The Huashanguan rapakivi pluton in Zhongxiang,Hubei Province,China,is the first discovered Proterozoic rapakivi pluton in the Yangtze block.Based on field and petrographical observations,a typical rapakivi texture was...The Huashanguan rapakivi pluton in Zhongxiang,Hubei Province,China,is the first discovered Proterozoic rapakivi pluton in the Yangtze block.Based on field and petrographical observations,a typical rapakivi texture was found in the northern portion of the Huashanguan granitic pluton.Almost all the K-feldspar phenocrysts were round to oval in shape and most had plagioclase coatings known as rapakivi phenocrysts.Alkali feldspars and quartz had two or more generations.Petrochemically,the Huashanguan rapakivi granites were characterized as having high values of Si,K,Fe,Th,U,La,Ga,Ce,Sm and LREE,low values of Ca,Mg,Sr,Nb,Y and HREE,and a negative Eu anomaly.These geochemical characteristics of the Huashanguan granites were concordant with typical rapakivi granites,and had an affinity to A-type granites.LA-ICP-MS U-Pb zircon dating also was conducted.The dating yielded a 207Pb/206Pb weighted mean age of 1851±18 Ma (MSWD =1.2),which represents the age of the pluton emplacement.The age of 803±170 Ma at the lower intercept in the concordia diagram corresponds to the age of a later deformation event which affected the pluton,and suggests that the Huashanguan pluton was influenced by Neoproterozoic thermo-tectonic events after its formation.The discovery of Paleoproterozoic Huashanguan rapakivi granites indicates continental rifting or a post-orogenic extensional event that took place in the Paleoproterozoic in the Yangtze block.These events may be related to the breakup of the Paleoproterozoic Columbia supercontinent.展开更多
SHRIMP U-Pb dating on magmatic zircons extracted from a riebeckite quartz syenite in the Huangyangshan pluton in Suizhou,the southern margin of Tongbai-Dabieshan yielded an age of 439±6Ma.According to the morphol...SHRIMP U-Pb dating on magmatic zircons extracted from a riebeckite quartz syenite in the Huangyangshan pluton in Suizhou,the southern margin of Tongbai-Dabieshan yielded an age of 439±6Ma.According to the morphology and high Th/U ratios of the zircons,the age is interpreted as crystallization timing of the pluton.The Huangyangshan pluton is composed of peralkaline quartz syenite,alkaline granite and syenite.All of the rocks are characterized by high agpaitic index(A.I.=(Na+K)/Al,molar ratio)and Fe-number[FeO_(T)/(FeO_(T)+MgO)],low CaO and MgO contents,enrichment of high field strength elements(i.e.Nb,Zr,Ga,Y,Hf)and light REEs,evidently negative Eu anomalies and high Ga/Al ratios,which are consistent with anorogenic A-type granitoids.Being part of the South Qinling-South Dabieshan Paleozoic alkaline rock belt,the Huangyangshan A-type granitoid pluton results from the Paleozoic extension-initial rifting in the northern margin of the Yangtze Craton related to the opening of the eastern Paleo-Tethyan Ocean.展开更多
Foliated garnet-bearing granite,usually associated with high pressure and ultrahigh-pressure(UHP) metamophic rocks,is a particular rock-type extensively exposed in the Mesozoic Dabie-Sulu orogenic belt of China.This s...Foliated garnet-bearing granite,usually associated with high pressure and ultrahigh-pressure(UHP) metamophic rocks,is a particular rock-type extensively exposed in the Mesozoic Dabie-Sulu orogenic belt of China.This study focuses on deformation features and SHRIMP zircon dating of foliated garnet granite in a high-pressure metamorphic unit from Huwan,western Dabie Mountains in order to resolve discrepancies in current versions of its petrogenesis and structural evolution.SHRIMP dating reveals a zircon age of 762 ± 15 Ma(MSWD=1.7) for Huwan granites,representing the Middle to Late Neoproterozoic age of intrusion and crystallization.Field and microstructural studies show that the Huwan granite body underwent multiple-stage deformation.The deformation was manifested by an early stage of rootless folding and imposition of relict foliation(S1);an Indosinian main stage marked by imposition of north-dipping penetrative gneissosity(S2) and development of ductile shear zones under NNE-SSW directed compression;and a final Indosinian stage of southward thrusting of the Huwan high-pressure unit.Shallow level extension prevailed after the Late Triassic,giving rise to south-dipping thrust faults and north-dipping normal faults.展开更多
The Tiefosi granitic pluton is located 5 km northwest of Xinyang City, northern Dabie Orogen, and was emplaced in the Proterozoic Qinling Group. SHRIMP zircon U-Pb dating suggests its crystallization at 436 ± 11 ...The Tiefosi granitic pluton is located 5 km northwest of Xinyang City, northern Dabie Orogen, and was emplaced in the Proterozoic Qinling Group. SHRIMP zircon U-Pb dating suggests its crystallization at 436 ± 11 Ma. It is composed of monzogranite and syenogranite containing some amounts of muscovite and few mafic minerals. The rocks are characterized by high and restricted SiO2 content, low FeO, Fe2O3 and MgO contents, high K2O/Na2O ratio, and display high-K calc-alkaline and peraluminous (ACNK>1.1) characteristics. They are generally enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE). They can be divided into three groups in light of rare earth elements (REE) and trace elements. Group I is moderate in ΣREE and characterized by the absence of Eu anomaly, high (La/Yb)N ratio, and moderate Rb/Sr and Rb/Ba ratios. Group II has moderately negative Eu anomaly, low (La/Yb)N ratio and high ΣREE contents, Rb/Sr and Rb/Ba ratios. Group III displays positive Eu anomaly, moderate (La/Yb)N ratio, and low ΣREE, Rb/Sr and Rb/Ba ratios. The calculated ? Nd(440Ma) values of the rocks vary from ?8.8 to ?9.9 and Nd depleted mantle model ages are about 2.0 Ga, which resemble those of the paragneisses from the Qinling Group. The results indicate that the Tiefosi granite is crust-derived, syn-collisional S-type granite. Generation of Group I was related to low degree melting of the Qinling Group, while Group II was formed by fractionational crystallization of plagioclase from Group I magmas, and Group III resulted possibly from magma mingling with plagioclase cumulates. The Tiefosi granite was formed within crustal level related to the collision between the North China and South China blocks in the Early Paleozoic time.展开更多
基金supported by the International Cooperation Project of the Ministry of Science and Technology of China (2007DFA21230)the Natural Science Foundation of Hubei Province (2009CDA004)+2 种基金the National Training Foundation of Geological Science Base (J083520)the National Innovation Experiment Program for University Students (1320311009)part of a Higher Education Key Project of Hubei Province (2009108)
文摘The Huashanguan rapakivi pluton in Zhongxiang,Hubei Province,China,is the first discovered Proterozoic rapakivi pluton in the Yangtze block.Based on field and petrographical observations,a typical rapakivi texture was found in the northern portion of the Huashanguan granitic pluton.Almost all the K-feldspar phenocrysts were round to oval in shape and most had plagioclase coatings known as rapakivi phenocrysts.Alkali feldspars and quartz had two or more generations.Petrochemically,the Huashanguan rapakivi granites were characterized as having high values of Si,K,Fe,Th,U,La,Ga,Ce,Sm and LREE,low values of Ca,Mg,Sr,Nb,Y and HREE,and a negative Eu anomaly.These geochemical characteristics of the Huashanguan granites were concordant with typical rapakivi granites,and had an affinity to A-type granites.LA-ICP-MS U-Pb zircon dating also was conducted.The dating yielded a 207Pb/206Pb weighted mean age of 1851±18 Ma (MSWD =1.2),which represents the age of the pluton emplacement.The age of 803±170 Ma at the lower intercept in the concordia diagram corresponds to the age of a later deformation event which affected the pluton,and suggests that the Huashanguan pluton was influenced by Neoproterozoic thermo-tectonic events after its formation.The discovery of Paleoproterozoic Huashanguan rapakivi granites indicates continental rifting or a post-orogenic extensional event that took place in the Paleoproterozoic in the Yangtze block.These events may be related to the breakup of the Paleoproterozoic Columbia supercontinent.
基金the National Natural Science Foundation of China(Grant No.40334037)the Besearch Fumd for the Doctoral Program of Higher Education(Grant No.20010491018).
文摘SHRIMP U-Pb dating on magmatic zircons extracted from a riebeckite quartz syenite in the Huangyangshan pluton in Suizhou,the southern margin of Tongbai-Dabieshan yielded an age of 439±6Ma.According to the morphology and high Th/U ratios of the zircons,the age is interpreted as crystallization timing of the pluton.The Huangyangshan pluton is composed of peralkaline quartz syenite,alkaline granite and syenite.All of the rocks are characterized by high agpaitic index(A.I.=(Na+K)/Al,molar ratio)and Fe-number[FeO_(T)/(FeO_(T)+MgO)],low CaO and MgO contents,enrichment of high field strength elements(i.e.Nb,Zr,Ga,Y,Hf)and light REEs,evidently negative Eu anomalies and high Ga/Al ratios,which are consistent with anorogenic A-type granitoids.Being part of the South Qinling-South Dabieshan Paleozoic alkaline rock belt,the Huangyangshan A-type granitoid pluton results from the Paleozoic extension-initial rifting in the northern margin of the Yangtze Craton related to the opening of the eastern Paleo-Tethyan Ocean.
基金Supported by the National Natural Science Foundation of China (Grant Nos.40802046 and 40334037)the Project of Science & Technology Research and Development from Sinopec (Grant No.P02009)
文摘Foliated garnet-bearing granite,usually associated with high pressure and ultrahigh-pressure(UHP) metamophic rocks,is a particular rock-type extensively exposed in the Mesozoic Dabie-Sulu orogenic belt of China.This study focuses on deformation features and SHRIMP zircon dating of foliated garnet granite in a high-pressure metamorphic unit from Huwan,western Dabie Mountains in order to resolve discrepancies in current versions of its petrogenesis and structural evolution.SHRIMP dating reveals a zircon age of 762 ± 15 Ma(MSWD=1.7) for Huwan granites,representing the Middle to Late Neoproterozoic age of intrusion and crystallization.Field and microstructural studies show that the Huwan granite body underwent multiple-stage deformation.The deformation was manifested by an early stage of rootless folding and imposition of relict foliation(S1);an Indosinian main stage marked by imposition of north-dipping penetrative gneissosity(S2) and development of ductile shear zones under NNE-SSW directed compression;and a final Indosinian stage of southward thrusting of the Huwan high-pressure unit.Shallow level extension prevailed after the Late Triassic,giving rise to south-dipping thrust faults and north-dipping normal faults.
基金the National Natural Science Foundation of China (GrantNo.40334037)the Fund for Creative Research Groups (Grant No.40521001)
文摘The Tiefosi granitic pluton is located 5 km northwest of Xinyang City, northern Dabie Orogen, and was emplaced in the Proterozoic Qinling Group. SHRIMP zircon U-Pb dating suggests its crystallization at 436 ± 11 Ma. It is composed of monzogranite and syenogranite containing some amounts of muscovite and few mafic minerals. The rocks are characterized by high and restricted SiO2 content, low FeO, Fe2O3 and MgO contents, high K2O/Na2O ratio, and display high-K calc-alkaline and peraluminous (ACNK>1.1) characteristics. They are generally enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE). They can be divided into three groups in light of rare earth elements (REE) and trace elements. Group I is moderate in ΣREE and characterized by the absence of Eu anomaly, high (La/Yb)N ratio, and moderate Rb/Sr and Rb/Ba ratios. Group II has moderately negative Eu anomaly, low (La/Yb)N ratio and high ΣREE contents, Rb/Sr and Rb/Ba ratios. Group III displays positive Eu anomaly, moderate (La/Yb)N ratio, and low ΣREE, Rb/Sr and Rb/Ba ratios. The calculated ? Nd(440Ma) values of the rocks vary from ?8.8 to ?9.9 and Nd depleted mantle model ages are about 2.0 Ga, which resemble those of the paragneisses from the Qinling Group. The results indicate that the Tiefosi granite is crust-derived, syn-collisional S-type granite. Generation of Group I was related to low degree melting of the Qinling Group, while Group II was formed by fractionational crystallization of plagioclase from Group I magmas, and Group III resulted possibly from magma mingling with plagioclase cumulates. The Tiefosi granite was formed within crustal level related to the collision between the North China and South China blocks in the Early Paleozoic time.
