ICP-MS zircon U-Pb dating  molybdenite Re-Os dating  adakite  Xinjiang

中文摘要:玉依塔斯是准噶尔东北缘新发现的一处中型斑岩型Cu-Au-Mo矿床，矿体产于早泥盆世石英闪长岩、闪长岩中。文章对玉依塔斯矿区主要侵入岩和地层开展了年代学研究，系统的LA-ICP-MS U-Pb锆石定年结果表明：凝灰岩、辉石闪长岩、含矿（石英）闪长岩、闪长岩、花岗岩测试结果分别为（426.2±1.6）Ma、（409.1±3.3）Ma、（396.8±3.0）Ma、（387.6±4.2）Ma、（388.0±10）Ma，显示出多阶段岩浆侵入的特征；含矿石英闪长岩的侵位时代与矿区辉钼矿的Re-Os年龄(（395.7±5.6）Ma)一致。含矿（石英）闪长岩的岩石地球化学特征表现出富集大离子亲石元素，亏损高场强元素的岛弧特征，表明玉依塔斯斑岩铜金钼矿的成矿构造背景为早-中泥盆世岛弧环境。中酸性侵入体成分的差异主要受控于源区部分熔融程度的差异，全岩Dy/Yb随着SiO₂增长发生显著的降低，指示了源区发生了角闪石分离结晶，合理解释了成矿岩浆具有的埃达克质特征。结合区域岩浆构造背景和成矿条件，文章认为玉依塔斯周边仍具有寻找大型斑岩Cu-Au-Mo的找矿潜力。

Abstract:The Yuyitasi is a newly discovered, medium-sized porphyry-type Cu-Au-Mo deposit located in the northeastern Junggar region, with orebodies hosted by Early Devonian quartz diorite and diorite. Geochronological study was conducted on the main intrusions and strata of the district. Systematic LA-ICP-MS U-Pb dating of zircons yields ages of (426.2 ± 1.6)Ma for tuff,(409.1 ± 3.3)Ma for pyroxene diorite,(396.8 ± 3.0)Ma for mineralized quartz diorite,(387.6±4.2)Ma for diorite, and (388.0±10)Ma for granite, indicating a multi-stage magmatic emplacement history. The emplacement age of the ore-bearing quartz diorite is consistent with the Re-Os age dating of molybdenite from the deposit((395.7±5.6)Ma). Geochemically, the mineralized quartz diorite is enriched in large-ion lithophile elements and depleted in high-field-strength elements, displaying a typical island-arc affinity and suggesting that the porphyry Cu-Au-Mo mineralization at Yuyitasi formed in an Early-Middle Devonian island-arc setting. Compositional variations among the intermediate-felsic intrusions are chiefly controlled by different degrees of partial melting in the source. Whole-rock Dy/Yb decreases markedly with increasing SiO₂, indicating fractional crystallization of amphibole at source area during magmatic evolution and providing a plausible explanation for the adakitic signature of the ore-forming magma. Taken together with the regional magmatic-tectonic framework and metallogenic conditions, these results suggest that the area surrounding the Yuyitasi still holds significant potential for discovering large porphyry Cu-Au-Mo deposits.