The ultraslow-spreading Southwest Indian Ridge （SWIR） to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely ...The ultraslow-spreading Southwest Indian Ridge （SWIR） to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely slow spreading rate, the easternmost SWIR was considered to be devoid of hydrothermal activity until the discovery of the inactive Mt. lourdanne hydrothermal field （27°51＇S, 63°56＇E） in 1998. During the COMRA DYl15-20 cruise in 2009, two additional hydrothermal fields （i.e., the Tiancheng （27°51＇S, 63°55＇E） and Tianzuo （27°57＇S, 63°32＇E） fields） were discovered. Further detailed investigations of these two hydrothermal sites were conducted by Chinese manned submersible liaolong in 2014-2015. The Tiancheng filed can he characterized as a low- temperature （up to 13.2℃） diffuse flow hydrothermal field, and is hosted by fractured basalts with hydrothermal fauna widespread on the seafloor. The Tianzuo hydrothermal field is an inactive sulfide field, which is hosted by ultramafic rocks and controlled by detachment fault. The discovery of the three hydrothermal fields around Segment #11 which receives more melt than the regional average, provided evidence for local enhanced magmatism providing heat source to drive hydrothermal circulation. We further imply that hydrothermal activity and sulfide deposits may be rather promising along the easternmost SWIR.展开更多
Polymetallic sulfides present in mid-ocean ridges(MORs)have become important strategic resources for humans,and a scientific metallogenic model is necessary for the investigation and exploration of these resources.Com...Polymetallic sulfides present in mid-ocean ridges(MORs)have become important strategic resources for humans,and a scientific metallogenic model is necessary for the investigation and exploration of these resources.Compared to fast-and slow-spreading MORs,ultraslow-spreading MORs show substantial differences in magma supply,tectonic activity,and oceanic crust structures.However,information on hydrothermal circulation and a metallogenic model related to sulfides along the ultraslow-spreading ridges is still limited,which hinders further exploration of these resources.In this study,the distribution of hydrothermal activities,as well as the characteristics of the structures,heat sources,fluid pathways,host rock types,fluid properties,and sulfide assemblages in typical hydrothermal fields along the ultraslow-spreading Southwest Indian Ridge(SWIR),have been studied.It is concluded that the hydrothermal systems along the SWIR can be categorized into three types,including local enhanced magma-controlled,one-way detachment/high-angle large-offset fault-controlled,and flip-flop detachment-controlled types,which are further categorized into five subtypes based on their distinct geological backgrounds.Herein,we present a sulfide metallogenic model called Local Enhanced Heat Supply-Deep Faults(eHeat-dFault)for the SWIR.The overall spreading rate remains almost constant(14-18 mm/year),while the magma supply is heterogeneous in the segment scale along the SWIR.Over the past two decades,various hydrothermal systems and sulfide deposits have been identified along the SWIR.A deep magma chamber(4-9 km)is developed in the ridge segment with sufficient magma supply owing to the local enhanced magma supply,while long-lived active deep detachment faults(up to 13 km)with associated metallogenic belts are developed in ridge segments with poor magma supply.Hence,the ultraslow-spreading MORs fulfill the necessary conditions of a sustained heat source and stable hydrothermal pathway for the formation of large-scale polymetallic sulfide depo展开更多
The orthogonal supersegment of the ultraslow-spreading Southwest Indian Ridge at 16°–25°E is characterized by significant along-axis variations of mantle potential temperature.A detailed analysis of multibe...The orthogonal supersegment of the ultraslow-spreading Southwest Indian Ridge at 16°–25°E is characterized by significant along-axis variations of mantle potential temperature.A detailed analysis of multibeam bathymetry,gravity,and magnetic data were performed to investigate its variations in magma supply and crustal accretion process.The results revealed distinct across-axis variations of magma supply.Specifically,the regionally averaged crustal thickness reduced systematically from around 7 Ma to the present,indicating a regionally decreasing magma supply.The crustal structure is asymmetric in regional scale between the conjugate ridge flanks,with the faster-spreading southern flank showing thinner crust and greater degree of tectonic extension.Geodynamic models of mantle melting suggested that the observed variations in axial crustal thickness and major element geochemistry can be adequately explained by an eastward decrease in mantle potential temperature of about40℃ beneath the ridge axis.In this work,a synthesized model was proposed to explain the axial variations of magma supply and ridge segmentation stabilities.The existence of large ridge-axis offsets may play important roles in controlling melt supply.Several large ridge-axis offsets in the eastern section(21°–25°E)caused sustained along-axis focusing of magma supply at the centers of eastern ridge segments,enabling quasi-stable segmentation.In contrast,the western section(16°–21°E),which lacks large ridge-axis offsets,is associated with unstable segmentation patterns.展开更多
The Southwest Indian Ridge,which is the slowest-spreading of the main ridges,separates the African and Antarctic plates.The slow expanding rate is associated with less density of hydrothermal vent fields,shorter longe...The Southwest Indian Ridge,which is the slowest-spreading of the main ridges,separates the African and Antarctic plates.The slow expanding rate is associated with less density of hydrothermal vent fields,shorter longevity of hydrothermal activity,cold mantle temperatures and thick lithosphere.However,the microbial communities adapting to such specific characteristics of this area have remained largely unexplored.To study the microbial diversity at the Southwest Indian Ridge,we sampled three sediment cores in a newly found inactive vent field,the Tianzuo field,and used high-throughput sequencing of 16S rRNA genes to reveal the microbial composition.Microbial communities of three sampling sites were very similar at the surface,and underwent a gradient change along depth.Gammaproteobacteria,namely Alteromonadaceae,Nitrosococcus and the JTB255 marine benthic group,were the most dominant bacterial taxa.Marine Group I was the dominant archaeal taxon in our samples.In addition,microbial populations capable of ammonia oxidation,nitrite oxidation,sulfur oxidation and manganese oxidation were detected to be the main chemolithoautotrophs.The enrichment of sulfur-oxidizing and manganese-oxidizing bacteria was observed in deep layers.When compared with other vent fields along different ocean ridges,the Tianzuo field showed distinct composition in both archaeal and bacterial communities.These results provide the first view of microbial communities of the Tianzuo field at the Southwest Indian Ridge,and give a better understanding of metabolic potential possessed by the microbial populations.展开更多
Polymetallic sulfides have attracted more attentions,which are regarded as one of the potential seabed mineral resources for their high grade of precious metal elements such as Cu,Zn,Pb,Au,and Ag.Since2007,there are f...Polymetallic sulfides have attracted more attentions,which are regarded as one of the potential seabed mineral resources for their high grade of precious metal elements such as Cu,Zn,Pb,Au,and Ag.Since2007,there are four China dayang cruises(CDCs)with eight legs totally,which have been carried out to investigate polymetallic sulfides on the southwest Indian ridge(SWIR),and eight hydrothermal vents have been found.In2011,the China Ocean Mineral Resources Research and Development Association(COMRA)and International Seabed Authority(ISA)signed a 15-year contract for exploration for polymetallic sulfides located on the SWIR between 46°S and 53°S.The area allocated to the COMRA is approximately 10,000 km2.In this paper,we review the recent research advances about hydrothermal activity of the SWIR by the CDCs.As for the sulfides exploration in the future,some aspects should be emphasized,such as the controlling factors of sulfide mineralization on the SWIR,prospecting methods of inactive and buried sulfide deposits,sulfides resources assessment method,and the nearbottom sulfides exploration technology systems.展开更多
基金The National Key Research and Development Program of China under contract Nos 2017YFC0306603,2018YFC0309901,2016YFC0304905,2017YFC0306803 and 2018YFC0309902the China Ocean Mineral Resources Research and Development Association Major Project under contract Nos DY135-S1-1-01 and DY135-S1-1-02
文摘The ultraslow-spreading Southwest Indian Ridge （SWIR） to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely slow spreading rate, the easternmost SWIR was considered to be devoid of hydrothermal activity until the discovery of the inactive Mt. lourdanne hydrothermal field （27°51＇S, 63°56＇E） in 1998. During the COMRA DYl15-20 cruise in 2009, two additional hydrothermal fields （i.e., the Tiancheng （27°51＇S, 63°55＇E） and Tianzuo （27°57＇S, 63°32＇E） fields） were discovered. Further detailed investigations of these two hydrothermal sites were conducted by Chinese manned submersible liaolong in 2014-2015. The Tiancheng filed can he characterized as a low- temperature （up to 13.2℃） diffuse flow hydrothermal field, and is hosted by fractured basalts with hydrothermal fauna widespread on the seafloor. The Tianzuo hydrothermal field is an inactive sulfide field, which is hosted by ultramafic rocks and controlled by detachment fault. The discovery of the three hydrothermal fields around Segment #11 which receives more melt than the regional average, provided evidence for local enhanced magmatism providing heat source to drive hydrothermal circulation. We further imply that hydrothermal activity and sulfide deposits may be rather promising along the easternmost SWIR.
基金supported by the National Key Research and Development Program(Grant No.2022YFE0140200)the National Major Research Instrument Development Project of the National Natural Science Foundation of China(Grant No.42127807)+1 种基金the Key Research and Development Program of Zhejiang Province(Grant No.2021C03016)the China Ocean Mineral Resources R&D Association(COMRA)“the 13th Five-year”Project(Grant No.DY135-S1-1).
文摘Polymetallic sulfides present in mid-ocean ridges(MORs)have become important strategic resources for humans,and a scientific metallogenic model is necessary for the investigation and exploration of these resources.Compared to fast-and slow-spreading MORs,ultraslow-spreading MORs show substantial differences in magma supply,tectonic activity,and oceanic crust structures.However,information on hydrothermal circulation and a metallogenic model related to sulfides along the ultraslow-spreading ridges is still limited,which hinders further exploration of these resources.In this study,the distribution of hydrothermal activities,as well as the characteristics of the structures,heat sources,fluid pathways,host rock types,fluid properties,and sulfide assemblages in typical hydrothermal fields along the ultraslow-spreading Southwest Indian Ridge(SWIR),have been studied.It is concluded that the hydrothermal systems along the SWIR can be categorized into three types,including local enhanced magma-controlled,one-way detachment/high-angle large-offset fault-controlled,and flip-flop detachment-controlled types,which are further categorized into five subtypes based on their distinct geological backgrounds.Herein,we present a sulfide metallogenic model called Local Enhanced Heat Supply-Deep Faults(eHeat-dFault)for the SWIR.The overall spreading rate remains almost constant(14-18 mm/year),while the magma supply is heterogeneous in the segment scale along the SWIR.Over the past two decades,various hydrothermal systems and sulfide deposits have been identified along the SWIR.A deep magma chamber(4-9 km)is developed in the ridge segment with sufficient magma supply owing to the local enhanced magma supply,while long-lived active deep detachment faults(up to 13 km)with associated metallogenic belts are developed in ridge segments with poor magma supply.Hence,the ultraslow-spreading MORs fulfill the necessary conditions of a sustained heat source and stable hydrothermal pathway for the formation of large-scale polymetallic sulfide depo
基金The Program of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0205the National Natural Science Foundation of China under contract Nos 41890813,41976066,41976064,91858207,91958211 and 91628301+3 种基金the Program of Chinese Academy of Sciences under contract Nos Y4SL021001,QYZDY-SSW-DQC005 and133244KYSB20180029the National Key Research and Development Program of China under contract Nos 2018YFC0309800 and2018YFC0310105the Guangdong Basic and Applied Basic Research Foundation under contract No.2021A1515012227the Program of China Ocean Mineral Resources Research and Development Association under contract No.DY135-S2-1-04。
文摘The orthogonal supersegment of the ultraslow-spreading Southwest Indian Ridge at 16°–25°E is characterized by significant along-axis variations of mantle potential temperature.A detailed analysis of multibeam bathymetry,gravity,and magnetic data were performed to investigate its variations in magma supply and crustal accretion process.The results revealed distinct across-axis variations of magma supply.Specifically,the regionally averaged crustal thickness reduced systematically from around 7 Ma to the present,indicating a regionally decreasing magma supply.The crustal structure is asymmetric in regional scale between the conjugate ridge flanks,with the faster-spreading southern flank showing thinner crust and greater degree of tectonic extension.Geodynamic models of mantle melting suggested that the observed variations in axial crustal thickness and major element geochemistry can be adequately explained by an eastward decrease in mantle potential temperature of about40℃ beneath the ridge axis.In this work,a synthesized model was proposed to explain the axial variations of magma supply and ridge segmentation stabilities.The existence of large ridge-axis offsets may play important roles in controlling melt supply.Several large ridge-axis offsets in the eastern section(21°–25°E)caused sustained along-axis focusing of magma supply at the centers of eastern ridge segments,enabling quasi-stable segmentation.In contrast,the western section(16°–21°E),which lacks large ridge-axis offsets,is associated with unstable segmentation patterns.
基金the National Science Foundation of China(41530967,41776173,41576129)the National Key Research and Development Program of China(2016YFC03007).
文摘The Southwest Indian Ridge,which is the slowest-spreading of the main ridges,separates the African and Antarctic plates.The slow expanding rate is associated with less density of hydrothermal vent fields,shorter longevity of hydrothermal activity,cold mantle temperatures and thick lithosphere.However,the microbial communities adapting to such specific characteristics of this area have remained largely unexplored.To study the microbial diversity at the Southwest Indian Ridge,we sampled three sediment cores in a newly found inactive vent field,the Tianzuo field,and used high-throughput sequencing of 16S rRNA genes to reveal the microbial composition.Microbial communities of three sampling sites were very similar at the surface,and underwent a gradient change along depth.Gammaproteobacteria,namely Alteromonadaceae,Nitrosococcus and the JTB255 marine benthic group,were the most dominant bacterial taxa.Marine Group I was the dominant archaeal taxon in our samples.In addition,microbial populations capable of ammonia oxidation,nitrite oxidation,sulfur oxidation and manganese oxidation were detected to be the main chemolithoautotrophs.The enrichment of sulfur-oxidizing and manganese-oxidizing bacteria was observed in deep layers.When compared with other vent fields along different ocean ridges,the Tianzuo field showed distinct composition in both archaeal and bacterial communities.These results provide the first view of microbial communities of the Tianzuo field at the Southwest Indian Ridge,and give a better understanding of metabolic potential possessed by the microbial populations.
基金supported by the COMRA Program (DY125-11-R-01,05)the National Basic Research Program of China (2012CB417305)+2 种基金the Natural Science Foundation of Zhejiang Province Program (LY12D06006)the Scientific Research Fund of the Second Institute of Oceanography, State Oceanic Administration (JG1203)the science parties of CDC 19 Leg 2&3, CDC 20 Leg 4–7, and CDC 21 Leg 5–7, who contributed to the success of the project
文摘Polymetallic sulfides have attracted more attentions,which are regarded as one of the potential seabed mineral resources for their high grade of precious metal elements such as Cu,Zn,Pb,Au,and Ag.Since2007,there are four China dayang cruises(CDCs)with eight legs totally,which have been carried out to investigate polymetallic sulfides on the southwest Indian ridge(SWIR),and eight hydrothermal vents have been found.In2011,the China Ocean Mineral Resources Research and Development Association(COMRA)and International Seabed Authority(ISA)signed a 15-year contract for exploration for polymetallic sulfides located on the SWIR between 46°S and 53°S.The area allocated to the COMRA is approximately 10,000 km2.In this paper,we review the recent research advances about hydrothermal activity of the SWIR by the CDCs.As for the sulfides exploration in the future,some aspects should be emphasized,such as the controlling factors of sulfide mineralization on the SWIR,prospecting methods of inactive and buried sulfide deposits,sulfides resources assessment method,and the nearbottom sulfides exploration technology systems.
