Scheelite Sm-Nd and quartz Ar-Ar dating were accomplished for the Woxi Au-Sb-W deposit in western hu-nan. The results show that the Sm and Nd concentrations of scheelite are relatively high, and Sm/Nd ratios are usual...Scheelite Sm-Nd and quartz Ar-Ar dating were accomplished for the Woxi Au-Sb-W deposit in western hu-nan. The results show that the Sm and Nd concentrations of scheelite are relatively high, and Sm/Nd ratios are usually high and variable. In the 147Sm/144Nd vs. 143Nd/144Nd diagram, the disseminated scheelites show a good linear array, which corresponds to an isochron age of 402 6 Ma and an initial 143Nd/144Nd ratio of 0.510544 9 (2s ) with a e Nd(t) value of -30.7. The Ar-Ar age spectra for 2 quartz samples display the saddle shape. The minimum apparent age, plateau age and isochron age of each quartz sample generally overlap within errors; and both the minimum apparent ages of 420 20 and 414 19 Ma coincide well with the scheelite Sm-Nd age. Both Sm-Nd and Ar-Ar dating results reveal that the Au-Sb-W mineralization at Woxi district took place in the Late Caledonian. This is in good agreement with the tectonic evolution of the Xuefengshan district and with some geo-chronological data available for Au, Sb and W deposits in this area. The low initial Nd isotope ratio of scheelites sug-gests that the fluid responsible for Au-Sb-W mineralization at the Woxi is of deep crustal origin and probably originated from the underlying Archaean continental basement rather than the host Proterozoic strata in western Hunan. The con-straints on the mineralization time and on the fluid source provide insight into the genesis of the Woxi deposit.展开更多
The study results of He and Ar isotopes from fluid inclusions in pyrites formed during mineralization stage of Jinding superlarge Pb-Zn deposit in west Yunnan, China are reported. The data show that the 40Ar/ 36Ar and...The study results of He and Ar isotopes from fluid inclusions in pyrites formed during mineralization stage of Jinding superlarge Pb-Zn deposit in west Yunnan, China are reported. The data show that the 40Ar/ 36Ar and 3He/ 4He ratios of fluid inclusions are respectively in the range of 301.7\385.7 and 0.03\0.06Ra, suggesting the ore-forming fluid is a kind of air saturated meteoric groundwater. On the basis of research on coupled relationships among He, Ar, S and Pb isotopes, the evolution history of ore-forming fluid of the deposit can be summarized as （i） air saturated meteogenic groundwater infiltrated down and was heated→ （ii） leached S, C and radiogenic He, Ar from the basinal strata → （iii） leached Pb and Zn from mantle-derived igneous rocks located in the bottom of the basin→ （iv） ore-forming fluid ascended and formed the deposit. Due to this process, the isotope signatures of crustal radiogenic He, atmospheric Ar （with partial radiogenic 40Ar）, crustal S and mantle-derived Pb remained in the ore-forming fluid.展开更多
Isotopic abundances and ratios of He and Ar found in inclusion fluids in pyrites formed in the Yaoling-Meiziwo tungsten miner-alization epoch show that the concentration of 4He varies widely,from 1.54×10-7 cm3 ST...Isotopic abundances and ratios of He and Ar found in inclusion fluids in pyrites formed in the Yaoling-Meiziwo tungsten miner-alization epoch show that the concentration of 4He varies widely,from 1.54×10-7 cm3 STP/g to 2609×10-7 cm3 STP/g.3He is 0.759×10-12 cm3 STP/g-3.463×10-12 cm3 STP/g.3He/4He is 0.0043-4.362 Ra,varying from crustal to mantle values.The concen-tration of 40Ar ranges from 0.624×10-7 cm3 STP/g to 8.89×10-7 cm3 STP/g.The 40Ar/36Ar varies extensively,from 330 to 2952,between atmospheric and crustal or mantle radiogenic values.Mantle-derived He is present in ore-forming fluids and the calcu-lated average proportion of the mantle He is 22%;the maximum is 67%.Our research results show that mantle-derived fluids play a significant role in tungsten mineralization.The fractionation of He and Ar indicate that there was 4He-enriched air-saturated water(MSAW) in the ore-forming fluid.The ore-forming fluid was a mixture of mantle fluid,crustal magmatic fluid and MSAW.The occurrence of a mantle component in ore-forming fluid indicates the large-scale W and Sn mineralization,including Yaol-ing-Meiziwo,in southeastern China was the result of crust and mantle interaction.The underplating or intrusion of voluminous basaltic magma formed by partial melting of the upper mantle provided the necessary heat to cause partial melting of the crust and the generation of voluminous S-type granitic magmas.Crustal magmatic fluid and mantle fluid with high 3He/4He were released from magma crystallization and fractionation,mixed with the circulating modified air-saturated water,and filled the extensional tectonic fractures,leading to the formation of world-class W and Sn deposits in southeastern China.展开更多
基金supported by the National Key Basic Research Program(Grant No.G1999043200)the National Natural Science Foundation for Outstanding Youth(Grant No.49925309)the Knowledge Innovation Research Program from the Chinese Academy of Sciences(Grant No.KZCX3-SW-125).
文摘Scheelite Sm-Nd and quartz Ar-Ar dating were accomplished for the Woxi Au-Sb-W deposit in western hu-nan. The results show that the Sm and Nd concentrations of scheelite are relatively high, and Sm/Nd ratios are usually high and variable. In the 147Sm/144Nd vs. 143Nd/144Nd diagram, the disseminated scheelites show a good linear array, which corresponds to an isochron age of 402 6 Ma and an initial 143Nd/144Nd ratio of 0.510544 9 (2s ) with a e Nd(t) value of -30.7. The Ar-Ar age spectra for 2 quartz samples display the saddle shape. The minimum apparent age, plateau age and isochron age of each quartz sample generally overlap within errors; and both the minimum apparent ages of 420 20 and 414 19 Ma coincide well with the scheelite Sm-Nd age. Both Sm-Nd and Ar-Ar dating results reveal that the Au-Sb-W mineralization at Woxi district took place in the Late Caledonian. This is in good agreement with the tectonic evolution of the Xuefengshan district and with some geo-chronological data available for Au, Sb and W deposits in this area. The low initial Nd isotope ratio of scheelites sug-gests that the fluid responsible for Au-Sb-W mineralization at the Woxi is of deep crustal origin and probably originated from the underlying Archaean continental basement rather than the host Proterozoic strata in western Hunan. The con-straints on the mineralization time and on the fluid source provide insight into the genesis of the Woxi deposit.
文摘The study results of He and Ar isotopes from fluid inclusions in pyrites formed during mineralization stage of Jinding superlarge Pb-Zn deposit in west Yunnan, China are reported. The data show that the 40Ar/ 36Ar and 3He/ 4He ratios of fluid inclusions are respectively in the range of 301.7\385.7 and 0.03\0.06Ra, suggesting the ore-forming fluid is a kind of air saturated meteoric groundwater. On the basis of research on coupled relationships among He, Ar, S and Pb isotopes, the evolution history of ore-forming fluid of the deposit can be summarized as （i） air saturated meteogenic groundwater infiltrated down and was heated→ （ii） leached S, C and radiogenic He, Ar from the basinal strata → （iii） leached Pb and Zn from mantle-derived igneous rocks located in the bottom of the basin→ （iv） ore-forming fluid ascended and formed the deposit. Due to this process, the isotope signatures of crustal radiogenic He, atmospheric Ar （with partial radiogenic 40Ar）, crustal S and mantle-derived Pb remained in the ore-forming fluid.
基金the National Basic Research Program of China (2007CB411404)the National Natural Science Foundation of China (40873034)the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2011)
文摘Isotopic abundances and ratios of He and Ar found in inclusion fluids in pyrites formed in the Yaoling-Meiziwo tungsten miner-alization epoch show that the concentration of 4He varies widely,from 1.54×10-7 cm3 STP/g to 2609×10-7 cm3 STP/g.3He is 0.759×10-12 cm3 STP/g-3.463×10-12 cm3 STP/g.3He/4He is 0.0043-4.362 Ra,varying from crustal to mantle values.The concen-tration of 40Ar ranges from 0.624×10-7 cm3 STP/g to 8.89×10-7 cm3 STP/g.The 40Ar/36Ar varies extensively,from 330 to 2952,between atmospheric and crustal or mantle radiogenic values.Mantle-derived He is present in ore-forming fluids and the calcu-lated average proportion of the mantle He is 22%;the maximum is 67%.Our research results show that mantle-derived fluids play a significant role in tungsten mineralization.The fractionation of He and Ar indicate that there was 4He-enriched air-saturated water(MSAW) in the ore-forming fluid.The ore-forming fluid was a mixture of mantle fluid,crustal magmatic fluid and MSAW.The occurrence of a mantle component in ore-forming fluid indicates the large-scale W and Sn mineralization,including Yaol-ing-Meiziwo,in southeastern China was the result of crust and mantle interaction.The underplating or intrusion of voluminous basaltic magma formed by partial melting of the upper mantle provided the necessary heat to cause partial melting of the crust and the generation of voluminous S-type granitic magmas.Crustal magmatic fluid and mantle fluid with high 3He/4He were released from magma crystallization and fractionation,mixed with the circulating modified air-saturated water,and filled the extensional tectonic fractures,leading to the formation of world-class W and Sn deposits in southeastern China.
