Study On The Occurrence State Of Associated Au In Jiama Coper-polymetallic Deposit, Tibet

Jiama copper-polymetallic deposit in Mozhugongka county of Tibet is located in the south-central Gangdise ore belt of Tibetan Plateau.And it is one of the most economic value of ultra-large type copper-polymetallic deposits. The deposit is not only huge in the scale, but also many main elements like copper and molybdenum reach the ultra-large type and except these two elements, other useful components such as gold, silver, lead and zinc all achieve a large scale. Based on the studying of gold'occurrence state, it will contribute to make good use of resources and improve the economic value of deposits, and it will also help us understand why Jiama copper polymetallic is different from other Gangdese Miocene porphyry copper deposits, riched in gold and other ore-forming elements.In the Gangdese metallogenic belt, it is very rare to see such huge orebody like Jiama deposite. It is huge, of complexe ore types and of rich ore-forming elements, and it belongs to porphyry– skarn deposite of high-grade ore body thickness. Moreover, at the margin of the main ore body, we have found independent gold of quartz diorite porphyry type, and therefore the study of the occurrence of gold in ore is of great significance.The discourse is on the basis of wide collecting predecessor's information, geological survey and drill core logging. And brings to success by ore samples collection, processing of the basic chemical analysis data of ore samples, identification of the polished thin section under the microscopy, electron probe microanalyser (pyrite, Copper, bornite, native gold-based) and scanning electron microscopy. Through those methods above, we have a preliminary grasp of the Jiama auriferous skarn-type ore geological features, the distribution and the precipitation process of gold's occurrences and migration. Finally, we achieved the following understanding:Through field investigation, profile measurement system, adit logging, rock and mineral identification, analysis and testing, it is ascertained to figure out that Jiama deposit is a porphyry - skarn copper-polymetallic ore. It has a high content of gold in ore, with an average grade of about 0.33g / t, the highest being 98.7g / t, and associated gold generally enriches in the copper-bearing ore of skarn. However, associated gold is in the condition of low content in hornstone orebody and porphyry orebody, which in general doesn't reach of the content of useful components associated. The gold rich ore is mainly located near the northeast ZK025 of the mining area, and vertically distributes in skarn copper-molybdenum ore body at an altitude of between 4280 ~ 4550 meters. Through a combination of analysis, gold and copper of the deposits is in the obvious positive correlation, and so is gold and sliver. While the correlation of gold and other elements is poor.The occurrence state of gold in orebody mainly has the following ways: firstly, Au appears in fracture of bornite in the form of native gold or it is partly wrapped in cracks of quartz; Secondly, Au presents among mineral particles of sphalerite and bornite in the way of native gold and electrum; Thirdly, Au produces at the edge of bornite and chalcopyrite in the way of native gold and electrum, forming structure of attachement gold ; Fourthly, Au is wrapped in polymetallic sulfide in the form of native gold and electrum, and chalcopyrite and bornite are the main carriers of inclusion gold. In addition, in the gangue minerals of the mining area, it is also found that there are copper gold and gold-bearing native silver which respectively form grain size of their own.The particle size of gold is relatively small, which belongs to microscopic gold.The size of most gold is among 0.06 ~ 0.0002 mm. In the process of beneficiation and metallurgy, the size of minerals needs grinding to 0.06mm below, which is good for the full recovery of gold. As the independent gold ore bodies mainly occur in pyrite and arsenopyrite, they should be dealt with differently in the process of beneficiation and metallurgy.