| The Anba gold deposit is structurally located within the Yangshan gold belt inthe Mian-Lue suture zone of the West Qinling orogen, whose area is only3km2, butthe gold resource accounts for more than ninety percent of the total ore belt.It’s notonly the research focus of gold ore belt but also that of the West Qinlingmineralization. The following conclusions could be made after studying thecharacteristics of gold-bearing minerals from Anba gold deposit.1.Based on the field and the microscopic observations, the main structure ofgold-bearing pyrite and arsenopyrite, includs automorphic granular structure,allotriomorphic crystalloblastic texture, zone texture, radial texture, poikilitic texture,colloidal structure, framboidal texture, etc. Common ore styles include vein style,disseminated style, crumb style and fractured style, etc.2. According to the field and systematic petro-graphic mineralography research,the diagenetic mineralization phases are divided into sedimentary metamorphic stage,hydrothermal mineralization stage and post-mineralization. The hydrothermalmineralization stage is further divided into three stages: stage of pyrite-quartz;Arsenopyrite-pyrite-quartz stage; Stibnite-natural gold-quartz-calcite stage.Especiallyin arsenopyrite-pyrite-quartz phase is the most important gold production phase3. Through the stereo binocular observation statistics, more than90%pyrite forthe main metallogenic period has poly crystal, simplex crystal is relatively rare,appeared a variety of poly crystal types, reflects the pyrite deposit is mainly formed inthe temperature which is moderate and the sulfur fugacity is most suitable for highgrowth environment. But pyrite particle size change is bigger.It reflects that thetemperature gradient is bigger in the process of the formation.Pyrites belong to theproduct of rapid cooling.4. Research on the crystal structure of pyrite and arsenopyrite with X-raydiffraction and high-resolution transmission electron microscopy (Sem) suggests thattheir lattice structure is very full, and with no obvious dislocations and deformation,and the writer did not find the gold content zone. Gold-Arsenic solubility curve showed that Au exist in the form of Au+or Au3+, a lattice gold occurrence in pyriteand arsenopyrite5. Pyrite inclusion explosion temperature curve indicates the evolution ofore-forming fluid from high to low temperatures in the process of gold mineralization.The late stage ore-forming fluid of low temperature impacts on the early stagegold-bearing minerals, which caused many poles in pyrite inclusion temperature curve,reflecting the characteristics of the multi-stage hydrothermal activity6. EMPA research shows that gold-bearing minerals has the feature of Fe、Slosses, pyrite S/Fe wandering around1in spatial terms, which indicates that thedeposit was formed through sedimentation and was modified by hydrothermal fluids;Arsenopyrite is rich in S and poor in As, which are the characteristics of gold-bearingarsenopyrite.LA-ICP-MS study suggests that the phyllite provides Au、 Agmetallogenic ore-forming materials7. Trace and rare earth elements show that Anba gold deposit belongs to the lowtemperature ore deposit, which is consistent with the results of explosion temperature;And the metamorphic hydrothermal; high field strength elements (HFSE) losses, andLREE strong enriches, speculated that it is the result of the Cl rich ore-forming fluid.Pyrite and arsenopyrite show strong δEu negative anomaly and weak δCe negativeanomaly, indicating weak reducing metallogenic environment... |
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