柿竹园和香炉山W多金属矿床中硫化物微量元素特征:来自原位LA-ICP-MS分析

华南包括两个世界级的W矿带,分别是南岭和江南造山带W成矿带。柿竹园W多金属矿床位于南岭地区,香炉山W矿床位于江南造山带东北部。两个矽卡岩W矿床都发育硫化物成矿阶段。但硫化物和成矿元素组成存在显著的差异。前者由含Pb、Zn、Ag硫化物和黝铜矿、银黝铜矿、含Ag斜方辉铅铋矿和铁硫锡铜矿硫盐组成;后者主要为磁黄铁矿。柿竹园远接触带Pb-Zn-Ag矿脉中硫化物(闪锌矿、黄铜矿、方铅矿和磁黄铁矿)较富集B、Mn、Cr、Sb、Sn和Hg,香炉山似层状矽卡岩和硫化物-白钨矿矿体中硫化物(磁黄铁矿、黄铜矿和闪锌矿)较富集W、Se和Bi。两个矿床中黄铜矿、闪锌矿和方铅矿较富集Ag,黄铜矿、闪锌矿富集In和Sn,闪锌矿还富集Cd。两个矿床中的硫化物微量元素分析表明与矽卡岩W矿成矿相关的硫化物可载有多种微量元素。这些元素参与到硫化物中程度由多种因素控制。具体如下,硫化物中B含量高低与成矿相关岩体中B含量相关;在相对高温和还原条件下,硫化物中W含量较高;闪锌矿中Mn和Cd与Zn发生取代作用; Cr可以一定程度进入到硫化物中,并受成矿流体中Cr含量影响; Se与S发生了一定程度的取代进入硫化物,并受流体中它的含量控制; Bi在闪锌矿与黄铜矿易形成固溶体;硫化物中Sb含量受初始流体中它的含量影响,方铅矿中易包裹一定的辉锑矿(Sb_2S_3)或含Sb的硫盐矿物; Ag是否形成独立的矿物相和进入哪些硫化物中,取决于流体中Ag的初始含量和硫化物的沉淀次序;硫化物中Hg的含量受温度影响。

Comparison of trace elements in sulfides from the Shizhuyuan and Xianglushan W polymetallic deposits: Constrained by LA-ICP-MS analysis

South China contains two world-class W metallogenic belts:the Nanling Region and the Jiangnan Orogen.Two important W polymetallic deposits, the Shizhuyuan and Xianglushan deposits, are located in these two belts, respectively. Obvious differences in the sulfide assemblies and ore-forming elements of the two W deposits developed during the sulfide mineralization stages. The former contains distal Pb-Zn-Ag sulfide veins, also involving some Ag-, Sn-, and Bi-bearing sulfosalts; while the latter has layer-like sulfide-scheelite orebodies. The sulfides (sphalerite, chalcopyrite, galena, and pyrrhotite) from the Shizhuyuan distal Pb-Zn-Ag veins have obvious enrichments of B, Mn, Cr, Sb, Sn, and Hg. In contrast, sulfides (pyrrhotite, chalcopyrite, and sphalerite) within layer-like sulfide-scheelite and skarn W orebodies from the Xianglushan deposit have high concentrations of W, Se, and Bi. In both deposits, chalcopyrite, sphalerite, and galena are apt to carry Ag. Furthermore, chalcopyrite and sphalerite are In and Sn enriched, and major Cd is enriched in sphalerite. This study proves that sulfides from skarn W deposits can be enriched in some trace and minor elements with mining value, which participate in the sulfides depending on the initial element contents of hydrothermal fluids, substitutional reactions, or physico-chemical conditions. In detail, B contents within the sulfides are depended on them enriched by genetically related magma. Under relatively high temperatures and reducing conditions, W may participate in sulfides. The Zn of sphalerite is commonly substituted by Mn and Cd. The sulfides may capture the Cr, which is affected by the Cr contents in the hydrothermal fluids. When Se contents are high enough in fluids, it will be present as the replacement with S and participate in sulfides. Sphalerite and chalcopyrite may contain some Bi-bearing solid solution. The Sb-enriched ore-forming fluid is important to Sb participating in the sulfides, and galena is apt to involve inclusions of Sb₂S₃ and Sb-bearing sulfosalts. The Ag contents within the ore-forming fluids and precipitation sequences of sulfide minerals pay an important role on sulfides capturing Ag. Hg contents within sulfides are affected by temperatures.