The geochemical features of the monzonitic granite in Qimantage Hutouya deposit area,Qinghai,in respect to the mineralization,suggest that this granite belongs to weak peraluminous and high-k calc alkaline rock series...The geochemical features of the monzonitic granite in Qimantage Hutouya deposit area,Qinghai,in respect to the mineralization,suggest that this granite belongs to weak peraluminous and high-k calc alkaline rock series. The REE of the samples show right slope with obvious LREE/HREE differentiation and negative Eu abnormity. The trace elements show enrichment of LILE( Rb,Th,U,La,Nd),and deleption of Ba,Sr,Nd,P,Ti. The Sr-Nb isotopic data indicate that the magma source is mainly aluminosilicate lower crust with a small amount of new crustal materials. The weighted mean zircon U-Pbage of the Hutouya monzonitic granite is 221±1.7 Ma,belonging to Late Triassic. The Hutouya monzonitic granite was formed in the tectonic setting of transition from compression to extension during Middle-Late Triassic.展开更多
The Jingren deposit is part of the Qimantage metallogenic belt within the eastern Kunlun orogenic belt,the largest metallogenic belt in Qinghai Province,northwestern China.Exploration data show that the metal resource...The Jingren deposit is part of the Qimantage metallogenic belt within the eastern Kunlun orogenic belt,the largest metallogenic belt in Qinghai Province,northwestern China.Exploration data show that the metal resources of the Jingren deposit are greater than 93000 t in a mining area of 76.15 km2,which indicates significant exploration potential in the near future.Three W–E-trending faults,F1-3,dominate the extension of the mineralization zone,which consists of chalcopyrite,pyrite,magnetite,galena,sphalerite,and molybdenite as well as bismuth-bearing minerals.The deposit contains a large amount of late Triassic intrusive rocks,however,previous research did not reach a consensus on the timing or the origin of the mineralization owing to a lack of geochronological data and poor exposure conditions.In the present study,Re-Os isotopic dating from six molybdenite samples collected from a borehole of the granodiorite in the Jingren deposit using negative thermal ionization mass spectrometry(NTIMS)showed 187 Re and 187 Os concentrations of 0.26–4.40 ppm and 1.03–16.46 ppb,respectively,with an initial 187 Os/188 Os value of 0.06±0.19.This proves that the Jingren deposit has a metallogenic age of(225±4)Ma and is the product of united mineralization of the Qimantage metallogenic belt and that the Jingren deposit might actually be an Indosinian metallogeny.In addition,the Re content of these samples,at 0.42 ppm to 7.00 ppm shows that the mineralization was derived mainly from a crustal source.Furthermore,electron probe microanalysis(EPMA)conducted on chalcopyrite obtained from 22 metallic mineral samples revealed(Fe+Cu)/S ratios of 1.801–1.947 with an average of 1.852,which is lower than the ideal value(1.875).Besides,the main ore body formed in a relatively higher temperature environment than the surrounding rocks in the Jingren deposit.These data indicate that the Jingren deposit formed in a metallogenic environment at lower temperature.Moreover,according to the TiO_(2)-Al_(2)O_(3)-(MgO+MnO)and TiO_(2)-Al_(2)O_(3)-MgO genetic classification diagram for magnetite,the Jingren deposit most likely belongs to the skarn family.In addition,the Co-Ni-As genetic classification diagram of the pyrite indicates sedimentary and skarn genetic characteristics.展开更多
Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance.In order to explore magnetite Fe^(2+)/Fe^(3+) ratios o...Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance.In order to explore magnetite Fe^(2+)/Fe^(3+) ratios of the Qimantag metallogenic belt,part of the Eastern Kunlun orogenic belt in the northeastern margin of the Qinghai–Tibetan plateau,western Central Orogenic Belt of China,and overcome the limitation of the traditional electronic probe,five different measurement methods are proposed and their respective advantages and disadvantages evaluated,with the composition data of the magnetite obtained using electron probe microanalysis(EPMA).The direct oxygen measurement method has a significant impact on the determination results of FeO and Fe2O3,but the accuracy and uniformity of the results are low.The valence method(Flank method)based on the spectral intensity ratio of Lαto Lβfor iron is also unreliable for FeO and Fe_(2)O^(3) measurements because it is difficult to establish a relationship between Lβ/Lα,the spectral intensity ratio,and the Fe^(2+)/Fe^(3+) content ratio.In comparison,the charge difference method,the surplus-oxygen method and the Mössbauer spectrum method are still the most favorable.Mössbauer spectroscopy,with its isomer movement particularly sensitive to the oxidation state of iron,yields results closer to 0.5,which is relatively reliable.Earlier magnetite deposits are located in intrusions or contact zones and formed by magmatic fluids with high Fe2+/Fe3+ratios,whereas later magnetite deposits are farther away from intrusions and have low Fe^(2+)/Fe^(3+) ratios.The transformation mechanism of hematite and magnetite in the Qimantage metallogenic belt is also studied.No large volume changes,such as pore filling and shrinkage fracture,were detected in the metallogenic belt,and the transformation mechanism is more similar to a reoxidation and reduction mechanism.展开更多
The Tieshidas Group in Qimantag, a branch of the East Kunlun Mountains, was classically considered the Caledonian basement, and classified into Middle-Upper Ordovician, Upper Ordovician or simply Lower Paleozoic. The ...The Tieshidas Group in Qimantag, a branch of the East Kunlun Mountains, was classically considered the Caledonian basement, and classified into Middle-Upper Ordovician, Upper Ordovician or simply Lower Paleozoic. The radiolarian fauna was found, for the first time, from a chert block in the Tieshidas Group at Yaziquandaban (Pass) north to Ayakum Lake. They are Astroentactinia?mirousi Gourmelon, As. cf biaciculata Nazarov, Archocyrtium cf. diductum Deflandre, Ar. aff. diductum Deflandre, Deflandrellium? sp., Entactinia vulgaris Won, En. cf. additiva Foreman, En.? sp., Entactinosphaera palimbola Foreman, Pylentonema? sp., Triaenosphaera sp. and Tr.7 sp. The geological age of this radiolarian fauna is Early Carboniferous. Evidently, the classical interpretation about the age of Tieshidas Group needs to be checked and modified. Except the Ordovician proved with the formerly discovered fossils, it also includes, at least, Lower Carboniferous rocks. There was still an oceanic basin at Qimantag during Early展开更多
基金Supported by Project of China Geological Survey(No.20150209-01-079)
文摘The geochemical features of the monzonitic granite in Qimantage Hutouya deposit area,Qinghai,in respect to the mineralization,suggest that this granite belongs to weak peraluminous and high-k calc alkaline rock series. The REE of the samples show right slope with obvious LREE/HREE differentiation and negative Eu abnormity. The trace elements show enrichment of LILE( Rb,Th,U,La,Nd),and deleption of Ba,Sr,Nd,P,Ti. The Sr-Nb isotopic data indicate that the magma source is mainly aluminosilicate lower crust with a small amount of new crustal materials. The weighted mean zircon U-Pbage of the Hutouya monzonitic granite is 221±1.7 Ma,belonging to Late Triassic. The Hutouya monzonitic granite was formed in the tectonic setting of transition from compression to extension during Middle-Late Triassic.
基金granted by National Key R&D Program of China(Grant No.2019YFC1805900)Scientific Research Project of Hunan Provincial Department of Education(Grant No.19C1178)Open Research Fund Program of Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring(Central South University,Hunan),Ministry of Education(Grant No.2019YSJS07)。
文摘The Jingren deposit is part of the Qimantage metallogenic belt within the eastern Kunlun orogenic belt,the largest metallogenic belt in Qinghai Province,northwestern China.Exploration data show that the metal resources of the Jingren deposit are greater than 93000 t in a mining area of 76.15 km2,which indicates significant exploration potential in the near future.Three W–E-trending faults,F1-3,dominate the extension of the mineralization zone,which consists of chalcopyrite,pyrite,magnetite,galena,sphalerite,and molybdenite as well as bismuth-bearing minerals.The deposit contains a large amount of late Triassic intrusive rocks,however,previous research did not reach a consensus on the timing or the origin of the mineralization owing to a lack of geochronological data and poor exposure conditions.In the present study,Re-Os isotopic dating from six molybdenite samples collected from a borehole of the granodiorite in the Jingren deposit using negative thermal ionization mass spectrometry(NTIMS)showed 187 Re and 187 Os concentrations of 0.26–4.40 ppm and 1.03–16.46 ppb,respectively,with an initial 187 Os/188 Os value of 0.06±0.19.This proves that the Jingren deposit has a metallogenic age of(225±4)Ma and is the product of united mineralization of the Qimantage metallogenic belt and that the Jingren deposit might actually be an Indosinian metallogeny.In addition,the Re content of these samples,at 0.42 ppm to 7.00 ppm shows that the mineralization was derived mainly from a crustal source.Furthermore,electron probe microanalysis(EPMA)conducted on chalcopyrite obtained from 22 metallic mineral samples revealed(Fe+Cu)/S ratios of 1.801–1.947 with an average of 1.852,which is lower than the ideal value(1.875).Besides,the main ore body formed in a relatively higher temperature environment than the surrounding rocks in the Jingren deposit.These data indicate that the Jingren deposit formed in a metallogenic environment at lower temperature.Moreover,according to the TiO_(2)-Al_(2)O_(3)-(MgO+MnO)and TiO_(2)-Al_(2)O_(3)-MgO genetic classification diagram for magnetite,the Jingren deposit most likely belongs to the skarn family.In addition,the Co-Ni-As genetic classification diagram of the pyrite indicates sedimentary and skarn genetic characteristics.
基金obtained grants from the National Key Research and Development Program Project"Enhanced Bioremediation Technology and Equipment for Chromium Residuation Site",the Scientific Research Project of Hunan Provincial Department of Education(Grant No.19C1178)the Construction Program for the First-Class Disciplines(Geography)of Hunan Province,China.The anonymous reviewers and editors are thanked for constructive suggestions on improving the quality of the manuscript.
文摘Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance.In order to explore magnetite Fe^(2+)/Fe^(3+) ratios of the Qimantag metallogenic belt,part of the Eastern Kunlun orogenic belt in the northeastern margin of the Qinghai–Tibetan plateau,western Central Orogenic Belt of China,and overcome the limitation of the traditional electronic probe,five different measurement methods are proposed and their respective advantages and disadvantages evaluated,with the composition data of the magnetite obtained using electron probe microanalysis(EPMA).The direct oxygen measurement method has a significant impact on the determination results of FeO and Fe2O3,but the accuracy and uniformity of the results are low.The valence method(Flank method)based on the spectral intensity ratio of Lαto Lβfor iron is also unreliable for FeO and Fe_(2)O^(3) measurements because it is difficult to establish a relationship between Lβ/Lα,the spectral intensity ratio,and the Fe^(2+)/Fe^(3+) content ratio.In comparison,the charge difference method,the surplus-oxygen method and the Mössbauer spectrum method are still the most favorable.Mössbauer spectroscopy,with its isomer movement particularly sensitive to the oxidation state of iron,yields results closer to 0.5,which is relatively reliable.Earlier magnetite deposits are located in intrusions or contact zones and formed by magmatic fluids with high Fe2+/Fe3+ratios,whereas later magnetite deposits are farther away from intrusions and have low Fe^(2+)/Fe^(3+) ratios.The transformation mechanism of hematite and magnetite in the Qimantage metallogenic belt is also studied.No large volume changes,such as pore filling and shrinkage fracture,were detected in the metallogenic belt,and the transformation mechanism is more similar to a reoxidation and reduction mechanism.
文摘The Tieshidas Group in Qimantag, a branch of the East Kunlun Mountains, was classically considered the Caledonian basement, and classified into Middle-Upper Ordovician, Upper Ordovician or simply Lower Paleozoic. The radiolarian fauna was found, for the first time, from a chert block in the Tieshidas Group at Yaziquandaban (Pass) north to Ayakum Lake. They are Astroentactinia?mirousi Gourmelon, As. cf biaciculata Nazarov, Archocyrtium cf. diductum Deflandre, Ar. aff. diductum Deflandre, Deflandrellium? sp., Entactinia vulgaris Won, En. cf. additiva Foreman, En.? sp., Entactinosphaera palimbola Foreman, Pylentonema? sp., Triaenosphaera sp. and Tr.7 sp. The geological age of this radiolarian fauna is Early Carboniferous. Evidently, the classical interpretation about the age of Tieshidas Group needs to be checked and modified. Except the Ordovician proved with the formerly discovered fossils, it also includes, at least, Lower Carboniferous rocks. There was still an oceanic basin at Qimantag during Early
