Two Stage Skarn And Superimposed Mineralization Of Suoerkuduke Cu-Mo Deposit In XinJiang, China

The Suoerkuduke Cu-Mo deposit is a typical skarn type deposit in the southwest region of northeastern margin of East Junggar. In this paper, we study on the geological characteristcs, diagenesis and mineralization chronology, petrogeochemistry, skarn mineralogy and rare earth element geochemistry, ore-forming fluid evolution, source of ore-forming materials, and then summarize the character of mineral geology also discuss the mineralization as well as combined with regional tectonic evolution history, attempting to establish the metallogenic model of Suoerkuduke mineralization system, which can help enriching the research on the metallogenic regularity and metallogenic prediction research on regional scale.The research results about the geological characteristcs and diagenesis and mineralization chronology can reveal that the Suoerkuduke Cu-Mo deposit is a typical skarn type which possess the superimposed mineralization characteristics. This deposit developed two periods skarn about early and late and associated with mineralization respectively. The early skarn metallogenic epoch mainly took place in the end of the middle Devonian(379.1±6.6Ma) with the ore-forming metals combination is the Fe-Cu-Mo combination which is associated with the trachydacite porphyry(387.6±1.8Ma); The late skarn metallogenic epoch mainly took place in the end of the late Carboniferousn(299.6±1.9Ma) with the ore-forming metals combination is the Fe-Cu-Mo combination which is associated with the granite porphyry (294.7±2.9Ma).The research results about the mineralogy and rare earth element geochemistry about early skarn and late skarn can reavel that the mineralization process of early skarn has experienced the change process of following:weak reduction-weak oxidizing conditions in the prograde stage�' the weak reduction conditions in the oxide stage �' the oxidizing conditions in the early phase of retrograde stage �' weak oxidizing-reduction conditions in the late phase of retrograde stage; The mineralization process of late skarn has experienced the change process of following: oxidizing conditions in the prograde stage �' weak oxidizing-weak reduction conditions in the retrograde stage �' weak reduction- reduction conditions in the quartz-sulphide stage �' reduction conditions in the quartz-calcite stage. Although there it has a significant difference between the specific metallogenic process, but the conversion between oxidation-reduction environment is mainly concentrate on the main metallogenic stage which belong to the early and late skarn respectively(retrograde stage of early skarn and quartz-sulphide stage of late skarn), and the convert of oxidation-deoxidation environment which created ideal conditions for the formation of a large number of metal sulfides.The research results about the metallogenic fluid can reavel that there are three major fluid inclusions type in the early skarn as following:aqueous liquid-rich fluid inclusion(WL type), aqueous vapor-rich fluid inclusion(WV type) and polyphase daughter mineral fluid inclusion(S1 type), and the original fluids belong to high-temperature H20-NaCl fluid system, the fluid in the main metallogenic stage was belong to the medium-high temperature salinity unsaturated fluid system, and with the strong fluid boiling. There are four major fluid inclusions type in the early skarn as following:aqueous liquid-rich fluid inclusion(WL type), aqueous vapor-rich fluid inclusion(WV type), polyphase daughter mineral fluid inclusion(S1 type), and aqueous daughter mineral fluid inclusion(S2 type), and the original fluids belong to high-temperature H2O-NaCl fluid system also, but the fluid in the main metallogenic stage was belong to the medium-low temperature salinity supersaturated fluid system, and with the the fluid boiling together with the fluid-mixing process. The fluid boiling in the main metallogenic stage which led to the solubility of Cu、Mo declined rapidly, and eventually resulted in the precipitate of metal sulfides. The fluid boiling was the main mechanism which led to the precipitate of ore material both about to the early and late skarn.Combined with regional tectonic evolution, in the Suoerkuduke Cu-Mo deposit, the early skarn mineralization system formed in an island arc tectonic setting which is relate to the subduction between Paleoasian ocean and Junggar plate in the middle Devonian. The dehydration of the subducted oceanic crust which induced the partial melting of the mantle-wedge, and then resulting in generation of water and ore-forming material-rich magma. Hydrothermal fluids exsolution took place during the process of magma intruded upward, then the fluids migration and metasomatism along the formation, which resulted in the formation of early skarn and mineralization. The late skarn mineralization system formed in an post-collisional tectonic setting, the mantle origin magma underplating and subsequent lithospheric extension could have been the geodynamic setting responsible for the partial melting of the youthful earth’s crust which mainly composed of the subduction of oceanic crust and material of wedge material. Hydrothermal fluids exsolution took place during the process of magma intruded upward, then the fluids migration along the tension crack and metasomatism with the formation and the early skarn, and eventually formed the late skarn and associated ore body which is characterized by the irregular vein.