The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform o...The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform ore bodies and veintype ones, controlled by the Early Permian strata and the Late Hercynian diorite intrusion, respectively. Due to the ambiguous genetic type of the stratiform ore bodies, there has been controversy on the relationship between them and veintype ore bodies. To determine the genetic type of stratiform ore bodies, laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) in situ trace elements and S–Pb isotope analysis have been carried on the sulfides in the stratiform ore bodies. Compared with that in skarn, Mississippi Valley-type(MVT), and epithermal deposits, sphalerite samples in the stratiform ore bodies of the Dongfengnanshan deposit are significantly enriched in Fe, Mn, and In, while depleted in Ga, Ge, and Cd, which is similar to the sphalerite in volcanic-associated massive sulfide(VMS) deposits. Co/Ni ratio of pyrrhotites in the stratiform ore bodies is similar to that in VMS-type deposits. The concentrations of Zn and Cd of chalcopyrites are similar to those of recrystallized VMS-type deposits. These characteristics also reflect the intermediate ore-forming temperature of the stratiform ore bodies in this deposit. Sulfur isotope compositions of sulfides are similar to those of VMS-type deposits, reflecting that sulfur originated from the Permian Miaoling Formation. Lead isotope compositions indicate mixed-source for lead. Moreover, the comparison of the Dongfengnanshan stratiform ore bodies with some VMStype deposits in China and abroad, on the trace elements and S–Pb isotope characteristics of the sulfides reveals that the stratiform ore bodies of the Dongfengnanshan deposit belong to the VMS-type, and have closely genetic relationship with the early Permian marine volcanic sedimentary rocks.展开更多
Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced...Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced from the spatial diagenesis-mineralization relationship,chronological data,physicochemical characteristics of mineral fluid inclusions,mineral or rock elements and isotopic geochemical characteristics.By objectively examining this scientific problem via a geological field survey and petrographic analysis of the Gaosongshan epithermal gold deposit,we recently discovered and verified the following points:(1) Pyrite-bearing spherical quartz aggregates (PSQA) occur in the rhyolitic porphyry;(2) the mineralization is structurally dominated by WNW- and ENE-trending systems and occurs mostly in hydrothermal breccias and pyrite-quartz veins,and the ore types are mainly hematite-crusted quartz,hydrothermal breccia,massive pyrite-quartz,etc.;(3) the alteration types consist of prevalent silicification,sericitization,propylitization and carbonation,with local adularization and illitization.The ore minerals are mainly pyrite,primary hematite,native gold,and electrum,with lesser amounts of chalcopyrite,magnetite,sphalerite,and galena,indicating a characteristic epithermal low-sulfidation deposit.The ore-forming fluid may have been primarily derived from magmatic fluid exsolved from a crystallizing rhyolitic porphyry magma.Further zircon U-Pb geochronology,fluid inclusion,physicochemical and isotopic geochemical analyses revealed that (1) rhyolitic porphyry magmatism occurred at 104.6 ± 1.0 Ma,whereas the crystallization of the PSQA occurred at 100.8 ± 2.1 Ma;(2) the hydrothermal fluid of the pre-ore stage was an exsolved CO2-bearing H2O-NaCl magmatic fluid that produced inclusions mainly composed of pure vapor (PV),vapor-rich (WV) and liquid-rich (WL) inclusions with a small number of melt-(M) and solid-bearing (S) inclusions;mineralization-stage quartz contains WL and rare PV,WV and pure liquid (PL) inclusions characterized by the H2O-NaCl system with low formation temperatures and low salinities;(3) the characteristics of hydrogen,oxygen,sulfur,and lead isotopes and those of rare earth elements (REEs) provide insight into the affinity between PSQA and orebodies resulting from juvenile crust or enriched mantle.Combined with previous research on the mineralogenetic epoch (99.32 ± 0.01 Ma),we further confirm that the mineralization of the deposit occurred in the late Early Cretaceous,which coincides with the extension of the continental margin induced by subduction of the Pacific Plate beneath the Eurasian Plate.The formation of the ore deposit was proceeded by a series of magmatic and hydrothermal events,including melting of enriched juvenile crust,upwelling,the eruption and emplacement of the rhyolitic magma,the exsolution and accumulation of magmatic hydrothermal fluid,decompression,the cooling and immiscibility/boiling of the fluid,and mixing of the magmatic fluid with meteoric water,in association with water-rock interaction.展开更多
Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history...Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history spanning the entire Quaternary period. Magma origin and evolution of Tengchong Cenozoic volcanic rocks were studied on the basis of Nd-Sr-Pb isotope and major and trace element data from different eruptions in the Ma'anshan area. Different samples within one eruption show relative identical lithologies, chemical and isotopic compositions. However, the geochemical features for the five eruptions are distinct from each other. These volcanic rocks show low Mg# values (〈45), moderate to high fractionation of LREEs and HREEs, and enrichment of Pb and Ba and depletion of Nb. Tengchong Cenozoic volcanic rocks were derived from an enriched mantle based on Nd-Sr-Pb isotopic studies. And lines of evidence show that crustal contamination should be involved before the eruption of different periods of Tengchong Cenozoic volcanic rocks. Older subducted components may be responsible for adakite recycling at various stages of evolution, which results in the origin of the enriched mantle source magma accounting for the isotopic features of Tengchong Cenozoic volcanic rocks. Segregated primitive magma pulsating injected into magma chamber, fractional crystallized and contaminated with crust component. Finally, magmas with distinct chemical and isotopic compositions for each eruption formed. The extension of the northeast segment of the Yingjiang tectonic belt triggered the pulsating eruption of the Cenozoic volcanics in the Tengchong area.展开更多
Detrital zircon U-Pb geochronology has become the gold standard in evaluating source to sink relationships in sedimentary basins. However, the physical and chemical robustness of zircon, which make it such a useful mi...Detrital zircon U-Pb geochronology has become the gold standard in evaluating source to sink relationships in sedimentary basins. However, the physical and chemical robustness of zircon, which make it such a useful mineral for provenance studies, is also a hindrance as zircon can be recycled through numerous sedimentary basins, thus obscuring the first cycle source to sink relationship. An elegant approach to addressing this potential issue is to compare the Pb isotope composition of detrital K-feldspar, a mineral which is unlikely to survive more than one erosion-transport-deposition cycle, with that of magmatic K-feldspar from potential basement source terranes. Here we present new in situ Pb isotope data on detrital K-feldspar from two Proterozoic arkosic sandstones from Western Australia, and magmatic K-feldspar grains from potential igneous source rocks, as inferred by the age and Hf isotope composition of detrital zircon grains. The data indicate that the detrital zircon and K-feldspar grains could not have been liberated from the same source rocks, and that the zircon has most likely been recycled through older sedimentary basins. These results provide a more complete understanding of apparently simple source to sink relationships in this part of Proterozoic Western Australia.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
We carried out Pb isotopes studies in sediments fromParatyBaylocated in the SE area of theRio de JaneiroStateto discriminate the signature of metal contamination from domestic sewage, industries, shipyards and geogeni...We carried out Pb isotopes studies in sediments fromParatyBaylocated in the SE area of theRio de JaneiroStateto discriminate the signature of metal contamination from domestic sewage, industries, shipyards and geogenic sources. The studied samples have been chosen in two sectors of the Bay, including the Paraty area andJuatingaBay. Sample preparation procedures included: 1) drying and granulometric separations (200 mesh);2) weighting;3) complete dissolution and 4) Pb isotope analysis obtained by MC-ICP-MS (ratios 208Pb/204Pb,207Pb/204Pb, 206Pb/204Pb). Preliminary results when plotted in the 207Pb/204Pbversus 208Pb/204Pb and 207Pb/206Pb versus 206Pb/204Pb diagrams showed three groups of signatures. The first group (samples PY-01, PY-03 PY-106 and PY-127) presented 207Pb/206Pb values in the range from 1.191 to 1.209. The isotope values may be interpreted as contribution of a pollutant sources of Pb not yet identified. The second group (PY-11, PY-13, PY-21, PY-22, PY-46, PY-51, PY-109 and PY-111) showed 207Pb/206Pb values in the range from 1.188 to 1.222. The last group (samples PY-123 and PY-135) presented higher 207Pb/ 206Pb values from 1.321 to 1.322 and probably represented oceanic signature. The Pb isotope data of the second group may be interpreted as the result of oceanic water and pollutant sources mixture from the continent. According to the literature the anomalous Pb signature is similar to anthropogenic source. The Pb isotope results here reported are coherent with the reported data from the continent area. We may conclude that significant isotopic differences in Pb signatures are consequence of anthropogenic Pb isotope signature. In this way, Pb isotope is an important tool to trace the changing sources of pollutant Pb (and other metals) in ocean environment.展开更多
A broad set of samples from the CVP has been analyzing Pb isotopes. Campanian Volcanic Province (CVP) has been produced by various ranges of mixing between three components: 1) MORB, 2) Hercynian basement and 3) upper...A broad set of samples from the CVP has been analyzing Pb isotopes. Campanian Volcanic Province (CVP) has been produced by various ranges of mixing between three components: 1) MORB, 2) Hercynian basement and 3) upper crust. Anyhow, the upper crust that has modified the Pb isotopic composition also shows trends towards an Achaean upper crust. This is consistent for all Mediterranean area. This is not in contrast with the past plate tectonic reconstruction. Also the surface sediments (GLOSS) may have been a mixing between the Achaean upper crust and a Hercynian component with an implication worldwide due to the rock cycle processes.展开更多
The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small u...The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian (426-422 Ma), and their zircons have ~Hf(t) values of-9.4 to 5.9 with the older TDMm ages (0.80-1.42 Ga). Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements (e.g., K, Rb, Th) and depleted in heavy rare earth elements and high field strength elements (e.g., Ta, Nb, Zr, Ti). Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle (0 ~ 2%o). The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.展开更多
Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb...Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb isotopic composition of feldspar hosted in granitic rocks(thirteen Archean and one Paleoproterozoic)from the northern Kongling terrane,Yangtze Craton,South China,is analyzed.The samples reveal a substantial variation in their Pb isotopic composition,spanning the gap between the 1.9 Ga and present-day geochrons,which indicates extensive resetting by later tectonothermal events.This resetting was interpreted to have likely resulted from Paleoproterozoic and Neoproterozoic tectonothermal events related to the assembly and breakup of the Columbia and Rodinia supercontinents.These results suggest that Pb isotopes should be used cautiously when tracing magma sources and petrogenesis in magmatic rocks that have experienced post-magmatic reworking.However,the in situ Pb isotopic composition of feldspar in ancient granitoids may also potentially be used to reveal later tectonothermal events.The extensive resetting of the Pb isotopic composition in feldspar by regional thermal events may also provide new insights into our understanding of the Pb isotope paradox.展开更多
Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. ...Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. The sphalerite rich pockets are concentrated within the dolostone of older Trikuta Formation while galena rich mineralization occurs in form of veins, lenses and pockets hosted within siliceous varieties of dolostone and quartzite belonging to younger Khairikot Formation. Sulphur isotope geochemistry is reported in the present paper for the sphalerire and galena from the area for first time. Overall?δ34S of sulphides varies from (+9.67‰ to +34.42‰). Sphalerite ores hosted within older Trikuta Formation and younger Khairikot Formation, however, show different?δ34S values. It ranged from +9.67‰ to +10.59‰ for the sphalarite hosted in Trikuta Formation and from +18.38‰ to +34.42‰ for sphalerite hosted within Khairikot Formation. Sulphur isotopic data and ore petrographic data suggest that there is two-generation of sphalerite present in the area.展开更多
The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magma...The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magmatic system, and the mineralization age was consistent with the diagenetic age. However,the relationship between granitic magmatism and mineralization is still unclear in the SJZ. In this study, CH-O-He-Ar and in-situ S-Pb isotope analyses were conducted to determine the sources of ore-forming fluids and metals, which were combined with geochemistry data of SJZ granitoids from previous studies to constrain the relationship between the magmatism and the mineralization. The C-H-O-He-Ar-S-Pb isotopic compositions suggested the SJZ ore-forming material and fluids were derived from a magmatic source, which has mixed a small amount of mantle-derived materials. In addition, the disseminated sulfide from the syenogranite has comparable S-Pb isotopic composition with the sulfide minerals from ore veins,suggesting that the generation of the SJZ ore-forming fluids has a close relationship with the syenogranite magmatism. Combining with the geochemical characters of the syenogranite, the authors proposed that the mantle-derived fingerprint of the SJZ ore-forming fluid might be caused by the parent magma of the syenogranite, which was derived from partial melting of the juvenile lower crust, and underwent the residual melts segregated from a crystal mush in the shallow magma reservoir. The extraction of the syenogranite parent magma further concentrated the fertilized fluids, which was crucial to mineralization of the SJZ Ag-Pb-Zn deposit.展开更多
The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of ...The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of the regional Zn-Pb mineralization remain controversial despite many investigations that have been conducted.The Wusihe Zn-Pb deposit is a representative large-scale Zn-Pb deposit in the northern SYG,which mainly occurs in the Dengying Formation and yields Zn-Pb resources of^3.7 Mt.In this paper,Zn and S isotopes,and Fe and Cd contents of sphalerite from the Wusihe deposit were investigated in an attempt to constrain the controls on Zn and S isotopic variations,the potential sources of ore-forming components,and the possible mineralization mechanisms.Both theδ66Zn andδ34S values in sphalerite from the Wusihe deposit increase systematically from the bottom to the top of the strata-bound orebodies.Such spatial evolution inδ66Zn andδ34S values of sphalerite can be attributed to isotopic Rayleigh fractionation during sphalerite precipitation with temperature variations.The strong correlations between the Zn-S isotopic compositions and Fe-Cd concentrations in sphalerite suggest that their variations were dominated by a similar mechanism.However,the Rayleigh fractionation mechanism cannot explain the spatial variations of Fe and Cd concentrations of sphalerite in this deposit.It is noted that the bottom and top sphalerites from the strata-bound orebodies document contrasting Zn and S isotopic compositions which correspond to the Zn and S isotopic characteristics of basement rocks and host rocks,respectively.Therefore,the mixing of two-source fluids with distinct Zn-S isotopic signatures was responsible for the spatial variations of Zn-S isotopic compositions of sphalerite from the Wusihe deposit.The fluids from basement rocks are characterized by relatively lighter Zn(~0.2‰)and S(~5‰)isotopic compositions while the fluids from host rocks are marked by relatively heavier Zn(~0.6‰)and S(~15‰)isotopic compositions.展开更多
基金supported by the National Natural Science Foundation of China (NSFC) (No. 41772062)
文摘The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform ore bodies and veintype ones, controlled by the Early Permian strata and the Late Hercynian diorite intrusion, respectively. Due to the ambiguous genetic type of the stratiform ore bodies, there has been controversy on the relationship between them and veintype ore bodies. To determine the genetic type of stratiform ore bodies, laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) in situ trace elements and S–Pb isotope analysis have been carried on the sulfides in the stratiform ore bodies. Compared with that in skarn, Mississippi Valley-type(MVT), and epithermal deposits, sphalerite samples in the stratiform ore bodies of the Dongfengnanshan deposit are significantly enriched in Fe, Mn, and In, while depleted in Ga, Ge, and Cd, which is similar to the sphalerite in volcanic-associated massive sulfide(VMS) deposits. Co/Ni ratio of pyrrhotites in the stratiform ore bodies is similar to that in VMS-type deposits. The concentrations of Zn and Cd of chalcopyrites are similar to those of recrystallized VMS-type deposits. These characteristics also reflect the intermediate ore-forming temperature of the stratiform ore bodies in this deposit. Sulfur isotope compositions of sulfides are similar to those of VMS-type deposits, reflecting that sulfur originated from the Permian Miaoling Formation. Lead isotope compositions indicate mixed-source for lead. Moreover, the comparison of the Dongfengnanshan stratiform ore bodies with some VMStype deposits in China and abroad, on the trace elements and S–Pb isotope characteristics of the sulfides reveals that the stratiform ore bodies of the Dongfengnanshan deposit belong to the VMS-type, and have closely genetic relationship with the early Permian marine volcanic sedimentary rocks.
基金financially supported by the National Key Research and Development Program of China (Grant No.2017YFC0601306)the National Natural Science Foundation of China (Grant No.41390444)+1 种基金the Program of the China Geological Survey(Grant No.DD20160344)supported by Team 707, Heilongjiang Bureau of Geological Exploration for Nonferrous Metals
文摘Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced from the spatial diagenesis-mineralization relationship,chronological data,physicochemical characteristics of mineral fluid inclusions,mineral or rock elements and isotopic geochemical characteristics.By objectively examining this scientific problem via a geological field survey and petrographic analysis of the Gaosongshan epithermal gold deposit,we recently discovered and verified the following points:(1) Pyrite-bearing spherical quartz aggregates (PSQA) occur in the rhyolitic porphyry;(2) the mineralization is structurally dominated by WNW- and ENE-trending systems and occurs mostly in hydrothermal breccias and pyrite-quartz veins,and the ore types are mainly hematite-crusted quartz,hydrothermal breccia,massive pyrite-quartz,etc.;(3) the alteration types consist of prevalent silicification,sericitization,propylitization and carbonation,with local adularization and illitization.The ore minerals are mainly pyrite,primary hematite,native gold,and electrum,with lesser amounts of chalcopyrite,magnetite,sphalerite,and galena,indicating a characteristic epithermal low-sulfidation deposit.The ore-forming fluid may have been primarily derived from magmatic fluid exsolved from a crystallizing rhyolitic porphyry magma.Further zircon U-Pb geochronology,fluid inclusion,physicochemical and isotopic geochemical analyses revealed that (1) rhyolitic porphyry magmatism occurred at 104.6 ± 1.0 Ma,whereas the crystallization of the PSQA occurred at 100.8 ± 2.1 Ma;(2) the hydrothermal fluid of the pre-ore stage was an exsolved CO2-bearing H2O-NaCl magmatic fluid that produced inclusions mainly composed of pure vapor (PV),vapor-rich (WV) and liquid-rich (WL) inclusions with a small number of melt-(M) and solid-bearing (S) inclusions;mineralization-stage quartz contains WL and rare PV,WV and pure liquid (PL) inclusions characterized by the H2O-NaCl system with low formation temperatures and low salinities;(3) the characteristics of hydrogen,oxygen,sulfur,and lead isotopes and those of rare earth elements (REEs) provide insight into the affinity between PSQA and orebodies resulting from juvenile crust or enriched mantle.Combined with previous research on the mineralogenetic epoch (99.32 ± 0.01 Ma),we further confirm that the mineralization of the deposit occurred in the late Early Cretaceous,which coincides with the extension of the continental margin induced by subduction of the Pacific Plate beneath the Eurasian Plate.The formation of the ore deposit was proceeded by a series of magmatic and hydrothermal events,including melting of enriched juvenile crust,upwelling,the eruption and emplacement of the rhyolitic magma,the exsolution and accumulation of magmatic hydrothermal fluid,decompression,the cooling and immiscibility/boiling of the fluid,and mixing of the magmatic fluid with meteoric water,in association with water-rock interaction.
基金supported by the Chinese Ministry of Science and Technology(Sinoprobe-05-03)Doctoral Fund of Ministry of Education of China(20110022120003)+1 种基金the Fundamental Research Funds for the Central UniversitiesOpen Fund of State Key Laboratory of Geological Processes and Mineral Resources(GPMR2011)
文摘Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history spanning the entire Quaternary period. Magma origin and evolution of Tengchong Cenozoic volcanic rocks were studied on the basis of Nd-Sr-Pb isotope and major and trace element data from different eruptions in the Ma'anshan area. Different samples within one eruption show relative identical lithologies, chemical and isotopic compositions. However, the geochemical features for the five eruptions are distinct from each other. These volcanic rocks show low Mg# values (〈45), moderate to high fractionation of LREEs and HREEs, and enrichment of Pb and Ba and depletion of Nb. Tengchong Cenozoic volcanic rocks were derived from an enriched mantle based on Nd-Sr-Pb isotopic studies. And lines of evidence show that crustal contamination should be involved before the eruption of different periods of Tengchong Cenozoic volcanic rocks. Older subducted components may be responsible for adakite recycling at various stages of evolution, which results in the origin of the enriched mantle source magma accounting for the isotopic features of Tengchong Cenozoic volcanic rocks. Segregated primitive magma pulsating injected into magma chamber, fractional crystallized and contaminated with crust component. Finally, magmas with distinct chemical and isotopic compositions for each eruption formed. The extension of the northeast segment of the Yingjiang tectonic belt triggered the pulsating eruption of the Cenozoic volcanics in the Tengchong area.
基金funded via an Australian Geophysical Observing System grant provided to Au Scope Pty Ltd.the AQ44 Australian Education Investment Fund programpartly funded by the Western Australian Exploration Incentive Scheme
文摘Detrital zircon U-Pb geochronology has become the gold standard in evaluating source to sink relationships in sedimentary basins. However, the physical and chemical robustness of zircon, which make it such a useful mineral for provenance studies, is also a hindrance as zircon can be recycled through numerous sedimentary basins, thus obscuring the first cycle source to sink relationship. An elegant approach to addressing this potential issue is to compare the Pb isotope composition of detrital K-feldspar, a mineral which is unlikely to survive more than one erosion-transport-deposition cycle, with that of magmatic K-feldspar from potential basement source terranes. Here we present new in situ Pb isotope data on detrital K-feldspar from two Proterozoic arkosic sandstones from Western Australia, and magmatic K-feldspar grains from potential igneous source rocks, as inferred by the age and Hf isotope composition of detrital zircon grains. The data indicate that the detrital zircon and K-feldspar grains could not have been liberated from the same source rocks, and that the zircon has most likely been recycled through older sedimentary basins. These results provide a more complete understanding of apparently simple source to sink relationships in this part of Proterozoic Western Australia.
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We carried out Pb isotopes studies in sediments fromParatyBaylocated in the SE area of theRio de JaneiroStateto discriminate the signature of metal contamination from domestic sewage, industries, shipyards and geogenic sources. The studied samples have been chosen in two sectors of the Bay, including the Paraty area andJuatingaBay. Sample preparation procedures included: 1) drying and granulometric separations (200 mesh);2) weighting;3) complete dissolution and 4) Pb isotope analysis obtained by MC-ICP-MS (ratios 208Pb/204Pb,207Pb/204Pb, 206Pb/204Pb). Preliminary results when plotted in the 207Pb/204Pbversus 208Pb/204Pb and 207Pb/206Pb versus 206Pb/204Pb diagrams showed three groups of signatures. The first group (samples PY-01, PY-03 PY-106 and PY-127) presented 207Pb/206Pb values in the range from 1.191 to 1.209. The isotope values may be interpreted as contribution of a pollutant sources of Pb not yet identified. The second group (PY-11, PY-13, PY-21, PY-22, PY-46, PY-51, PY-109 and PY-111) showed 207Pb/206Pb values in the range from 1.188 to 1.222. The last group (samples PY-123 and PY-135) presented higher 207Pb/ 206Pb values from 1.321 to 1.322 and probably represented oceanic signature. The Pb isotope data of the second group may be interpreted as the result of oceanic water and pollutant sources mixture from the continent. According to the literature the anomalous Pb signature is similar to anthropogenic source. The Pb isotope results here reported are coherent with the reported data from the continent area. We may conclude that significant isotopic differences in Pb signatures are consequence of anthropogenic Pb isotope signature. In this way, Pb isotope is an important tool to trace the changing sources of pollutant Pb (and other metals) in ocean environment.
文摘A broad set of samples from the CVP has been analyzing Pb isotopes. Campanian Volcanic Province (CVP) has been produced by various ranges of mixing between three components: 1) MORB, 2) Hercynian basement and 3) upper crust. Anyhow, the upper crust that has modified the Pb isotopic composition also shows trends towards an Achaean upper crust. This is consistent for all Mediterranean area. This is not in contrast with the past plate tectonic reconstruction. Also the surface sediments (GLOSS) may have been a mixing between the Achaean upper crust and a Hercynian component with an implication worldwide due to the rock cycle processes.
基金financially supported by the National Natural Science Foundation of China(No.41272093)China geological survey project(No.12120114080901)
文摘The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian (426-422 Ma), and their zircons have ~Hf(t) values of-9.4 to 5.9 with the older TDMm ages (0.80-1.42 Ga). Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements (e.g., K, Rb, Th) and depleted in heavy rare earth elements and high field strength elements (e.g., Ta, Nb, Zr, Ti). Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle (0 ~ 2%o). The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.
基金supported by the Key Laboratory of Gold Mineralization Processes and Resource Utilization,MNRShandong Provincial Key Laboratory of Metallogenic Geological Process and Resource Utilization(Grant No.KFKT202103)National Natural Science Foundation of China(Grant No.41876037)。
文摘Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb isotopic composition of feldspar hosted in granitic rocks(thirteen Archean and one Paleoproterozoic)from the northern Kongling terrane,Yangtze Craton,South China,is analyzed.The samples reveal a substantial variation in their Pb isotopic composition,spanning the gap between the 1.9 Ga and present-day geochrons,which indicates extensive resetting by later tectonothermal events.This resetting was interpreted to have likely resulted from Paleoproterozoic and Neoproterozoic tectonothermal events related to the assembly and breakup of the Columbia and Rodinia supercontinents.These results suggest that Pb isotopes should be used cautiously when tracing magma sources and petrogenesis in magmatic rocks that have experienced post-magmatic reworking.However,the in situ Pb isotopic composition of feldspar in ancient granitoids may also potentially be used to reveal later tectonothermal events.The extensive resetting of the Pb isotopic composition in feldspar by regional thermal events may also provide new insights into our understanding of the Pb isotope paradox.
文摘Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. The sphalerite rich pockets are concentrated within the dolostone of older Trikuta Formation while galena rich mineralization occurs in form of veins, lenses and pockets hosted within siliceous varieties of dolostone and quartzite belonging to younger Khairikot Formation. Sulphur isotope geochemistry is reported in the present paper for the sphalerire and galena from the area for first time. Overall?δ34S of sulphides varies from (+9.67‰ to +34.42‰). Sphalerite ores hosted within older Trikuta Formation and younger Khairikot Formation, however, show different?δ34S values. It ranged from +9.67‰ to +10.59‰ for the sphalarite hosted in Trikuta Formation and from +18.38‰ to +34.42‰ for sphalerite hosted within Khairikot Formation. Sulphur isotopic data and ore petrographic data suggest that there is two-generation of sphalerite present in the area.
基金supported financially by the China Geological Survey project [DD20160123 (DD-16-049, D1522), DD20160050, DD20190370]the Fundamental Research Funds for the Central Universities (310827171122)the National Natural Science Foundation of China (Grant 41672068)。
文摘The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magmatic system, and the mineralization age was consistent with the diagenetic age. However,the relationship between granitic magmatism and mineralization is still unclear in the SJZ. In this study, CH-O-He-Ar and in-situ S-Pb isotope analyses were conducted to determine the sources of ore-forming fluids and metals, which were combined with geochemistry data of SJZ granitoids from previous studies to constrain the relationship between the magmatism and the mineralization. The C-H-O-He-Ar-S-Pb isotopic compositions suggested the SJZ ore-forming material and fluids were derived from a magmatic source, which has mixed a small amount of mantle-derived materials. In addition, the disseminated sulfide from the syenogranite has comparable S-Pb isotopic composition with the sulfide minerals from ore veins,suggesting that the generation of the SJZ ore-forming fluids has a close relationship with the syenogranite magmatism. Combining with the geochemical characters of the syenogranite, the authors proposed that the mantle-derived fingerprint of the SJZ ore-forming fluid might be caused by the parent magma of the syenogranite, which was derived from partial melting of the juvenile lower crust, and underwent the residual melts segregated from a crystal mush in the shallow magma reservoir. The extraction of the syenogranite parent magma further concentrated the fertilized fluids, which was crucial to mineralization of the SJZ Ag-Pb-Zn deposit.
基金funded by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB18030302)the National Key R&D Program of China (2017YFC0602503)the National Natural Science Foundation of China (U1812402, 41430315, 41573011, 41625006)
文摘The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of the regional Zn-Pb mineralization remain controversial despite many investigations that have been conducted.The Wusihe Zn-Pb deposit is a representative large-scale Zn-Pb deposit in the northern SYG,which mainly occurs in the Dengying Formation and yields Zn-Pb resources of^3.7 Mt.In this paper,Zn and S isotopes,and Fe and Cd contents of sphalerite from the Wusihe deposit were investigated in an attempt to constrain the controls on Zn and S isotopic variations,the potential sources of ore-forming components,and the possible mineralization mechanisms.Both theδ66Zn andδ34S values in sphalerite from the Wusihe deposit increase systematically from the bottom to the top of the strata-bound orebodies.Such spatial evolution inδ66Zn andδ34S values of sphalerite can be attributed to isotopic Rayleigh fractionation during sphalerite precipitation with temperature variations.The strong correlations between the Zn-S isotopic compositions and Fe-Cd concentrations in sphalerite suggest that their variations were dominated by a similar mechanism.However,the Rayleigh fractionation mechanism cannot explain the spatial variations of Fe and Cd concentrations of sphalerite in this deposit.It is noted that the bottom and top sphalerites from the strata-bound orebodies document contrasting Zn and S isotopic compositions which correspond to the Zn and S isotopic characteristics of basement rocks and host rocks,respectively.Therefore,the mixing of two-source fluids with distinct Zn-S isotopic signatures was responsible for the spatial variations of Zn-S isotopic compositions of sphalerite from the Wusihe deposit.The fluids from basement rocks are characterized by relatively lighter Zn(~0.2‰)and S(~5‰)isotopic compositions while the fluids from host rocks are marked by relatively heavier Zn(~0.6‰)and S(~15‰)isotopic compositions.