Study On The Superficial Characteristics And Rock-forming Processes And Ore-forming Processes Of The Mauniuping Rare Earth Deposit In Western Sichuan

Maoniuping rare earth deposit is the most important REE production base in the Mianning-Decchang rare earth metallogenic belt,and the mineralization is closely related to the Alkaline-Carbonatite complex.Although ore deposit material source,ore-forming fluid evolution,diagenetic metallogenic epoch and metallogenic model have been studied,there are still many problems to be discussed.On the basis of previous studies,this study comprehensively studied the shallow characteristics of joints and vein occurrence,indicator minerals and alteration zoning,and carried out diagenetic chronology,whole rock major trace and Sr-Nd isotope test,in-situ micro element test of minerals and nano mineral observation,combined with the measured geophysical characteristics.This paper reveals the regional diagenetic and metallogenic tectonic background,the evolution process of ore-forming fluid,and the new migration form of rare earth elements,and establishes a unique diagenetic and metallogenic model,which provides a basis for inversion of the deep mineralization and further prospecting.Some conclusion and results are made as following:1.The Maoniuping deposit is controlled by multistage fault structure.First-order tectonic faults such as Anninghe fault control the output of the whole rare-earth metallogenic belt.Secondary faults such as Ha-Ha faults control the distribution of carbonate and alkaline rocks.Tertiary faults control the output of the ore body.The results of geophysical exploration show that there are three fault ore-controlling structures.The orebodies of the Maoniuping deposit show two main structural metallogenic styles in different structural parts of the shallow structural belt:vein ore bodies filled in brittle fault zones,showing near SN,NE and NWW directions,and breccia-vein ore bodies filled in shallow breccia tube,with unclear directions?2.The Cenozoic magmatic rocks in the Maoniuping deposite are composed of Carbonatite,Syenite,Basic dyke and Alkaline granite porphyry.Field investigation shows that the sequence of diagenesis and mineralization is:Syenite-Basic dike-Carbonatite-Vein-Alkaline granite porphyry.The diagenetic materials are all from the same EMI and EMII mixed enriched mantle source region,rock is caused by multiple partial melting.The U-Pb dating results of apatite in the pyroxene were 25.5�1.4Ma,and the weighted average age was 23.62�0.88 Ma.The basic dyke and syenite in the mining area constitute a set of bimodal intrusive rocks.The diagenetic tectonic setting is determined to be post collisional extension.The genesis of multiple partial melting is different from typical bimodal intrusive rocks,which may represent a new bimodal intrusive rock diagenetic model.3.The REE in the ore-forming fluid of Maoniuping deposit originated from the dissolution of magmatic carbonate rocks.The Natrification and Barite in the hydrothermal solution can promote the mineralization of calcite in carbonate rock.4.We have observed bastnaesite nanoparticles in nature for the first time,it can be a new situation of REE migration and precipitation.The growth of bastnaesite nanoparticles is random attachment and rearrangement,and the stress source may be tectonic stress.