河南新县大银尖钼矿床成岩成矿作用地球化学及地质意义  

Geochemistry of Mineralization and Granitic Magmatism of Dayinjian Mo deposit,Xinxian County,Henan Province and Its Geological Significance

作　　者：杨梅珍[1,2] 曾键年[2] 李法岭[3] 潘思东[2] 陆建培[2] 任爱群[3] 

机构地区：[1]地质过程与矿产资源国家重点实验室(中国地质大学),湖北武汉430074 [2]中国地质大学,湖北武汉430074 [3]河南省地质矿产勘查开发局第三地质调查队,河南信阳464000

出　　处：《地球学报》2011年第3期279-292,共14页Acta Geoscientica Sinica

基　　金：地质过程与矿产资源国家重点实验室开放课题(编号:GPMR201014);河南省国土资源厅2007年度省"两权价款"地质科研计划项目(项目编号:2882)联合资助

摘　　要：大银尖钼矿床产于大别变质核杂岩带北缘,为典型的与花岗侵入岩有关的石英脉-矽卡岩型复合型的岩浆热液矿床。对大银尖钼矿床开展了成矿岩体地球化学以及岩体和矿石S,Pb多元同位素联合示踪研究。结果表明,产于矿床不同部位不同类型钼矿石金属硫化物的δ34S变化很小(5.26‰～6.30%),显示规模较大、硫同位素相对均一的岩浆热液体系特征。成矿岩体显示明显较高的δ34S(+16.86‰),可能反映岩浆强烈的H2S脱挥发分作用。成矿岩体和矿石的低放射性成因铅同位素组成特征(206Pb/204Pb)t:16.876～16.732,(207Pb/204Pb)t:15.206～15.321,(208Pb/204Pb)t:37.570～37.271,和成矿岩体极低的εNd(t)(-20.1)、高(87Sr/86Sr)i(0.7237)和极高的T2DM(2.4Ga),表明成岩成矿物质形成于中下地壳古老大别杂岩的熔融作用。根据大银尖成矿岩体低Sr丰度(<50×10-6)、高Yb(1.8×10-6)较强的Eu负异常(δEu<0.5)和较低的(La/Yb)N(7.8～9.6)海鸥式稀土配分模型和最新年代学资料综合分析认为,大银尖钼矿床成岩成矿作用与大别造山带伸展减薄后正常厚度陆壳的熔融作用密切相关,是大别造山带岩石圈拆沉减薄深部动力学过程的浅表响应。The Dayinjian Mo deposit located on the northern margin of the Dabie metamorphic core complex rock belt is a typical quartz vein-skarn Mo mineralization related to granitic magmatism. The authors studied petrogeochemistry of Dayinjian mineralized monzonite granite and Pb and S multielement isotopic trace of granite and ores. δ34S values of the sulfides range between 5.26 and 6.30 per mil, and vary insignificantly with the location and type in the ore deposit, the high δ34S values of granite suggest intense degassing of H2S of granitic melt. The low radioactivity-generated Pb isotopic composition of mineralized granite and ores （206Pb/204Pb）t： 16.876-16.732, （207Pb/204Pb）t： 15.206-15.321, （208Pb/204Pb）t： 37.570-37.271 and the high （87Sr/86Sr）i（0.7237）, very low εNd（t） （-20.1）and high T2DM（2.4 Ga） of the mineralized granite indicate that the granite and ore-forming materials were derived from partial melting of low-middle crust composed of old Dabie metamorphic complex rocks. According to geochemical characteristics of Dayinjian granite such as relatively low Sr （〈50×10^-6） and high Yb （〉1.8×10^-6） content, comparatively strong negative Eu anomaly （SEu〈0.5）, rather low （La/Yb）N （7.8-9.6）and sea gull-shaped REE distribution pattern, together with the newest geochronologic data, it can be concluded that the magmatism and mineralization of the Dayinjian Mo deposit were related to partial melting of the continental crust with normal thickness after extension and thinning of Dabie orogen, and seemed to be the surface response to the deep dynamic process of lithospheric delamination and thinning in the Dabie orogenic belt.

关 键 词：大别山 二长花岗岩 硫同位素 Sr—Nd—Pb同位素 岩石地球化学 大银尖钼矿床 

分 类 号：P618.65[天文地球—矿床学] P59[天文地球—地质学]