The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits.This paper outlines the...The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits.This paper outlines the geochemical features of 24 surface sediments and one sediment core(26 V-GC 01,294 cm)along the South Mid-Atlantic Ridge(SMAR)from 18°S to 22°S,an area where hydrothermal active fields have yet to be discovered.The surface sediments mainly consist of biogenic carbonates,aluminosilicates,and hydrothermal Fe-Mn(oxy)oxides.The core sediments primarily comprise organic matter,detrital materials,hydrothermal components,and substances scavenged from seawater.The rare Earth element(REE)patterns suggest the presence of hydrothermal contributions within the surface and core sediments.The enrichment factors for Fe,Mn,Cu,and Zn in surface sediments suggest these metals are concentrated at the 19°S,21°S,and 21.5°S segments,further indicating their potential as hydrothermal active fields.Downcore variations of Fe,Mn,P,Cu,Pb,V,and Co suggest at least six episodes of hydrothermal activity.The impact of hydrothermal processes on the sediments from SMAR 18°S to 22°S indicates that the study area has the potential to host a significant number of hydrothermal active fields.展开更多
The geochemistry of sediments is primarily controlled by their provenances,and different tectonic settings have distinctive provenance characteristics and sedimentaryprocesses. So, it is possible to distinctive proven...The geochemistry of sediments is primarily controlled by their provenances,and different tectonic settings have distinctive provenance characteristics and sedimentaryprocesses. So, it is possible to distinctive provenances, depositional environments and tectonicsettings in the development of a sedimentary basin with the geochemistry of the clastic rocks. Theanalytical results of the present paper demonstrate that sediments in the Songliao prototype basinare enriched in silica (SiO_2=66.48-80.51 percent), and their sumREE are 30-130 times of that ofchondrite with remarkable Eu anomalies. In discriminating diagrams of Eu/Eu* vs sumREE and (La/Yb)_Nvs sumREE, most samples locate above the line Eu/Eu*=1, on the right of the line Eu/Eu*/sumREE=1and under the line La/Yb)_N/sumREE=1/8, which indicates that the depositional environment ofsediments in the basin was oxidizing. In addition, variations of MgO, TiO_2, Al_2O_3, FeO + Fe_2O_3,Na_2O and CaO vs SiO_2 reflect a tendency of increasing mineral maturity of sediments in the basin.Analyses also show that the protolytes of the sediments in the basin were felsic igneous rocks, andthe Songliao prototype basin was in a tectonic setting of an island arc on an active continentalmargin, with violent sinistral strike-slip.展开更多
The Cuddalore Formation of the Cauvery Basin received siliciclastic detritus from inland areas of the Southern Granulite Terrain(SGT).It represented continental-fluvial sedimentation in the eastern continental margin ...The Cuddalore Formation of the Cauvery Basin received siliciclastic detritus from inland areas of the Southern Granulite Terrain(SGT).It represented continental-fluvial sedimentation in the eastern continental margin of South India during the Miocene.Indian Summer Monsoon was thought to be initiated in the early Miocene and intensified during the middle Miocene causing major climatic shifts in the Indian subcontinent.In the present work,detailed mineralogical and geochemical studies on the siliciclastic Cuddalore Formation have been carried out to understand the provenance and paleoclimatic conditions during the Miocene.The paleocurrent direction,textural immaturity and framework detrital modes of sandstones suggest rapid uplift of basement and sediment source from nearby Madras Block of SGT.Various diagnostic immobile trace element ratios such as Th/Sc,Co/Th,La/Sc,La/Co suggest a tonalite-trondhjemite-granodiorite-charnockite provenance,and somewhat more felsic composition of source area compared to the present upper continental crust(UCC).Rare earth element mixed model suggests that sediments were dominantly(80%)sourced from felsic charnockite,with a minor contribution(20%)from mafic granulites.Higher abundance of advanced-weathering products like kaolinite,very high(>98)chemical index of alteration(CIA)values,severe depletion of mobile elements(Ca,Na,K,Mg,Ba,Rb)in comparison to UCC,significantly higher a Mg,a Ca,a Na,a K,a Sr and a Ba values(higher than the unity),all suggest the extreme chemical weathering in source terrain and/or in the sedimentary basin.Calculations based on CIA show high average surface temperature between 29.3℃and 29.5℃and high mean annual precipitation ranging from 2339 mm/yr to 2467 mm/yr.The geochemical data are consistent with the paleogeographic position of the depositional basin(Cauvery Basin)and suggest the deposition of Cuddalore sediments(the Cuddalore Formation)in a nearequatorial location under a warm climate condition with abundant monsoonal precipitation.展开更多
Chemical weathering can occur on Earth and other rocky planets with liquid water on their surfaces.As the Curiosity Mission has revealed that fluvio-lacustrine depositional environments once prevailed in Gale Crater,i...Chemical weathering can occur on Earth and other rocky planets with liquid water on their surfaces.As the Curiosity Mission has revealed that fluvio-lacustrine depositional environments once prevailed in Gale Crater,investigation of sediment geochemistry to interpret chemical weathering history and the possible influence of climate fluctuation seems feasible on Mars.This study examines the relationship between temperature and the degree of weathering inferred from weathering indices,and applies the suitable weathering indices to a compilation of published datasets from Gale Crater sediment.The selected weathering indices(CIA,CIW,PIA,V,W,and WIP)consistently suggest an increase followed by a more gradual increase and decrease in weathering intensity up-section,which might reflect climate variations.However,diagenetic and/or hydrothermal alteration seem to have overprinted the primary weathering signature.展开更多
基金Supported by the China Ocean Mineral Resources R&D Association(No.DY135-S2-2)the Basic Scientific Fund for National Public Research Institutes of China(No.2021Q01)the National Natural Science Foundation of China(Nos.42106080,42006180,42276080)。
文摘The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits.This paper outlines the geochemical features of 24 surface sediments and one sediment core(26 V-GC 01,294 cm)along the South Mid-Atlantic Ridge(SMAR)from 18°S to 22°S,an area where hydrothermal active fields have yet to be discovered.The surface sediments mainly consist of biogenic carbonates,aluminosilicates,and hydrothermal Fe-Mn(oxy)oxides.The core sediments primarily comprise organic matter,detrital materials,hydrothermal components,and substances scavenged from seawater.The rare Earth element(REE)patterns suggest the presence of hydrothermal contributions within the surface and core sediments.The enrichment factors for Fe,Mn,Cu,and Zn in surface sediments suggest these metals are concentrated at the 19°S,21°S,and 21.5°S segments,further indicating their potential as hydrothermal active fields.Downcore variations of Fe,Mn,P,Cu,Pb,V,and Co suggest at least six episodes of hydrothermal activity.The impact of hydrothermal processes on the sediments from SMAR 18°S to 22°S indicates that the study area has the potential to host a significant number of hydrothermal active fields.
文摘The geochemistry of sediments is primarily controlled by their provenances,and different tectonic settings have distinctive provenance characteristics and sedimentaryprocesses. So, it is possible to distinctive provenances, depositional environments and tectonicsettings in the development of a sedimentary basin with the geochemistry of the clastic rocks. Theanalytical results of the present paper demonstrate that sediments in the Songliao prototype basinare enriched in silica (SiO_2=66.48-80.51 percent), and their sumREE are 30-130 times of that ofchondrite with remarkable Eu anomalies. In discriminating diagrams of Eu/Eu* vs sumREE and (La/Yb)_Nvs sumREE, most samples locate above the line Eu/Eu*=1, on the right of the line Eu/Eu*/sumREE=1and under the line La/Yb)_N/sumREE=1/8, which indicates that the depositional environment ofsediments in the basin was oxidizing. In addition, variations of MgO, TiO_2, Al_2O_3, FeO + Fe_2O_3,Na_2O and CaO vs SiO_2 reflect a tendency of increasing mineral maturity of sediments in the basin.Analyses also show that the protolytes of the sediments in the basin were felsic igneous rocks, andthe Songliao prototype basin was in a tectonic setting of an island arc on an active continentalmargin, with violent sinistral strike-slip.
文摘The Cuddalore Formation of the Cauvery Basin received siliciclastic detritus from inland areas of the Southern Granulite Terrain(SGT).It represented continental-fluvial sedimentation in the eastern continental margin of South India during the Miocene.Indian Summer Monsoon was thought to be initiated in the early Miocene and intensified during the middle Miocene causing major climatic shifts in the Indian subcontinent.In the present work,detailed mineralogical and geochemical studies on the siliciclastic Cuddalore Formation have been carried out to understand the provenance and paleoclimatic conditions during the Miocene.The paleocurrent direction,textural immaturity and framework detrital modes of sandstones suggest rapid uplift of basement and sediment source from nearby Madras Block of SGT.Various diagnostic immobile trace element ratios such as Th/Sc,Co/Th,La/Sc,La/Co suggest a tonalite-trondhjemite-granodiorite-charnockite provenance,and somewhat more felsic composition of source area compared to the present upper continental crust(UCC).Rare earth element mixed model suggests that sediments were dominantly(80%)sourced from felsic charnockite,with a minor contribution(20%)from mafic granulites.Higher abundance of advanced-weathering products like kaolinite,very high(>98)chemical index of alteration(CIA)values,severe depletion of mobile elements(Ca,Na,K,Mg,Ba,Rb)in comparison to UCC,significantly higher a Mg,a Ca,a Na,a K,a Sr and a Ba values(higher than the unity),all suggest the extreme chemical weathering in source terrain and/or in the sedimentary basin.Calculations based on CIA show high average surface temperature between 29.3℃and 29.5℃and high mean annual precipitation ranging from 2339 mm/yr to 2467 mm/yr.The geochemical data are consistent with the paleogeographic position of the depositional basin(Cauvery Basin)and suggest the deposition of Cuddalore sediments(the Cuddalore Formation)in a nearequatorial location under a warm climate condition with abundant monsoonal precipitation.
基金supported by the NRF grant funded by the Korean Government(MSIT,No.2022R1A2C1004798)Global-Learning&Academic research institution for Master’s·PhD students,and Postdocs(LAMP)Program of the National Research Foundation of Korea(NRF)grant funded by the Ministry of Education(No.RS-2023-00301702).
文摘Chemical weathering can occur on Earth and other rocky planets with liquid water on their surfaces.As the Curiosity Mission has revealed that fluvio-lacustrine depositional environments once prevailed in Gale Crater,investigation of sediment geochemistry to interpret chemical weathering history and the possible influence of climate fluctuation seems feasible on Mars.This study examines the relationship between temperature and the degree of weathering inferred from weathering indices,and applies the suitable weathering indices to a compilation of published datasets from Gale Crater sediment.The selected weathering indices(CIA,CIW,PIA,V,W,and WIP)consistently suggest an increase followed by a more gradual increase and decrease in weathering intensity up-section,which might reflect climate variations.However,diagenetic and/or hydrothermal alteration seem to have overprinted the primary weathering signature.
