新疆喀拉通克铜镍硫化物矿床成矿岩浆作用过程

Petrogenesis of Kalatongke Cu-Ni sulfide deposit in Xinjiang

喀拉通克铜镍硫化物矿床3个主要含矿镁铁质岩体的主量元素、微量元素和铂族元素组成分析及母岩浆组成估算结果表明：3个岩体中不同类型岩石的主要氧化物含量的变化具玄武质岩浆结晶分异的特征;在MgO含量为10%-15%区间,SiO2含量迅速增高;微量元素和稀土元素原始地幔标准化配分模式相似,具Nb和Ta亏损,K、Sr富集的特征。与1号和2号岩体相比,3号岩体中大离子亲石元素及轻稀土元素相对富集,（La/Yb）N介于6.8-9.2之间,δEu显示轻微负异常,在460m深度表现出Cu-Ni等成矿元素与SiO2含量同时剧变的特征,铂族元素配分模式与2号岩体相似。上述结果显示,3个岩体可能是同源岩浆不同期次的产物,原始岩浆为高镁玄武岩浆。成矿岩浆演化过程中经历的岩浆分离结晶作用和富硅地壳组分混染可能是成矿岩浆硫饱和及硫化物熔离的主要诱因。

Three main ore-bearing mafic intrusions in the Kalatongke Cu-Ni sulfide deposit of Xinjiang were investigated for major element, trace element and platinum group element （PGE） compositions. MgO content of the parent magma was estimated by Fo values of the olivine and chemical compositions of the whole rock. The results show that different types of rocks in the three intrusions show a systematical variation of major oxides with decreasing MgO contents, which is characteristic of basaltic magma crystallization, whereas SiO2 contents display rapid increase in the MgO contents range of 10%～15%. The three intrusions exhibit similar Primitive Mantle （PM） -normalized distribution patterns of trace elements and rare earth elements, and significant Nb and Ta-depletion. The No. 3 intrusion is enriched in large ion lithophile elements （LILEs） and LREEs with the （La/Yb）N ranging from 6.8 to 9.2, relative to the No. 1 and No. 2 intrusions, and shows a slight negative anomaly of δEu. The No. 3 intrusion shows a simultaneous content variation between SiO2 and Cu-Ni as well as some other ore-forming elements at the depth of about 460 m, and exhibits similar PM-normalized distribution patterns of PGE to the No.2 intrusion. It is inferred that the three mafic intrusions in the Kalatongke Cu-Ni sulfide deposit were probably formed by different stages of intrusions derived from the same source, and that their parent magma with MgO contents of about 9.3wt% underwent crystallization differentiation, crustal contamination and addition of a Si-rich oxide component. The main factors responsible for sulfur oversaturation and sulfide segregation might have been the addition of a Si-rich oxide component and the fractional crystallization.