新疆西天山查岗诺尔铁矿床成矿时代——来自石榴子石Sm-Nd等时线年龄的信息  

Metallogenic epoch of Chagangnuoer iron deposit in western Tianshan Mountains,Xinjiang: Information from garnet Sm-Nd isochron age

作　　者：洪为[1] 张作衡[1] 李华芹 李凤鸣[3] 刘兴忠[4] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]武汉地质矿产研究所,湖北武汉430205 [3]新疆维吾尔自治区地质矿产勘查开发局,新疆乌鲁木齐830000 [4]新疆维吾尔自治区地质矿产勘查开发局第三地质大队,新疆库尔勒841000

出　　处：《矿床地质》2012年第5期1067-1074,共8页Mineral Deposits

基　　金：国家重点基础研究发展计划(2012CB416803);国家科技支撑计划(2011BAB06B02-05);地质矿产调查评价项目(1212011085060)联合资助

摘　　要：查岗诺尔铁矿床赋存在大哈拉军山组中-上部的安山质火山碎屑岩和火山熔岩内,主矿体FeⅠ周围发育大量以石榴子石为代表的高温热液蚀变,精确厘定高温热液蚀变的时间是确定成矿作用是与火山作用有关还是由岩体侵入作用所导致的关键。石榴子石与磁铁矿体的关系最为密切,其形成时间稍早或同时于磁铁矿。石榴子石Sm-Nd同位素测试结果表明,147Sm/144Nd值为0.2792~0.5481,143Nd/144Nd值为0.512950~0.513501,7个样品拟合的线性关系良好,获得的Sm-Nd等时线年龄为（316.8±6.7）Ma,指示了高温热液蚀变的时间,表明主要磁铁矿体的形成时代为早石炭世晚期,成矿作用及高温热液蚀变可能不是矿区内二叠纪岩体侵入携带的岩浆热液与大理岩发生矽卡岩化所导致,而可能是大哈拉军山组火山岩喷发后的岩浆期后热液与下伏大理岩发生接触交代反应引起的。The large-size Chagangnuoer iron deposit is hosted in die-upper part of Carboniferous Dahalajunshan Formation, andesite and andesitic volcaniclastic rocks in the mid- with widespread high hydrothermal alteration （repre- sented by garnet） distributed extensively around the uppermost ore body FeI. The precise formation age of high hydrothermal alteration is the key to judging whether iron metallogeny was related to volcanism or intrusive ac- tivity. Garnet, which had a closely genetic relationship with magnetite, was formed simultaneously with or slightly earlier than magnetite. Garnet Sm-Nd isotope analyses reveal that 1473m/144Nd values vary between 0. 2792 and 0. 5481 while 143Nd/144Nd ratios vary between 0.512950 and 0. 513501. Data of seven ples form a good linear fitting relationship, yielding the Sm-Nd isochron age of （316.8 ± 6.7） Ma, which repre- sents the formation epoch of high-temperature hydrothermal alteration. The result indicates that magnetite in- tergrown with garnet was formed at the late stage of Early Carboniferous period. Therefore, the iron metalloge- ny and high hydrothermal alteration might have resulted from the metasomatism between the post-magmatic hy- drothermal solution derived from eruption of Dahalajunshan Formation volcanic rocks and the underlying marble, rather than the skarnization caused by the reaction between magmatic hydrothermal solution from Permian intru- sion and marble in the ore district.

关 键 词：地球化学 成矿时代 石榴石Sm-Nd等时线年龄 查岗诺尔铁矿 西天山 新疆 

分 类 号：P618.31[天文地球—矿床学]