西天山莱历斯高尔一带铜(钼)矿成矿斑岩体矿物学特征及其成岩成矿意义

Mineralogy of ore-bearing porphyries in Lailisigao'er area of the West Tianshan Mountain and its implications for petrogenesis and mineralization

莱历斯高尔一带斑岩体位于伊犁板块北部的别珍套-科古琴晚古生代岛弧中段。莱历斯高尔一带斑岩型矿床主要分布有直线距离不足1km的莱历斯高尔钼矿和3571铜矿,与成矿作用关系密切的斑岩体的岩性为二长闪长斑岩和花岗闪长斑岩。通过较系统的矿物学研究发现,本区岩石类型属于造山带钙碱性花岗岩类,成岩物质主要来源于地壳,并且有少量地幔物质加入。斑岩体形成于相对高温(740～790℃)、高fO2(10-9～10-11Pa)的环境。3571铜矿斑岩体压力估算范围为140～230MPa,而莱历斯高尔钼矿斑岩体压力估算范围为300～430MPa,显示3571铜矿斑岩体较莱历斯高尔钼矿斑岩体的侵位深度要浅。结合本区的地质背景和岩石地球化学特征等研究成果,推测3571铜矿斑岩体相当于莱历斯高尔钼矿的浅成相,其深部可能存在类似于莱历斯高尔的钼矿,具有钼矿的找矿前景。

The West Tianshan area is located in the northern part of the Yili plate between the Junggar plate and the Tarim plate, and is an orogenic belt between the Junggar plate and the Yili basin. Porphyry deposits are mainly developed in Lailisigao＇ er area lying in the central part of the Late Paleozoic Biezhentao-kokirqin arc island. The straight distance between the 3571 Cu deposit and the Lailisigao＇ er Mo deposit is less than 1 kin. The ore-bearing porphyries are predominated by monzodioritic porphyry and granodioritic porphyry. Systematic petrological and mineralogical investigation indicates that the rocks are orogenic calc-alkalic granites formed under the conditions of anhydrous high-temperature （740-790℃ ） and high oxygen fugacity （10^-9 - 10^-11 Pa）. Porphyries in the 3571 copper deposit were emplaced shallower than those in the Lailisigao＇ er ore deposit, as evidenced by the estimation of the pressure （the former being 140 -230 MPa and the latter 300 - 430 MPa）. In addition, they were derived chiefly from the crust contaminated by mantle materials. Based on geological setting and geochemical characteristics, it is inferred that the dykes outcropped in the 3571 copper deposit may correspond to the upper part of the dykes from the Lailisigao＇ er ore deposit, and therefore the area beneath the 3571 ore district should be regarded as a potential target for the prospecting of porphyry Mo deposit.