The Guandimao and Wawutang plutons are located at the center of Hunan, South China. The former is mainly composed of biotite monzonitic granites/granodiorites and two-mica monzonltic granites, but the latter only cons...The Guandimao and Wawutang plutons are located at the center of Hunan, South China. The former is mainly composed of biotite monzonitic granites/granodiorites and two-mica monzonltic granites, but the latter only consists of biotite monzonitic granites. The zircon ages of 203.0±1.6 Ma （biotite monzonitic granites） and 208.0-23.2 Ma （two-mica monzonltic granites） for the Guandimao pluton and 204±3 Ma for the Wawutang pluton obtained with the LA-ICP-MS U-Pb dating indicate that they were formed during the late Indosinian. In consideration of other geochronological data from Indosinian rocks of South China and adjacent regions, it is inferred that the two plutons were derived from crustal materials by decompressional melting in a post-collisional tectonic setting during spontaneous thinning of the thickened curst. Moreover, the inherited zircon age of 1273±57 Ma from the Wawutang pluton indicates that the source of the two plutons is related to the early Proterozoic crustal basement.展开更多
Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or ura...Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or uranium matrix effect and alpha dose matrix effect,and illustrates the correction of these three effects.In addition,we point out the limitation and possible problems of the existing correction methods.展开更多
The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO<sub>2</sub> and low K<s...The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO<sub>2</sub> and low K<sub>2</sub>O,and depletion of light rare earth elements.They should be originated from a depleted asthenosphere mantle, belonging to ancient oceanic crust ophiolitic volcanic rock association.Compared with the Longba tholeiitic basalt,the Ganlongtang tholeiitic basalt shows展开更多
Listwanite is a suite of silica-carbonate alteration products formed when CO2-bearing hydrothermal fluids meet and react with serpentinized mafic and ultramafic rocks （Robinson et al., 2005）. This alteration product...Listwanite is a suite of silica-carbonate alteration products formed when CO2-bearing hydrothermal fluids meet and react with serpentinized mafic and ultramafic rocks （Robinson et al., 2005）. This alteration product is of great economic significance. Gold, mercury, magnesite and base metal deposits are often associated with listwanite. In China, the petrogenesis of listwanite and related mineralization has received insufficient attention to date. This outcropping paper reports the study along the northeast edge of the of listwanite Baer ophiolite,展开更多
Geochemical studies on the arnphibolites in the Songshugou ophiolite from Shangnan County, Shaanxi Province demonstrate that the protolith of the amphibolites is tholeiitic. The arnphibolites can be classified into tw...Geochemical studies on the arnphibolites in the Songshugou ophiolite from Shangnan County, Shaanxi Province demonstrate that the protolith of the amphibolites is tholeiitic. The arnphibolites can be classified into two groups according to their REE patterns and trace element features. Rocks of the first group are depleted in LREE while rocks of the second group are slightly depleted in LREE or flat from LREE to HREE without significant Eu anomaly. The first group of rocks have (La/Yb)N=0.33-0.55, (La/Sm)N= 0.45-0.65, and their La/Nb, Ce/Zr, Zr/Nb, Zr/Y and Ti/Y ratios are averaged at 1.20, 0.12, 31.02, 2.92 and 198, respectively, close to those of typical N-MORB. The second group of rocks have (La/Yb)N=0.63-0.95, (La/ Sm)N = 0.69--0.90, and their average La/Nb, Ce/Zr, Zr/Nb, Zr/Y and Ti/Y ratios are 0.82, 0.83, 1.15, 0.16, 19.00, 2.58 and 225, respectively, which lie between those of typical N-MORB and E-MORB but closer to the former. The two groups of rocks both exhibit flat patterns from Th to Yb in the highly incompatible elements spider diagram, but the first group of rocks have lower element abundances than the modern N-MORB, indicating a derivation of their mantle source from more depleted mantle source than the present N-MORB. The abundances of Th, Ta, Nb, La and Ce in the second group of rocks are slightly higher than those of the present N-MORB, and other elements, such as Hf, Zr, Sm, Ti, Y and Yb, are close to those of the N-MORB, indicating that the original magma was derived from depleted mantle but mixed with the enriched mantle. These characteristics, combined with the regional geology and previous studies, provide further evidence that the mafic-ultramafic rocks have the features of a typical ophiolite.Zircon grains from the amphibolite are generally rounded, and in most of them a distinguishable core-mantle texture is preserved as shown in the cathodoluminescence (CL) images. The core or core-mantle parts of the zircon grains are also rounded, same as those in basalts from other regions of the world. The LA-ICP-MS trace element and U-Pb isotopic analyses show that the zircon grains from the amphibolites are similar to the typical magmatic zircon in terms of their very low U and Th contents (62.36-0.10 μg/g and 78.47-0.003 μg/g, respectively). Seven pits from the core and core-mantle parts of the zircon grains yielded an average weighted 206Pb/ 238U age of 973±35 (2σ) Ma with the Th/U ratios range from 0.01 to 8.38 and mostly greater than 0.23. This age is consistent within the error range with the whole-rock Sm-Nd isochron age of 1030±46 Ma for the same kind of rocks reported by Dong et al. (1997a). In a combined analysis with the zircon positions on the CL images and the corresponding Th/U ratios, the age of 973±35 Ma is probably the formation age of tholeiite, the protolith of the Songshugou amphibolite. The geochronological determination gives further evidence that the Songshugou ophiolite was formed during the Neoproterozoic. In addition, there is one pit from the rim of a zircon grain giving a 206Pb/ 238U age of 5721199 (1σ) Ma with a Th/U ratio of 0.08. It may represent the age of the accretionary zircon in the amphibolite-facies metamorphism.展开更多
The multi-stage intrusions of intermediate-acid magma occur in the Bangpu mining district, the petrogenic ages of which have been identified. The times and sequences of their emplacement have been collated and stipula...The multi-stage intrusions of intermediate-acid magma occur in the Bangpu mining district, the petrogenic ages of which have been identified. The times and sequences of their emplacement have been collated and stipulated in detail in this paper by using the laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） zircon U-Pb dating method. The ages of biotite monzogranite that were formed before mineralization in the southwest of this mining district are 70±1 Ma （mean square of weighted deviates （MSWD） =9.5, n=8） and 60.60±0.31 Ma （MSWD=3.8, n=16）, which belong to the late Cretaceous-early Paleocene in age. That means, they are products of an early tectonicmagmatic event of the collision between the Indian and Asian continentals. The ages of ore-bearing monzogranite porphyry and ore-bearing diorite porphyrite are 16.23±0.19 Ma （MSWD=2.0, n=26） and 15.16±0.09 Ma （MSWD=3.9, n=5） separately, which belong to the middle Miocene in age; namely, they are products of the Gangdese post-collision extensional stage when crust-mantle materials melted and mixed as well as magmatic intrusion simultaneously occurred. Some zircons with ages of 203.6±2.2 Ma （MSWD=1.18, n=7） were captured in the ore-bearing diorite porphyrite, which shows that there had been tectono-magmatic events in the late Triassic-early Jurassic. Molybdenum （copper） ore-bodies produced in the monzogranite porphyry and copper （molybdenum） ore-bodies produced in the diorite porphyrite are the main ore types in this ore deposit. The model ages of Re-Os isotopic dating for the 11 molybdenite are 13.97-15.84 Ma, while isochron ages are 14.09±0.49 Ma （MSWD=26）. The isochron ages of seven molybdenite from molybdenum （copper） ore with monzogranite porphyry type are 14.11±0.31 Ma （MSWD=5.2）. There is great error in the isochron ages of four molybdenite from copper （molybdenum） ore with diorite porphyrite type, and their weighted average model ages of 14.6±1.2 Ma （MSWD=41）, which generally represent the mineralization age. The results about the Re-Os isotopic dating of molybdenite in the ore of different types have limited exactly that, the minerlazation age of this ore deposits is about 14.09 Ma, which belongs to the middle Miocene mineralization. The Bangpu deposit has a uniform metallogenic dynamics background with the porphyry type and skarn-type deposits such as Jiama, Qulong and others.展开更多
Information about the protolith of the Huangtuling granulite in North Dabieshan has been unavailable. The complex evolution history of the rock and its host basement must be further discussed. LA-ICP-MS U-Pb dating wa...Information about the protolith of the Huangtuling granulite in North Dabieshan has been unavailable. The complex evolution history of the rock and its host basement must be further discussed. LA-ICP-MS U-Pb dating was conducted on three textural domains in zircon from a high-temperature, high-pressure felsic granulite in the Huangtuling area, North Dabieshan, Central China. The metamorphic growth-derived detrital zircon domain yields a 207^ pb/206^Pb age in the range of （2 49±54 ） -- （2 500±180） Ma. The magmatic genesis-derived detrltal zircon domain gives a 207^pb/ 206^Pb age ranging from 2 628 Ma to 2 690 Ma, with an oldest 206^ pb/ 238^U age of （2 790 ± 150） Ma. The metamorphic overgrowth or metamorphic recrystallization zircon domain yields a diesordia with an upper intercept age of （2 044. 7 ± 29.3 ） Ma. Compositions of the mineral assemblage, major element geochemistry, and especially the complex interior texture of the zircon suggest that the prololith of the felsic granulite is of sedimentary origin. Results show that the protolith material of the granulite came from a provenance with a complex thermal history, i.e. -2.8 Ga magmatlsm and -2.5 Ga metamorphism, and was deposited in a basin not earlier than 2.5 Ga. The high-temperature and high-pressure granulite-facies metamorphic age was precisely constrained at （2.04±0.03） Ga, which indicates the granulite in Huangtuling area should be a relict of a Paleoproterozoic UHT （ultrahigh temperature） metamorphosed slab.展开更多
The Wurinitu molybdenum deposit,located in Honggor,Sonid Left Banner of Inner Mongolia,China,is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite...The Wurinitu molybdenum deposit,located in Honggor,Sonid Left Banner of Inner Mongolia,China,is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite.The wall rocks are composed of Variscan porphyritic-like biotite granite and the Lower Ordovician Wubin'aobao Formation.LA-ICP-MS zircon U-Pb dating of the fine-grained granite reveals two stages of zircons,one were formed at 181.7±7.4 Ma and the other at 133.6±3.3 Ma.The latter age is believed to be the formation age of the fine-grained granite,while the former may reflect the age of inherited zircons,based on the morphological study of the zircon and regional geological setting.The Re-Os model age of molybdenite is 142.2±2.5 Ma,which is older than the diagenetic age of the fine-grained granite.Therefore the authors believe that the metallogenic age of the Wurinitu molybdenum deposit should be nearly 133.6±3.3 Ma or slightly later,i.e.,Early Cretaceous.Combined with regional geological background research,it is speculated that the molybdenum deposits were formed at the late Yanshanian orogenic cycle in the Hingganling-Mongolian orogenic belt,belonging to the relaxation epoch posterior to the compression and was associated with the closure of the Mongolia-Okhotsk Sea.展开更多
1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margi...1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margin of Yunkai post-Caledonian uplift.Multiple type granites are widely distributed in Hetai district,including Caledonian,Indosinian and Yanshanian granites.Based on different展开更多
The LA-ICP-MS U-Pb zircon dating of eight typical samples from four units of the Bozhushan granite intrusion in southeastern Yunnan Province, constrains the age of acidic magmatic intrusion in this area. Both the osci...The LA-ICP-MS U-Pb zircon dating of eight typical samples from four units of the Bozhushan granite intrusion in southeastern Yunnan Province, constrains the age of acidic magmatic intrusion in this area. Both the oscillatory zoning and chondrite-normalized REE patterns characterized by LREE-depletion and HREE-enrichment with positive Ce anomaly and negative Eu anomaly indicate the magmatic genesis of these zircons. Eight zircon samples from the Bozhushan granite yielded a mean 206 Pb/ 238 U age of (85.58±1.0) Ma (MSWD=4.1) to (88.10±0.66) Ma (MSWD=1.8). These chronology data suggest an accurate isotopic age for the intrusion of the Bozhushan granite, and are different from the published age data of 48 to 111.5 Ma. The geochronology data of the Gejiu, Dulong and Dachang super-large deposits and related Yanshanian granites indicated that there occurred large-scale granitic magmatism and mineralization events in western Nanling region during the Late Cretaceous.展开更多
In situ carbonate U-Pb dating is gaining popularity,and it has great potential for application in petroleum geology.However,the low U content(<10μg/g)and high common Pb content of carbonate minerals,along with the...In situ carbonate U-Pb dating is gaining popularity,and it has great potential for application in petroleum geology.However,the low U content(<10μg/g)and high common Pb content of carbonate minerals,along with the uneven distribution of U and Pb and the lack of matrix-matched reference material make carbonate U-Pb dating inaccurate and less successful,which limits the widespread application in geosciences.This study evaluated the limitations of in situ carbonate U-Pb dating and proposed a method to rationally determine the laser ablation parameters of samples by improving the experimental approach based on the laser ablation sector field inductively coupled plasma mass spectrometry(LA-SF-ICP-MS).By setting a different spot size and laser frequency for the reference material and unknown samples in the same session based on the U content of the sample,the ablation craters of the reference material and unknown samples were given the same depth/width ratio,avoiding systematic offset caused by differences in down-hole element fractionation and reducing the consume of reference material.Depending on the heterogeneous distribution of U and Pb contents in carbonate minerals,the method of grid screening and setting ablation spots during screening were used to quickly select domains with high U and low common Pb,which improves the efficiency of setting laser spots and the success rate of dating,as well as reduces the experimental time and economic cost.The accuracy and success rate of carbonate U-Pb dating were effectively improved by improving the experimental method,and the technique was applied to two carbonate samples with low U and high common Pb contents that were difficult to date by traditional methods.The two samples are the saddle dolomite in the central Sichuan Basin and the calcite cement in the sandstone reservoir of the Cretaceous Qingshuihe Formation in the South Junggar Basin.The robust ages have been obtained,which constrains the timing of the diagenetic and hydrocarbon accumulation process in the studied area.展开更多
LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within...LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within errors.It is the first time that the microgranular enclaves age in Kalamaili area was determined.Petrochemistry and geochemistry research shows the characteristics of host rock as follows:展开更多
The Langshan Group is an important constituent of the Precambrian metamorphic rocks in the Langshan area.The accurate determination of its metamorphic age is of great scientific significance for the further study of t...The Langshan Group is an important constituent of the Precambrian metamorphic rocks in the Langshan area.The accurate determination of its metamorphic age is of great scientific significance for the further study of the Precambrian geological evolution in the region.Disputes remain regarding the metamorphism and deformation overprinting of the Langshan Group.This paper presents a detailed study comprising a field geological investigation,petrological observations,and zircon U-Pb aging of garnet-bearing mica quartz schists in the BangBang District.The result of detrital zircon U-Pb dating from the metamorphosed volcanic sedimentary rock series and geological investigation of the garnet-bearing mica quartz schists suggest the strata formed in the Neoproterozoic.The results from cathodoluminescence(CL)image analysis and U-Pb dating of zircons indicate a large number of metamorphic zircons exist in the garnet-bearing mica quartz schists.The metamorphic overgrowth rims of zircon from two samples were analyzed by LA-ICP-MS.The ^(206)Pb/^(238)U weighted average age of ca.244 Ma of the zircon metamorphism rims represents the timing of Indosinian greenschist-amphibolite facies metamorphism in the Langshan area,which may be in response to the collision-type orogeny of the North China and Siberian plates in the Late Paleozoic.Acid-intermediate magmatic intrusive activities occurred in the Langshan area,and metamorphic events developed at the same time or at a later stage during the closure of the Paleo-Asian Ocean.展开更多
基金This research was supported by the National Natural Science Foundation of China （No. 40372036）the Key Project of the Ministry of Education, China （No. 306007）.
文摘The Guandimao and Wawutang plutons are located at the center of Hunan, South China. The former is mainly composed of biotite monzonitic granites/granodiorites and two-mica monzonltic granites, but the latter only consists of biotite monzonitic granites. The zircon ages of 203.0±1.6 Ma （biotite monzonitic granites） and 208.0-23.2 Ma （two-mica monzonltic granites） for the Guandimao pluton and 204±3 Ma for the Wawutang pluton obtained with the LA-ICP-MS U-Pb dating indicate that they were formed during the late Indosinian. In consideration of other geochronological data from Indosinian rocks of South China and adjacent regions, it is inferred that the two plutons were derived from crustal materials by decompressional melting in a post-collisional tectonic setting during spontaneous thinning of the thickened curst. Moreover, the inherited zircon age of 1273±57 Ma from the Wawutang pluton indicates that the source of the two plutons is related to the early Proterozoic crustal basement.
文摘Matrix effect primarily impacts the accuracy and precision of zircon LA-ICP-MS U-Pb data.This paper describes three types of matrix effect in zircon LA-ICPMS U-Pb dating,i.e.,the element matrix effect,high Ddpa or uranium matrix effect and alpha dose matrix effect,and illustrates the correction of these three effects.In addition,we point out the limitation and possible problems of the existing correction methods.
文摘The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO<sub>2</sub> and low K<sub>2</sub>O,and depletion of light rare earth elements.They should be originated from a depleted asthenosphere mantle, belonging to ancient oceanic crust ophiolitic volcanic rock association.Compared with the Longba tholeiitic basalt,the Ganlongtang tholeiitic basalt shows
基金funded by the Key project of national natural science funds (40930313)Chinese Geological Survey Project Funds (12120114061801, 12120114057701 and 12120114061501)
文摘Listwanite is a suite of silica-carbonate alteration products formed when CO2-bearing hydrothermal fluids meet and react with serpentinized mafic and ultramafic rocks （Robinson et al., 2005）. This alteration product is of great economic significance. Gold, mercury, magnesite and base metal deposits are often associated with listwanite. In China, the petrogenesis of listwanite and related mineralization has received insufficient attention to date. This outcropping paper reports the study along the northeast edge of the of listwanite Baer ophiolite,
基金the National NaturalScience Foundation of China(Grant No:140032010-C,49972063)the National Key Basic Researchand Development Project of China(Grant No:G1999075508)+1 种基金the Ministry of Education's Teachers Fund(No:40133020) the Opening Fund of Key Laboratory of Lithosphere Tectonics.
文摘Geochemical studies on the arnphibolites in the Songshugou ophiolite from Shangnan County, Shaanxi Province demonstrate that the protolith of the amphibolites is tholeiitic. The arnphibolites can be classified into two groups according to their REE patterns and trace element features. Rocks of the first group are depleted in LREE while rocks of the second group are slightly depleted in LREE or flat from LREE to HREE without significant Eu anomaly. The first group of rocks have (La/Yb)N=0.33-0.55, (La/Sm)N= 0.45-0.65, and their La/Nb, Ce/Zr, Zr/Nb, Zr/Y and Ti/Y ratios are averaged at 1.20, 0.12, 31.02, 2.92 and 198, respectively, close to those of typical N-MORB. The second group of rocks have (La/Yb)N=0.63-0.95, (La/ Sm)N = 0.69--0.90, and their average La/Nb, Ce/Zr, Zr/Nb, Zr/Y and Ti/Y ratios are 0.82, 0.83, 1.15, 0.16, 19.00, 2.58 and 225, respectively, which lie between those of typical N-MORB and E-MORB but closer to the former. The two groups of rocks both exhibit flat patterns from Th to Yb in the highly incompatible elements spider diagram, but the first group of rocks have lower element abundances than the modern N-MORB, indicating a derivation of their mantle source from more depleted mantle source than the present N-MORB. The abundances of Th, Ta, Nb, La and Ce in the second group of rocks are slightly higher than those of the present N-MORB, and other elements, such as Hf, Zr, Sm, Ti, Y and Yb, are close to those of the N-MORB, indicating that the original magma was derived from depleted mantle but mixed with the enriched mantle. These characteristics, combined with the regional geology and previous studies, provide further evidence that the mafic-ultramafic rocks have the features of a typical ophiolite.Zircon grains from the amphibolite are generally rounded, and in most of them a distinguishable core-mantle texture is preserved as shown in the cathodoluminescence (CL) images. The core or core-mantle parts of the zircon grains are also rounded, same as those in basalts from other regions of the world. The LA-ICP-MS trace element and U-Pb isotopic analyses show that the zircon grains from the amphibolites are similar to the typical magmatic zircon in terms of their very low U and Th contents (62.36-0.10 μg/g and 78.47-0.003 μg/g, respectively). Seven pits from the core and core-mantle parts of the zircon grains yielded an average weighted 206Pb/ 238U age of 973±35 (2σ) Ma with the Th/U ratios range from 0.01 to 8.38 and mostly greater than 0.23. This age is consistent within the error range with the whole-rock Sm-Nd isochron age of 1030±46 Ma for the same kind of rocks reported by Dong et al. (1997a). In a combined analysis with the zircon positions on the CL images and the corresponding Th/U ratios, the age of 973±35 Ma is probably the formation age of tholeiite, the protolith of the Songshugou amphibolite. The geochronological determination gives further evidence that the Songshugou ophiolite was formed during the Neoproterozoic. In addition, there is one pit from the rim of a zircon grain giving a 206Pb/ 238U age of 5721199 (1σ) Ma with a Th/U ratio of 0.08. It may represent the age of the accretionary zircon in the amphibolite-facies metamorphism.
基金supported by the "973"Project for Basic Research of China (No. 2011CB403103)Ministry of Land and Resources’ Special Funds for Scientific Research on Public Causes (No. 200911007-02)China Geological Survey’ Special Funds for Scientific Research on Qinghai-Tibet Plateau (No. 1212010012005)
文摘The multi-stage intrusions of intermediate-acid magma occur in the Bangpu mining district, the petrogenic ages of which have been identified. The times and sequences of their emplacement have been collated and stipulated in detail in this paper by using the laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） zircon U-Pb dating method. The ages of biotite monzogranite that were formed before mineralization in the southwest of this mining district are 70±1 Ma （mean square of weighted deviates （MSWD） =9.5, n=8） and 60.60±0.31 Ma （MSWD=3.8, n=16）, which belong to the late Cretaceous-early Paleocene in age. That means, they are products of an early tectonicmagmatic event of the collision between the Indian and Asian continentals. The ages of ore-bearing monzogranite porphyry and ore-bearing diorite porphyrite are 16.23±0.19 Ma （MSWD=2.0, n=26） and 15.16±0.09 Ma （MSWD=3.9, n=5） separately, which belong to the middle Miocene in age; namely, they are products of the Gangdese post-collision extensional stage when crust-mantle materials melted and mixed as well as magmatic intrusion simultaneously occurred. Some zircons with ages of 203.6±2.2 Ma （MSWD=1.18, n=7） were captured in the ore-bearing diorite porphyrite, which shows that there had been tectono-magmatic events in the late Triassic-early Jurassic. Molybdenum （copper） ore-bodies produced in the monzogranite porphyry and copper （molybdenum） ore-bodies produced in the diorite porphyrite are the main ore types in this ore deposit. The model ages of Re-Os isotopic dating for the 11 molybdenite are 13.97-15.84 Ma, while isochron ages are 14.09±0.49 Ma （MSWD=26）. The isochron ages of seven molybdenite from molybdenum （copper） ore with monzogranite porphyry type are 14.11±0.31 Ma （MSWD=5.2）. There is great error in the isochron ages of four molybdenite from copper （molybdenum） ore with diorite porphyrite type, and their weighted average model ages of 14.6±1.2 Ma （MSWD=41）, which generally represent the mineralization age. The results about the Re-Os isotopic dating of molybdenite in the ore of different types have limited exactly that, the minerlazation age of this ore deposits is about 14.09 Ma, which belongs to the middle Miocene mineralization. The Bangpu deposit has a uniform metallogenic dynamics background with the porphyry type and skarn-type deposits such as Jiama, Qulong and others.
文摘Information about the protolith of the Huangtuling granulite in North Dabieshan has been unavailable. The complex evolution history of the rock and its host basement must be further discussed. LA-ICP-MS U-Pb dating was conducted on three textural domains in zircon from a high-temperature, high-pressure felsic granulite in the Huangtuling area, North Dabieshan, Central China. The metamorphic growth-derived detrital zircon domain yields a 207^ pb/206^Pb age in the range of （2 49±54 ） -- （2 500±180） Ma. The magmatic genesis-derived detrltal zircon domain gives a 207^pb/ 206^Pb age ranging from 2 628 Ma to 2 690 Ma, with an oldest 206^ pb/ 238^U age of （2 790 ± 150） Ma. The metamorphic overgrowth or metamorphic recrystallization zircon domain yields a diesordia with an upper intercept age of （2 044. 7 ± 29.3 ） Ma. Compositions of the mineral assemblage, major element geochemistry, and especially the complex interior texture of the zircon suggest that the prololith of the felsic granulite is of sedimentary origin. Results show that the protolith material of the granulite came from a provenance with a complex thermal history, i.e. -2.8 Ga magmatlsm and -2.5 Ga metamorphism, and was deposited in a basin not earlier than 2.5 Ga. The high-temperature and high-pressure granulite-facies metamorphic age was precisely constrained at （2.04±0.03） Ga, which indicates the granulite in Huangtuling area should be a relict of a Paleoproterozoic UHT （ultrahigh temperature） metamorphosed slab.
基金support by China Geological Survey (1212010911028)NSFC(40802020)+1 种基金Ministry of Land and Resources(1212010633902,1212010633903 and 121201 0711814)CUGB(GPMR 0735)
文摘The Wurinitu molybdenum deposit,located in Honggor,Sonid Left Banner of Inner Mongolia,China,is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite.The wall rocks are composed of Variscan porphyritic-like biotite granite and the Lower Ordovician Wubin'aobao Formation.LA-ICP-MS zircon U-Pb dating of the fine-grained granite reveals two stages of zircons,one were formed at 181.7±7.4 Ma and the other at 133.6±3.3 Ma.The latter age is believed to be the formation age of the fine-grained granite,while the former may reflect the age of inherited zircons,based on the morphological study of the zircon and regional geological setting.The Re-Os model age of molybdenite is 142.2±2.5 Ma,which is older than the diagenetic age of the fine-grained granite.Therefore the authors believe that the metallogenic age of the Wurinitu molybdenum deposit should be nearly 133.6±3.3 Ma or slightly later,i.e.,Early Cretaceous.Combined with regional geological background research,it is speculated that the molybdenum deposits were formed at the late Yanshanian orogenic cycle in the Hingganling-Mongolian orogenic belt,belonging to the relaxation epoch posterior to the compression and was associated with the closure of the Mongolia-Okhotsk Sea.
基金co-funded by the China Geological Survey (No.12120114052801)the DREAM project of MOST, China (NO. 2016YFC0600401)
文摘1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margin of Yunkai post-Caledonian uplift.Multiple type granites are widely distributed in Hetai district,including Caledonian,Indosinian and Yanshanian granites.Based on different
基金supported by Hu Zhaochu and Zheng Shu of the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Wuhan)the National Natural Science Foundation of China (No. 40872074)+1 种基金the National Key Basic Research Program (No. 2007CB411408)the State Key Laboratory of Ore Deposit Geochemistry(No. KCZX20090106) for their financial support
文摘The LA-ICP-MS U-Pb zircon dating of eight typical samples from four units of the Bozhushan granite intrusion in southeastern Yunnan Province, constrains the age of acidic magmatic intrusion in this area. Both the oscillatory zoning and chondrite-normalized REE patterns characterized by LREE-depletion and HREE-enrichment with positive Ce anomaly and negative Eu anomaly indicate the magmatic genesis of these zircons. Eight zircon samples from the Bozhushan granite yielded a mean 206 Pb/ 238 U age of (85.58±1.0) Ma (MSWD=4.1) to (88.10±0.66) Ma (MSWD=1.8). These chronology data suggest an accurate isotopic age for the intrusion of the Bozhushan granite, and are different from the published age data of 48 to 111.5 Ma. The geochronology data of the Gejiu, Dulong and Dachang super-large deposits and related Yanshanian granites indicated that there occurred large-scale granitic magmatism and mineralization events in western Nanling region during the Late Cretaceous.
基金supported by the Scientific Research and Technological Development Project of China National Petroleum Corporation (Grant Nos.2021DJ0105,2021DJ0203,2021DJ0303)the National Natural Science Foundation of China (Grant Nos.42172164,42002177)。
文摘In situ carbonate U-Pb dating is gaining popularity,and it has great potential for application in petroleum geology.However,the low U content(<10μg/g)and high common Pb content of carbonate minerals,along with the uneven distribution of U and Pb and the lack of matrix-matched reference material make carbonate U-Pb dating inaccurate and less successful,which limits the widespread application in geosciences.This study evaluated the limitations of in situ carbonate U-Pb dating and proposed a method to rationally determine the laser ablation parameters of samples by improving the experimental approach based on the laser ablation sector field inductively coupled plasma mass spectrometry(LA-SF-ICP-MS).By setting a different spot size and laser frequency for the reference material and unknown samples in the same session based on the U content of the sample,the ablation craters of the reference material and unknown samples were given the same depth/width ratio,avoiding systematic offset caused by differences in down-hole element fractionation and reducing the consume of reference material.Depending on the heterogeneous distribution of U and Pb contents in carbonate minerals,the method of grid screening and setting ablation spots during screening were used to quickly select domains with high U and low common Pb,which improves the efficiency of setting laser spots and the success rate of dating,as well as reduces the experimental time and economic cost.The accuracy and success rate of carbonate U-Pb dating were effectively improved by improving the experimental method,and the technique was applied to two carbonate samples with low U and high common Pb contents that were difficult to date by traditional methods.The two samples are the saddle dolomite in the central Sichuan Basin and the calcite cement in the sandstone reservoir of the Cretaceous Qingshuihe Formation in the South Junggar Basin.The robust ages have been obtained,which constrains the timing of the diagenetic and hydrocarbon accumulation process in the studied area.
文摘LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within errors.It is the first time that the microgranular enclaves age in Kalamaili area was determined.Petrochemistry and geochemistry research shows the characteristics of host rock as follows:
基金funded by the work program of the National Key Research Program of China(No.2016YFC0600502)。
文摘The Langshan Group is an important constituent of the Precambrian metamorphic rocks in the Langshan area.The accurate determination of its metamorphic age is of great scientific significance for the further study of the Precambrian geological evolution in the region.Disputes remain regarding the metamorphism and deformation overprinting of the Langshan Group.This paper presents a detailed study comprising a field geological investigation,petrological observations,and zircon U-Pb aging of garnet-bearing mica quartz schists in the BangBang District.The result of detrital zircon U-Pb dating from the metamorphosed volcanic sedimentary rock series and geological investigation of the garnet-bearing mica quartz schists suggest the strata formed in the Neoproterozoic.The results from cathodoluminescence(CL)image analysis and U-Pb dating of zircons indicate a large number of metamorphic zircons exist in the garnet-bearing mica quartz schists.The metamorphic overgrowth rims of zircon from two samples were analyzed by LA-ICP-MS.The ^(206)Pb/^(238)U weighted average age of ca.244 Ma of the zircon metamorphism rims represents the timing of Indosinian greenschist-amphibolite facies metamorphism in the Langshan area,which may be in response to the collision-type orogeny of the North China and Siberian plates in the Late Paleozoic.Acid-intermediate magmatic intrusive activities occurred in the Langshan area,and metamorphic events developed at the same time or at a later stage during the closure of the Paleo-Asian Ocean.
