The Maoping tungsten deposit is located in the Nanling W-Sn metallogenic belt in South China.Greisen and quartz vein types of mineralization developed in this deposit.Protolithionite occurs in the granite.Zinnwaldite ...The Maoping tungsten deposit is located in the Nanling W-Sn metallogenic belt in South China.Greisen and quartz vein types of mineralization developed in this deposit.Protolithionite occurs in the granite.Zinnwaldite is occurs mainly in greisen and wolframite-quartz veins whereas phengite is found in the underground quartz veinlets.In granite and greisen,protolithionite,and zinnwaldite are partly replaced by Li-phengite.LA-ICP-MS trace element analyses of micas and wolframite are employed to characterize the ore-forming source and evolution of ore forming fluids.Micas show compositional variation trend in vertical directions with a decrease of W,Sn,Nb,and Ta and an increase of MgO,V,Ni,and Co.Wolframite in greisen has higher Mo,Sn,Nb,Ta,and REEs than those in quartz veins.All wolframites show similar REE patterns with enrichment of HREE.Wolframites in greisen and quartz veins have negative Eu anomalies,while wolframites in quartz veinlet display positive Eu anomalies.Compositions of mica and wolframite from different mining levels of the Maoping deposit suggest that the ore-forming fluids are dominated by magmatic hydrothermal fluids in the deep with a slight addition of meteoric water in the shallow.Brittle fractureinduced depressurization and fluid mixing controlled the evolution of ore-forming fluids and possibly lead to the wolframite deposition.展开更多
热电离质谱法(Thermal ionization mass spectrometry,简称TIMS)是一种测量同位素丰度比的经典分析方法,在地质学和核工业领域得到广泛应用。热电离质谱法测铀同位素丰度比时一般采用三带结构,由于铀的第一电离能较高,需要较高的电离温...热电离质谱法(Thermal ionization mass spectrometry,简称TIMS)是一种测量同位素丰度比的经典分析方法,在地质学和核工业领域得到广泛应用。热电离质谱法测铀同位素丰度比时一般采用三带结构,由于铀的第一电离能较高,需要较高的电离温度,长时间测试蒸发出铀化合物或电离出的铀离子在灯丝支架上沉积,影响灯丝支架上悬浮高压与源电压间的绝缘电阻,降低两者之间的电压差,导致绝大部分离子因动能不足无法进入离子透镜,最终影响离子流的稳定性,引起测试时信号产生波动。针对热电离质谱仪灯丝支架铀沉积导致的灯丝支架绝缘失效问题,采用激光剥蚀电感耦合等离子体质谱法(Laser ablation inductively coupled plasma mass spectrometry,简称LA-ICP-MS)对灯丝支架铀沉积分布进行了分析,取得以下结果:建立了LA-ICP-MS原位表面分析技术,其最佳激光频率为10 Hz,能量密度为6 J·cm-2,束斑直径为60μm。校准曲线相关系数R2=0.9992,表明建立的方法线性关系良好。应用建立的方法,测定了灯丝支架表面铀沉积的分布特征。结果显示:灯丝支架表面铀沉积随着灯丝支架使用时间的增加,对应的绝缘电阻变小;并沿着支架向两端延伸,铀沉积量逐渐降低。铀沉积主要集中在电离带灯丝支架中心上端,且蒸发带上铀沉积量明显低于电离带。同时绝缘挡片可以有效降低陶瓷绝缘体上铀的沉积,因此可以通过增大绝缘挡片来提高灯丝支架的绝缘效果。展开更多
基金the National Key R&D Program of China(2016YFC0600207)Key Program of Natural Science Foundation of China(41830428)the"CAS Hundred Talents"Project to JF Gao.We are grateful to Dr.Juan Li at the School of Earth Sciences and Engineering,Nanjing University for taking BSE images.We also thank the staff of the Nanjing FocuMS Technology Co.Ltd.for their kind help in in situ LA-ICP-MS analysis.Finally,thanks for Helene Legros,Lili Chen,Guanglai Li,and Zeying Zhu's help and advice.
文摘The Maoping tungsten deposit is located in the Nanling W-Sn metallogenic belt in South China.Greisen and quartz vein types of mineralization developed in this deposit.Protolithionite occurs in the granite.Zinnwaldite is occurs mainly in greisen and wolframite-quartz veins whereas phengite is found in the underground quartz veinlets.In granite and greisen,protolithionite,and zinnwaldite are partly replaced by Li-phengite.LA-ICP-MS trace element analyses of micas and wolframite are employed to characterize the ore-forming source and evolution of ore forming fluids.Micas show compositional variation trend in vertical directions with a decrease of W,Sn,Nb,and Ta and an increase of MgO,V,Ni,and Co.Wolframite in greisen has higher Mo,Sn,Nb,Ta,and REEs than those in quartz veins.All wolframites show similar REE patterns with enrichment of HREE.Wolframites in greisen and quartz veins have negative Eu anomalies,while wolframites in quartz veinlet display positive Eu anomalies.Compositions of mica and wolframite from different mining levels of the Maoping deposit suggest that the ore-forming fluids are dominated by magmatic hydrothermal fluids in the deep with a slight addition of meteoric water in the shallow.Brittle fractureinduced depressurization and fluid mixing controlled the evolution of ore-forming fluids and possibly lead to the wolframite deposition.
