湖南宝山铜多金属矿床流体包裹体特征及氢氧同位素地球化学的初步研究  

Preliminary studies on the fluid inclusions and H-O isotopic geochemistry of the Baoshan copper polymetallic deposit,Hunan Province

作　　者：轩一撒 袁顺达[2] 弥佳茹 赵盼捞 原垭斌[2] 张东亮[3] 

机构地区：[1]中科遥感科技集团有限公司,天津300000 [2]中国地质科学院矿产资源研究所,北京100037 [3]中南大学地球科学与信息物理学院,长沙410083

出　　处：《岩石学报》2017年第3期873-886,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41373047;41173052;41672095);中央级公益性科研院所基本业务费专项资金(K1204);地质调查项目(N1307)联合资助

摘　　要：宝山矿床处于NE向钦杭成矿带与EW向南岭成矿带的结合部位,是湘南地区最大的铜多金属矿床,成矿斑岩主要为花岗闪长斑岩,其中铜钼矿体主要分布于花岗质岩体与碳酸盐岩接触带的矽卡岩中,铅锌矿体则分布于断裂破碎带和石炭系的层间裂隙带中。本文以宝山铜多金属矿床为研究对象,在详细野外调查的基础上,系统开展了镜下观察、流体包裹体显微测温、激光拉曼分析以及H-O同位素分析,进而对宝山矿床的成矿流体演化进行了初步研究,获得了如下认识:(1)该矿床成矿演化过程可分为矽卡岩阶段、退化蚀变阶段、金属硫化物阶段及萤石-方解石脉阶段;(2)包裹体类型以富液相包裹体为主,成矿流体主要为H_2O-NaCl体系,含少量的CO_2,偶见含子晶包裹体;(3)矽卡岩阶段流体包裹体均一温度分布在430~>550℃,主要集中在550℃以上,盐度范围为13.4%~21.98%NaC leqv;退化蚀变阶段的均一温度范围为211.8~395℃,在260~320℃和360~395℃出现两个峰值,盐度范围为3.71%~19.53%NaCleqv,该阶段围压由静岩压力向静水压力转变;金属硫化物阶段均一温度分布于156.7~323.1℃,主要为190~240℃,盐度范围为3.71%~19.84%NaC leqv;萤石-方解石脉阶段中的包裹体均一温度为100~266.5℃,主要集中于145~180℃,盐度分布在0.71%~18.3%NaC leqv。宝山矿床成矿压力介于23.8~169.9Mpa之间,利用静岩压力-静水压力梯度可得宝山矿床成矿深度约为2.25~6.29km,主要为4~6km;(4)退化蚀变阶段流体的37‰~7.47‰之间,δD_(H_2O)值介于3. 64‰;金属硫化物阶段和萤石-方解石脉阶段的δ^(18)O_(H_2O)值为-70‰^-δ^(18)O_(H_2O)值介于0.33‰~5.28‰之间,表明有大量的大气降水混入。因此,成矿流体从早阶段到晚阶段,由岩浆热液演变为大气降水,流体混合作用可能是矿质沉淀的主要机制。宝山铜多金属矿床是早期高温中高盐度流体向低温低盐度流体演化过程中形成的�The Baoshan deposit is the largest Cu deposit in southern Hunan Province,which is located on the connection part of Qin-Hang NE-trending ore belt and Nanling EW-trending polymetallic metallogenic belt. The Cu-polymetallic mineralization is associated with granodiorite porphyry. Copper-molybdenum ore bodies occur as disseminated ore in skarn between granodiorite porphyry and carbonate rocks,while lead-zinc sulfide ores occur as veins in the fault damage zone and within intrastratal fracture belts of the Carboniferous strata. Based on detailed field investigation of the Baoshan copper polymetallic deposit,we have carried out systematic microscope observation,detailed micro-thermometric measurement of the fluid inclusions,Laser Raman spectroscopic and H-O isotopic analyses,and preliminarily discussed the fluid evolution of the deposit. The following conclusions are obtained：（1） The mineralization of the Baoshan deposit can be divided into four stages,i. e.,the skarn stage,retrograde stage,metal sulfides stage and fluorite-calcite stage;（2） The main types of fluid inclusions for Baoshan deposit are liquid-rich inclusions. The ore-forming fluid of Baoshan deposit belongs to H2O-Na Cl system. There is a little CO2 in the gas phase and a few NaCl daughter minerals in the fluid inclusions;（3） The homogenization temperatures of the fluid inclusions range from 430℃ to 550℃（ mainly above 550℃） and the salinities are between13. 4% and 21. 98% Na Cleqv in the skarn stage. The homogenization temperatures of the fluid inclusions range from 211. 8℃ to 395℃（mainly 260 - 320℃ and 360 - 395℃） and the salinities range from 3. 71% to 19. 53% Na Cleqv in the retrograde stage. The dramatic decrease in pressure from skarn stage to retrograde stage can be probably attributed in the transition from lithostatic pressure to hydrostatic pressure. In metal sulfides stage,the homogenization temperatures range from 156. 7℃ to 323. 1℃（ mainly 190 - 240℃）and the salinities range from 3. 71% to 19. 84%

关 键 词：流体包裹体 流体演化 铜多金属矿床 湖南宝山 

分 类 号：P597.2[天文地球—地球化学] P618.41[天文地球—地质学]