藏东玉龙斑岩铜矿带磷灰石微量元素地球化学特征研究  

Investigation of the geochemical characteristics of apatite trace elements from the Yulong porphyry copper belt, Eastern Tibet

作　　者：张红[1] 梁华英[2] 赵燕[1] 凌明星[2] 孙卫东[3,4,5] 

机构地区：[1]西北大学地质学系,大陆动力学国家重点实验室,陕西西安710069 [2]中国科学院广州地球化学研究所,中国科学院矿物学与成矿学重点实验室,广东广州510640 [3]中国科学院海洋研究所深海中心,山东青岛266071 [4]青岛海洋科学与技术国家实验室,山东青岛266237 [5]中国科学院青藏高原地球科学卓越创新中心,北京100101

出　　处：《地球化学》2018年第1期14-32,共19页Geochimica

基　　金：国家自然青年科学基金(41402064);大陆动力学国家重点实验室自主研发课题和中国博士后基金(BSH13048)

摘　　要：藏东玉龙斑岩铜矿是我国最大的斑岩型铜矿带。该铜矿带分布有大量的花岗斑岩体,这些斑岩体具有相似的全岩地球化学特征,仅小部分成矿,多数并未发现有工业价值的金属矿床。副矿物磷灰石除具有和全岩高度一致的地球化学属性外,其微量元素含量及比值等对反映成矿过程中的流体演化和岩浆来源具有明显的指示意义。本文对玉龙铜矿带周缘的6个成矿和4个不成矿斑岩体磷灰石进行了主元素和微量元素地球化学特征研究,结果显示含矿斑岩磷灰石富Sr、Ba、Th、Pb和Zr,贫Y,同时显示出富稀土元素、轻重稀土分馏明显和具Ce正异常的地球化学特征。研究还显示,相对于不成矿斑岩,成矿斑岩磷灰石的Sr/Eu、Sr/Ce、Sr/Y和Th/U比值相对较低且变化范围相对较小,而Ce/Pb、Lu/Hf比值较高且变化范围较大,La/Yb比值及变化范围与不含矿斑岩接近。此外,成矿斑岩磷灰石高的Ce/Pb和Lu/Hf和低的Sr/Ce、Sr/Eu、Sr/Y和Th/U比值说明成矿斑岩形成于更高的氧逸度环境。The Yulong porphyry copper deposit, located in the eastern Tibetan Plateau, is the largest porphyry copper deposit belt in China, and has developed large amounts of granitic porphyries that show similar geochemical features. However, only a small portion of these granitic porphyries is metallogenie, because most of them are poor in ore content. The geochemical properties of the accessory mineral apatite are highly consistent with those of the entire rock. Thus, the trace elements and ratios are sensitive indicators for fluid evolution and magma sourcing during the metallogenic process. Herein, we present the major and trace element compositions of six samples of ore-bearing porphyries and four samples of barren porphyries around the Yulong copper deposit belt The results reveal that apatite grains in ore-bearing porphyries are characterized by enriched Sr, Ba, Th, Pb, Zr, and ∑REE, poor Y, and displayed highly fractionatcd heavy and light rare earth elements with slightly positive Ce anomalies. Compared to apatites from barren porphyries, the trace element ratios of apatites and their correlations show that most apatites from ore-bearing porphyries have relatively low ratios and narrow ranges of Sr/Eu, Sr/Ce,Sr/Y, and Th/U, and relatively high ratios and large variations of Ce/Pb and Lu/Hf, and approximative ratios and ranges of La/Yb. In addition, the relatively large variations of Ce/Pb and Lu/Hf and relatively low ratios of Sr/Ce, Sr/Eu, Sr/Y, and Th/U indicate that the ore-bearing porphyries were formed in an environment of high oxygen fugacity.

关 键 词：玉龙斑岩铜矿带 含矿斑岩 不含矿斑岩 磷灰石 微量元素 

分 类 号：P595[天文地球—地球化学]