东天山地区图拉尔根铜镍硫化物矿床成因及成矿过程

东天山地区图拉尔根大型铜镍硫化物岩浆矿床是近年找矿的重大突破。通过矿床中坑道穿脉的精细研究,表明 岩体的岩相由角闪橄榄岩、橄榄辉石岩、辉石岩与辉长岩组成,不同岩相的稀土元素配分曲线平行过渡变化,暗示各岩相是同源岩浆演化而成。岩相的分布及其接触关系、岩石地球化学及区域构造等指示图拉尔根矿床发生了后期变位。元素地球化学及同位素地球化学研究显示,岩体来自尖晶石稳定的亏损型地幔源区,亏损型地幔部分熔融与消减板片脱水物质混合导致图拉尔根岩体富集轻稀土元素而保持了MORB型同位素特征。岩浆上升过程中经历了微弱(<5%)的上地壳混染。铂族元素地球化学研究显示矿床中铂族含量较低,主要是因为地幔部分熔融较低(约16%),部分铂族元素残留在地幔中所致。

Genesis and metallogenic process of Tulargen large scale Cu-Ni sulfide deposit in eastern Tianshan area, Xinjiang

Tulargen large scale Cu-Ni sulfide deposit is an important exploring discovery in eastern Tianshan in recent years. Study on the sections in the Tulargen gallery, the intrusion is mainly composed of amphibole peridotite, olivine pyroxenites, pyroxenites and gabbro from upper part to lower part, the chondrite-normalized REE patterns from different lithofacies show parallel lines, which indicates different lithofaces have the same magma source and experiencing similar evolution process. Tulargen deposit should have experienced deflection of occurrence, which can be inferred from the distribution and contacting relationship of different lithofaces, litho-geochemistry and regional tectonics also support this idea. Element-geochemistry and Sr, Nd, Pb isotopes prove that the primary magma source of Tulargen intrusion is from spinel-stable depleted mantle. Tulargen intrusion hosting enrichment REE patterns and MORB-type isotope features is possibly because the magma from partial melting of depleted mantle mixes with dehydration of subduction plate. The magma forming Tulargen intrusion has experienced weak contamination (<5%) of upper crust. PGE geochemistry indicates low partial melting (<16%) of depleted mantle leading to low PGE concentrations in Tulargen deposit, some PGE are still left in the mantle.