青海沱沱河地区多才玛铅锌矿床成因:原位S和Pb同位素证据  

Ore genesis of the Duocaima Pb-Zn deposit,Tuotuohe area,Qinghai Province,China: Evidences from in situ S and Pb isotopes

作　　者：贾文彬[1,2,3] 李永胜 严光生[4] 吕志成[2,3] 于晓飞[2,3] JIA WenBin;LI YongSheng;YAN GuangSheng;Lu ZhiCheng;YU XiaoFei(School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;Development and Research Center, China Geological Survey, Beijing 100037, China;Technical Guidance Center for Mineral Resources Exploration, MLR, Beijing 100083, China;China Geological Survey, Beijing 100037, China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质调查局发展研究中心,北京100037 [3]国土资源部矿产勘查技术指导中心,北京100083 [4]中国地质调查局,北京100037

出　　处：《岩石学报》2018年第5期1285-1298,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划"973"项目(2015CB452606;2009CB421008);整装勘查区找矿预测与技术应用示范项目(DD20160050)联合资助

摘　　要：青海沱沱河地区多才玛铅锌矿床是西南三江特提斯北段新生代铅锌矿集区的典型矿床之一,本文首次应用飞秒激光剥蚀多接受器等离子体质谱法对多才玛铅锌矿床中金属硫化物的原位S和Pb同位素进行了测定。结果显示:黄铁矿、方铅矿和闪锌矿的原位S同位素的δ^(34)S_(V-CDT)值介于-26.34‰～4.24‰之间,均值-12.15‰(n=20),其中闪锌矿的δ^(34)S_(V-CDT)值介于-10.30‰～-3.52‰,均值-7.39‰(n=9);方铅矿的δ^(34)S_(V-CDT)值为-26.34‰～-11.74‰,均值-20.36‰(n=9);黄铁矿的δ^(34)S_(V-CDT)值分别为2.50‰,4.24‰。矿床δ^(34)S数据范围较宽,总体表现为富集负值硫的特征,说明有机质可能参与成矿。岩浆热液期发育的黄铁矿δ^(34)S值具有深源特征,沉积热液期发育的方铅矿和闪锌矿的δ^(34)S值表明成矿过程存在还原作用,指示盆地地层还原流体的混入,综上可认为多才玛铅锌矿床硫具有混合来源的特征。方铅矿原位Pb同位素结果为^(206)Pb/^(204)Pb=18.866～18.929,^(207)Pb/^(204)Pb=15.674～15.689,^(208)Pb/^(204)Pb=39.052～39.174。方铅矿与地层的Pb同位素组成一致,位于上地壳平均Pb演化线之上,具上地壳和地幔混合俯冲带铅的特征,表明其成矿物质的来源多样。结合矿床学、矿物学及同位素数据,本文认为多才玛铅锌矿床S元素主要来源于赋矿围岩,Pb金属元素主要来源于藏北钾质火山岩,侵入地层岩浆与盆地流体的混合是金属硫化物沉淀的重要机制。The Duocaima Pb-Zn deposit in Tuotuohe area,Qinghai Province is one of the typical deposits of the Cenozoic Pb-Zn metallogenic region in the northern Sanjiang-Tethys. In this paper,in-situ S and Pb isotope data of metallic sulfide in Duocaima deposit is first determine by fs LA-MC-ICPMS method. The results show that the δ^34 SV-CDTvalues of metal sulfides range from-26. 34‰ -4. 24‰,with an average of-12. 15‰,which the sphalerite,galena and pyrite has δ^34 SV-CDTvalues ranging from-10. 30‰ --3. 52‰（ mean =-7. 39‰,n = 9）,26. 34‰ --11. 74‰（ mean =-20. 36‰,n = 9） and 2. 50‰ to 4. 24‰,respectively. The widely ranged data suggests the enrichment of the negative sulfur,which may indicate the involvement of organic matter in the mineralization. The δ^34 SV-CDTvalue of pyrite developed in the magmatic hydrothermal stage has deep source features,however,theδ^34 SV-CDTvalue of galena and sphalerite developed during the depositional hydrothermal stage indicate that there are reduction in the mineralization process. Meanwhile,the incorporation of reducing fluid in the basin formation is necessary,so that the sulfur of Duocaima Pb-Zn deposit has the characteristics of mixed sources. In situ Pb isotopes of galena analyzed by fs LA-MC-ICPMS results are-（206） Pb/^204 Pb within 18. 866 - 18. 929（ average at 18. 897）,^207 Pb/^204 Pb within 15. 674 - 15. 689（ average at 15. 680）,^208 Pb/^204 Pb within 39. 052 - 39. 174（ average at 39. 120）. The Pb isotopic composition of galena and stratum is consistent with the average lead evolution line in the upper crust,with the characteristics of the upper crust and mantle mixed subduction zone lead,indicating that the ore-forming materials is diverse. Based on Mineral deposits,Mineralogy and isotope data,the S and Pb mainly derived from the surrounding rock,northern Tibetan volcanic rocks,respectively. The mechanism of sedimentation is the mixture of the intrusive stratum magma with the basin fluid.

关 键 词：三江特提斯 多才玛铅锌矿 原位S和Pb同位素 物质来源 矿床成因 

分 类 号：P618.42[天文地球—矿床学]