Methane(CH4)is a powerful greenhouse gas and its largest reservoir on Earth is held in marine sediments.CH4 in marine sediments is mainly stored in gas-hydrate reservoirs and deep sedimentary strata along continental ...Methane(CH4)is a powerful greenhouse gas and its largest reservoir on Earth is held in marine sediments.CH4 in marine sediments is mainly stored in gas-hydrate reservoirs and deep sedimentary strata along continental margins,where large amounts of deep-sourced CH4 ascend to different degrees toward the seafloor.However,the amount of deep-sourced CH4 and its role in subseafloor carbon and sulfur cycling remains poorly constrained.We analyzed sulfate(SO_(4)^(2-))profiles of 157 sites along with previous published 85 sites to determine the regional distribution and amount of SO_(4)^(2-) reduction for an area of 1.23×10^(5) km^(2) of the northern South China Sea.Then we compared these obtained results with estimates based on sedimentation rates from the same area.Significantly higher regional SO_(4)^(2-) flux estimates based on SO_(4)^(2-) profiles(4.26×10^(-3)Tmol a^(-1)),compared to lower estimates based on sedimentation rates(1.23×10^(-3)Tmol a^(-1)),reflect abundant ascending deep-sourced CH4.The difference of the regional SO_(4)^(2-) flux estimates(3.03×10^(-3)Tmol a^(-1))represents the amount of SO_(4)^(2-) reduced by CH_(4) through the anaerobic oxidation of CH_(4)(AOM).Deep-sourced CH_(4) contributes 71%to total SO_(4)^(2-) consumption in the study area,largely exceeding SO_(4)^(2-) consumption by organoclastic sulfate reduction.Our findings substantiate that deep-sourced CH4 governs subseafloor carbon and sulfur cycling to a previously underrated extent,fueling extensive chemosynthesis-based ecosystems along continental slope and rise.展开更多
A large number of gases are releasing from the medium-high temperature geothermal fields distributed along the large-scale strike-slip fault zones in the southeastern margin of the Tibetan Plateau.In this study,11 hot...A large number of gases are releasing from the medium-high temperature geothermal fields distributed along the large-scale strike-slip fault zones in the southeastern margin of the Tibetan Plateau.In this study,11 hot spring water and the associated bubbling gas samples were collected along the Xianshuihe-Anninghe fault zones(XSH-ANHFZ)and analyzed for chemical and isotopic compositions.The δ^(18)_(H_(2)O) and δD_(H_(2)O) values indicate that hot spring waters are predominantly meteoric origin recharged from different altitudes.Most water samples are significantly enriched in Na^(+) and HCO_(3) due to the dissolution of regional evaporites,carbonates and Na-silicates.^(3)He/^(4)He ratios of the gas samples are 0.025-2.73 times the atmospheric value.The ^(3)He/^(4)He ratios are high in the Kangding region where the dense faults are distributed,and gradually decrease with increasing distance from Kangding towards both sides along the Xianshuihe fault zones(XSHFZ).Hydrothermal fluids have dissolved inorganic carbon(DIC)concentrations from 2 to 42 mmol L^(-1),δ^(13)C_(DIC) from -6.9‰ to 1.3‰,δ^(13)C_(CO_(2)) from -7.2‰ to -3.6‰ and Δ^(14)C from -997‰ to -909‰.Combining regional geochemical and geological information,the CO_(2)sources can be attributed to deep-sourced CO_(2)from mantle and metamorphism of marine carbonate,and shallow-sourced CO_(2)from the dissolution of marine carbonate and biogenic CO_(2).The mass balance model shows that 11±6% of the DIC is sourced from the dissolution of shallow carbonate minerals,9±8% formed by pyrolysis of sedimentary organic matter,80±9% derived from deep metamorphic origin and mantle-derived CO_(2).Among them,the deep-sourced CO_(2)in Anninghe fault zones(ANHFZ)is merely metamorphic carbon,whereas ca.12% and ca.88% of the deep-sourced CO_(2)in the XSHFZ are derived from the mantle and metamorphic carbon,respectively.The average deep-sourced CO_(2)flux in the Kangding geothermal field is estimated to be 160 ta^(-1).If all the hot springs in various fault zones in the southeastern margin of the Tibetan Plateau are taken into account,the regional deep-sourced CO_(2)flux would reach ca.10^(5) ta^(-1).These results show that the deep-sourced CO_(2)released from nonvolcanic areas might account for a considerable proportion of the total amount of global deep-sourced carbon degassing,which should be paid more attention to.展开更多
1 Geology Extensively developed on the southwestern margin of the Yangtze massif are epithermal deposits suchas gold, silve r, antimony, mercury, arsenic, uranium, copper and lead-zinc ore deposits, as well asbarite, ...1 Geology Extensively developed on the southwestern margin of the Yangtze massif are epithermal deposits suchas gold, silve r, antimony, mercury, arsenic, uranium, copper and lead-zinc ore deposits, as well asbarite, fluorite, iceland spar and rock crystal deposits, which constitute a unique low-temperature metallogenic domain. Except for the Gongguan deposit, the important Sb deposits in China are concentrated inthis low-temperature metallogenic domain, constituting the Hunan-Guizhou-Guangxi-Yunnan Sb ore belt.In general this ore belt extends in the NNE direction, measuring 1 900 km or more in length and 200 kmin width. A total of 505 Sb deposits (or occurrences) are known, accounting for 85.5 % of the展开更多
Ultramafic hypoxenoliths found in the alkali-rich porphyry in the Liuhe Village, Heqing, Yunnan, China, are of great significance in understanding the origin and evolution of the porphyry. This paper discusses the min...Ultramafic hypoxenoliths found in the alkali-rich porphyry in the Liuhe Village, Heqing, Yunnan, China, are of great significance in understanding the origin and evolution of the porphyry. This paper discusses the mineralogical features of the hypoxenoliths. It shows that the xenoliths are characterized by the upper mantle rocks modified to certain extent by the enriched mantle fluid metasomatism in the mantle environment, with the enriched mantle property of low-degree partial melting. This constitutes the important mineralogical evidence for the petrogenesis and mineralization of alkali-rich porphyry.展开更多
基金supported by the National Natural Science Foundation of China(41730528,42225603,and 42176056)the Shanghai Pujiang Program(Grant No 21PJ1404700)。
文摘Methane(CH4)is a powerful greenhouse gas and its largest reservoir on Earth is held in marine sediments.CH4 in marine sediments is mainly stored in gas-hydrate reservoirs and deep sedimentary strata along continental margins,where large amounts of deep-sourced CH4 ascend to different degrees toward the seafloor.However,the amount of deep-sourced CH4 and its role in subseafloor carbon and sulfur cycling remains poorly constrained.We analyzed sulfate(SO_(4)^(2-))profiles of 157 sites along with previous published 85 sites to determine the regional distribution and amount of SO_(4)^(2-) reduction for an area of 1.23×10^(5) km^(2) of the northern South China Sea.Then we compared these obtained results with estimates based on sedimentation rates from the same area.Significantly higher regional SO_(4)^(2-) flux estimates based on SO_(4)^(2-) profiles(4.26×10^(-3)Tmol a^(-1)),compared to lower estimates based on sedimentation rates(1.23×10^(-3)Tmol a^(-1)),reflect abundant ascending deep-sourced CH4.The difference of the regional SO_(4)^(2-) flux estimates(3.03×10^(-3)Tmol a^(-1))represents the amount of SO_(4)^(2-) reduced by CH_(4) through the anaerobic oxidation of CH_(4)(AOM).Deep-sourced CH_(4) contributes 71%to total SO_(4)^(2-) consumption in the study area,largely exceeding SO_(4)^(2-) consumption by organoclastic sulfate reduction.Our findings substantiate that deep-sourced CH4 governs subseafloor carbon and sulfur cycling to a previously underrated extent,fueling extensive chemosynthesis-based ecosystems along continental slope and rise.
基金supported by China Seismic Experimental Site(CSES)(Grant No.2019CSES0104)the National Natural Science Foundation of China(Grant No.41930642)。
文摘A large number of gases are releasing from the medium-high temperature geothermal fields distributed along the large-scale strike-slip fault zones in the southeastern margin of the Tibetan Plateau.In this study,11 hot spring water and the associated bubbling gas samples were collected along the Xianshuihe-Anninghe fault zones(XSH-ANHFZ)and analyzed for chemical and isotopic compositions.The δ^(18)_(H_(2)O) and δD_(H_(2)O) values indicate that hot spring waters are predominantly meteoric origin recharged from different altitudes.Most water samples are significantly enriched in Na^(+) and HCO_(3) due to the dissolution of regional evaporites,carbonates and Na-silicates.^(3)He/^(4)He ratios of the gas samples are 0.025-2.73 times the atmospheric value.The ^(3)He/^(4)He ratios are high in the Kangding region where the dense faults are distributed,and gradually decrease with increasing distance from Kangding towards both sides along the Xianshuihe fault zones(XSHFZ).Hydrothermal fluids have dissolved inorganic carbon(DIC)concentrations from 2 to 42 mmol L^(-1),δ^(13)C_(DIC) from -6.9‰ to 1.3‰,δ^(13)C_(CO_(2)) from -7.2‰ to -3.6‰ and Δ^(14)C from -997‰ to -909‰.Combining regional geochemical and geological information,the CO_(2)sources can be attributed to deep-sourced CO_(2)from mantle and metamorphism of marine carbonate,and shallow-sourced CO_(2)from the dissolution of marine carbonate and biogenic CO_(2).The mass balance model shows that 11±6% of the DIC is sourced from the dissolution of shallow carbonate minerals,9±8% formed by pyrolysis of sedimentary organic matter,80±9% derived from deep metamorphic origin and mantle-derived CO_(2).Among them,the deep-sourced CO_(2)in Anninghe fault zones(ANHFZ)is merely metamorphic carbon,whereas ca.12% and ca.88% of the deep-sourced CO_(2)in the XSHFZ are derived from the mantle and metamorphic carbon,respectively.The average deep-sourced CO_(2)flux in the Kangding geothermal field is estimated to be 160 ta^(-1).If all the hot springs in various fault zones in the southeastern margin of the Tibetan Plateau are taken into account,the regional deep-sourced CO_(2)flux would reach ca.10^(5) ta^(-1).These results show that the deep-sourced CO_(2)released from nonvolcanic areas might account for a considerable proportion of the total amount of global deep-sourced carbon degassing,which should be paid more attention to.
文摘1 Geology Extensively developed on the southwestern margin of the Yangtze massif are epithermal deposits suchas gold, silve r, antimony, mercury, arsenic, uranium, copper and lead-zinc ore deposits, as well asbarite, fluorite, iceland spar and rock crystal deposits, which constitute a unique low-temperature metallogenic domain. Except for the Gongguan deposit, the important Sb deposits in China are concentrated inthis low-temperature metallogenic domain, constituting the Hunan-Guizhou-Guangxi-Yunnan Sb ore belt.In general this ore belt extends in the NNE direction, measuring 1 900 km or more in length and 200 kmin width. A total of 505 Sb deposits (or occurrences) are known, accounting for 85.5 % of the
文摘Ultramafic hypoxenoliths found in the alkali-rich porphyry in the Liuhe Village, Heqing, Yunnan, China, are of great significance in understanding the origin and evolution of the porphyry. This paper discusses the mineralogical features of the hypoxenoliths. It shows that the xenoliths are characterized by the upper mantle rocks modified to certain extent by the enriched mantle fluid metasomatism in the mantle environment, with the enriched mantle property of low-degree partial melting. This constitutes the important mineralogical evidence for the petrogenesis and mineralization of alkali-rich porphyry.
