西澳大利亚Forrestania绿岩带构造特征及Ni-Cu-Au成矿规律与找矿发现

Forrestania Greenstone Belt Structural Features and Ni-Cu-Au Metallogenic Pattern, Prospecting Findings in Western Australia

Forrestania绿岩带(FGB)位于西澳大利亚Yilgarn克拉通东南部,是澳大利亚重要的Ni-Cu-Au成矿带,属于澳大利亚一级Ni、Cu成矿远景区和三级Au成矿远景区。FGB地区的Ni-Cu矿床主要与带内的超镁铁质岩墙有关,属于富硫化物接触交代型成矿,主要以巨厚层状产出在基底长英质碎屑沉积岩和上覆的科马提岩之间。FGB地区金矿的形成主要与北北西向和北北东向构造内的石英脉有关,属于石英脉型金矿,是含镍硫化物富集(Ni)、多期后成矿构造运动、岩浆活动、变质作用和热液交代(Au)等多种地质活动长期复杂混合的产物。其形成过程主要分为以下几个阶段:早期Ni的沉积阶段、早期区域构造运动阶段、持续构造活动阶段、Ni矿体解体和Au元素富集阶段、Au矿脉的形成阶段。根据上述理论指导,笔者分析成矿特征后,选出Au成矿远景区,进行物化探综合勘查,圈定出异常区域,并在异常区内发现了较好的矿化线索。通过实践证明了理论推断的可信度。

The Forrestania greenstone belt （FGB） is situated in the southeast part of Yilgaru craton, Western Australia, a major Ni-Cu- Au metallogenic belt in Australia and Grade I Ni-Cu ore deposit prospect, Grade III Au ore deposit prospect. The Ni-Cu ore deposit in FGB is mainly related to uhramafic dikes, belongs to sulfide rich contact metasomatic ore deposit, shaped as very thick layer appeared between basement felsic clastic sedimentary rocks and overlying komatiite. The formation of gold ore deposit in FGB is mainly related to quartz veins within NNW and NNE structures, belongs to quartz vein type gold ore deposit, a result of long-term multiple geological activities complicated merging including nickel sulfide enrichment, multiple guest tectogenesis, magmatic activity, metamorphism and hydrothermal metasomatism （gold）. Its formation process can be divided into some main stages： early nickel deposit stage, early tectonic movement stage, durative tectonic activity stage, nickel ore disaggregation and gold enrichment stage, and gold vein formation stage. Under the above theory guidance, after ore-forming characteristic analysis, the authors have sorted out gold ore-forming prospects, car- ried out integrated geophysical and geochemical prospecting, and circled out anomalous areas, in which, better mineralization clues have been found. The reliability of the theory has been demonstrated through practices.