Objective The Bayanhua Nb-enriched gabbro is newly discovered in the Diyanmiao-Meilaotewula SSZ-type ophiolitic m61ange belt of the Hegenshan suture zone, Inner Mongolia. Nb-enriched arc gabbros are usually believed ...Objective The Bayanhua Nb-enriched gabbro is newly discovered in the Diyanmiao-Meilaotewula SSZ-type ophiolitic m61ange belt of the Hegenshan suture zone, Inner Mongolia. Nb-enriched arc gabbros are usually believed to result from partial melting of the mantle wedge peridotites metasomatized by slab melts derived from the subducting oceanic slab, which represent arc magmatic markers of the oceanic subduction zone. However, whether the Hegenshan ocean basin of the Paleo-Asian Ocean was in its subduction stage in the Early Permian requires further study for a final conclusion, and what is the evolution process of the oceanic subduction and lithospheric mantle of the Hegenshan suture zone remains speculative for the lack of further definitely petrological and chronological evidence and constraints. Therefore, this study carried out zircon LA-ICP-MS U-Pb geochronology and geochemistry on the Bayanhua Nb-enriched gabbro to discuss its origin, in order to provide new evidence for the tectonic evolution of the Hegenshan suture zone of the eastern Central Asian Orogenic Belt.展开更多
The Guandimao and Wawutang plutons are located at the center of Hunan, South China. The former is mainly composed of biotite monzonitic granites/granodiorites and two-mica monzonltic granites, but the latter only cons...The Guandimao and Wawutang plutons are located at the center of Hunan, South China. The former is mainly composed of biotite monzonitic granites/granodiorites and two-mica monzonltic granites, but the latter only consists of biotite monzonitic granites. The zircon ages of 203.0±1.6 Ma （biotite monzonitic granites） and 208.0-23.2 Ma （two-mica monzonltic granites） for the Guandimao pluton and 204±3 Ma for the Wawutang pluton obtained with the LA-ICP-MS U-Pb dating indicate that they were formed during the late Indosinian. In consideration of other geochronological data from Indosinian rocks of South China and adjacent regions, it is inferred that the two plutons were derived from crustal materials by decompressional melting in a post-collisional tectonic setting during spontaneous thinning of the thickened curst. Moreover, the inherited zircon age of 1273±57 Ma from the Wawutang pluton indicates that the source of the two plutons is related to the early Proterozoic crustal basement.展开更多
Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or ura...Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or uranium matrix effect and alpha dose matrix effect,and illustrates the correction of these three effects.In addition,we point out the limitation and possible problems of the existing correction methods.展开更多
The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO<sub>2</sub> and low K<s...The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO<sub>2</sub> and low K<sub>2</sub>O,and depletion of light rare earth elements.They should be originated from a depleted asthenosphere mantle, belonging to ancient oceanic crust ophiolitic volcanic rock association.Compared with the Longba tholeiitic basalt,the Ganlongtang tholeiitic basalt shows展开更多
Listwanite is a suite of silica-carbonate alteration products formed when CO2-bearing hydrothermal fluids meet and react with serpentinized mafic and ultramafic rocks （Robinson et al., 2005）. This alteration product...Listwanite is a suite of silica-carbonate alteration products formed when CO2-bearing hydrothermal fluids meet and react with serpentinized mafic and ultramafic rocks （Robinson et al., 2005）. This alteration product is of great economic significance. Gold, mercury, magnesite and base metal deposits are often associated with listwanite. In China, the petrogenesis of listwanite and related mineralization has received insufficient attention to date. This outcropping paper reports the study along the northeast edge of the of listwanite Baer ophiolite,展开更多
This investigation reports the first discovery of more than 70 tuff intervals in the Upper Triassic,South Qilian Basin.Petrographic and geochemical analyses were carried out on ten tuff samples and zircon U-Pb dating ...This investigation reports the first discovery of more than 70 tuff intervals in the Upper Triassic,South Qilian Basin.Petrographic and geochemical analyses were carried out on ten tuff samples and zircon U-Pb dating were on three.Thin section and X-ray diffraction(XRD)results indicate that the tuffs were composed of crystal shards and altered glass shards;crystal shards include plagio-clase and quartz.Most of the tuffs had been transformed into illite/smectite mixed-layers(I/S).In addition,calcite,pyrite,dolomite and siderite were also identified in some of the tuff samples.Analysis of major elements suggests that the tuffs are peraluminous high-K calcalkaline series.Trace elements indicate that the tuffs are enriched in high field strength elements(HFSE),including Th,U,Ta,Zr and Hf.Geochemical characteristics suggest that the tuffs originated from comendite pantellerite and rhyolite from within plate setting.Zircon U-Pb dating(236.0±1.7,231.4±1.6,and 223.1±3.9 Ma)indicate that the tuffs were erupted in the Late Triassic.Comparative chronology and geochemical analyses suggest that the West Qinling belt and the East Kunlun belt are the potential source regions of these tuffs,and they originated from the within plate magma during a post-collisional period.展开更多
Garnet is a primary mineral in skarn deposits and plays a significant role in recording copious mineralization and metallogenic information.This study systematically investigates the geochemistry and geochronology of ...Garnet is a primary mineral in skarn deposits and plays a significant role in recording copious mineralization and metallogenic information.This study systematically investigates the geochemistry and geochronology of garnet and zircon in the Dafang Au-Pb-Zn-Ag deposit,which represents prominent gold mineralization in southern Hunan,China.Garnet samples with distinct zoning patterns and compositional variations were identified using various analytical techniques,including Backscattered Electron(BSE)imaging,Cathodoluminescence(CL)response,textural characterization,and analysis of rare-earth elements(REE),major contents,and trace element compositions.The garnet was dated U-Pb dating,which yielded a lower intercept age of 161.06±1.93 Ma.This age is older than the underlying granodiorite porphyry,which has a concordia age of 155.13±0.95 Ma determined by zircon U-Pb dating.These results suggest that the gold mineralization may be related to the concealed granite.Two groups of garnet changed from depleted Al garnet to enriched Al garnet,and the rare earth element(REE)patterns of these groups were converted from light REE(LREE)-enriched and heavy REE(HREE)-depleted with positive europium(Eu)anomalies to medium REE(MREE)-enriched from core to rim zoning.The different REE patterns of garnet in various zones may be attributed to changes in the fluid environment and late superposition alteration.The development of distal skarn in the southern Hunan could be a significant indicator for identifying gold mineralization.展开更多
The Hesar pluton in the northern Urumieh-Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves(MMEs).Whole rock geochemistry,mineral chemistry,zircon U-Pb and Sr-Nd isotopes were measured.It is suggested th...The Hesar pluton in the northern Urumieh-Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves(MMEs).Whole rock geochemistry,mineral chemistry,zircon U-Pb and Sr-Nd isotopes were measured.It is suggested that the rocks are metaluminous(A/CNK=1.32-1.45),subduction-related I-type calc-alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures.The host rocks yielded an U-Pb crystallization age of 37.3±0.4 Ma for gabbro-diorite.MMEs have relatively low SiO_(2) contents(52.9-56.6 wt%)and high Mg^(#)(49.8-58.7),probably reflecting a mantle-derived origin.Chondrite-and mantle-normalized trace element patterns are characterized by LREE and LILE enrichment,HREE and HFSE depletion with slight negative Eu anomalies(Eu/Eu^(*)=0.86-1.03).The host rocks yield(^(87)Sr/^(86)Sr)_(i) ratios of 0.70492-0.70510,positive ε_(Nd)(t)values of+1.55-+2.06 and T_(DM2)of 707-736 Ma,which is consistent with the associated mafic microgranular enclaves((^(87)Sr/^(86)Sr)_(i)=0.705014,ε_(Nd)(t)=+1.75,T_(DM2)=729 Ma).All data suggest magma-mixing for enclave and host rock formation,showing a complete equilibration between mixed-mafic and felsic magmas,followed by rapid diffusion.The T_(DM1)(Nd)and T_(DM2)(Nd)model ages and U-Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantlederived magmas in a pre-collisional setting of Arabian-Eurasian plates.Clinopyroxene composition indicates a crystallization temperature of~1000℃ and a depth of~9 km.展开更多
The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UH...The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.展开更多
We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing s...We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive εNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2O5 (～1.00%), TiO2 (～3.08%) and HFSE (e.g., Nb=9.53–10.27 ppm). Their Nd isotopic compositions (εNd(t)=6.8–8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (A/CNK=0.84–0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) is consistent with “SSZ-type” plagiogranite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive εHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (εNd(t)=7.5–8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active continental margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling asthenosphere below the slab window may have provided significant thermodynamic conditions.展开更多
基金funded by the National Natural Science Foundation of China (grant No.41502211)the China Geological Survey (grants No.1212011120701 and 1212011120711)Hebei Province Education Department (grant No.ZC20165013)
文摘Objective The Bayanhua Nb-enriched gabbro is newly discovered in the Diyanmiao-Meilaotewula SSZ-type ophiolitic m61ange belt of the Hegenshan suture zone, Inner Mongolia. Nb-enriched arc gabbros are usually believed to result from partial melting of the mantle wedge peridotites metasomatized by slab melts derived from the subducting oceanic slab, which represent arc magmatic markers of the oceanic subduction zone. However, whether the Hegenshan ocean basin of the Paleo-Asian Ocean was in its subduction stage in the Early Permian requires further study for a final conclusion, and what is the evolution process of the oceanic subduction and lithospheric mantle of the Hegenshan suture zone remains speculative for the lack of further definitely petrological and chronological evidence and constraints. Therefore, this study carried out zircon LA-ICP-MS U-Pb geochronology and geochemistry on the Bayanhua Nb-enriched gabbro to discuss its origin, in order to provide new evidence for the tectonic evolution of the Hegenshan suture zone of the eastern Central Asian Orogenic Belt.
基金This research was supported by the National Natural Science Foundation of China （No. 40372036）the Key Project of the Ministry of Education, China （No. 306007）.
文摘The Guandimao and Wawutang plutons are located at the center of Hunan, South China. The former is mainly composed of biotite monzonitic granites/granodiorites and two-mica monzonltic granites, but the latter only consists of biotite monzonitic granites. The zircon ages of 203.0±1.6 Ma （biotite monzonitic granites） and 208.0-23.2 Ma （two-mica monzonltic granites） for the Guandimao pluton and 204±3 Ma for the Wawutang pluton obtained with the LA-ICP-MS U-Pb dating indicate that they were formed during the late Indosinian. In consideration of other geochronological data from Indosinian rocks of South China and adjacent regions, it is inferred that the two plutons were derived from crustal materials by decompressional melting in a post-collisional tectonic setting during spontaneous thinning of the thickened curst. Moreover, the inherited zircon age of 1273±57 Ma from the Wawutang pluton indicates that the source of the two plutons is related to the early Proterozoic crustal basement.
文摘Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or uranium matrix effect and alpha dose matrix effect,and illustrates the correction of these three effects.In addition,we point out the limitation and possible problems of the existing correction methods.
文摘The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO<sub>2</sub> and low K<sub>2</sub>O,and depletion of light rare earth elements.They should be originated from a depleted asthenosphere mantle, belonging to ancient oceanic crust ophiolitic volcanic rock association.Compared with the Longba tholeiitic basalt,the Ganlongtang tholeiitic basalt shows
基金funded by the Key project of national natural science funds (40930313)Chinese Geological Survey Project Funds (12120114061801, 12120114057701 and 12120114061501)
文摘Listwanite is a suite of silica-carbonate alteration products formed when CO2-bearing hydrothermal fluids meet and react with serpentinized mafic and ultramafic rocks （Robinson et al., 2005）. This alteration product is of great economic significance. Gold, mercury, magnesite and base metal deposits are often associated with listwanite. In China, the petrogenesis of listwanite and related mineralization has received insufficient attention to date. This outcropping paper reports the study along the northeast edge of the of listwanite Baer ophiolite,
基金supported by the National Natural Science Foundation of China(Nos.41702144,42002194)the Natural Science Basic Research Plan of Shaanxi Province,China(Nos.2019JQ-991,2020JQ-746).
文摘This investigation reports the first discovery of more than 70 tuff intervals in the Upper Triassic,South Qilian Basin.Petrographic and geochemical analyses were carried out on ten tuff samples and zircon U-Pb dating were on three.Thin section and X-ray diffraction(XRD)results indicate that the tuffs were composed of crystal shards and altered glass shards;crystal shards include plagio-clase and quartz.Most of the tuffs had been transformed into illite/smectite mixed-layers(I/S).In addition,calcite,pyrite,dolomite and siderite were also identified in some of the tuff samples.Analysis of major elements suggests that the tuffs are peraluminous high-K calcalkaline series.Trace elements indicate that the tuffs are enriched in high field strength elements(HFSE),including Th,U,Ta,Zr and Hf.Geochemical characteristics suggest that the tuffs originated from comendite pantellerite and rhyolite from within plate setting.Zircon U-Pb dating(236.0±1.7,231.4±1.6,and 223.1±3.9 Ma)indicate that the tuffs were erupted in the Late Triassic.Comparative chronology and geochemical analyses suggest that the West Qinling belt and the East Kunlun belt are the potential source regions of these tuffs,and they originated from the within plate magma during a post-collisional period.
基金financially supported by the National Key Research and Development Plan(Grant No.2023YFC2906801)。
文摘Garnet is a primary mineral in skarn deposits and plays a significant role in recording copious mineralization and metallogenic information.This study systematically investigates the geochemistry and geochronology of garnet and zircon in the Dafang Au-Pb-Zn-Ag deposit,which represents prominent gold mineralization in southern Hunan,China.Garnet samples with distinct zoning patterns and compositional variations were identified using various analytical techniques,including Backscattered Electron(BSE)imaging,Cathodoluminescence(CL)response,textural characterization,and analysis of rare-earth elements(REE),major contents,and trace element compositions.The garnet was dated U-Pb dating,which yielded a lower intercept age of 161.06±1.93 Ma.This age is older than the underlying granodiorite porphyry,which has a concordia age of 155.13±0.95 Ma determined by zircon U-Pb dating.These results suggest that the gold mineralization may be related to the concealed granite.Two groups of garnet changed from depleted Al garnet to enriched Al garnet,and the rare earth element(REE)patterns of these groups were converted from light REE(LREE)-enriched and heavy REE(HREE)-depleted with positive europium(Eu)anomalies to medium REE(MREE)-enriched from core to rim zoning.The different REE patterns of garnet in various zones may be attributed to changes in the fluid environment and late superposition alteration.The development of distal skarn in the southern Hunan could be a significant indicator for identifying gold mineralization.
基金supported by the Iran National Science Foundation(INSF)(Grant No.98012578)projects from the National Natural Science Foundation of China(Grant Nos.41473033,41673031)。
文摘The Hesar pluton in the northern Urumieh-Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves(MMEs).Whole rock geochemistry,mineral chemistry,zircon U-Pb and Sr-Nd isotopes were measured.It is suggested that the rocks are metaluminous(A/CNK=1.32-1.45),subduction-related I-type calc-alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures.The host rocks yielded an U-Pb crystallization age of 37.3±0.4 Ma for gabbro-diorite.MMEs have relatively low SiO_(2) contents(52.9-56.6 wt%)and high Mg^(#)(49.8-58.7),probably reflecting a mantle-derived origin.Chondrite-and mantle-normalized trace element patterns are characterized by LREE and LILE enrichment,HREE and HFSE depletion with slight negative Eu anomalies(Eu/Eu^(*)=0.86-1.03).The host rocks yield(^(87)Sr/^(86)Sr)_(i) ratios of 0.70492-0.70510,positive ε_(Nd)(t)values of+1.55-+2.06 and T_(DM2)of 707-736 Ma,which is consistent with the associated mafic microgranular enclaves((^(87)Sr/^(86)Sr)_(i)=0.705014,ε_(Nd)(t)=+1.75,T_(DM2)=729 Ma).All data suggest magma-mixing for enclave and host rock formation,showing a complete equilibration between mixed-mafic and felsic magmas,followed by rapid diffusion.The T_(DM1)(Nd)and T_(DM2)(Nd)model ages and U-Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantlederived magmas in a pre-collisional setting of Arabian-Eurasian plates.Clinopyroxene composition indicates a crystallization temperature of~1000℃ and a depth of~9 km.
基金supported by the National Nature Science Foundation of China(Grant no.41972050).
文摘The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.
基金Supported by China Geological Survey (Grant No. 1212010610611) the Ministry of Land and Resources (Grant No. 200811015)
文摘We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive εNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2O5 (～1.00%), TiO2 (～3.08%) and HFSE (e.g., Nb=9.53–10.27 ppm). Their Nd isotopic compositions (εNd(t)=6.8–8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (A/CNK=0.84–0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) is consistent with “SSZ-type” plagiogranite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive εHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (εNd(t)=7.5–8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active continental margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling asthenosphere below the slab window may have provided significant thermodynamic conditions.
