个旧超大型锡多金属矿床成矿流体来源的氦同位素证据  

Origin of ore-forming fluids of Gejiu super-large Sn-polymetallic ore deposit: Evidence from helium isotopes

作　　者：张欢[1] 高振敏[1] 马德云[1] 陶琰[1] 凌荣祥[1] 

机构地区：[1]中国科学院矿床地球化学开放实验室

出　　处：《兰州大学学报（自然科学版）》2006年第3期20-24,共5页Journal of Lanzhou University(Natural Sciences)

基　　金：云南省-中国科学院科技合作资助项目(2000YK-05).

摘　　要：对取自个旧超大型锡多金属矿床层状矿体和接触带矿体的黄铁矿和磁黄铁矿样品进行流体包裹体的He同位素测定,其成矿流体中3He和4He的质量浓度分别为1．43×10-13-9．39×10-13 cm3／g和 0．64×10-6-3．25×10-6cm3／g,ρ3He／ρ4He=0．06-0．21 Ra.在考虑可导致矿体中成矿流体氦同位素质量浓度比值发生变化的各种因素的基础上,讨论了个旧锡多金属矿床成矿流体的成因．结果表明氦同位素地球化学资料反映出该矿床早期成矿流体中氦主源于地幔,应为海水与地幔流体混合形成．而后期大量富含地壳放射成因氦的燕山期花岗岩成矿流体对早期形成的矿源层或矿体进行叠加、改造．个旧超大型锡多金属矿床不是单纯的花岗岩成因矿床,也不是单纯的海底喷流成因矿床,而是同生沉积与岩浆热液叠加、改造的复合成因矿床．The ore genesis model for Gejiu tin polymetallic ore deposit has again become the focus since the submarine exhalative hydrothermal evidencewas found and sedex type was brought forward by Zhou Jian-ping. The major debate focuses on whether the ore bodies formed during the Yanshanian magmatic- hydrothermal event or they were the products of Trassic syn-sedimentary exhalative -hydrothermal event. This presents new helium isotope data from fluid inclusions of pyrite and magnetite from stratiform ore body and contact zone ore body, and their data show that the 3He and aHe ratios of fluid inclusions are respectively in the range of 1.43×10^-13 ～9.39×10^-13cm^3/g and 0.64×10^-6 ～3.25×10^-6 cm^3/g, and the value of 3He /aHe in the range of 0.78～6.22×10^-7. On the basis of combined consideration on the facts influencing the value of the isotope, we discussed the origin of ore-forming fluids of Gejiu. The result indicates that the value of He isotope that we measured suggests that mantle-derived fluids were involved in the ore-forming fluids of early stage. The ore-forming fluids were likely mixed of seawater with mantle-derivatives. In the mid-late Yanshanian period, the intense tectonic movement had resulted in the intrusion into the layers of the Gejiu group, and the magmatic hydrothermal solution with high temperature makes the mineralogenetic materials mobilized and superimposed to each ore bed. We think that the Gejiu tin deposit is the result of both hydrothermal sedimentary mineralization and magmatic hydrothermal mineralization, i.e., a hydrothermal sedimentary-magmatic hydrothermal mineralization superposed ore deposit.

关 键 词：HE同位素 地幔流体 超大型锡多金属矿床 个旧 

分 类 号：P59[天文地球—地球化学]