投稿时间：2021-09-14
修订日期：2022-01-15
网络发布日期：2022-05-06
中文摘要:拔旺矿床是丹池成矿带南段五圩矿田内近年来探明的一个锡锌多金属矿床，其锌储量达中型，矿体呈切层脉状或似层状产于上石炭统—下二叠统南丹组第三、四段灰岩中。缺乏精确可靠的成矿年代学判据，是该矿床成因认识存在较大分歧的重要原因之一，严重制约了地质勘探工作的深入。文章应用LA-MC-ICP-MS原位U-Pb同位素测年手段，对拔旺矿床Ⅰ号矿体中锡石样品进行了研究，获得BW4、BW5两件样品的207Pb/206Pb-238U/206Pb谐和年龄分别为（93.1±4.8）Ma（n=24，MSWD=1.5）和（85.3±6.3）Ma（n=23，MSWD=2.1），206Pb/207Pb-238U/207Pb等时线年龄分别为（89.3±6.3）Ma（n=24，MSWD=0.86）和（82.9±5.3）Ma（n=23，MSWD=1.08）。结合矿床地质特征和前人发表的成岩-成矿年代学成果，表明拔旺矿床锡多金属成矿作用主要发生在晚白垩世早期，与燕山晚期岩浆热液活动关系密切。区域地质及年代学对比表明，右江盆地晚白垩世存在与新特提斯洋或古太平洋俯冲-后撤作用相关的大规模花岗质岩浆成岩-锡成矿事件。
Abstract:The Bawang deposit is a medium-size Sn-Zn polymetallic deposit discovered in the Wuxu ore-field in the southern section of the Nandan-Hechi metallogenic belt in recent years. The orebodies in the deposit occur in the limestone of the Third and Fourth Members of Nandan Formation of Upper Carboniferous-Lower Permian in the form of veins cross-cutting the strata or layer-like veins. Lacking of accurate and reliable geochronogical data, the genesis of this deposit is controversial greatly, which affects or has restriction to the further progress of the geological prospecting in the region.This paper has reported the in-situ LA-MC-ICP-MS U-Pb isotope dating of cassiterite from the No.1 orebody of Bawang deposit.The result showed that the 207Pb/206Pb-238U/206Pb concordia ages of cassiterite samples (BW4 and BW5) were（93.1 ±4.8）Ma (n=24, MSWD=1.5) and（85.3 ±6.3）Ma (n=23, MSWD=2.1) respectively, and the 206Pb /207Pb-238U /207Pb isochron ages of the corresponding cassiterite samples were（89.3±6.3）Ma (n=24, MSWD=0.86) and（82.9±5.3）Ma (n=23, MSWD=1.08). The geological characteristics, combined with previous results of petrogenesis-metallogeny geochronology, indicated that the mineralization of this deposit might mainly be in the early phase of Late Cretaceous, which relates closely to the Late Yanshanian magmatic hydrothermal events. Moreover, regional geology and geochronology further suggest that there were Late Cretaceous large-scale granitic magmatism and tin polymetallic mineralization events related to the subduction-retreat of the Neo-Tethys or Paleo Pacific Plate in the Youjiang Basin.
keywords:geochemistry cassiterite LA-MC-ICP-MS U-Pb age Bawang Sn-Zn polymetallic deposit Danchi-Hechi metallogenic belt Guangxi
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基金项目:国家重点研发计划项目(编号:2017YFC0602602、2016YFC0600207)和湖南省自然科学青年基金项目(编号:2019JJ50292)联合资助
引用文本：
梁恩云,曾广乾,刘庚寅,邹光均,黄远能.2022.广西五圩矿田拔旺锡锌多金属矿床成矿时代的限定——来自LA-MC-ICP-MS锡石U-Pb定年的证据[J].矿床地质,41(2):359~371LIANG EnYun,ZENG GuangQian,LIU GengYin,ZOU GuangJun,HUANG YuanNeng.2022.New precise timing constraint for Bawang Sn-Zn polymetallic deposit, Wuxu ore-field, Guangxi: Evidence from LA-MC-ICP-MS cassiterite U-Pb dating[J].Mineral Deposits41(2):359~371
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