The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of ...The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of these issues will help to reveal the magmatic processes and continental growth of Central Asia.The A-type granites in Zhaheba include the Ashutasi alkaline granites and the Yuyitasi syenogranites,which were emplaced at 321.5±4.8 Ma and 321.7±0.6 Ma,respectively.The major rock-forming minerals are orthoclase,perthite,arfvedsonite and quartz,which exhibit the following principal geochemical characteristics of A2-type granites.(1)Their REE distribution curves each exhibit a‘V’-shaped pattern and a marked depletion in Eu.They are rich in large-ion lithophile elements Rb,Th and U as well as high-field-strength elements Nb,Ta,Zr and Hf,but significantly depleted in Ba,Sr,P and Ti.(2)Their(^(87)Sr/^(86)Sr)i values(0.7021-0.7041),εNd(t)values(4.57-5.16)and REE distribution patterns are in basic agreement with those of the Kalamaili A-type granite belt in East Junggar.The T DM2 values of the alkaline granites and syenogranites range from 661 to 709 Ma.The A-type granites may be the products of upwelling asthenosphere-triggered partial melting of immature lower crust.The alkaline granites were late-stage products of crystallization and differentiation.Compared to the syenogranites,the alkaline granites are significantly lower in K_(2)O,Na_(2)O,Al_(2)O 3,FeO,MgO and CaO,but significantly higher in incompatible elements(e.g.,SiO_(2),Rb,and Sr).The magmatic crystallization temperatures of the syenogranites and alkaline granites are 874℃ and 819℃,respectively.As their age gradually decreases(peak ages:322 Ma and 307 Ma,respectively),there is a gradual decrease in the T_(DM2)of the A-type granites and a gradual increase in theεNd(t)value from the Ulungur belt to the Kalamaili belt in East Junggar.The study of A-type granites is therefore one of the keys to understanding the laws and mechanisms of crustal accretion during the Phanerozoic period,as well as also being of great significance for understanding the Paleozoic accretion.展开更多
The system of mineral deposit statistical prediction methods , based on the similarity - analogy theory , searching anomaly theory and the theory of ore - controlling by quantitative assemblage of metallotects , can b...The system of mineral deposit statistical prediction methods , based on the similarity - analogy theory , searching anomaly theory and the theory of ore - controlling by quantitative assemblage of metallotects , can be summarized into the following aspects : (1) concluding main ore - controlling conditions and ore - hunting indicators from typical deposits; (2)establishing geological concept model of deposits ; (3)selecting geological variable and dividing study units and granting specific value for each variable; (4) by the use of geological and mathematical geology method , building predication model , delineating prospective area for exploration and estimating the total resources; (5) evaluating the prospecting work . It is good practice to use this system for metallogenic prognosis and regional prospecting of gold deposit in East Junggar , Xinjiang and has achieved great success . As a result , we discovered the Kubusu gold mineralized belt . delineated prospective area - estimated total resources of gold in the belt and found out Kubusu gold deposit .展开更多
The magma source,petrogenesis,tectonic setting and its geochronology of the Late Paleozoic A-type granites,which widely exposed in Zhaheba area,East Junggar,have not been well constrained so far(Fig.1 a,b).A better un...The magma source,petrogenesis,tectonic setting and its geochronology of the Late Paleozoic A-type granites,which widely exposed in Zhaheba area,East Junggar,have not been well constrained so far(Fig.1 a,b).A better understanding of above issues will help us to reveal the magmatic processes and the continental growth of Central Asia(Xiao et al.,2009).展开更多
The Middle Devonian volcanic rocks in the northern area of East Junggar, located between the Ertix andUlungur rivers of northern Xinjiang, may be divided into basic and acid ones. It is evident that a compositionalgap...The Middle Devonian volcanic rocks in the northern area of East Junggar, located between the Ertix andUlungur rivers of northern Xinjiang, may be divided into basic and acid ones. It is evident that a compositionalgap exists between the two groups so that the volcanic rocks are not in line with a calc-alkaline series becausethe intermediate rocks are absent in the area. The fact shows that the volcanic rocks are a typical bimodal asso-ciation. The formation of the bimodal association of volcanic rocks in the area was closely related to continen-tal rifting or continental extension in the Middle Devonian. In such a tectonic setting, magmas were first pro-duced by partial melting of the mantle. Where crustal thinning was greater, the magmas ascended and eruptedon the surface directly so that the basic volcanic rocks formed, but olivine and/or partial pyroxenefractionation occurred in the magmas during their ascent through the thinning crust. On the other hand, wherecrustal thinning was less, ascending mantle-derived magmas reached the lower crust and accumulated there, re-sulting in partial melting of the lower crust and thus giving rise to the contaminated magma which was consoli-dated as acid volcanic rocks on the surface.展开更多
A large area of Late Paleozoic intrusions occursalong the Kalamaili fault in North Xinjiang,which is divided into I-type and A-type granite(Liu et al.,2013),and are the ideal objects for revealing the geological evolu...A large area of Late Paleozoic intrusions occursalong the Kalamaili fault in North Xinjiang,which is divided into I-type and A-type granite(Liu et al.,2013),and are the ideal objects for revealing the geological evolution of this region.However,the study of the granodioritic pluton in East Junggar is particularly weak.展开更多
SHRIMP U-Pb zircon dating on the Xileketehalasu granodiorite porphyry and Kalasayi monodiorite porphyry that intrude middle Devonian Beitashan Formation at the north part of east Junggar region shows that they were fo...SHRIMP U-Pb zircon dating on the Xileketehalasu granodiorite porphyry and Kalasayi monodiorite porphyry that intrude middle Devonian Beitashan Formation at the north part of east Junggar region shows that they were formed at 381±6 Ma and 376±10 Ma respectively. They are interpreted as subduction-related granitic rocks, which is the first report that the isotopic ages for the granitic rocks range from 350 to 390 Ma. Another determined age for the Kalasayi monodiorite porphyry is 408±9 Ma, representing the age of underlain Lower Devonian volcanic rocks. Thus, the U-Pb dates suggest that the northeastward subduction of Junggar ocean from southwest occurred at 408 to 376 Ma (the real inter- val may be larger). Because the ore-bearing porphyry intruded following the formation of the volcanic rocks of middle Devonian Beitashan Formation, their tec- tonic setting is similar to the Andes Mountains that hosts world-class porphyry copper deposits, and the researched area could be regarded as a potential area for prospecting large porphyry copper deposits.展开更多
The East Junggar is an important part of the Central Asian Orogenic Belt(CAOB).Using in situ zircon dating and Hf isotopic analysis by LA-ICP-MS and MC-ICP-MS,respectively,a detrital zircon of 4040 Ma age was found in...The East Junggar is an important part of the Central Asian Orogenic Belt(CAOB).Using in situ zircon dating and Hf isotopic analysis by LA-ICP-MS and MC-ICP-MS,respectively,a detrital zircon of 4040 Ma age was found in sedimentary sequences from the Aermantai ophiolitic mélange,East Junggar.This is the oldest age record in the East Junggar terrane,and also marks the first zircon locality in the CAOB with an age older than 4.0 Ga,which is attributed to the Hadean crust.The 4040 Ma detrital zircon has anεHf(t)value of–5.2 and a two-stage Hf modal age of 4474 Ma,suggesting the presence of very old(Hadean)crustal material in the source area.Beside peak ages of 446 Ma,we found four age groups of 3.6–3.1 Ga,2.53–2.37 Ga,1.14–0.89 Ga and 0.47–0.42 Ga from 141 effective measuring points.The age of 426±4 Ma for the five youngest detrital zircons defines the lower limit of the deposition time of sedimentary sequencess in the Aermantai ophiolitic mélange.The 0.47–0.42 Ga zircons exhibit176Hf/177Hf ratios of 0.282156 to 0.282850,corresponding to variableεHf(t)values from–9.3 to 12.0 and Hf model ages from2011 to 646 Ma.These characteristics are similar to those of the early Paleozoic igneous and gneissic zircons from the Altai,but significantly different from those of the East Junggar.Based on the material structures of felspathic greywacke,the morphology,internal texture and age distributions of dated detrital zircons,in combination with a study of the regional geological data,it is suggested that the sedimentary sequences in the Aermantai ophiolitic mélange was deposited in the Late Silurian,with the main provenance from the Altai Orogen in the north.This indicates that the early Paleozoic ocean represented by the Aermantai ophiolitic mélange was readily closed during the Late Silurian,and the northern edge of the East Junggar terrane was accreted to the Altai Orogen.The joint of them then served as a marginal orogen in the southern edge of the Siberia Paleocontinent.展开更多
基金This work was supported by the National Key Research and Development Program of China(2018YFC0604002)the Geological Survey program of China Geological Survey(DD20221643-6)the Fundamental Research Funds of Chinese Academy of Geological Sciences(JKY21021,JKY202122).
文摘The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of these issues will help to reveal the magmatic processes and continental growth of Central Asia.The A-type granites in Zhaheba include the Ashutasi alkaline granites and the Yuyitasi syenogranites,which were emplaced at 321.5±4.8 Ma and 321.7±0.6 Ma,respectively.The major rock-forming minerals are orthoclase,perthite,arfvedsonite and quartz,which exhibit the following principal geochemical characteristics of A2-type granites.(1)Their REE distribution curves each exhibit a‘V’-shaped pattern and a marked depletion in Eu.They are rich in large-ion lithophile elements Rb,Th and U as well as high-field-strength elements Nb,Ta,Zr and Hf,but significantly depleted in Ba,Sr,P and Ti.(2)Their(^(87)Sr/^(86)Sr)i values(0.7021-0.7041),εNd(t)values(4.57-5.16)and REE distribution patterns are in basic agreement with those of the Kalamaili A-type granite belt in East Junggar.The T DM2 values of the alkaline granites and syenogranites range from 661 to 709 Ma.The A-type granites may be the products of upwelling asthenosphere-triggered partial melting of immature lower crust.The alkaline granites were late-stage products of crystallization and differentiation.Compared to the syenogranites,the alkaline granites are significantly lower in K_(2)O,Na_(2)O,Al_(2)O 3,FeO,MgO and CaO,but significantly higher in incompatible elements(e.g.,SiO_(2),Rb,and Sr).The magmatic crystallization temperatures of the syenogranites and alkaline granites are 874℃ and 819℃,respectively.As their age gradually decreases(peak ages:322 Ma and 307 Ma,respectively),there is a gradual decrease in the T_(DM2)of the A-type granites and a gradual increase in theεNd(t)value from the Ulungur belt to the Kalamaili belt in East Junggar.The study of A-type granites is therefore one of the keys to understanding the laws and mechanisms of crustal accretion during the Phanerozoic period,as well as also being of great significance for understanding the Paleozoic accretion.
基金The study is supported by the key project of the State Education Committee of China
文摘The system of mineral deposit statistical prediction methods , based on the similarity - analogy theory , searching anomaly theory and the theory of ore - controlling by quantitative assemblage of metallotects , can be summarized into the following aspects : (1) concluding main ore - controlling conditions and ore - hunting indicators from typical deposits; (2)establishing geological concept model of deposits ; (3)selecting geological variable and dividing study units and granting specific value for each variable; (4) by the use of geological and mathematical geology method , building predication model , delineating prospective area for exploration and estimating the total resources; (5) evaluating the prospecting work . It is good practice to use this system for metallogenic prognosis and regional prospecting of gold deposit in East Junggar , Xinjiang and has achieved great success . As a result , we discovered the Kubusu gold mineralized belt . delineated prospective area - estimated total resources of gold in the belt and found out Kubusu gold deposit .
基金supported by the National Key Research and Development Program of China(Grant No.2018YFC0604002)the China Geological Survey Program(Grant No.DD20190071)
文摘The magma source,petrogenesis,tectonic setting and its geochronology of the Late Paleozoic A-type granites,which widely exposed in Zhaheba area,East Junggar,have not been well constrained so far(Fig.1 a,b).A better understanding of above issues will help us to reveal the magmatic processes and the continental growth of Central Asia(Xiao et al.,2009).
文摘The Middle Devonian volcanic rocks in the northern area of East Junggar, located between the Ertix andUlungur rivers of northern Xinjiang, may be divided into basic and acid ones. It is evident that a compositionalgap exists between the two groups so that the volcanic rocks are not in line with a calc-alkaline series becausethe intermediate rocks are absent in the area. The fact shows that the volcanic rocks are a typical bimodal asso-ciation. The formation of the bimodal association of volcanic rocks in the area was closely related to continen-tal rifting or continental extension in the Middle Devonian. In such a tectonic setting, magmas were first pro-duced by partial melting of the mantle. Where crustal thinning was greater, the magmas ascended and eruptedon the surface directly so that the basic volcanic rocks formed, but olivine and/or partial pyroxenefractionation occurred in the magmas during their ascent through the thinning crust. On the other hand, wherecrustal thinning was less, ascending mantle-derived magmas reached the lower crust and accumulated there, re-sulting in partial melting of the lower crust and thus giving rise to the contaminated magma which was consoli-dated as acid volcanic rocks on the surface.
基金supported financially by the NSFC projects(Grant Nos.U1403291,41830216,and 41802074)projects of the China Geological Survey(Grant Nos.DD20160024,DD20160123,and DD20160345)IGCP 662.
文摘A large area of Late Paleozoic intrusions occursalong the Kalamaili fault in North Xinjiang,which is divided into I-type and A-type granite(Liu et al.,2013),and are the ideal objects for revealing the geological evolution of this region.However,the study of the granodioritic pluton in East Junggar is particularly weak.
基金supported by the National Natural Science Foundation of China(Grant No.40072061)National 305 Project(Grant No.2001BA609A-07-02)+1 种基金Program for New Century Excellent Talents in University(Grant No.NCET-04-0728)"973"Project(Grant No.2001 CB409807).
文摘SHRIMP U-Pb zircon dating on the Xileketehalasu granodiorite porphyry and Kalasayi monodiorite porphyry that intrude middle Devonian Beitashan Formation at the north part of east Junggar region shows that they were formed at 381±6 Ma and 376±10 Ma respectively. They are interpreted as subduction-related granitic rocks, which is the first report that the isotopic ages for the granitic rocks range from 350 to 390 Ma. Another determined age for the Kalasayi monodiorite porphyry is 408±9 Ma, representing the age of underlain Lower Devonian volcanic rocks. Thus, the U-Pb dates suggest that the northeastward subduction of Junggar ocean from southwest occurred at 408 to 376 Ma (the real inter- val may be larger). Because the ore-bearing porphyry intruded following the formation of the volcanic rocks of middle Devonian Beitashan Formation, their tec- tonic setting is similar to the Andes Mountains that hosts world-class porphyry copper deposits, and the researched area could be regarded as a potential area for prospecting large porphyry copper deposits.
文摘The East Junggar is an important part of the Central Asian Orogenic Belt(CAOB).Using in situ zircon dating and Hf isotopic analysis by LA-ICP-MS and MC-ICP-MS,respectively,a detrital zircon of 4040 Ma age was found in sedimentary sequences from the Aermantai ophiolitic mélange,East Junggar.This is the oldest age record in the East Junggar terrane,and also marks the first zircon locality in the CAOB with an age older than 4.0 Ga,which is attributed to the Hadean crust.The 4040 Ma detrital zircon has anεHf(t)value of–5.2 and a two-stage Hf modal age of 4474 Ma,suggesting the presence of very old(Hadean)crustal material in the source area.Beside peak ages of 446 Ma,we found four age groups of 3.6–3.1 Ga,2.53–2.37 Ga,1.14–0.89 Ga and 0.47–0.42 Ga from 141 effective measuring points.The age of 426±4 Ma for the five youngest detrital zircons defines the lower limit of the deposition time of sedimentary sequencess in the Aermantai ophiolitic mélange.The 0.47–0.42 Ga zircons exhibit176Hf/177Hf ratios of 0.282156 to 0.282850,corresponding to variableεHf(t)values from–9.3 to 12.0 and Hf model ages from2011 to 646 Ma.These characteristics are similar to those of the early Paleozoic igneous and gneissic zircons from the Altai,but significantly different from those of the East Junggar.Based on the material structures of felspathic greywacke,the morphology,internal texture and age distributions of dated detrital zircons,in combination with a study of the regional geological data,it is suggested that the sedimentary sequences in the Aermantai ophiolitic mélange was deposited in the Late Silurian,with the main provenance from the Altai Orogen in the north.This indicates that the early Paleozoic ocean represented by the Aermantai ophiolitic mélange was readily closed during the Late Silurian,and the northern edge of the East Junggar terrane was accreted to the Altai Orogen.The joint of them then served as a marginal orogen in the southern edge of the Siberia Paleocontinent.
