新疆霍什布拉克碱长花岗岩地球化学及成矿作用

GEOCHEMISTRY AND METALLOGENESIS OF HUOSHI BULAK ALKALI-FELDSPAR GRANITE, XINJIANG

霍什布拉克碱长花岗岩侵入二叠纪地层中 ,侵位时间 2 6 1 5± 2 7Ma .矿物组合以条纹长石、石英和斜长石为主 .化学成分上富硅、富碱、富REE ,A/NKC =0 87～ 1 0 4,LREE/HREE =2 41,并且具有强烈的铕负异常 .微量元素中Cu、Au、W、Sn、Pb明显富集 ,岩体属含锡多金属的含矿岩体 ,对锡多金属成矿有利 .在花岗质岩浆演化过程中 ,伴随有Sn、Mo、Fe、Nb、Ta、REE、Cu、Pb、Zn、Au矿化 。

The Huoshi Bulak alkali-feldspar granite, located in the south of Huoshi Bulak of Artux City, Xinjiang,intruded into Early Permian Bieliangjin group and Late Permian Kutiereke group. The isotopic age of the alkali-feldspar granite intrusion is 261.5±2.7 Ma. A detailed study on geology, petrology, mineralogy and geochemistry of the alkali-feldspar granite shows that the granite is composed mainly of perthite(70%-75%),quartz(23%-27%),plagioclase(1%-2%),biotite(<1%) and muscovite(<1%). The accessory minerals in these rocks include magnetite, anatase, zircon, rutile, titanite, tourmaline, fluorite etc. The chemical composition is characterized by rich SiO 2(73.20%-76.86%),total alkaline-rich(Na 2O+K 2O=7.91%-10.54%),high total REE(ΣREE=515.90×10 -6),σ=1.98-3.70,A/NKC=0.87-1.04,LREE/HREE=2.41, (La/Yb) N=6.34,(La/Sm) N=5.12,and intensive europium deletion (δEu=0.12). Of the trace elements, Huoshi Bulak alkali-feldspar granite is with high Li, Rb, Nb, Zr, Th, Ni and Sc, enriched in F and B,poor in Cr, Co, Ni, V, Sr and Ba. Metallogenetically, the granite is obviously rich in Cu, Au, W, Sn, Pb and Zn, showing characters of Sn-polymetallic rock body, which is favorable for Sn-polymetallic mineralization. The metallogenesis of Haoshi Bulak orefield, which is related to the magmatic activity, is produced by the magmatic differentiation. The magmatic activity provided ore-forming materials and hydrothermal fluid. The emplacement of the rock body formed skarn and hornfels in the surrounding rocks, accompanied by Sn,Mo, Fe, Nb, Ta, REE, Cu, Pb and Au mineralization that is regularly distributed in the contact belt and outside of the rock body.