江西焦里夕卡岩银铅锌钨矿床的矿化夕卡岩分带和流体演化

Skarn Mineralization Zonation and Fluid Evolution in the Jiaoli Deposit, Jiangxi Province

江西上犹焦里夕卡岩银多金属矿床产于燕山期花岗闪长岩和上寒武统变质砂岩、粉砂岩和结晶灰岩的外接触带。矿床的矿化夕卡岩分带十分明显,自岩体接触带向东和向上,夕卡岩类型、矿物成分和矿石类型依次发生变化,由含白钨矿(伴有银铅锌矿)的钙夕卡岩演变为含银铅锌(钨)矿的锰质夕卡岩。前者主要由钙铝榴石、钙铁辉石、透辉石、硅灰石、萤石和白钨矿等组成;后者则由锰质钙铝榴石、锰铝榴石、锰质钙铁辉石、锰质透辉石、钙蔷薇辉石、锰质符山石和锰质阳起石组成,伴有闪锌矿、方铅矿、磁黄铁矿、辉银矿、自然银和少量白钨矿。流体包裹体研究表明,自岩体接触带往围岩方向,流体的温度呈现逐渐降低、盐度逐渐减小、密度值逐渐变高的演化趋势。其中,含钨钙夕卡岩的均一温度峰值区为420～340℃,盐度(NaCl_(eq))12.7％～8％;含银铅锌锰质夕卡岩的温度峰值区为360～320℃,盐度(NaCl_(eq))11.7％～4.5％;而晚期含矿退化热液阶段石英、萤石等交代矿物的均一温度范围较宽(380～160℃),反映了夕卡岩期后酸性淋滤阶段金属硫化物形成温度。矿化夕卡岩分带是银多金属矿床的重要找矿标志。

The Jiaoli Ag-Pb-Zn-W skarn deposit is located in southern Jiangxi Province, China. The orebodies occur in the exocontact zone between a Yanshanian (171. 6-173. 3 Ma) granodiorite and Upper Cambrian metasandstone and crystalline limestone. Skarn mineralization zoning in the deposit is very pronounced. From the intrusive contract zone to country wall rocks, two ore-bearing skarn zones may be distinguished: proximal scheelite-bearing calcic skarn zone and Ag-Pb-Zn-bearing manganoan skarn zone. The W-bearing calcic skarn is composed of grossular, andradite, diopside , wollastonite, scheelite, and f luorite; while the Ag-Pb-Zn-bearing manganoan skarn consists mainly of manganoan grossular, spessartine, manganoan actinolite, and manganoan vesuvianite, associated with sphalerite, galena, pyrrhotite, argentite, silver, and minor scheelite. Study of the fluid inclusions suggests that ore-bearing fluids flowed from the deep contract zone of the intrusion in the west to the shallow depth in the east. With decreasing temperatures and salinities, the peak values of homogenization temperatures in the W-bearing calcic skarn are 420-340℃. Their salinities range from 12. 7% - 8 % (NaCleq ). In the Ag-Pb-Zn-bearing manganoan skarn, the peak values of homogenization temperatures are 360°-320℃ with salinities being 11. 7%-4. 5% (NaCleq). While for late ore-bearing retrograde hydrothermal metasomatic products, fluolite and quartz, their homogenization temperatures range from 380 to 180℃.