贵州泥堡卡林型金矿断控型矿体的地层和岩性条件研究

Research on Lithology and Stratigraphy Conditions of Fault-controlled Orebody in Nibao Carlin-type Gold Deposit, Guizhou Province

贵州泥堡卡林型金矿是黔西南碳酸盐岩台地相区首次发现的大型断控型矿床,其主要控制因素除断层之外,地层和岩性也是不可忽视的重要因素。岩石学研究表明:断控型矿体的主要赋矿围岩是含钙质(沉)火山角砾凝灰岩,而不是前人认为的"砾屑砂岩";具有块状构造的(沉)火山角砾凝灰岩在构造作用下裂隙发育,岩石孔隙度明显增高,热液作用下易形成厚度大且品位高的断控型金矿体。同时,根据含矿岩石主要含火山成分的特点,认为这套地层应该划归为二叠系峨眉山玄武岩组,而不是前人划分的龙潭组。含钙质(沉)火山角砾凝灰岩和二叠系峨眉山玄武岩组分别是形成断控型矿体的重要岩性和地层条件。提出在碳酸盐岩相区寻找类似泥堡金矿的断控型矿体时,除了考虑断层外,还要考虑是否有合适的地层和有利的赋矿岩性。

Nibao gold deposit is a large carlin-type fault-controlled gold deposit first discovered in a carbonate platform in southwestern Guizhou Province of China,where stratabound gold deposit is the predominant type,in addition to the fault,the formation and lithology are also important factors that can not be ignored.The study of petrology shows that the fault-controlled orebodies are hosted by calcareous（sedimentary） volcanic breccia tuffs rather than＂gravel sandstones＂considered by predecessors. These massive（sedimentary） volcanic breccia tuffs tend to be rich in fractures and increase porosity under the action of tectonic,and can easily form faultcontrolled gold orebodies with large thickness and high grade under the action of hydrothermal fluid.Meanwhile,Longtan Formation divided by predecessors should be reclassified as Permian Emeishan Basalt Formation based on the characteristics of main volcanic compositions of ore-bearing rocks,rather than Longtan Formation divided by predecessors. The calcareous（sedimentary） volcanic breccia tuff and Permian Emeishan Basalt Formation are the significant lithologic and stratigraphic factors to form the fault-controlled gold orebodies.We propose that besides the faults,the lithology and stratigraphy should be paid more attention when the exploration will be undertaken on fault-controlled deposits,similar like Nibao gold deposit on carbonate platform in the future.