Tongbai-Dabie orogenic belt in Central China is a part of the collisional belt between the Yangtze and North China cratons. It represents one of the most extensive ultrahigh-pressure （UHP） and high-pressure （HP） m...Tongbai-Dabie orogenic belt in Central China is a part of the collisional belt between the Yangtze and North China cratons. It represents one of the most extensive ultrahigh-pressure （UHP） and high-pressure （HP） metamorphic rocks in the world. The Pb isotope mapping in this area is a significant method to constrain the crustal structure and tectonic evolution and to identify the tectonic boundaries within the vertical tectonic stack. Based on the Pb isotope compositions of the Dabie complex （DBC）, the Tongbai complex （TBC）, UHP and HP metamorphic rocks and associated foliated granites, the lower metamorphosed rocks from North Huaiyang （NHY） tectonic belt, and Cretaceous granites in the Tongbai-Dabie orogenic belt, we determined the Pb isotope geochemical map of the Tongbai-Dabie orogenic belt. The Pb isotope map shows that the Pb isotope compositions are similar within each geological body or lithotectonic unit, but the Pb isotope compositions of different lithotectonic units show systematic variations in the Tongbai-Dabie orogenic belt. The NHY tectonic belt contrasts strongly with the Tongbai-Dabie UHP.HP metamorphic belt in Pb isotope compositions. It is suggested that the line along the Xiaotian-Mozitan fault, the north limit of the Tongbai-Dabie UHP and HP metamorphic rocks, represents an important tectonic boundary. Within the Tongbai-Dabie HP -UHP metamorphic belt, to the south of Xiaotian-Mozitan fault, the vertical variations of Pb isotope compositions in different lithotectonic units and the spatial relationship among different major lithotectonic units have been constrained.展开更多
The Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite. Sr...The Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite. Sr-Nd-Pb isotopes of the intrusions show that the porphyritic syenogranite has initial ^87Sr/^86Sr ratios of 0.70418-0.70952, ENd（t） values of 1.3 to 2.1 （t=143 Ma）, ^206Pb/^204Pb ratios of 19.191-19.573, ^207Tpb/^204pb ratios of 15.551-15.572, and ^208Pb/^204Pb ratios of 38.826-39.143. The monzogranite has initial 87Sr/86Sr ratios of 0.70293-0.71305, εNd（t） values of 1.1 to 2.0 （t=-147 Ma）, ^206Pb/^204pb ratios of 19.507-20.075, ^207Pb/^204Pb ratios of 15.564-15.596, and ^208Pb/^204Pb ratios of 39.012-39.599. The calculated Nd model ages （TDM） for monzogranite and porphyritic syenogranite range from 866 to 1121 Ma and 795 to 1020 Ma, respectively. The granitic rocks in the Hashitu area have the same isotope range as granites in the southern parts of the Great Hinggan Range. The isotope composition indicates that these granites are derived from the partial melting of a juvenile lower crust originating from a depleted mantle with minor contamination by ancient continental crust. The integrating our results with published data and the Late Mesozoic regional tectonic setting of the region suggest that the granites in the Hashitu area formed in an intra-continent extensional setting, and they are related to the thinning of the thickened lithosphere and upwelling of the asthenosphere.展开更多
The Indosinian post-collisional Wulong pluton intruded into the Mesoproterozoic Fuping Group, South Qinling, central China. In the southern part of the pluton, some mafic enclaves have sharp or gradational contact rel...The Indosinian post-collisional Wulong pluton intruded into the Mesoproterozoic Fuping Group, South Qinling, central China. In the southern part of the pluton, some mafic enclaves have sharp or gradational contact relationships with the host biotite granodiorite. Geochemistry, zircon LA-ICP MS （laser ablation inductively-coupled plasma mass spectrometry） U-Pb chronology and Sr- Nd-Pb isotope geochemistry of the pluton are reported in this paper. The biotite granodiorite shows close compositional similarities to high-silica adakite. Its chondrite-normalized REE patterns are characterized by strong HREE depletion （Yb = 0.33--0.96 10-6 and Y = 4.77-11.19 ×10^-6）, enrichment of Ba （775-1386 x 10-6） and Sr （643-1115 × 10^-6） and high Sr/Y （57.83-159.99） and Y/Yb （10.99-14.32） ratios, as well as insignificant Eu anomalies （6Eu = 0.70-0.83）, suggesting a feldspar-poor, garnet±amphibole-rich residual mineral assemblage. The mafic enclaves have higher MgO （4.15- 8.13%）, Cr （14.79-371.31 × 10-6）, Ni （20.00-224.24× 10^-6） and Nb/Ta （15.42-21.91） than the host granodiorite, implying that they are mantle-derived and might represent underplated mafic magma. Zircon LA-ICP MS dating of the granodiorite yields a ^206pb/^238U weighted mean age of 208±2 Ma （MSWD=0.50, 1σ）, which is the age of emplacement of the host biotite granodiorite. This age indicates that the Wulong pluton formed during the late-orogenic or post-collisional stage （〈242±21 Ma） of the South Qinling belt. The host biotite granodiorite displays ^87Sr/^86Sr = 0.7059-0.7062, Isr = 0.7044-- 0.7050,^143Nd/^144Nd = 0.51236-0.51238, εNd（t）= -2.26 to -2.66 to ^206Pb/^204pb = 18.099-18.209, ^207pb/^204pb = 15.873-15.979 and ^208pb/^204pb = 38.973-39.430. Those ratios are similar to those of the Mesoproterozoic Yaolinghe Group in the South Qinling. Furthermore, its Nd isotopic model age （-1.02 Ga） is consistent with the age （-1.1 Ga） of the Yaolinghe Group. Based on the integrated geological and geochemical studies, coupled with previous studies, the authors suggest that the Wulong adakitic biotite granodiorite was probably generated by dehydration melting of the Yaolinghe Group-like thickened mafic crust, triggered by underplating of mafic magma at the boundary of the thickened mafic crust and hot lithospheric mantle, and that the Wulong adakitic biotite granodiorite may have resulted from thinning and delamination of the lower crust or breakoff of the subducting slab of the Mianlue ocean during the Indosinian post-collisional orogenic stage of the Qinling orogenic belt.展开更多
Voluminous Early Cretaceous granitoids and associated large-scale ore deposits are distributed within the southern Great Xing'an Range(SGXR),NE China.Based on previously published geochronology and zircon Hf-isoto...Voluminous Early Cretaceous granitoids and associated large-scale ore deposits are distributed within the southern Great Xing'an Range(SGXR),NE China.Based on previously published geochronology and zircon Hf-isotope data,Hf isotope mapping is undertaken to improve our understanding of crustal architecture and its controls on ore deposits.The ore-related Early Cretaceous granitoids were sourced predominantly from juvenile crust,with the involvement of variable proportions of ancient crustal materials.The crustal architecture,as inferred from Hf isotopic contour maps,indicates two distinct Hf isotopic domains in SGXR,including(1)a higher-ε_(Hf)(+7 to+11)juvenile crust containing minor ancient crustal material,and(2)a lower-ε_(Hf)(+2 to+6)juvenile crust containing a greater proportion of ancient crustal materials.The Hf isotopic maps identify links between crustal architecture and regional metallogeny.Copper deposits and other deposits with significant Cu production are restricted mainly to the higher-ε_(Hf)juvenile crustal regions in the northern and eastern SGXR.Deposits dominated by other metals(e.g.,Mo,Sn,W,Pb,Zn,and Ag)occur mainly in the lower-ε_(Hf)juvenile crustal regions in the southern and western SGXR.Interaction between juvenile crust-derived melts and ancient crustal components played an important role on the distribution of various ore metals.展开更多
A modified renormalization approach based on that proposed by Druce et al.is presented.The over-all agreement between the spectra calculated here and the accurate spectra is significantly improved.We also useDurce’s ...A modified renormalization approach based on that proposed by Druce et al.is presented.The over-all agreement between the spectra calculated here and the accurate spectra is significantly improved.We also useDurce’s approach to generate the renormalized spectra.It is shown that in our microscopic study,both of the ap-proaches are very useful to the determination of several free parameters of fermion residual interactions.展开更多
Located along the southern part of the West Qinling orogenic belt,the Yangshan gold deposit is one of the largest in China.The major gold ores of Yangshan are disseminated in metasedimentary host rocks with minor nati...Located along the southern part of the West Qinling orogenic belt,the Yangshan gold deposit is one of the largest in China.The major gold ores of Yangshan are disseminated in metasedimentary host rocks with minor native gold amounts in stibnite-gold quartz veins.Pyrite and arsenopyrite are the major Au-bearing minerals.Hydrothermal muscovite from gold-bearing quartz veins was dated using the in situ Rb-Sr method to determine the formation age of the Yangshan gold deposit.The Rb-Sr isochron date of the muscovite yielded 210.1±5.6 Ma(MSWD=1.2).This date is near the lower end of the period of the mineralized granitic dykes(210.49-213.10 Ma).Two stages of gold enriching process are recognized in the gold-bearing pyrite:the first is incorporated with the Co,Cu,As,Ni enrichment;and the second is accompanied by Bi,Co,Ni,Pb,Cu,Sb concentration.The in-situ sulfur isotopic values of pyrites show a restrictedΔ34s range of-1.43‰to 2.86‰with a mean value of 0.43‰.Trace-element mapping and in-situ sulfur isotopic analysis of pyrite suggest that the sulfur deposits are likely derived from a magmatic source and likely assimilated by sulfur from the sedimentary bedrock.Thus,magmatism plays a critical role in the formation of the Yangshan gold deposit.展开更多
The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous.Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67±0.7 to 85.97±0...The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous.Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67±0.7 to 85.97±0.6 Ma.The intrusive rocks are peraluminous(A/CNK=1.03 to 1.33)and calc-alkaline,showing an affinity towards I-type granite.Large ion lithophilic elements are enriched in K and Rb,while high field strength elements are depleted.Moreover,light rare earth elements are significantly enriched,showing a slight negative Eu anomaly(Eu/Eu^(*)=0.39 to 0.58).Shenxianshui granite has a relatively high initial Sr isotope ratio(^(87)Sr/^(86)Sr)_(i)(0.7098-0.7105),negative ε_(Nd)(t)values(−7.99 to−7.44)and negative ε_(Hf)(t)values(−8.37 to−2.58).Combined with previous studies,these characteristics suggest that the Shenxianshui alkaline granites were formed in a post-collision extensional environment.The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials.Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation.The abundance of ore-forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements.展开更多
An isotopic study was systemically carried out on the granitic complex,diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model ...An isotopic study was systemically carried out on the granitic complex,diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model of diagenesis and metallogenesis.Results show that the initial Nd and Sr isotopic compositions of the granitic complex are in the range of 0.70425-0.70505 for（87Sr/86Sr）i, 0.51243-0.51264 for INd,and -1.31 to ＋2.64 forεNd（t）;those of the diorite-porphyrite are in the range from 0.70438-0.70448 for（87Sr/86Sr）,,0.51259-0.51261 for INd,and ＋1.56 to ＋2.09 forεNd（t）.For ores and sulfides,the（87Sr/86Sr）i,7Nd,andεNd（t） values are in the range from 0.70440-0.70805,0.51259- 0.51279 and ＋1.72 to ＋5.56,respectively.The Pb isotopic ratios of the granitic complex range from 18.2992-18.6636 for 206Pb/204Pb,from 15.5343-15.5660 for 207Pb/204Pb,and from 38.1640-38.5657 for 208Pb/204Pb For diorite-porphyrite,the isotopic ratios of 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb are 18.3919,15.5794 and 38.3566,respectively,whereas those of the ores and ore sulfides vary from 18.2275-18.3770 for 206Pb/204Pb,from 15.5555-15.5934 for 207Pb/204Pb and from 38.1318-38.3131 for 208Pb/204Pb.The results indicate that the mineralization was correlated to the formation and evolution of the granitic complex and the diorite-porphyrite.Combining with the reported data in petrologic characteristics,elemental geochemistry and chronology,conclusions can be drawn that the geodynamic settings of diagenesis and metallogenesis of this deposit were consistent with the subduction of the Izanagi oceanic plate during the Early Cretaceous.The diorite-porphyrite was formed by the emplacement of the adakitic magma triggered by partial melting of the enriched mantle,which originated from the derivative continental lithospheric mantle metasomatized by dehydration fluids from the subducting oceanic crust.The granitic complex was produced by fractional crystallization of the mixture between the adakitic magma and the high-K calc-alkaline acidic magma,which were generated by the remelting of the lower crust in the course of intraplate upwelling of the adakitic magma.The ore-bearing fluid reservoir convened in a late stage of the evolution of the mixed magma chamber.展开更多
Si-Fe-Mn-oxyhydroxides dredged at the PACMANUS （Papua New Guinea-Australia-Canada-Manus） hydrothermal field, Eastern Manus Basin, have 87Sr/SSSr=0.708 079-0.708 581; eNd=5.149 833-6.534 826; 208pb/204pb=38.245-38.44...Si-Fe-Mn-oxyhydroxides dredged at the PACMANUS （Papua New Guinea-Australia-Canada-Manus） hydrothermal field, Eastern Manus Basin, have 87Sr/SSSr=0.708 079-0.708 581; eNd=5.149 833-6.534 826; 208pb/204pb=38.245-38.440; 207pb/204pb=lS.503-15.560; 206pb/204pb=lS.682-18.783. s7sr/sSSr isotope ratios are relatively homogeneous and close to the value of the surrounding seawater （0.709 16）. The content of Sr in the samples contributed by seawater was estimated to be 76.7%-83.1% of total amount. The mixing temperature of hydrothermal fluids and seawater were ranging from 53.2℃ to 72.2℃ and the hydrothermal activities were unstable when the samples precipitated. The eNd values of all the samples are positive, which differ from the values of ferromanganese nodules （crusts） with hydrogenic origin. Nd was mainly derived from substrate rocks leached by hydrothermal circulation and preserved the hydrothermal signature. Ph isotopic compositions of most samples show minor variability except Sample #9-2 that has relatively high values of Pb isotopes. The Pb may be derived from the Eastern Manus Basin rocks leached by the hydrothermal fluid. The slightly lower 28pb/204pb and 207pb/204pb values of the samples indicated that the hydrothermal circulation in PACMANUS was not entire and sufficient, or that hydrothermal circulation had transient changes in the past. Si-Fe-Mn-oxyhydroxides in the samples preserved the heterogeneities of local rocks.展开更多
Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetal...Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetallic mineralization.These ore-bearing porphyries include monzogranite,granodiorite,and quartz diorite porphyries.A new granite aplite dyke was found in the south of Jiama.Its age,genesis,and relationship with ore-related magmatism are obscure.Here,its emplacement age and petrogenesis were determined using mineralogy,zircon U-Pb dating,geochemistry,and Sr-Nd-Pb isotope studies.The zircon LA-ICP-MS U-Pb age of the aplite dyke is 16.66±0.21 Ma(n=14,MSWD=0.66),earlier than that of the ore-bearing porphyries(~15 Ma)in Jiama.Furthermore,the aplite exhibits high amounts of silicon(SiO_(2)=73.39%-74.74%),potassium(K_(2)O=5.12%-6.61%),aluminum(Al_(2)O_(3)=14.25%-14.69%),and light/heavy rare earth elements(LREE/HREE=12.12-16.19)as well as negative europium(δEu=0.47-0.72)and weak negative cerium anomalies(δCe=0.84-0.93).The aplite dyke is characteristic of metaluminous-peraluminous I-type granite,which is rich in large-ion lithophile elements(Rb,Ba,Th and U)and depleted in high-field-strength elements(Nb,P and Ti).The aplite dyke and ore-bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust,according to whole-rock geochemistry and Sr-Nd-Pb isotope data,but the dyke and ore-bearing porphyries were emplaced from the same magma chamber at different times.Thus,the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.展开更多
The Cenozoic Himalayan leucogranite-pegmatite belt has been a hotspot for rare metal exploration in recent years.To determine the genesis of the pegmatite in the Himalayan region and its relationship with the Greater ...The Cenozoic Himalayan leucogranite-pegmatite belt has been a hotspot for rare metal exploration in recent years.To determine the genesis of the pegmatite in the Himalayan region and its relationship with the Greater Himalayan Crystalline Complex(GHC),the Gyirong pegmatite in southern Tibet was chosen for geochronological and geochemical studies.The dating analyses indicate that the U-Th-Pb ages of zircon,monazite,and xenotime exhibit large variations(38.6‒16.1 Ma),with the weighted average value of the four youngest points is 16.5±0.3 Ma,which indicates that the final stage of crystallization of the melt occurred in the Miocene.The age of the muscovite Ar-Ar inverse isochron is 15.2±0.4 Ma,which is slightly later than the intrusion age,showing that a cooling process associated with rapid denudation occurred at 16‒15 Ma.TheεHf(t)values of the Cenozoic anatectic zircons cluster between−12 and−9 with an average of−11.4.The Gyirong pegmatite shows high contents of Si,Al,and K,a high Al saturation index,and low contents of Na,Ca,Fe,Mn,P,Mg,and Ti.Overall,the Gyirong pegmatite is enriched in Rb,Cs,U,K,Th and Pb and depleted in Nb,Ta,Zr,Ti,Eu,Sr,and Ba.The samples show a high 87Sr/86Sr(16 Ma)ratio of ca.0.762 and a lowεNd(16 Ma)value of−16.0.The calculated average initial values of 208Pb/204Pb(16 Ma),207Pb/204Pb(16 Ma)and 206Pb/204Pb(16 Ma)of the whole rock are 39.72,15.79 and 19.56,respectively.The Sr-Nd-Pb-Hf isotopic characteristics of the Gyirong pegmatite are consistent with those of the GHC.This study concludes that the Gyirong pegmatite represents a typical crustal‒derived anatectic pegmatite with low metallogenic potential for rare metals.The Gyirong pegmatite records the long‒term metamorphism and partial melting process of the GHC,and reflects the crustal thickening caused by thrust compression at 39‒29 Ma and the crustal thinning induced by extensional decompression during 28‒15 Ma.展开更多
The Neoproterozoic Sugetbrak Formation in the Aksu area,which is located at the northwest margin of Tarim Block,comprises mafic rocks and provides key records of the evolution of the Rodinia supercontinent.However,the...The Neoproterozoic Sugetbrak Formation in the Aksu area,which is located at the northwest margin of Tarim Block,comprises mafic rocks and provides key records of the evolution of the Rodinia supercontinent.However,the genetic relationship among these mafic rocks exposed in different geographical sections are still unclear.In this study,the petrology,geochemistry,and Sr-Nd-Pb isotope geochemistry of the mafic rocks exposed in the Aksu-Wushi and Yuermeinark areas have been studied in some detail along three sections.The authors found that the mafic rocks in these three typical sections were mainly composed of pyroxene and plagioclase,containing a small amount of Fe-Ti oxides and with typical diabasic textures.All the mafic rocks in this region also showed similar geochemical compositions.They were characterised by high TiO_(2)contents(1.47%–3.59%)and low MgO(3.52%–7.88%),K_(2)O(0.12%–1.21%).Large ionic lithophile elements(LILEs)(Rb,Sr,and Cs)were significantly depleted.Meanwhile,high field strength elements(HFSEs)were relatively enriched.In the samples,light rare earth elements(LREEs)were enriched,while heavy rare earth elements(HREEs)were depleted.Based on the Zr/Nb,Nb/Y,and Zr/TiO_(2)ratios,the Aksu mafic rocks belong to a series of sub-alkaline and alkaline transitional rocks.The mafic rocks along the three typical sections showed similar initial values of^(87)Sr/^(86)Sr(I_(Sr))(0.7052–0.7097)and ε_(Nd)(t)(–0.70 to–5.35),while the Pb isotopic compositions with^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb and^(208)Pb/^(204)Pb values of 16.908–17.982,15.487–15.721,37.276–38.603,respectively.Most of the samples plot into the area near EM-Ⅰ,indicating that the magma of the mafic rocks might have derived from a relatively enriched mantle with some crustal materials involved.The geochemical element characteristics of most samples showed typical OIB-type geochemical characteristics indicating that the source region had received metasomatism of recycled materials.Combining with the regional geological background and geochemical data,we inferred that the mafic rocks of the Sugetbrak Formation in the Aksu area were formed in an intraplate rift environment.Summarily,based on our study,the mafic rocks of the Sugetbrak Formation in the Aksu area were derived from a common enriched mantle source,and they were product of a magmatic event during the rift development period caused by the breakup of the Rodinia supercontinent.展开更多
Late Early Paleozoic mafic-ultramafic dykes and volcanic rocks from the South Qinling belt are char- acterized by εNd( t ) = +3.28― +5.02, (87Sr/86Sr)i= 0.70341― 0.70555, (206Pb/204Pb)i = 17.256― 18.993, (207Pb/20...Late Early Paleozoic mafic-ultramafic dykes and volcanic rocks from the South Qinling belt are char- acterized by εNd( t ) = +3.28― +5.02, (87Sr/86Sr)i= 0.70341― 0.70555, (206Pb/204Pb)i = 17.256― 18.993, (207Pb/204Pb)i= 15.505―15.642, (208Pb/204Pb)i=37.125―38.968, ?8/4=21.18―774.43, ?7/4=8.11―18.82. These charac- teristics suggest that they derived from a Middle Neoproterozoic mantle with isotopic compositions of mixed HIMU, EMII and minor EMI components. We interpret that these rocks were melting products of depleted mantle modified by subducted ancient oceanic crust and continental margin sediments along the northern margin of Yangtze block during Early Neoproterozoic.展开更多
文摘Tongbai-Dabie orogenic belt in Central China is a part of the collisional belt between the Yangtze and North China cratons. It represents one of the most extensive ultrahigh-pressure （UHP） and high-pressure （HP） metamorphic rocks in the world. The Pb isotope mapping in this area is a significant method to constrain the crustal structure and tectonic evolution and to identify the tectonic boundaries within the vertical tectonic stack. Based on the Pb isotope compositions of the Dabie complex （DBC）, the Tongbai complex （TBC）, UHP and HP metamorphic rocks and associated foliated granites, the lower metamorphosed rocks from North Huaiyang （NHY） tectonic belt, and Cretaceous granites in the Tongbai-Dabie orogenic belt, we determined the Pb isotope geochemical map of the Tongbai-Dabie orogenic belt. The Pb isotope map shows that the Pb isotope compositions are similar within each geological body or lithotectonic unit, but the Pb isotope compositions of different lithotectonic units show systematic variations in the Tongbai-Dabie orogenic belt. The NHY tectonic belt contrasts strongly with the Tongbai-Dabie UHP.HP metamorphic belt in Pb isotope compositions. It is suggested that the line along the Xiaotian-Mozitan fault, the north limit of the Tongbai-Dabie UHP and HP metamorphic rocks, represents an important tectonic boundary. Within the Tongbai-Dabie HP -UHP metamorphic belt, to the south of Xiaotian-Mozitan fault, the vertical variations of Pb isotope compositions in different lithotectonic units and the spatial relationship among different major lithotectonic units have been constrained.
基金part of the ongoing project "Superimposed tectonic activities and large-scale oreforming processes of the Hinggan-Mongolia Orogenic Belt"financially supported by the State Basic Research Program of China(2013CB429805)
文摘The Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite. Sr-Nd-Pb isotopes of the intrusions show that the porphyritic syenogranite has initial ^87Sr/^86Sr ratios of 0.70418-0.70952, ENd（t） values of 1.3 to 2.1 （t=143 Ma）, ^206Pb/^204Pb ratios of 19.191-19.573, ^207Tpb/^204pb ratios of 15.551-15.572, and ^208Pb/^204Pb ratios of 38.826-39.143. The monzogranite has initial 87Sr/86Sr ratios of 0.70293-0.71305, εNd（t） values of 1.1 to 2.0 （t=-147 Ma）, ^206Pb/^204pb ratios of 19.507-20.075, ^207Pb/^204Pb ratios of 15.564-15.596, and ^208Pb/^204Pb ratios of 39.012-39.599. The calculated Nd model ages （TDM） for monzogranite and porphyritic syenogranite range from 866 to 1121 Ma and 795 to 1020 Ma, respectively. The granitic rocks in the Hashitu area have the same isotope range as granites in the southern parts of the Great Hinggan Range. The isotope composition indicates that these granites are derived from the partial melting of a juvenile lower crust originating from a depleted mantle with minor contamination by ancient continental crust. The integrating our results with published data and the Late Mesozoic regional tectonic setting of the region suggest that the granites in the Hashitu area formed in an intra-continent extensional setting, and they are related to the thinning of the thickened lithosphere and upwelling of the asthenosphere.
文摘The Indosinian post-collisional Wulong pluton intruded into the Mesoproterozoic Fuping Group, South Qinling, central China. In the southern part of the pluton, some mafic enclaves have sharp or gradational contact relationships with the host biotite granodiorite. Geochemistry, zircon LA-ICP MS （laser ablation inductively-coupled plasma mass spectrometry） U-Pb chronology and Sr- Nd-Pb isotope geochemistry of the pluton are reported in this paper. The biotite granodiorite shows close compositional similarities to high-silica adakite. Its chondrite-normalized REE patterns are characterized by strong HREE depletion （Yb = 0.33--0.96 10-6 and Y = 4.77-11.19 ×10^-6）, enrichment of Ba （775-1386 x 10-6） and Sr （643-1115 × 10^-6） and high Sr/Y （57.83-159.99） and Y/Yb （10.99-14.32） ratios, as well as insignificant Eu anomalies （6Eu = 0.70-0.83）, suggesting a feldspar-poor, garnet±amphibole-rich residual mineral assemblage. The mafic enclaves have higher MgO （4.15- 8.13%）, Cr （14.79-371.31 × 10-6）, Ni （20.00-224.24× 10^-6） and Nb/Ta （15.42-21.91） than the host granodiorite, implying that they are mantle-derived and might represent underplated mafic magma. Zircon LA-ICP MS dating of the granodiorite yields a ^206pb/^238U weighted mean age of 208±2 Ma （MSWD=0.50, 1σ）, which is the age of emplacement of the host biotite granodiorite. This age indicates that the Wulong pluton formed during the late-orogenic or post-collisional stage （〈242±21 Ma） of the South Qinling belt. The host biotite granodiorite displays ^87Sr/^86Sr = 0.7059-0.7062, Isr = 0.7044-- 0.7050,^143Nd/^144Nd = 0.51236-0.51238, εNd（t）= -2.26 to -2.66 to ^206Pb/^204pb = 18.099-18.209, ^207pb/^204pb = 15.873-15.979 and ^208pb/^204pb = 38.973-39.430. Those ratios are similar to those of the Mesoproterozoic Yaolinghe Group in the South Qinling. Furthermore, its Nd isotopic model age （-1.02 Ga） is consistent with the age （-1.1 Ga） of the Yaolinghe Group. Based on the integrated geological and geochemical studies, coupled with previous studies, the authors suggest that the Wulong adakitic biotite granodiorite was probably generated by dehydration melting of the Yaolinghe Group-like thickened mafic crust, triggered by underplating of mafic magma at the boundary of the thickened mafic crust and hot lithospheric mantle, and that the Wulong adakitic biotite granodiorite may have resulted from thinning and delamination of the lower crust or breakoff of the subducting slab of the Mianlue ocean during the Indosinian post-collisional orogenic stage of the Qinling orogenic belt.
基金funded by the National Natural Science Foundation of China(No.41903043)China Postdoctoral Science Foundation(No.2018M642948)Program of China Geological Survey Bureau:1:50000 Regional Geological Survey of Tubuqin,Bayar Tuhushuo,Hadayingzi,Alahada,and Yidanjialaga in Inner Mongolia(No.DD20160048-15)。
文摘Voluminous Early Cretaceous granitoids and associated large-scale ore deposits are distributed within the southern Great Xing'an Range(SGXR),NE China.Based on previously published geochronology and zircon Hf-isotope data,Hf isotope mapping is undertaken to improve our understanding of crustal architecture and its controls on ore deposits.The ore-related Early Cretaceous granitoids were sourced predominantly from juvenile crust,with the involvement of variable proportions of ancient crustal materials.The crustal architecture,as inferred from Hf isotopic contour maps,indicates two distinct Hf isotopic domains in SGXR,including(1)a higher-ε_(Hf)(+7 to+11)juvenile crust containing minor ancient crustal material,and(2)a lower-ε_(Hf)(+2 to+6)juvenile crust containing a greater proportion of ancient crustal materials.The Hf isotopic maps identify links between crustal architecture and regional metallogeny.Copper deposits and other deposits with significant Cu production are restricted mainly to the higher-ε_(Hf)juvenile crustal regions in the northern and eastern SGXR.Deposits dominated by other metals(e.g.,Mo,Sn,W,Pb,Zn,and Ag)occur mainly in the lower-ε_(Hf)juvenile crustal regions in the southern and western SGXR.Interaction between juvenile crust-derived melts and ancient crustal components played an important role on the distribution of various ore metals.
基金The project supported by the National Natural Science Foundation of China
文摘A modified renormalization approach based on that proposed by Druce et al.is presented.The over-all agreement between the spectra calculated here and the accurate spectra is significantly improved.We also useDurce’s approach to generate the renormalized spectra.It is shown that in our microscopic study,both of the ap-proaches are very useful to the determination of several free parameters of fermion residual interactions.
基金financially supported by China Geological Survey Project(Grant No.DD20220971)。
文摘Located along the southern part of the West Qinling orogenic belt,the Yangshan gold deposit is one of the largest in China.The major gold ores of Yangshan are disseminated in metasedimentary host rocks with minor native gold amounts in stibnite-gold quartz veins.Pyrite and arsenopyrite are the major Au-bearing minerals.Hydrothermal muscovite from gold-bearing quartz veins was dated using the in situ Rb-Sr method to determine the formation age of the Yangshan gold deposit.The Rb-Sr isochron date of the muscovite yielded 210.1±5.6 Ma(MSWD=1.2).This date is near the lower end of the period of the mineralized granitic dykes(210.49-213.10 Ma).Two stages of gold enriching process are recognized in the gold-bearing pyrite:the first is incorporated with the Co,Cu,As,Ni enrichment;and the second is accompanied by Bi,Co,Ni,Pb,Cu,Sb concentration.The in-situ sulfur isotopic values of pyrites show a restrictedΔ34s range of-1.43‰to 2.86‰with a mean value of 0.43‰.Trace-element mapping and in-situ sulfur isotopic analysis of pyrite suggest that the sulfur deposits are likely derived from a magmatic source and likely assimilated by sulfur from the sedimentary bedrock.Thus,magmatism plays a critical role in the formation of the Yangshan gold deposit.
基金supported by the National Natural Science Foundation of China(Grant Nos.41972312 and 41672329)Kunming University of Science and Technology"Double First-class"Science and Technology Special Project(Grant No.202202AG050006).
文摘The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous.Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67±0.7 to 85.97±0.6 Ma.The intrusive rocks are peraluminous(A/CNK=1.03 to 1.33)and calc-alkaline,showing an affinity towards I-type granite.Large ion lithophilic elements are enriched in K and Rb,while high field strength elements are depleted.Moreover,light rare earth elements are significantly enriched,showing a slight negative Eu anomaly(Eu/Eu^(*)=0.39 to 0.58).Shenxianshui granite has a relatively high initial Sr isotope ratio(^(87)Sr/^(86)Sr)_(i)(0.7098-0.7105),negative ε_(Nd)(t)values(−7.99 to−7.44)and negative ε_(Hf)(t)values(−8.37 to−2.58).Combined with previous studies,these characteristics suggest that the Shenxianshui alkaline granites were formed in a post-collision extensional environment.The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials.Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation.The abundance of ore-forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements.
基金supported by the National Natural Science Foundation of China(Nos.40472050 and 40772050)the Natural Science Foundation of Jilin Provincial Science and Technology(grant no.20080452)+1 种基金funds from the State Key Laboratory for Mineral Deposits Research,Nanjing University(2006-2005,2006- 2008)Key Laboratory of Mineral Resources, Chinese Academy of Sciences(2009-2012)
文摘An isotopic study was systemically carried out on the granitic complex,diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model of diagenesis and metallogenesis.Results show that the initial Nd and Sr isotopic compositions of the granitic complex are in the range of 0.70425-0.70505 for（87Sr/86Sr）i, 0.51243-0.51264 for INd,and -1.31 to ＋2.64 forεNd（t）;those of the diorite-porphyrite are in the range from 0.70438-0.70448 for（87Sr/86Sr）,,0.51259-0.51261 for INd,and ＋1.56 to ＋2.09 forεNd（t）.For ores and sulfides,the（87Sr/86Sr）i,7Nd,andεNd（t） values are in the range from 0.70440-0.70805,0.51259- 0.51279 and ＋1.72 to ＋5.56,respectively.The Pb isotopic ratios of the granitic complex range from 18.2992-18.6636 for 206Pb/204Pb,from 15.5343-15.5660 for 207Pb/204Pb,and from 38.1640-38.5657 for 208Pb/204Pb For diorite-porphyrite,the isotopic ratios of 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb are 18.3919,15.5794 and 38.3566,respectively,whereas those of the ores and ore sulfides vary from 18.2275-18.3770 for 206Pb/204Pb,from 15.5555-15.5934 for 207Pb/204Pb and from 38.1318-38.3131 for 208Pb/204Pb.The results indicate that the mineralization was correlated to the formation and evolution of the granitic complex and the diorite-porphyrite.Combining with the reported data in petrologic characteristics,elemental geochemistry and chronology,conclusions can be drawn that the geodynamic settings of diagenesis and metallogenesis of this deposit were consistent with the subduction of the Izanagi oceanic plate during the Early Cretaceous.The diorite-porphyrite was formed by the emplacement of the adakitic magma triggered by partial melting of the enriched mantle,which originated from the derivative continental lithospheric mantle metasomatized by dehydration fluids from the subducting oceanic crust.The granitic complex was produced by fractional crystallization of the mixture between the adakitic magma and the high-K calc-alkaline acidic magma,which were generated by the remelting of the lower crust in the course of intraplate upwelling of the adakitic magma.The ore-bearing fluid reservoir convened in a late stage of the evolution of the mixed magma chamber.
基金The National Key Basic Research Program of China under contract No.2013CB429700the National Special Fund for the 12th Five Year Plan of COMRA under contract No.DY125-12-R-05+3 种基金the National Special Fund for the 12th Five Year Plan of COMRA under contract Nos DY125-12-R-02 and DY125-11-R-05the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11030302the National Natural Science Foundation of China under contract Nos 41325021,40830849 and 40976027Shandong Province Natural Science Foundation of China for Distinguished Young Scholars under contract No.JQ200913
文摘Si-Fe-Mn-oxyhydroxides dredged at the PACMANUS （Papua New Guinea-Australia-Canada-Manus） hydrothermal field, Eastern Manus Basin, have 87Sr/SSSr=0.708 079-0.708 581; eNd=5.149 833-6.534 826; 208pb/204pb=38.245-38.440; 207pb/204pb=lS.503-15.560; 206pb/204pb=lS.682-18.783. s7sr/sSSr isotope ratios are relatively homogeneous and close to the value of the surrounding seawater （0.709 16）. The content of Sr in the samples contributed by seawater was estimated to be 76.7%-83.1% of total amount. The mixing temperature of hydrothermal fluids and seawater were ranging from 53.2℃ to 72.2℃ and the hydrothermal activities were unstable when the samples precipitated. The eNd values of all the samples are positive, which differ from the values of ferromanganese nodules （crusts） with hydrogenic origin. Nd was mainly derived from substrate rocks leached by hydrothermal circulation and preserved the hydrothermal signature. Ph isotopic compositions of most samples show minor variability except Sample #9-2 that has relatively high values of Pb isotopes. The Pb may be derived from the Eastern Manus Basin rocks leached by the hydrothermal fluid. The slightly lower 28pb/204pb and 207pb/204pb values of the samples indicated that the hydrothermal circulation in PACMANUS was not entire and sufficient, or that hydrothermal circulation had transient changes in the past. Si-Fe-Mn-oxyhydroxides in the samples preserved the heterogeneities of local rocks.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC2905001)National Natural Science Foundation of China(Grant Nos.42272093 and 42230813)+2 种基金Basic Research Fund of Chinese Academy of Geological Sciences(Grant Nos.JKYZD202316,KJ2102,KK2116,and JKY202208)Geological Survey Project(Grant No.DD20221684)China Scholarship Council(Grant No.CSC202206400059)。
文摘Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetallic mineralization.These ore-bearing porphyries include monzogranite,granodiorite,and quartz diorite porphyries.A new granite aplite dyke was found in the south of Jiama.Its age,genesis,and relationship with ore-related magmatism are obscure.Here,its emplacement age and petrogenesis were determined using mineralogy,zircon U-Pb dating,geochemistry,and Sr-Nd-Pb isotope studies.The zircon LA-ICP-MS U-Pb age of the aplite dyke is 16.66±0.21 Ma(n=14,MSWD=0.66),earlier than that of the ore-bearing porphyries(~15 Ma)in Jiama.Furthermore,the aplite exhibits high amounts of silicon(SiO_(2)=73.39%-74.74%),potassium(K_(2)O=5.12%-6.61%),aluminum(Al_(2)O_(3)=14.25%-14.69%),and light/heavy rare earth elements(LREE/HREE=12.12-16.19)as well as negative europium(δEu=0.47-0.72)and weak negative cerium anomalies(δCe=0.84-0.93).The aplite dyke is characteristic of metaluminous-peraluminous I-type granite,which is rich in large-ion lithophile elements(Rb,Ba,Th and U)and depleted in high-field-strength elements(Nb,P and Ti).The aplite dyke and ore-bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust,according to whole-rock geochemistry and Sr-Nd-Pb isotope data,but the dyke and ore-bearing porphyries were emplaced from the same magma chamber at different times.Thus,the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.
基金sponsored by the National Key R&D Programme of China(2021YFC2901803)National Natural Science Foundation of China(92055314 and 41802095)+2 种基金the China Geological Survey(DD20230049 and DD20220983)is a contribution to the International Geoscience Programme(IGCP-741)Academician Bao-jun Liu Foundation of Southwest Geological Science and Technology Innovation Center.
文摘The Cenozoic Himalayan leucogranite-pegmatite belt has been a hotspot for rare metal exploration in recent years.To determine the genesis of the pegmatite in the Himalayan region and its relationship with the Greater Himalayan Crystalline Complex(GHC),the Gyirong pegmatite in southern Tibet was chosen for geochronological and geochemical studies.The dating analyses indicate that the U-Th-Pb ages of zircon,monazite,and xenotime exhibit large variations(38.6‒16.1 Ma),with the weighted average value of the four youngest points is 16.5±0.3 Ma,which indicates that the final stage of crystallization of the melt occurred in the Miocene.The age of the muscovite Ar-Ar inverse isochron is 15.2±0.4 Ma,which is slightly later than the intrusion age,showing that a cooling process associated with rapid denudation occurred at 16‒15 Ma.TheεHf(t)values of the Cenozoic anatectic zircons cluster between−12 and−9 with an average of−11.4.The Gyirong pegmatite shows high contents of Si,Al,and K,a high Al saturation index,and low contents of Na,Ca,Fe,Mn,P,Mg,and Ti.Overall,the Gyirong pegmatite is enriched in Rb,Cs,U,K,Th and Pb and depleted in Nb,Ta,Zr,Ti,Eu,Sr,and Ba.The samples show a high 87Sr/86Sr(16 Ma)ratio of ca.0.762 and a lowεNd(16 Ma)value of−16.0.The calculated average initial values of 208Pb/204Pb(16 Ma),207Pb/204Pb(16 Ma)and 206Pb/204Pb(16 Ma)of the whole rock are 39.72,15.79 and 19.56,respectively.The Sr-Nd-Pb-Hf isotopic characteristics of the Gyirong pegmatite are consistent with those of the GHC.This study concludes that the Gyirong pegmatite represents a typical crustal‒derived anatectic pegmatite with low metallogenic potential for rare metals.The Gyirong pegmatite records the long‒term metamorphism and partial melting process of the GHC,and reflects the crustal thickening caused by thrust compression at 39‒29 Ma and the crustal thinning induced by extensional decompression during 28‒15 Ma.
基金funded by the Key Laboratory of DeepEarth Dynamics of Ministry of Natural Resources(J1901-201)China Geological Survey Program(D20090002)。
文摘The Neoproterozoic Sugetbrak Formation in the Aksu area,which is located at the northwest margin of Tarim Block,comprises mafic rocks and provides key records of the evolution of the Rodinia supercontinent.However,the genetic relationship among these mafic rocks exposed in different geographical sections are still unclear.In this study,the petrology,geochemistry,and Sr-Nd-Pb isotope geochemistry of the mafic rocks exposed in the Aksu-Wushi and Yuermeinark areas have been studied in some detail along three sections.The authors found that the mafic rocks in these three typical sections were mainly composed of pyroxene and plagioclase,containing a small amount of Fe-Ti oxides and with typical diabasic textures.All the mafic rocks in this region also showed similar geochemical compositions.They were characterised by high TiO_(2)contents(1.47%–3.59%)and low MgO(3.52%–7.88%),K_(2)O(0.12%–1.21%).Large ionic lithophile elements(LILEs)(Rb,Sr,and Cs)were significantly depleted.Meanwhile,high field strength elements(HFSEs)were relatively enriched.In the samples,light rare earth elements(LREEs)were enriched,while heavy rare earth elements(HREEs)were depleted.Based on the Zr/Nb,Nb/Y,and Zr/TiO_(2)ratios,the Aksu mafic rocks belong to a series of sub-alkaline and alkaline transitional rocks.The mafic rocks along the three typical sections showed similar initial values of^(87)Sr/^(86)Sr(I_(Sr))(0.7052–0.7097)and ε_(Nd)(t)(–0.70 to–5.35),while the Pb isotopic compositions with^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb and^(208)Pb/^(204)Pb values of 16.908–17.982,15.487–15.721,37.276–38.603,respectively.Most of the samples plot into the area near EM-Ⅰ,indicating that the magma of the mafic rocks might have derived from a relatively enriched mantle with some crustal materials involved.The geochemical element characteristics of most samples showed typical OIB-type geochemical characteristics indicating that the source region had received metasomatism of recycled materials.Combining with the regional geological background and geochemical data,we inferred that the mafic rocks of the Sugetbrak Formation in the Aksu area were formed in an intraplate rift environment.Summarily,based on our study,the mafic rocks of the Sugetbrak Formation in the Aksu area were derived from a common enriched mantle source,and they were product of a magmatic event during the rift development period caused by the breakup of the Rodinia supercontinent.
基金Supported jointly by the National Natural Science Foundation of China (Grant Nos. 40372039, 40521001)Ministry of Education of China (Grant Nos. IRT0441 and B07039)the State Key Laboratory of Geological Progresses and Mineral Re-sources (Grant No. MGMR2002-27)
文摘Late Early Paleozoic mafic-ultramafic dykes and volcanic rocks from the South Qinling belt are char- acterized by εNd( t ) = +3.28― +5.02, (87Sr/86Sr)i= 0.70341― 0.70555, (206Pb/204Pb)i = 17.256― 18.993, (207Pb/204Pb)i= 15.505―15.642, (208Pb/204Pb)i=37.125―38.968, ?8/4=21.18―774.43, ?7/4=8.11―18.82. These charac- teristics suggest that they derived from a Middle Neoproterozoic mantle with isotopic compositions of mixed HIMU, EMII and minor EMI components. We interpret that these rocks were melting products of depleted mantle modified by subducted ancient oceanic crust and continental margin sediments along the northern margin of Yangtze block during Early Neoproterozoic.
