Font Size: a A A

Study On Geological And Geochemical Characteristics And Genesis Of Dongguashan Copper (Gold) Deposit, Tongling,Anhui Province

Posted on:2015-06-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z F LiuFull Text:PDF
GTID:1220330434451689Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
Abstract:The sources of ore-forming materials and the genesis of Dongguashan copper (gold) deposit is a very controversial and attractive scientific problem. In this thesis, the detailed field observation and investigation and systematic geochemical analyses are carried out, based on the summary of predecessors’works. The outcomes and innovative points include:(1) The identifying of metallizing phases of this deposit were divided based on orebodies (veins) interspersed relations, mineral association relations and metasomatic relations between mineral. The results indicate that there were porphyry-type and skarn-type mineralization in Dongguashan mineral district. And the porphyry-type mineralization period can be divided into magnetite stage and quartz-sulfide stage, Skarn period can be divided into skarn stage, retrograde alteration mineralization stage and quartz-carbonate stage.(2) The geological and geochemical characteristics of rockbody were detailed analyzed and Magma source, the diagenesis environment and diagenesis process of magma were studied. The results indicate that magma was mainly derived from deep which experienced fractional crystallization during the process of rock formation and the rockbody belong to "I" type granitoids. Fractional crystallization and assimilationary-hybridization were the main mechanism of rock formation.(3)The comparison on typomorphic characteristics of different mineralization types of pyrite, pyrrhotite, chalcopyrite and magnetite were conducted based on the analysis of Electron Microprobe (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). It indicates that the formation of different mineralization types of pyrite, pyrrhotite, chalcopyrite and magnetite related to magmatic hydrothermal. Various types of pyrite, pyrrhotite, chalcopyrite mineralization formed in the same ore-forming fluid system, and magnetite manifested as skarn genesis. (4) According to the time sequence of the ore-forming stages, the systematic researches on the petrography, homogenization temperature, salinity, density, pressure and the vapor-liquid composition of fluid inclusion were conducted, and the ore-forming processes of the fluid are discussed. There were gas and liquid two-phase fluid inclusions (type Ⅰ) and daughter minerals-bearing fluid inclusions (type Ⅱ) of skarn stage and retrograde alteration mineralization stage. Multiple types of inclusions coexisted in the same mineral, and the homogenization temperatures were similar, but the homogenization methods were difference. It displayed that the fluid may have been boiling during the skarn stage and retrograde alteration mineralization stage. Following the mineralization, the high temperature and inhomogeneous initial fluid change into a homogeneous fluid, and the temperature, salinity, density and pressure of ore-forming fluid gradually decreased.(5) For the purpose of identifying material composition of Dongguashan copper (gold) deposit, isotope dates of hydrogen, oxygen, sulfur and lead were determined and compared in different mineralization types of this ore district. The comparison on isotope dates of sulfur and lead between Dongguashan and typical skarn deposits in Tongling district were also conducted for better understanding the source of components in Dongguashan. The results indicate that different types of orebodies have the same source of components, their ore-forming fluids are mainly magmatic water. Results of sulfur isotope suggests that its magmatic source which is in agreement with the typical skarn deposit in this area. Isotope determination indicates that the lead of orebodies having different types of is mainly mantle-derived, associated with magmatism.(6) The key ore-controlling factors are summarized, the genesis of the deposit is discussed, and the ore-forming model is created. The Yanshanian magmatic activities contributed to the formation of Dongguashan deposit with the material source, fluid source and heat source. The Devonian, Carboniferous and Permian strata were involved in the ore-forming process. The nearly NS and EW fracture, NE Qingshan anticline, as well as the inter-layer detachment structure and contact zones in the Carboniferous stratum control the localization of orebody. It is considered that the Dongguashan copper (gold) deposit is a porphyry-skarn deposit controlled by the magmatic activities, lithology of strata and various structures.
Keywords/Search Tags:Ore-forming mechanism, geological and geochemicalcharacteristics, isotope geochemical, ore-controlling factors, ore genesis, Dongguashan copper (gold) deposit
PDF Full Text Request
Related items