广西丹池成矿带拔旺铁锌锡矿床方解石U-Pb定年和微区XRF面扫描  

Calcite U-Pb Dating and Micro-XRF Analysis Constraint on Formation of Bawang Zn-Fe-Sn Deposit in Danchi Metallogenic Belt, South China

作　　者：肖昌浩 韦昌山[1,2] 张宇 陈正乐[1,2,3] 乐兴文[5] 余树青[6] Xiao Changhao;Wei Changshan;Zhang Yu;Chen Zhengle;Le Xingwen;Yu Shuqing(Laboratory of Dynamic Diagenesis and Metallogenesis,Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China;Laboratory of Deep Earth Sciences and Technology of Ministry of National Resources,Beijing 100094,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;No.4 Geology Team of Guangxi Zhuang Autonomic Region,Nanning 530033,China;Mineral Resources Reserve Evaluation Center of Guangxi Autonomous Region,Nanning 530029,China)

机构地区：[1]中国地质科学院地质力学研究所动力成岩成矿实验室,北京100081 [2]自然资源部古地磁与古构造重建重点实验室,北京100081 [3]自然资源部深地科学与探测技术实验室,北京100094 [4]中国地质大学地球科学与资源学院,北京100083 [5]广西壮族自治区第四地质队,广西南宁530033 [6]广西壮族自治区矿产资源储量评审中心,广西南宁530029

出　　处：《地球科学》2024年第12期4335-4350,共16页Earth Science

基　　金：中国地质调查局项目(Nos.DD20240127,DD20230344,DD20190161,DD20160053);中国地质科学院基本科研业务费专项经费(No.DZLXJK202203)。

摘　　要：广西丹池成矿带是我国重要的有色金属产业基地,锡矿床成因及锡锌与锑成矿关系一直是地质学界的研究热点.由于锑矿床缺少精确的年代学数据,导致二者关系不清.拔旺锌铁锡矿床是近年发现产于丹池成矿带南段五圩矿田西部古溶洞中的新类型锡矿床.前人研究显示五圩矿田经历锌→锡→锑成矿演化,获得了锡成矿阶段锡石U-Pb年代为90 Ma左右.在前期矿田构造、矿物学和锡石U-Pb年代学研究基础上,开展了与辉锑矿共生阶段方解石U-Pb年代学和矿石微区X射线荧光光谱仪面扫描(μ-XRF mapping)研究.μ-XRF面扫描显示拔旺矿床经历了闪锌矿→石英-锡石→毒砂的矿物生成顺序,该特征与以往矿相学研究结果一致.上述结果表明,μ-XRF面扫描可以作为矿物生成顺序研究的快速分析手段之一.方解石U-Pb年代学研究显示,辉锑矿-方解石脉形成年龄62.8±1.1 Ma(MSWD=2.6;2σ).年代学、矿相学及μ-XRF面扫描研究证实拔旺矿床经历了早期锌锡成矿作用,晚期经历了锑成矿作用,二者相差~30 Ma.前人H-O同位素及闪锌矿微量元素研究显示,锌锡成矿流体以岩浆流体为主,锑成矿流体为盆地卤水.在此次年代学和前人研究基础上,总结了拔旺锌铁锡多金属矿床的成因,提出其可能为与深部隐伏岩体有关的远端热液矿床,隐伏岩体与围岩中成矿流体压力差可能是形成远端热液矿床的驱动力.五圩背斜西翼乃至丹池断裂-褶皱带西翼能干性差异显著的Si-Ca界面是形成古喀斯特充填型矿床有利部位之一.Danchi metallogenic belt is one of the most important nonferrous metal industry bases.It is to be the research focus owing to the large scale of Sn and Sb metal budget.The genesis of Sn-polymetallic mineralization during the Late Cretaceous and the relationship between Zn-Sn and Sb mineralization in the belt remain unclear.The Bawang deposit,a recently discovered paleokarst infilled type deposit,occurs in the west limb of the Wuxu anticline.Basing on the earlier study of structural analysis,mineralogy,and cassiterite U-Pb ages,in this study it presents element mapping of ores by micro-XRF(μ-XRF)analysis,and in situ U-Pb laser ablation-magnetic sectorfield-inductively coupled plasma mass spectrometer(LA-SF-ICP-MS)ages of calcite during the antimony mineralization stage.Micro-XRF analysis revealed that the sphalerite,cassiterite-quartz,and arsenopyrite mineralization have taken place in order in the Bawang deposit.Calcite U-Pb dating provides a lower intercept ages of 62.8±1.1 Ma(MSWD=2.6;2σ).Combined with previous ages of Zn-Sn mineralization,mineralogy,andμ-XRF analysis,the Zn-Sn mineralization is 30 Ma earlier than Sb mineralization.The pressure contrast existed between the fluid pressure at the site of ore deposition and the fluid pressure within the concealed intrusion is the key dynamics of fluid flow for the tin mineralization.

关 键 词：方解石U-Pb年龄 微区XRF分析 早古新世 拔旺Fe-Zn-Sn矿床 丹池成矿带 华南 矿床学 

分 类 号：P611.1[天文地球—矿床学]