Changbaishan,an intraplate volcano,is characterized by an approximately 6 km wide summit caldera and last erupted in 1903.Changbaishan experienced a period of unrest between 2002 and 2006.The activity developed in thr...Changbaishan,an intraplate volcano,is characterized by an approximately 6 km wide summit caldera and last erupted in 1903.Changbaishan experienced a period of unrest between 2002 and 2006.The activity developed in three main stages,including shield volcano(basalts),cone-construction(trachyandesites to trachytes with minor basalts),and caldera-forming stages(trachytes to comendites).This last stage is associated with one of the more energetic eruptions of the last millennium on Earth,the 946 CE,VEI 7 Millennium Eruption(ME),which emitted over 100 km^(3) of pyroclastics.Compared to other active calderas,the plumbing system of Changbaishan and its evolution mechanisms remain poorly constrained.Here,we merge new whole-rock,glass,mineral,isotopic,and geobarometry data with geophysical data and present a model of the plumbing system.The results show that the volcano is characterized by at least three main magma reservoirs at different depths:a basaltic reservoir at the Moho/lower crust depth,an intermediate reservoir at 10-15 km depth,and a shallower reservoir at 0.5-3 km depth.The shallower reservoir was involved in the ME eruption,which was triggered by a fresh trachytic melt entering a shallower reservoir where a comenditic magma was stored.The trachytes and comendites originate from fractional crystallization processes and minor assimilation of upper crust material,while the less evolved melts assimilate lower crust material.Syn-eruptive magma mingling occurred during the ME eruption phase.The magma reservoirs of the caldera-forming stage partly reactivate those of the cone-construction stage.The depth of the magma storage zones is controlled by the layering of the crust.The plumbing system of Changbaishan is vertically extensive,with crystal mush reservoirs renewed by the replenishment of new trachytic to trachyandesitic magma from depth.Unlike other volcanoes,evidence of a basaltic recharge is lacking.The interpretation of the signals preceding possible future eruptions should consider the multi-level nature of t展开更多
Clay-type Li deposits are poised to play a pivotal role in addressing the surging global demand for Li.The McDermitt clay-type Li deposit,located in Nevada,is the largest Li deposit in the United States,with Li hosted...Clay-type Li deposits are poised to play a pivotal role in addressing the surging global demand for Li.The McDermitt clay-type Li deposit,located in Nevada,is the largest Li deposit in the United States,with Li hosted by a clay-rich sequence of smectite-dominated intervals and illite-dominated intervals,respectively.However,the occurrence of Li and the genesis of Li-bearing minerals within smectite-dominated intervals have not been thoroughly investigated in previous research.Here,we studied the mineralogy,the in-situ Li distribution,and the bonding environments of Li within the smectite intervals using a combination of instru-mental techniques including scanning electron microscope,transmission electron microscope,time-of-flight secondary ion mass spectrometry,and nuclear magnetic resonance.Our results indicate that the smectite exhibits low crystallinity characteristics of lacustrine clay authigenesis and is com-monly found tofill the interstices among volcanic minerals or envelop them;Li is mainly hosted by Mg-smectite rather than the volcanic minerals.Within the tuffaceous sediment samples,the volcanic glass has undergone a transformation,resulting in its complete disappearance and alteration into clay minerals.Owing to the octahedral sites of Mg-smectite bounded in Li,it is referred to be hectorite.We interpret that the hectorite’s precipitation occurs in a high saline-alkaline water environment,a result of McDermitt tuffdissolution.This conclusion can be supported by the coexistence of spherulitic calcite and hectorite.Overall,this study confirms hectorite as the main Li-bearing mineral and increases the understanding of the genetic model of hectorite formation in intracontinental caldera basins.展开更多
This work assessed the impact of land use and land cover (LULC) change on the socio-economic conditions of the inhabitants in the Mount Bambouto Caldera from 1980-2016. To achieve this, three time series satellite ima...This work assessed the impact of land use and land cover (LULC) change on the socio-economic conditions of the inhabitants in the Mount Bambouto Caldera from 1980-2016. To achieve this, three time series satellite images;Landsat Thematic Mapper (TM) (1980), Landsat Enhanced Thematic Mapper (ETM) (2001), and Landsat 8 Operational Land Imager (OLI) (2016) scenes were employed to investigate the changes in LULC. The use of satellite images was supplemented with individual interviews, discussions with focus groups and key informants, and direct field observations. Five categories of LULC classes were identified namely: thick woody vegetation (natural forest and oil palms), light vegetation (croplands), savannah (grasslands), buildings (settlements), and bare grounds. The results showed that between 1980 and 2016, croplands, buildings and bare lands increased by 4%, 0.43% and 5.7% respectively while savannah/grassland and natural forest decreased by 4.4% and 5.8% respectively. Household survey revealed soil fertility decline and lack of credit schemes to be major constraints to crop production. Many religious holidays contribute to seasonal food shortages and the community faces a host of socio-economic and institutional challenges. Consequently, majority of house-holds are destitute, live in abject poverty;which is an indication of the need for interventions by government and other development stakeholders to tackle the problems of soil fertility, land use change and food insecurity.展开更多
The eastern side of Alta Floresta Mineral Province(AFMP)(União do Norte region)comprises an effusive/-subvolcanic phase,explosive phase,and epiclastic rocks.The effusive/subvolcanic phase comprises massive porphy...The eastern side of Alta Floresta Mineral Province(AFMP)(União do Norte region)comprises an effusive/-subvolcanic phase,explosive phase,and epiclastic rocks.The effusive/subvolcanic phase comprises massive porphyritic rhyolite with different degrees of crystallinity,porphyritic rhyolite with flow structure,and microcrystalline rhyolite.The explosive phase is characterized by welded lapilli tuff,lapilli tuff with flow structure,stratified lapilli tuff,and tuff with accretionary lapilli.Sandstones and siltstones characterize epiclastic rocks.There are porphyritic rhyolite dikes that cut the volcanic sequence.The rocks of the Colíder Group are rhyolites(>70%SiO2)with calcic-alkaline to alkaline-calcic affinity.A rhyolitic rock is predominantly ferroan and metaluminous,while a pyroclastic rock is predominantly magnesian to ferroan and meta-to peraluminous in composition.The rocks have a high LREE content,and slight fractionation of HREE suggests they have hybrid geochemical characteristics of high potassium calc-alkaline,shoshonitic,and suggestive affinities of A-type magmas,probably produced in a post-collisional orogenic environment.These rocks have a relatively high level of Ba and Rb and a negative anomaly for Sr,P,Nb,Ta,and Ti,suggesting an intra-plate mantle source with contributions from a metasomatized mantle edge.The rocks do not have adakitic characteristics nor fertility for Cu-Au(Sr/Y<1.9 and LaN/YbN<38.0)as in other regions of the AFMP.The welded lapilli tuff rocks show U-Pb age of 1838±17 Ma and 1817±2 Ma and are the older explosive phases.The effusive/subvolcanic phase has U-Pb ages of 1800±3 Ma and 1792±3 Ma obtained in the massive porphyritic rhyolite.The age interval of approximately 46 Ma(1838–1792 Ma)suggests the presence of two or more volcanic cycles or distinct volcanic events.Based on the interpretation of volcanic and epiclastic deposits and remote sensing products,the paleoenvironmental reconstruction includes subaerial with effusive/subvolcanic and explosive stages in a probable ero展开更多
The study on empowerment strategies for tourism sustainability was carried out in 16 geosites located in seven regencies. These include Karo, Dairi, Simalungun, Samosir, Toba Samosir, North Tapanuli, and Humbang Hasun...The study on empowerment strategies for tourism sustainability was carried out in 16 geosites located in seven regencies. These include Karo, Dairi, Simalungun, Samosir, Toba Samosir, North Tapanuli, and Humbang Hasundutan, in Toba Caldera Region (TCA), North Sumatra Province. The empowerment strategies will enhance local and national tourism development policy directives, boost development geared towards community tourism interests, and achieve GGN directives according to the concepts outlined by UNESCO. This geotourism development has been formulated through a synthesis of various investigations including the analyses of government references, potential tourist attractions, and SWOT. Furthermore, the SWOT analysis showed that a travel plan combining the elements of cultural heritage and geosites is an alternative empowerment for sustainable regional development through geotourism, using Pusuk Bukit as a pilot area. Geosites have been mapped as the basis for Toba Caldera’s development.展开更多
基金funded by the National Natural Science Foundation of China under Grant Nos.41972313 and 41790453by the Engineering Research Center of Geothermal Resources Development Technology and Equipment,Ministry of Education,Jilin University,China.
文摘Changbaishan,an intraplate volcano,is characterized by an approximately 6 km wide summit caldera and last erupted in 1903.Changbaishan experienced a period of unrest between 2002 and 2006.The activity developed in three main stages,including shield volcano(basalts),cone-construction(trachyandesites to trachytes with minor basalts),and caldera-forming stages(trachytes to comendites).This last stage is associated with one of the more energetic eruptions of the last millennium on Earth,the 946 CE,VEI 7 Millennium Eruption(ME),which emitted over 100 km^(3) of pyroclastics.Compared to other active calderas,the plumbing system of Changbaishan and its evolution mechanisms remain poorly constrained.Here,we merge new whole-rock,glass,mineral,isotopic,and geobarometry data with geophysical data and present a model of the plumbing system.The results show that the volcano is characterized by at least three main magma reservoirs at different depths:a basaltic reservoir at the Moho/lower crust depth,an intermediate reservoir at 10-15 km depth,and a shallower reservoir at 0.5-3 km depth.The shallower reservoir was involved in the ME eruption,which was triggered by a fresh trachytic melt entering a shallower reservoir where a comenditic magma was stored.The trachytes and comendites originate from fractional crystallization processes and minor assimilation of upper crust material,while the less evolved melts assimilate lower crust material.Syn-eruptive magma mingling occurred during the ME eruption phase.The magma reservoirs of the caldera-forming stage partly reactivate those of the cone-construction stage.The depth of the magma storage zones is controlled by the layering of the crust.The plumbing system of Changbaishan is vertically extensive,with crystal mush reservoirs renewed by the replenishment of new trachytic to trachyandesitic magma from depth.Unlike other volcanoes,evidence of a basaltic recharge is lacking.The interpretation of the signals preceding possible future eruptions should consider the multi-level nature of t
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.92162214,41773015,and U1812402)the Key Research and Development Program of Yunnan Province(202103AQ100003).
文摘Clay-type Li deposits are poised to play a pivotal role in addressing the surging global demand for Li.The McDermitt clay-type Li deposit,located in Nevada,is the largest Li deposit in the United States,with Li hosted by a clay-rich sequence of smectite-dominated intervals and illite-dominated intervals,respectively.However,the occurrence of Li and the genesis of Li-bearing minerals within smectite-dominated intervals have not been thoroughly investigated in previous research.Here,we studied the mineralogy,the in-situ Li distribution,and the bonding environments of Li within the smectite intervals using a combination of instru-mental techniques including scanning electron microscope,transmission electron microscope,time-of-flight secondary ion mass spectrometry,and nuclear magnetic resonance.Our results indicate that the smectite exhibits low crystallinity characteristics of lacustrine clay authigenesis and is com-monly found tofill the interstices among volcanic minerals or envelop them;Li is mainly hosted by Mg-smectite rather than the volcanic minerals.Within the tuffaceous sediment samples,the volcanic glass has undergone a transformation,resulting in its complete disappearance and alteration into clay minerals.Owing to the octahedral sites of Mg-smectite bounded in Li,it is referred to be hectorite.We interpret that the hectorite’s precipitation occurs in a high saline-alkaline water environment,a result of McDermitt tuffdissolution.This conclusion can be supported by the coexistence of spherulitic calcite and hectorite.Overall,this study confirms hectorite as the main Li-bearing mineral and increases the understanding of the genetic model of hectorite formation in intracontinental caldera basins.
文摘This work assessed the impact of land use and land cover (LULC) change on the socio-economic conditions of the inhabitants in the Mount Bambouto Caldera from 1980-2016. To achieve this, three time series satellite images;Landsat Thematic Mapper (TM) (1980), Landsat Enhanced Thematic Mapper (ETM) (2001), and Landsat 8 Operational Land Imager (OLI) (2016) scenes were employed to investigate the changes in LULC. The use of satellite images was supplemented with individual interviews, discussions with focus groups and key informants, and direct field observations. Five categories of LULC classes were identified namely: thick woody vegetation (natural forest and oil palms), light vegetation (croplands), savannah (grasslands), buildings (settlements), and bare grounds. The results showed that between 1980 and 2016, croplands, buildings and bare lands increased by 4%, 0.43% and 5.7% respectively while savannah/grassland and natural forest decreased by 4.4% and 5.8% respectively. Household survey revealed soil fertility decline and lack of credit schemes to be major constraints to crop production. Many religious holidays contribute to seasonal food shortages and the community faces a host of socio-economic and institutional challenges. Consequently, majority of house-holds are destitute, live in abject poverty;which is an indication of the need for interventions by government and other development stakeholders to tackle the problems of soil fertility, land use change and food insecurity.
文摘The eastern side of Alta Floresta Mineral Province(AFMP)(União do Norte region)comprises an effusive/-subvolcanic phase,explosive phase,and epiclastic rocks.The effusive/subvolcanic phase comprises massive porphyritic rhyolite with different degrees of crystallinity,porphyritic rhyolite with flow structure,and microcrystalline rhyolite.The explosive phase is characterized by welded lapilli tuff,lapilli tuff with flow structure,stratified lapilli tuff,and tuff with accretionary lapilli.Sandstones and siltstones characterize epiclastic rocks.There are porphyritic rhyolite dikes that cut the volcanic sequence.The rocks of the Colíder Group are rhyolites(>70%SiO2)with calcic-alkaline to alkaline-calcic affinity.A rhyolitic rock is predominantly ferroan and metaluminous,while a pyroclastic rock is predominantly magnesian to ferroan and meta-to peraluminous in composition.The rocks have a high LREE content,and slight fractionation of HREE suggests they have hybrid geochemical characteristics of high potassium calc-alkaline,shoshonitic,and suggestive affinities of A-type magmas,probably produced in a post-collisional orogenic environment.These rocks have a relatively high level of Ba and Rb and a negative anomaly for Sr,P,Nb,Ta,and Ti,suggesting an intra-plate mantle source with contributions from a metasomatized mantle edge.The rocks do not have adakitic characteristics nor fertility for Cu-Au(Sr/Y<1.9 and LaN/YbN<38.0)as in other regions of the AFMP.The welded lapilli tuff rocks show U-Pb age of 1838±17 Ma and 1817±2 Ma and are the older explosive phases.The effusive/subvolcanic phase has U-Pb ages of 1800±3 Ma and 1792±3 Ma obtained in the massive porphyritic rhyolite.The age interval of approximately 46 Ma(1838–1792 Ma)suggests the presence of two or more volcanic cycles or distinct volcanic events.Based on the interpretation of volcanic and epiclastic deposits and remote sensing products,the paleoenvironmental reconstruction includes subaerial with effusive/subvolcanic and explosive stages in a probable ero
文摘The study on empowerment strategies for tourism sustainability was carried out in 16 geosites located in seven regencies. These include Karo, Dairi, Simalungun, Samosir, Toba Samosir, North Tapanuli, and Humbang Hasundutan, in Toba Caldera Region (TCA), North Sumatra Province. The empowerment strategies will enhance local and national tourism development policy directives, boost development geared towards community tourism interests, and achieve GGN directives according to the concepts outlined by UNESCO. This geotourism development has been formulated through a synthesis of various investigations including the analyses of government references, potential tourist attractions, and SWOT. Furthermore, the SWOT analysis showed that a travel plan combining the elements of cultural heritage and geosites is an alternative empowerment for sustainable regional development through geotourism, using Pusuk Bukit as a pilot area. Geosites have been mapped as the basis for Toba Caldera’s development.
