摘要
新疆东天山地区发育一系列与铜镍硫化物矿化和与钒钛磁铁矿矿化相关的过渡型镁铁—超镁铁质岩体,初步统计这些岩体有香山西岩体、牛毛泉岩体、土墩南(二红洼)岩体和红梁子岩体。本文主要通过锆石U-Pb法对牛毛泉岩体和红梁子岩体进行定年工作,并利用角闪石40Ar/39Ar热年代学方法对牛毛泉岩体和二红洼岩体的侵位年龄进行约束。测试结果表明,牛毛泉岩体年龄为289.7±2.4Ma,红梁子岩体年龄为309.7±1.5Ma,二红洼岩体年龄为274.2±5.7Ma。此外,本文还对这类杂岩体进行了主量、微量元素和同位素测试工作。结果表明,岩石系列既有碱性也有钙碱性和拉斑系列,m/f比值0.44～4.76,属铁质基性岩;MgO、FeO、CaO、Na2O+K2O、TiO2、SiO2成分及相关岩石化学参数,均表现具有含钒钛磁铁矿化和含铜镍矿化岩石的双重和过渡特征;岩石的稀土分馏,曲线的倾斜程度变化较大,轻、重稀土比值(∑LREE/∑HREE)为1.39～5.47,(La/Yb)N比值变化较大,在0.79～4.65之间,铕异常变化较大(0.85～2.33),经原始地幔标准化大离子亲石元素和高场强元素的富集程度相差不大,总体上样品中普遍具有Th、Ta、Nb、Ti等亏损,Sr、Ba富集趋势;εNd(t)值绝大多数为正值,[n(87Sr)/n(86Sr)]i值普遍较低,显示这类岩体源区为亏损岩石圈地幔,并经历较强的分异作用。
A series of transitional mafic—ultramafic rocks related to both copper—nickel sulfide and vanadium—titanium magnetite occurred in the Eastern Tianshan Mountains, such as the Xiangshanxi, the Niumaoquan, Tudunnan （Er’hongwa） and Hongliangzi mafic—ultramafic rocks. With zircon U-Pb and amphibole 40Ar/39Ar thermochronology method, the ages of the Niumaoquan, the Er’hongwa and the Hongliangzi mafic—ultramafic rocks can be obtained. The results show that the Niumaoquan mafic—ultramafic rock emplaced at the age of 289.7±2.4 Ma, Er’hongwa rock at 274.2±5.7 Ma and Hongliangzi rock at 309.7±1.5 Ma. In addition, the major elements, trace elements, REE and Sr—Nd isotopic compositons of these mafic—ultramafic rocks are analysed. The results show that these rocks are composed of both alkaline series, calc-alkaline series and tholeiitic series rocks. The ratios of magnesium and iron （m/f） is from 0.44 to 4.76, which belongs to ferro-basic rocks series. The compositions and parameters of MgO, FeO, CaO, （Na2O＋K2O）, TiO2 and SiO2 show that these mafic—ultramafic rocks have features of both related to V—Ti—magnitite deposit and Cu—Ni sulphide deposit or have transitional features of them. REE fractionation and model curve changed clearly. LREE/ HREE ranges from 1.39 to 5.47, and [n（La）/n（Yb）]N ranges from 0.79 to 4.65 and they varied clearly. In addition, δEu anomaly changes from 0.85 to 2.33. Enrichment between primitive mantle-normalized large-ion lithophile elements and high field strength elements is not obvious, but overall samples generally have depleted with Th, Ta, Nb, Ti and enriched with Sr and Ba. The vast majority of the value of εNd（t） is positive, and [n（87Sr）/n（86Sr）]i values are generally lower, which indicated that this type of rock source area is the depleted lithospheric mantle, and experienced a strong differentiation.
出处
《地质论评》
CAS
CSCD
北大核心
2012年第6期1145-1160,共16页
Geological Review
基金
国家重点基础研究发展规划项目(编号2007CB411304
2001CB409806)
国家自然科学基金资助项目(编号40672061)
全国危机矿山项目(编号200699105)的成果
