胶东金青顶金矿床成矿流体来源的黄铁矿微量元素及He-Ar同位素证据

Trace element and He-Ar isotopic evidence of pyrite for the source of ore-forming fluids in the Jinqingding gold deposit,eastern Shandong Province

金青顶金矿床是目前国内最大的石英单脉型金矿,其金储量超过50 t,规模为大型。对该矿床成矿流体性质和来源的研究十分必要。笔者通过Ⅱ号矿体主要载金矿物黄铁矿微量元素的研究发现,其Co/Ni为2.317～11.734(平均7.17),显示主要为热液成因;高场强元素(HFSE)特征显示,成矿早期以富F流体为主,主成矿期以富Cl流体为主;稀土配分模式显示成矿物质并不是直接来源于围岩昆嵛山二长花岗岩。对黄铁矿流体包裹体He、Ar同位素特征的研究表明,3He/4He、40Ar/36Ar分别为0.1～2.2 Ra(平均值0.60 Ra),462.7～1 507.5(平均值831),显示成矿流体主要源自地壳,并与深部幔源流体发生了不同程度的混合,且上升过程中有少量大气降水加入。

The Jinqingding gold deposit with identified reserves of more than 50t is currently the largest lode gold deposit in terms of single vein gold resources and is also a superlarge gold deposit located in the middle part of the Muping-Rushan gold belt in Jiaodong;nevertheless,the genetic type and source of ore-forming fluids in the gold deposit constitute a problem that needs urgent solution.A study of trace elements and REE compositions and features of gold-bearing pyrite from No.Ⅱ ore body of the Jinqingding gold deposit reveals that the pyrite displays hydrothermal characteristics with Co/Ni ratios from 2.317 to 11.734（7.17 on average）.The HFSE indicates that the ore-forming fluid originally belonged to the F-rich system and generally evolved into the Cl-rich system at the chief metallogenic stage,and the distribution patterns of REE shows that the source of matallogenic materials was not mainly from Mesozoic Kunyunshan monzonitic granite.According to an analysis of the characteristic parameters（3He/4He=0.1～2.2 Ra（0.60 Ra on average））,40Ar/36Ar =462.7～1507.5（831 on average）,it is considered that the source of matallogenic materials was mainly derived from the lower crust and was contaminated by meteoric water during the intrusion,and the mantle fluids were involved in the metallogenic process.