摘要
西准达尔布特—包古图地区出露两类中酸性侵入岩,一类为海西晚期(<270Ma)花岗岩基,另一类为海西中晚期(330～320Ma)中酸性小斑岩体,包古图斑岩铜矿赋存于后者。岩石主量和微量元素分析表明,包古图含矿小斑岩基本满足埃达克岩的条件,即SiO2>56%,Al2O3>15%,MgO<3%,贫Y和Yb(Y<18×10-6,Yb<1.9×10-6),高Sr(>400×10-6),HREE明显亏损,其Nd和Sr同位素组成与洋中脊玄武岩(MORB)组成接近。但部分样品MgO含量较高(>3%),轻稀土元素丰度较低,偏离埃达克岩的组成范围。根据斑岩的地球化学组成并结合区域地质特征,笔者认为包古图含矿斑岩形成于与洋内俯冲有关的岛弧环境,但洋壳板片的初始熔体在上升过程中受到了地幔橄榄岩的不均匀混染。
In the Darbute-Baogutu area, western Junggar, there outcrop two types of intermediate-acid intrusive rocks ：late Hercynian （〈270 Ma） granite batholiths and late-mid Hercynian （330 - 320 Ma） intermediate-acid small porphyry bodies. The Baogutu porphyry copper deposit is hosted in the latter. The Major element and trace element analysis of the rocks indicate that the Baogutu copper-bearing small porphyry in the mine meets the conditions of adakitic rocks, i.e. ：SiO2〉56%, Al2O3〉15%, MgO〈3%, Y〈18×10^-6, Yb〈 1.9×10^-6 and Sr〉400×10^-6 and pronounced HREE depletion. Its Nd and Sr isotopic compositions are close to that of MORB. However, the composition of some samples, which is characterized by relatively high MgO contents （〉3%） and a relatively low LREE abundance）, is deviated from the compositional range of adakitic rocks. According to the geochemical composition of porphyries, combined with the regional geological characteristics, the authors think that the Baogutu copper-bearing porphyry originated in an island-arc environment related to intraoceanic subduction but that the initial melt of the oceanic crustal slab was subjected to inhomogeneous contamination with mantle peridotite during its rise.
出处
《中国地质》
CAS
CSCD
2006年第3期626-631,共6页
Geology in China
基金
国家重点基础研究发展规划项目(2001CB409805)
国家自然科学基金项目(40473028)
关键词
斑岩铜矿
埃达克岩
晚古生代岛弧
新疆西准
adakitic rock
porphyry copper deposit
Late Paleozoic island arc
western Junggar
Xinjiang
