The Liziyuan gold deposit,situated on the south side of the Shangdan suture zone,West Qinling Orogen,occurs in metamorphic volcanic rocks(greenschist facies)of the early Paleozoic Liziyuan Group and in Indosinian Tian...The Liziyuan gold deposit,situated on the south side of the Shangdan suture zone,West Qinling Orogen,occurs in metamorphic volcanic rocks(greenschist facies)of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite.Orebodies in the Liziyuan gold field are controlled by the ductile-brittle shear zone,and by thrusting nappe faults related to the Indosinian orogeny.In detail,this paper analyzed the geological characteristics of the Liziyuan gold field,and the Pb isotopes of the Lziyuan host rocks,granitoids(Tianzishan monzogranite and Jiancaowan syenite porphyry),sulfides,and auriferous quartz veins by multiple-collector inductively coupled plasma mass spectrometry(MC-ICPMS).In addition,previous data on the sulfur,hydrogen,and oxygen isotopes were employed to discuss the possible sources of the ore-forming fluids and materials,and to further understand the tectonic setting of the Liziyuan gold deposit.The sulfides and their host rocks(Lziyuan Group),Tianzishan monzogranite and Jiancaowan syenite porphyry,and auriferous quartz veins have similar Pb isotopic compositions.Zartman’s plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves.In the△β-△γdiagram,which genetically classifies the lead isotopes,most of the data fall within the range of the subduction-zone lead mixed with upper crust and mantle.This indicates that a complex source of the ore lead formed in the orogenic environment.Theδ34S values of the sulfides range from 3.90 to 8.50‰(average6.80‰),with a pronounced mode at 5.00‰-8.00‰.These values are consistent with that of orogenic gold deposits worldwide,indicating that the sulfur sourced mainly from reduced metamorphic fluids.The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the oreforming fluids,with possible mixing of minor magmatic fluids,but the late stage was dominated by meteoric water.The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide.展开更多
Inductively coupled plasma mass spectrometry(ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO3 acids in high-t...Inductively coupled plasma mass spectrometry(ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO3 acids in high-temperature and high-pressure closed-vessel digestion technique were used to decompose some Chinese reference materials, and thirty seven elements were determined by ICP-MS. Most of the results for Chinese soil reference materials were found to be in reasonable agreement with the reference values, except Cs, Ta, Li, Ge, Zn, Nd, Tb and Ta whose values need to be revised. Their precisions were typically lower than 5% RSD. However, the Precisions of Chinese clay reference materials, especially for GBW03102 and GBW03102a, were significantly different with reference values, probably reflecting the existence of a coarser-grained fraction(>70 μm) in samples, and the formation of fluorides in Al-rich samples during sample decomposition by using the mixture of HF and HNO3 acids. Moreover, thirty-seven trace elements covering the mass range from Li to U in four Chinese clay reference materials were firstly provided with good precision and accuracy in this study.展开更多
In the Songpan-Garze fold belt of the northeastern Tibetan Plateau,an Indosinian lithospheric delamination model has been proposed,based on previous investigation of widespread granitoids.However,this model lacks comp...In the Songpan-Garze fold belt of the northeastern Tibetan Plateau,an Indosinian lithospheric delamination model has been proposed,based on previous investigation of widespread granitoids.However,this model lacks comparable information from volcanism in the area.During the Indosinian delamination in the Songpan-Garze fold belt,whether partial melting of litho-spheric mantle taken place is debated.This paper reports U-Pb zircon LA-ICP-MS ages,geochemical and Sr-Nd-Hf isotopic compositions from the Aba and Wasai calc-alkaline volcanic rocks in the central Songpan-Garze fold belt.Obtained magma crystallization ages are 210±3 Ma for the Aba andesite and 205±1 Ma for the Wasai andesite.These are consistent with magma crystallization ages of the late Indosinian granitoids in the Songpan-Garze fold belt that formed in a post-collisional tectonic setting.The Aba and Wasai andesites have distinct geochemical singnatures.The former has higher Al2O3,K2O,Rb but lower Na2O,Ba and Sr contents,suggesting differences in their magmatic evolution.The Aba andesites have ISr values of 0.7070-0.7076 andεNd(t)values of-3.9 to-5.3,and the Wasai andesites have ISr values of 0.7075-0.7077 andεNd(t)values of-3.6 to-3.9.Zircons showεHf(t)values of-3.7 to 0.3 for the Aba andesites and-2.7 to 5.5 for the Wasai andesites.Geochemical and Sr-Nd-Hf isotopic compositions indicate that fractional crystallization and crustal assimilation processes are not key roles for their magma evolution,implying that their chemical compositions are those of primary melts.We suggest that the magma of the Aba andesites originated predominantly from a crustal source,with a minor mantle-derived component.The source region of the magma was likely at the crust-mantle boundary.The magma of the Wasai andesites resulted from partial melting of lithospheric mantle,which was probably metasomatized by fluids so that it was amphibole bearing.The petrogenesis of the Aba and Wasai andesites provides an additional evidence for the lithospheric delamination in the the Songpan-Garze fold belt,indicating that this process invoked mantle asthenosphere upwelling and caused the partial melting of remaining lithospheric mantle.展开更多
基金jointly provided by the National Natural Science Foundation of China(Grant Nos.41421002,41730426,41272092,and 41030423)MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest UniversityNorthwest University Graduate Innovation and Creativity Fund(YZZ17190)
文摘The Liziyuan gold deposit,situated on the south side of the Shangdan suture zone,West Qinling Orogen,occurs in metamorphic volcanic rocks(greenschist facies)of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite.Orebodies in the Liziyuan gold field are controlled by the ductile-brittle shear zone,and by thrusting nappe faults related to the Indosinian orogeny.In detail,this paper analyzed the geological characteristics of the Liziyuan gold field,and the Pb isotopes of the Lziyuan host rocks,granitoids(Tianzishan monzogranite and Jiancaowan syenite porphyry),sulfides,and auriferous quartz veins by multiple-collector inductively coupled plasma mass spectrometry(MC-ICPMS).In addition,previous data on the sulfur,hydrogen,and oxygen isotopes were employed to discuss the possible sources of the ore-forming fluids and materials,and to further understand the tectonic setting of the Liziyuan gold deposit.The sulfides and their host rocks(Lziyuan Group),Tianzishan monzogranite and Jiancaowan syenite porphyry,and auriferous quartz veins have similar Pb isotopic compositions.Zartman’s plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves.In the△β-△γdiagram,which genetically classifies the lead isotopes,most of the data fall within the range of the subduction-zone lead mixed with upper crust and mantle.This indicates that a complex source of the ore lead formed in the orogenic environment.Theδ34S values of the sulfides range from 3.90 to 8.50‰(average6.80‰),with a pronounced mode at 5.00‰-8.00‰.These values are consistent with that of orogenic gold deposits worldwide,indicating that the sulfur sourced mainly from reduced metamorphic fluids.The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the oreforming fluids,with possible mixing of minor magmatic fluids,but the late stage was dominated by meteoric water.The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide.
基金supported by the National Natural Science Foundation of China (41272004)the MOST Special Funds from the State Key Laboratory of Continental Dynamics
文摘Inductively coupled plasma mass spectrometry(ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO3 acids in high-temperature and high-pressure closed-vessel digestion technique were used to decompose some Chinese reference materials, and thirty seven elements were determined by ICP-MS. Most of the results for Chinese soil reference materials were found to be in reasonable agreement with the reference values, except Cs, Ta, Li, Ge, Zn, Nd, Tb and Ta whose values need to be revised. Their precisions were typically lower than 5% RSD. However, the Precisions of Chinese clay reference materials, especially for GBW03102 and GBW03102a, were significantly different with reference values, probably reflecting the existence of a coarser-grained fraction(>70 μm) in samples, and the formation of fluorides in Al-rich samples during sample decomposition by using the mixture of HF and HNO3 acids. Moreover, thirty-seven trace elements covering the mass range from Li to U in four Chinese clay reference materials were firstly provided with good precision and accuracy in this study.
基金supported by National Natural Science Foundation of China(Grant Nos.40773019 and 40821061)Ministry of Education of China and the State Administration of Foreign Expert Affairs of China(Grant No.B07039)
文摘In the Songpan-Garze fold belt of the northeastern Tibetan Plateau,an Indosinian lithospheric delamination model has been proposed,based on previous investigation of widespread granitoids.However,this model lacks comparable information from volcanism in the area.During the Indosinian delamination in the Songpan-Garze fold belt,whether partial melting of litho-spheric mantle taken place is debated.This paper reports U-Pb zircon LA-ICP-MS ages,geochemical and Sr-Nd-Hf isotopic compositions from the Aba and Wasai calc-alkaline volcanic rocks in the central Songpan-Garze fold belt.Obtained magma crystallization ages are 210±3 Ma for the Aba andesite and 205±1 Ma for the Wasai andesite.These are consistent with magma crystallization ages of the late Indosinian granitoids in the Songpan-Garze fold belt that formed in a post-collisional tectonic setting.The Aba and Wasai andesites have distinct geochemical singnatures.The former has higher Al2O3,K2O,Rb but lower Na2O,Ba and Sr contents,suggesting differences in their magmatic evolution.The Aba andesites have ISr values of 0.7070-0.7076 andεNd(t)values of-3.9 to-5.3,and the Wasai andesites have ISr values of 0.7075-0.7077 andεNd(t)values of-3.6 to-3.9.Zircons showεHf(t)values of-3.7 to 0.3 for the Aba andesites and-2.7 to 5.5 for the Wasai andesites.Geochemical and Sr-Nd-Hf isotopic compositions indicate that fractional crystallization and crustal assimilation processes are not key roles for their magma evolution,implying that their chemical compositions are those of primary melts.We suggest that the magma of the Aba andesites originated predominantly from a crustal source,with a minor mantle-derived component.The source region of the magma was likely at the crust-mantle boundary.The magma of the Wasai andesites resulted from partial melting of lithospheric mantle,which was probably metasomatized by fluids so that it was amphibole bearing.The petrogenesis of the Aba and Wasai andesites provides an additional evidence for the lithospheric delamination in the the Songpan-Garze fold belt,indicating that this process invoked mantle asthenosphere upwelling and caused the partial melting of remaining lithospheric mantle.
