Geochemistry And Zonation Of The Galinge Iron Deposit, Qinghai Province

Galinge skarn iron polymetallic ore deposit is located in the western Qinghai province and in the central Qimantage metallogenic belt.Orebody is located in the contact zone between granodiorites, adamellite and dolomitic marble,and in the marble and altered andesites which are distributed along NWW rupture structural fracture zone in the exocontact zone.From the invading contact zone to the east, the zonation of skarn minerals is obvious,and it was mainly divided into three ore-bearing skarn zones:magnesian skarn zone with Fe,calcium skarn zone with Fe and Cu and manganoan-calcium skarn zone with Fe,Pb and Zn. Through the comparison with the deposits in the east of China, we found that manganone-calcium skarn zone is a type of transition to the manganone skarn zone, it has the significance for prospecting mineralization type related to the manganone skarn.Through the mineral assemblage divides the metallogenic periods, involves skarn period, hydrothermal period and sulfide period. Different periods have different stages, skarn period is divided into early, middle and late stages, and hydrothermal period is divided into early and late two stages. The main chemical composition in early stages of skarn period is grossular (Gro67～99) and diopsite (Di96～98); The main chemical composition in the late stage of skarn is andradite (Ad78-98) and hedenbergite (Hd68～84).The whole rock geochemical compositions of granitoids and enclaves indicate that all samples belong to the high kalium calc-alkali suite and metaluminous, and related with either subduction regime or continental collision, further analysis on trace elements prove that the source of the Galinge granitoid magmas was affected by the partial melts of extensional lithosphere in a back-arc eviroment. The REE distribution patterns are characterized by LREE enrichments compared to HREE, and the felsic rocks have further obvious weak negative Eu anomalies, however, the mafic rocks don’t have. All the samples also have enrichments in LILE (e.g., K, U, Sr) and depletion in HFSE (e.g., Nb, Ta, Ti, and Zr). The LA-MC-ICP MS zircon U-Pb data show that the granodiorite was formed during Indosinian period (229Ma). Zircon Lu-Hf isotope analysis indicate that the magma that formed the granodiorite was mainly derived from lower crust remelting in a digenesis process with a minor component derived from the mantle.The P-T-X evolution pathways of hydrothermal fluid includes three stages. Different internals of temperature and salinity are in correspondence with the different skarn stages.