造山带铜镍硫化物矿床的岩浆起源:以东天山黄山南铜镍矿床为例

位于中亚造山带南缘的新疆东天山地区因其出露大量的二叠纪镁铁质-超镁铁质岩体并产出一系列铜镍硫化物矿床而成为近年来地质学界关注的焦点.选择新疆东天山地区黄山南含铜镍矿镁铁质-超镁铁质岩体为研究对象，对其开展了系统的岩石学、矿物学和地球化学研究，以探讨造山带铜镍硫化物矿床的岩浆起源与性质.黄山南岩体主要由方辉橄榄岩、二辉橄榄岩、橄榄二辉岩、（橄榄）辉长苏长岩和闪长岩组成.各岩相显示富集大离子亲石元素和轻稀土元素、强烈亏损Nb-Ta、Ti，类似于典型岛弧火山岩特征.黄山南镁铁质-超镁铁质岩具有较大变化范围的ε_Nd（t=282.5 Ma）值（-1.31~4.22）和（87Sr/86Sr）_i比值（0.703 2~0.706 9）以及高的（206Pb/204Pb）_i比值（17.67~18.90），暗示其来源于一个适度富集的亏损地幔并经历了5%~20%新生地壳物质混染和~5%上地壳物质混染.根据橄榄石最高Fo牌号（摩尔含量为86.6%）计算的黄山南母岩浆为苦橄质岩浆（MgO=12.11%、FeO_Total=11.14%、Ni=306×10-6），指示其岩浆源区应为软流圈和交代地幔楔共同熔融的源区.黄山南橄榄石低的Ca（< 725×10-6）和100×Mn/Fe（1.18~1.38）、高的Ni（1 451×10-6~2 813×10-6）和Mn/Zn（11.09~23.53），暗示黄山南母岩浆来源于含有辉石岩的不均一橄榄岩地幔源区.因此，我们推测黄山南岩体的原始岩浆来源于早期经历过俯冲流体改造的含有辉石岩的交代岩石圈地幔源区. 

Origin of Ore-Forming Magmas Associated with Ni-Cu Sulfide Deposits in Orogenic Belts:Case Study of Permian Huangshannan Magmatic Ni-Cu Sulfide Deposit,East Tianshan,NW China

The East Tianshan is situated along the southern margin of the Central Asian Orogenic Belt, and its outcrops of a series of important magmatic Ni-Cu sulfide deposits hosted by mafic-ultramafic intrusions are the focus of recent studies. In this study, it presents a systematic study of petrology, mineralogy and geochemistry of the Huangshannan sulfide ore-bearing mafic-ultramafic intrusion of the East Tianshan region, in order to further discuss the origin and nature of its parental magma. The Huangshannan intrusion consists of an ultramafic unit, which is composed of harzburgite, lherzolite and olivine websterite, and a mafic unit, which is composed of (olivine) gabbronorite and diorite. The rocks of the intrusion are characterized by enrichments of large ion lithophile elements, light rare earth elements and strong negative Nb-Ta, Ti anomalies, similar to that of typical arc volcanics. These rocks also have variable isotope compositionsε_Nd(t=282.5 Ma)=(-1.31)-4.22;(87Sr/86Sr)_i=0.703 2-0.706 9;(206Pb/204Pb)_i=17.67-18.90], indicating the parental magma was derived from a moderately enriched depleted mantle source and contaminated by 5%-20% juvenile arc crust and then by ~5% upper crustal materials. According to its highest Fo olivine, the estimated parental magma of the Huangshannan intrusion has 12.11% MgO, 11.14% FeO_Total and 306×10-6 Ni, indicating the picritic magma was generated from partial melting of both the asthenosphere and mantle wedge. The low Ca (< 725×10-6), 100×Mn/Fe (1.18-1.38) and high Ni (1 451×10-6-2 813×10-6), Mn/Zn (11.09-23.53) ratios of the Huangshannan olivines indicate the Huangshannan parental magma may be derived from pyroxenite in a modally enriched peridotite mantle source. Therefore, it speculates that the Huangshannan primary magmas were likely derived from a lithospheric pyroxenite mantle source as the result of slab-derived fluid modification during previous subduction.