新疆东天山白石泉Cu-Ni硫化物矿床杂岩体的地球化学特征及其对矿床成因和构造背景的制约  

Geochemistry of Baishiquan Cu-Ni-bearing mafic-ultramafic complex in East Tianshan,Xinjiang:Constraints on ore genesis and tectonic setting

作　　者：李金祥[1] 秦克章[1] 徐兴旺[1] 孙赫[1] 程松林[2] 吴华[2] 莫新华[2] 

机构地区：[1]中国科学院矿产资源重点实验室中国科学院地质与地球物理研究所,北京100029 [2]新疆地质矿产勘查开发局地质六大队,新疆哈密839000

出　　处：《矿床地质》2007年第1期43-57,共15页Mineral Deposits

基　　金：中国科学院知识创新工程重要方向项目(KZCX2-YW-107;KZCX3-SW-137);国家科技攻关新疆305项目东天山东段铜镍矿专题(2003BA612A-06-07)的联合资助

摘　　要：新疆东天山白石泉Cu-Ni硫化物矿床位于中天山地块北缘，阿齐库都克-沙泉子断裂带南侧。杂岩体w（SiO2）为40％～59％，具有高Mg的特征和拉斑系列的演化趋势。MgO、MnO和FeO含量与SiO2呈负相关，Al2O3、TiO2、Na2O与SiO2呈正相关；Co、Ni、Cr与SiO2呈负相关。稀土元素球粒陨石标准化配分曲线为轻稀土富集型，LREE／HREE为2．5～7．84，（La/Yb）N为1．94～8．24，δEu为0．71～1．28。白石泉杂岩体稀土元素非常类似的配分型式，表明其来自同一源区，是同一原始岩浆分异演化的产物。杂岩体总体上富集大离子亲石元素（LILE：Rb、Ba、Sr）和活泼的不相容亲石元素（HILE：U），相对亏损高场强元素（HFSE：Nb、Ta、Zr、HI、Ti），表明地幔源区可能受到俯冲板片脱水的交代。硫化物饱和可能是由于大量含Fe、Mg矿物的结晶而造成的，地壳混染很弱。年代学和野外地质证据表明，白石泉杂岩体形成于晚古生代末碰撞造山后期的伸展构造环境下。晚古生代末碰撞造山挤压-伸展转变期是大规模成矿的有利时期。The Baishiquan Cu-Ni sulfide deposit is located in the northern part of the Central Tianshan Massif, south of the Aqikuduke-Shaquanzi fault of the East Tianshan Mountains. The complex has high Mg and assumes a tholeiitic trend, with SiO2 ranging from 41% to 59%. MgO, MnO, FeO, Co, Ni and Cr abundances exhibit a negative correlation with SiO2, whereas Al2O3, TiO2 and Na2O exhibit a positive correlation with SiO2. Total REE concentration, in the range from 20.59×10^-6 to 147.80×10^-6, increases from ultramafic to dioritic rocks. Chondrite-normalized REE patterns are LREE-rich, with LREE/HREE 2.5-7.84, （La/Yb）N 1.94- 8.24, and δEu 0.71-1.28. Similar REE patterns indicate that the magma sources of Baishiquan complex are the same, and it is the product of fractionation from the same primary magma. On the whole, all of the rocks are obviously enriched in large-ion lithophile elements （LILE： Rb, Ba, Sr） and mobile highly incompatible lithophile elements （HILE： U）, and relatively depleted in high field strength elements （HFS： Nb, Ta, Zr, Hf, Ti, P）. These geochemical characteristics suggest that the source mantle may have been modified by previous subduction dehydration. The primary magma of such mafic-ultramafic intrusions was probably mantle-derived high Mg tholeiitic magma. The Baishiquan Cu-Ni deposit belongs to small intrusion related ore deposit under orogenic setting, and the mechanism of mineralization is the ＂injection of sulfide-bearing magmas segregated at depth＂. Sulfide saturation resulted from the fractionation of significant Fe, Mg-bearing minerals, with the contamination by a small amount of crustal material. Geochronology and field evidence indicate that it was formed in an extensional tectonic setting after the collision. The transitional from compression to extension were the most important periods for large-scale mineralization in the post-coUisional regime during Late Carboniferous-Early Permian

关 键 词：地球化学 矿床成因 构造背景 白石泉 Cu—Ni矿床 东天山 

分 类 号：P618.41[天文地球—矿床学] P618.63[天文地球—地质学]