西天山察汉乌苏铁矿锆石U-Pb年代学及Lu-Hf同位素示踪

Zircon U-Pb Dating and Lu-Hf Isotopic Tracing in the Chahanwusu Iron Mine,Western Tianshan

察汉乌苏铁矿位于西天山阿吾拉勒晚古生代裂谷带东段,矿体赋存于下石炭统大哈拉军山组第三段火山岩中。通过对察汉乌苏铁矿矿体顶板围岩进行岩石学、岩石地球化学、同位素年代学分析来探讨火山岩形成的构造环境、成岩时代及成岩物质来源。地球化学分析表明,察汉乌苏铁矿矿体顶板围岩为钙碱性系列,构造环境为岛弧。通过锆石U-Pb测年,获得^(206)Pb/^(238)U加权平均年龄为(324.3±3.4)Ma,属早石炭世晚期。二阶段模式年龄tMD2变化于618.40~903.84 Ma,具古老地壳的源区属性,察汉乌苏铁矿成岩物质来源于亏损地幔并有基底物质的加入。

Chahanwusu iron mine is situated at the east of the late Paleozoic rift zone in the Awulale,Western Tianshan.The ore bodies occur in the volcanic rocks of the third member from the lower Carboniferous Dahalajunshan formation.Structure setting,diagenesis phase and mineral source of volcanic rocks in Chahanwusu iron mine were discussed in this paper through performing petrology,petrochemistry and isotopic geochronology on roof rocks.Geochemical analysis shows that the roof rocks are dominated by calc alkaline series developing in island arc.Weighted average age of ^(206)Pb/^(238)U derived from zircon U-Pb dating is 324.3±3.4 Ma,indicating that minerals were formed at late Early Carboniferous.Two-phase age(tMD2)varies from 618.40 Ma to 903.84 Ma,suggesting that minerals were mainly sourced from ancient crust.The lithogenous material of the Chahanwusu iron mine was derived from depleted mantle mixed with material from basement.