胶东地区招贤深部金矿床金和载金矿物化学成分及其地质意义

胶东地区-1000 m以下深部找矿的重大突破,使得探明储量已达5000多t,成为探讨深部金的赋存状态及成矿作用的天然实验室。招贤金矿为焦家成矿带近年深部找矿重大突破之一,矿体主要产于-1260 m以深的晚侏罗世二长花岗岩中,受控于焦家断裂。金属矿物主要为黄铁矿、黄铜矿和银金矿等,脉石矿物包括石英、绢云母、方解石、钾长石等。围岩蚀变以钾长石化、硅化、黄铁绢英岩化、碳酸盐化为主。金矿物以自然金和银金矿为主,呈裂隙金或包体金分布于黄铁矿中,少数不可见金呈晶隙金分布于黄铁矿等矿物中。其中,黄铁矿w(S)=52.227%～54.915%、w(Fe)=44.749%～47.134%,原子个数比S/Fe=1.99～2.11,化学式FeS_1.99～FeS_2.11;黄铜矿w(S)=34.282%～35.140%、w(Fe)=29.263%～30.268%,w(Cu)=33.130%～34.114%,化学式Cu_0.96FeS_2.01～Cu_1.01FeS_2.10,平均化学式为C...

Geological significances and geochemical compositions of gold and gold-bearing minerals from Zhaoxian deeply-seated gold deposit, Jiaodong area

The major breakthroughs in deep gold prospecting -1000 m below the surface in the Jiaodong area have made the proved reserves reach more than 5000 tons, which makes Jiaodong to be a natural laboratory to explore the gold occurrence and mineralization in the deep area. The Zhaoxian gold deposit is one of the major breakthroughs in deep prospecting area of the Jiaojia metallogenic belt recently. The orebodies mainly occur below -1260 m within the Late Jurassic monzogranite, and are controlled by the Jiaojia Fault. Ore minerals are mainly pyrite, chalcopyrite and electrum, and gangue minerals include K-feldspar, quartz, sericite and calcite. The alteration is mainly characterized by K-feldspathization, silicification, pyrite-sericitization and carbonatation. The gold occurs as native gold and electrum, which are mainly distributed in the pyrite as fissure gold or inclusion gold, and partly as invisible gold in the crystal interstices of pyrite. The sulfur contents of the pyrite range from 52.227% to 54.915%, and iron contents of the pyrite vary from 44.749% to 47.134%. The pyrites have atomic number ratios (S/Fe) of 1.99~2.11, and chemical formula of FeS_1.99~FeS_2.11. Meanwhile, the sulfur contents of the chalcopyrite range from 34.282% to 35.140%, iron contents of the chalcopyrite vary from 29.263% to 30.268%, and copper contents of the chalcopyrite range from 33.130% to 34.114%. The chalcopyrite has chemical formula of Cu _0.96FeS_2.01~Cu_1.01FeS_2.10, and the average chemical formula of Cu_0.99FeS_2.06. The Au contents in the gold minerals are 55.430%~95.473%, and the Ag contents vary from 2.908% to 44.961%. Moreover, the fineness of gold is high (538~951), with an increasing trend from shallow to deep part. In addition, the overall Co/Ni rations in pyrite are greater than 1 with an increasing trend from shallow to deep part, in comparison, the overall As contents are high with a decreasing trend. In conclusion, it is inferred that the Zhaoxian gold deposit was formed from magmatic hydrothermal fluid and has deep metallogenic potential.