Geology And Fluid Geochemistry Of The Hamaling Porphyry Cu-Mo Deposit, Tongling, Anhui Province

Hamaling deposit is a skarn-porphyry multiple Cu-Mo deposit newly discovered in the Tongling Cu(Au)ore-concentrated district of Anhui Province and appears special and typical in the Middle-Lower Yangtze metallogenic belt.This deposit is dominated by porphyry orebodies.A comprehensive study has been carried out on the ore deposit geology and fluid geochemistry of this deposit in order to ascertain its geological characteristics and ore-forming fluid geochemical features.Derivation and evolution of ore-forming fluid and mineralization process of the deposit have been discussed based on the obtained geological and geochemical data.According to the crosscutting relationships of the veinlets and the mineral assemblages,the alteration and mineralization process of the Hamaling porphyry Cu(Mo)deposit can be divided into six stages as follows: potassic feldspar,sericite-quartz,quartz-molybdenite,quartz-pyrite,Cu-polymetallic sulfides and calcite stages.The fluid inclusion analyses show that from the potassic feldspar and sericitequartz stages through the quartz-molybdenite,quartz-pyrite,and Cu-polymetallic sulfides stages to the calcite stage,temperature of ore-forming fluid varies from>425? through 350? to 126?.Correspondingly,its salinity changes from 55.8%NaCleq through 17.5%NaCleq to 1.39%NaCleq,and its pressure from 65 MPa through 38 MPa to 6MPa.The hydrogen and oxygen isotopic analyses indicate that the early ore-forming fluid is predominated by magmatic water,whereas the late ore-forming fluid is a mixing fluid of magmatic water with meteoric water.The geological and geochemical analyses support the occurrence of water-rock interaction,boiling and mixing during the evolution of ore-forming fluid in the Hamaling ore deposit.The mixing of magmatic water with meteoric water results in the precipitation of ore-forming materials.