甘肃党河南山某金矿碲化物的发现及其成因探讨

摘要

Based on Electron Probe Micro-Analysis (EPMA),tellurides such as petzite,hessite, calaverite,hessite,tellurbimuth were found in a gold deposit in the Danghenanshan area of Gansu province for the first time.According to electron probe microscopic image observation,these telluride minerals are relatively small and have no intergrowth.However,there is a close rela-tionship between telluride minerals and pyrite.Telluride minerals are mainly included in pyrite and some exists among the grain of pyrite and quartz or the crack of pyrite.Based on the associa-tion of different telluride and pyrite,this study speculates that the mineral precipitation sequen-ceis is calaverite,petzite,hessite,tellurbimuth,and hessite.According to the mineral assem-blage characteristics and ore-forming temperature,the values of fTe2 and fS2 during ore forming are limited.The range of lgfTe2 of ore forming fluids is -15.2 to >-1 1.2 and the range of lg-fS2 is -1 6.7 to-14.4.The source of gold and tellurium significantly associates with adakitic pla-giogranite which is formed by the partially melting of subducted slab occurred during the Caledo-nian.Ore-forming elements are thus concentrated and brought to the near surface to form thetelluride-bearing gold deposit.%利用电子探针显微分析技术首次在甘肃党河南山某金矿中发现了碲金银矿、碲银矿、碲金矿、碲铅矿、碲铋矿等碲化物。通过电子探针显微图像观察,发现研究区碲化物均较为细小,赋存状态多以独立矿物形式存在,无连生、交生现象,但空间上与黄铁矿关系密切,多被黄铁矿包裹或产于黄铁矿、石英粒间和黄铁矿裂隙。根据不同碲化物与黄铁矿之间的共生组合关系,推测其形成顺序为碲金矿→碲金银矿→碲铅矿→碲铋矿→碲银矿。依据碲化物矿物组合特征及成矿温度,对其形成时 f Te2与 f S2进行了限定,lgf Te2范围为-15.2~>-11.2,lgf S2范围为-16.7~-14.4。并认为金矿中 Au、Te 来源与加里东期埃达克质斜长花岗岩体有较大联系,可能为俯冲板片部分熔融形成的埃达克质岩浆与地幔楔相互作用,将成矿元素富集后带入近地表形成含碲化物的金矿床。