摘要
夏日哈木是近年来在东昆仑成矿带探明的一个超大型岩浆型Ni-Co硫化物矿床,然而,随着矿区深部和外围找矿工作的不断深入,矿区内相继发现与岩浆硫化物型矿体特征明显不同的热液型Pb-Zn±Cu±Ag矿体,已探明的金属量达10万吨。为进一步揭示热液型矿体的成因及其产出背景,本文系统地开展了矿化蚀变特征和成矿年代学研究工作。新发现的热液型矿体主要呈似层状产于古元古代金水口群白沙河岩组的大理岩与片麻岩的层间构造带内,矿石矿物主要为方铅矿、闪锌矿和黄铜矿,脉石矿物为辉石、石榴子石、绿帘石、绿泥石、榍石、磷灰石、石英及方解石等。电子探针分析结果显示,辉石属于透辉石-钙铁辉石系列,矿物端员组分为DiHdJo;石榴子石属于钙铝榴石-锰铝榴石系列,矿物端员组分为GroAnd(Spe+Alm);绿帘石和绿泥石均有高Mn特征。综合以上矿物学研究工作,认为其属于夕卡岩型矿体。LA-ICP-MS微量元素分析显示,榍石稀土元素总量较低,稀土配分模式为右倾的轻稀土富集型,Th/U为0.23~1.97,平均值为0.94,与典型的热液榍石稀土元素组成相近。LA-ICP-MS微区原位U-Pb定年获得的热液榍石Pb校正后的Pb/U加权平均年龄为(413.3±3.6) Ma(n=23, MSWD=0.96);热液磷灰石Pb校正后的Pb/U加权平均年龄为(414±13) Ma(n=17, MSWD=1.03),代表夕卡岩型矿体成矿作用发生于早泥盆世,与岩浆型镍钴硫化物矿体的成矿时代在误差范围内基本一致。结合成矿地质条件,本文认为夏日哈木矿区发育具有时空联系的岩浆型与热液型两套成矿系统,区域伸展背景下幔源岩浆上涌导致地壳岩石发生部分熔融,形成浅部酸性岩浆房,熔体沿着伸展作用形成的构造薄弱带上升,分异产生岩浆流体,与古元古代金水口群大理岩发生接触交代作用,形成夕卡岩型Pb-Zn±Cu±Ag矿体。此外,本文为东昆仑成矿带泥盆纪夕卡岩型铅锌成矿�
The Xiarihamu deposit is a giant magmatic Ni-Co sulfide deposit discovered recently in the East Kunlun metallogenic belt. With the advancement of deep, peripheral ore prospecting, however, some distinct hydrothermal Pb-Zn-(Cu, Ag) orebodies—which are obviously different from the magmatic sulfide deposit—have been found at the Xiarihamu mining area, with nearly 100,000 tons of proven reserves. In order to further reveal their genesis and production background, a systematic study of the mineral alteration characteristics and metallogenic chronology of the newly discovered hydrothermal orebodies is carried out. The hydrothermal orebodies are mainly stratified in the marble/gneiss interlayer structural belt of the Paleoproterozoic Baishahe Formation of the Jinshuikou Group. The main metallic minerals are galena and sphalerite, followed by chalcopyrite, and the gangue minerals are pyroxene, garnet, epidote, chlorite, titanite, apatite, quartz, calcite, etc. According to EPMA analysis, the pyroxene is mainly composed of the diopside-hedenbergite series, with the end component mainly DiHdJo;the garnet belongs to the andradite-spessartine series, with the end component mainly GroAnd(Spe + Alm);and the epidote and chlorite in the skarn are both characterized by high Mn contents. Based on the above results it is considered that the hydrothermal orebodies are of skarn type. The trace element composition of the hydrothermal titanite from the skarn is similar to that of typical hydrothermal titanite according to LA-ICP-MS analysis. It has relatively low ΣREE, is enriched in LREE, with small LREE/HREE fractionation, and has a Th/U ratio of 0.23-1.97(averaging 0.94). By LA-ICP-MS in-situ U-Pb dating thePb/U weighted mean age(afterPb correction) of the hydrothermal titanite is(413.3 ± 3.6) Ma(n = 23, MSWD = 0.96), and for the hydrothermal apatite it is(414 ± 13) Ma(n = 17, MSWD = 1.03). These results indicate that mineralization of the skarn orebodies occurred in the Early Devonian, which is consistent with the metallogen
作者
陈欣
王辉
毛景文
于淼
乔建峰
王治安
CHEN Xin;WANG Hui;MAO Jingwen;YU Miao;QIAO Jianfeng;WANG Zhian(School of Earth Sciences and Resources,Chang’an University,Xi’an 710061,China;Ministry of Natural Resources Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,China;Qinghai No.5 Geological Mineral Exploration Institute,Xining 810003,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2023年第2期347-369,共23页
Earth Science Frontiers
基金
国家自然科学基金项目(41902074)
长安大学中央高校基本科研业务费专项资金项目(300102271202)。
