Titanite(CaTi2SiO5) is an important accessory mineral not only in magmatic and metamorphic rocks,but also commonly in hydrothermal mineral deposits. It incorporates appreciable amounts(usually 10×10-6 s to 100&#...Titanite(CaTi2SiO5) is an important accessory mineral not only in magmatic and metamorphic rocks,but also commonly in hydrothermal mineral deposits. It incorporates appreciable amounts(usually 10×10-6 s to 100×10-6 s) of U and Th into its structure and has a closure temperature of Pb diffusion higher than 660～700 ℃(Scott and St-Onge,1995) ,making it an ideal U-Th-Pb geochronometer. The Daye metallogenic district is located in the west of the giant Middle-Lower Yangtze River(MLYR) Cu-Fe-Au province,eastern China and is well endowed with Fe,Cu,and polymetallic skarn deposits.展开更多
The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formati...The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ34S values（ranging from 14.0‰ to 17.6‰） of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt（MLYRB）.The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of 208Pb/204Pb,207Pb/204Pb,and-206Pb/204Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages：the -3He/-4He（R/Ra） and 40Ar/-36Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water（MASW） during fluid evolution.The Triassic evaporites played an important role in the mineralization process.展开更多
基金supported by the NSFC(Grants Nos.90814004 and 40821061)
文摘Titanite(CaTi2SiO5) is an important accessory mineral not only in magmatic and metamorphic rocks,but also commonly in hydrothermal mineral deposits. It incorporates appreciable amounts(usually 10×10-6 s to 100×10-6 s) of U and Th into its structure and has a closure temperature of Pb diffusion higher than 660～700 ℃(Scott and St-Onge,1995) ,making it an ideal U-Th-Pb geochronometer. The Daye metallogenic district is located in the west of the giant Middle-Lower Yangtze River(MLYR) Cu-Fe-Au province,eastern China and is well endowed with Fe,Cu,and polymetallic skarn deposits.
基金supported by the National Basic Research Program of China(973 Program:2012CB416802)the National Special Research Programs for Non-Profit Trades(Sponsored by MLR,201311136)the Basic Scientific Research Operation Cost of StateLeveled Public Welfare Scientific Research Courtyard (K1203)
文摘The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ34S values（ranging from 14.0‰ to 17.6‰） of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt（MLYRB）.The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of 208Pb/204Pb,207Pb/204Pb,and-206Pb/204Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages：the -3He/-4He（R/Ra） and 40Ar/-36Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water（MASW） during fluid evolution.The Triassic evaporites played an important role in the mineralization process.
