Jianshanzi volcanic rocks at Qinghe valley in the northern Liaoning were considered belonging to Early Proterozoic Gaojiayu Formation of Liaohe Group, or to Early Cambrian Beidagou Formation of Qinghezhen Group, or Mi...Jianshanzi volcanic rocks at Qinghe valley in the northern Liaoning were considered belonging to Early Proterozoic Gaojiayu Formation of Liaohe Group, or to Early Cambrian Beidagou Formation of Qinghezhen Group, or Middle-Late Proterozoic Shenjiapu Formation-Complex of Kaiyuan Group-complex. Dating the zircons from the dacite with schistosity is 2 506 Ma in method of U-Pb (SHRIMP). This evidence indicates the rocks may be referred to Late Permian in age. Discovery of the rocks is significant to re-recognize stratigraphic property of "Liaohe Group", regional geotectonic location and revolution of orogenic zone in Qinghe valley of the northern Liaoning.展开更多
The Sipu region of North Guangxi is located in the southwest of the "Jiangnan Ancient Land",where there are developed the oldest stratum in southern China,the Proterozoic Sipu Group,and there are also largel...The Sipu region of North Guangxi is located in the southwest of the "Jiangnan Ancient Land",where there are developed the oldest stratum in southern China,the Proterozoic Sipu Group,and there are also largely ex-posed mafic intrusive rocks,mafic volcanic rocks and copper-nickel sulfide deposits.Both mafic intrusive rocks and volcanic rocks are rich in MgO(6.52%-26.39%),but poor in K2O(0.05%-1.00%) and TiO2(0.33%-0.89%).They are also rich in trace elements such as Rb and Ba while poor in Ta,Nb and the like.Both of them have medium con-tents of rare-earth elements,30.26×10-6-126.71×10-6,in which LREEs are slightly rich with ΣLREE/ΣHREE of 1.35-2.46,δEu 0.79-1.33,displaying weak or no δEu anomaly,with the same geochemical features.The right-inclined distribution patterns and the features show that magma would be formed at the comagmatic un-diagenetic stage.All studies show that mafic intrusive rocks and volcanic rocks are the products of the same source region evolving in different stages and times.The copper-nickel sulfide deposits are characterized by liquation,crys-tallization and fractionation of mafic rocks,and have some interrelations with mafic intrusive rocks and volcanic rocks with respect to magmatic genesis.展开更多
Samples were systematically collected from metamorphic basic volcanic rocks in the Jiehekou and Xiyupi areas on both sides of the L黮iang Mountains, Shanxi Province and analyzed for their major elements, trace element...Samples were systematically collected from metamorphic basic volcanic rocks in the Jiehekou and Xiyupi areas on both sides of the L黮iang Mountains, Shanxi Province and analyzed for their major elements, trace elements and rare earth elements (REE). The geochemical charac-teristics of their major, trace and rare-earth elements indicated that the metamorphic basic volcanic rocks in this area were emplaced in the tectonic environment like a modern continental rift. Sm-Nd and Rb-Sr isotope chronological studies demonstrated that the Jiehekou Group metamorphic basic volcanic rocks were formed during the 2600-Ma crust/mantle differentiation event, and were trans-formed by granulite facies metamorphism during the late Neo-Archaean period (2500 Ma ?, mak-ing the Sm-Nd systematics of the rocks reset. During the late Paleoproterozoic period (1800 Ma ? the Rb-Sr systematics of the rocks were disturbed again in response to the L黮iang movement. Since the extent of disturbance was so weak that the Sm-Nd systematics was not affected, the age of 1600 Ma obtained from this area seems to be related to local magmatic activities within the craton. Research results lend no support to the idea that the L黮iang Group was formed during the Archaean. Instead, it should be formed during the Proterozoic.展开更多
The volcanic rocks of the Xiong'er Group occur widely in the southern part of the North China Craton, which mark the beginning of the cover in the southern part of the North China Craton. The age of the volcanic r...The volcanic rocks of the Xiong'er Group occur widely in the southern part of the North China Craton, which mark the beginning of the cover in the southern part of the North China Craton. The age of the volcanic rocks is thus crucial to understand the tectonic regime and evolutionary history of the North China Craton in the Proterozoic age. Zircons from five volcanic rocks and intrusions were dated by U-Pb SHRIMP method. The results indicate that the Xiong'er Group formed in 1.80--1.75 Ga of Paleo-Proterozoic. Since the Xiong'er Group formed earlier than the Changcheng System, the earliest rocks in the Changcheng System is therefore assumed to be formed in 1.75 Ga. A thermal-tectonic event of ca. 1.84 Ga is indicated by new zircon U-Pb SHRIMP ages in the southern part of the North China Craton. The volcanic rocks of the Xiong'er Group thus represent the initial magmatism of the Paleo-Proterozoic breakup of the North China Craton. Numerous inherited zircons in the volcanic rocks mainly formed in ～2.20 Ga, indicating that the source magma of the volcanic rocks may be derived from the ～2.20 Ga crust, or from a mantle magma with significant contamination of the ～2.20 Ga crust.展开更多
This paper briefly introduces the right Proterozoic geological sections of both the Linjiawan Formation,Cangshuipu Group and the Hengluchong Formation,Banxi Group in Hunan Province,China,respectively;in detail compare...This paper briefly introduces the right Proterozoic geological sections of both the Linjiawan Formation,Cangshuipu Group and the Hengluchong Formation,Banxi Group in Hunan Province,China,respectively;in detail compares their main characteristics such as bed lithology,diagenetic epoch and position in the Proterozoic;and demonstrates the Linjiawan Formation,Cangshuipu Group is congruent objectively with Hunan’s Proterozoic stratigraphic sequence;as well as notes it is significant to further study and to discuss the division and correlation of the molasse－ volcanic formation at Cangshuipu,Yiyang City,Hunan.展开更多
Whether or not Grenvillian orogeny occurred in South China still remains highly controversial because high-quality,discriminating data are lacking,and therefore,the key to resolve this matter is to find datable volcan...Whether or not Grenvillian orogeny occurred in South China still remains highly controversial because high-quality,discriminating data are lacking,and therefore,the key to resolve this matter is to find datable volcanic and/or sedimentary rocks related to Grenvillian orogeny. Such rocks are apparently present in the Fuliangpeng Member from the lower-middle part of Kunyang Group in central Yunnan; here the unit is more than 100 m thick and consists of andesitic ignimbrite,tuffite,terrigeous clastic rocks and carbonates. These volcanic rocks,developed south of the Sibao fold-thrust belts,represent the earliest calc-alkaline volcanic activity in late Precambrian time from central Yunnan and are coeval with both a change in sedimentary facies from detritus to carbonates and the beginning of seismite development elsewhere. Two samples for SHRIMP analysis were collected from this volcanic unit. Sample G3-29-2,from the bottom of Fuliangpeng Member,is an ignimbrite,and about 100 zircon crys-tals recovered from it have euhedral shapes and display relatively simple sector zonation under cathodoluminescent (CL) imaging,suggesting a magmatogenic origin. Twenty-five of the zircons were analyzed and a weighed-mean U-Pb age of 1032±9 Ma was obtained. Sample G3-29-3 from uppermost part of Fuliangpeng Member is a tuffite,and many rounded,evidently detrital zircons were recovered. Nine of these zircons were analyzed,and the oldest single-grain U-Pb zircon age is 1938±26 Ma,im-plying that Paleoproterozoic basement developed in Cathaysia. The dating result,combined with the geotectonic research on the Fuliangpeng Member,leads us to conclude that late Mesoproterozoic orogenic volcanic activity occurred in the western part of South China,and that the related collision of Yangtze and Cathaysian cratons was an integral part of the assembly of Rodinia.展开更多
Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing'an-Mongolian Orogenic Belt(XMOB).Zircon U-Pb ages of eight volcanic rocks...Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing'an-Mongolian Orogenic Belt(XMOB).Zircon U-Pb ages of eight volcanic rocks from the Budate Group and two basement granites in the Hailar Basin were reported in this study.The dating results indicated that the formation of these volcanic rocks was consistent with the emplacement of Late Paleozoic basement granite in age(356-290 Ma),i.e.,Early Carboniferous to Early Permian rather than Early Mesozoic.Combined with regional geology,it was concluded that the Budate Group is the component of the basement of the Hailar Basin,and these volcanic rocks were formed at an active continental margin,which is related to the closure of the Hegen Mountains suture zone.The captured Neoproterozoic zircons(814-873 Ma) were probably derived from the Neoproterozoic basement materials in the Ergun Block,implying the close genetic relationships between the Ergun Block(including the Hailar Basin) and the Siberian Block.展开更多
YANGBA Formation of Bikou Group is located in south Qinling, a famous orogenic belt separating Chinesecontinent into two parts: North China plate and Yangzi plate. The Yangba Formation comprises the maficand felsic vo...YANGBA Formation of Bikou Group is located in south Qinling, a famous orogenic belt separating Chinesecontinent into two parts: North China plate and Yangzi plate. The Yangba Formation comprises the maficand felsic volcanic rocks formed in an ancient seafloor environment during the Proterozoic era. The suitesof mafic and felsic volcanic rocks are petrochemically divided into tholeiite and calc-alkaline dacite, respectively, showing characteristics of bimodal volcanic rock mainly by lithology and major element content, and a lack of typical intermediate rocks. These signatures indicate that the volcanic rocks of YangbaFormation were generated in rift tectonics setting. The tholeiites of Yangba Formation are similar in trace element content to mid-ridge basalt, displaying a slight depletion to enrichment in light rare earth elements (LREE’s) (La/Yb_n = 0.6-1.4), slightfractionation between LREE (La/Sm_n =0.55-1.14) and HREE (Gd/Lu_n = 1.09-1.50), and relative flat patterns in whole. The decoupling of Eu to its neighboring elements in two samples likely indicates an effect of fractional crystallization in magma evolution. The La-La/Sm, Ni-La, Ni-Th, Ni-Ta,and Ni-Hf diagrams all support a conclusion that the mafic rocks are generated by partial melting pro-展开更多
文摘Jianshanzi volcanic rocks at Qinghe valley in the northern Liaoning were considered belonging to Early Proterozoic Gaojiayu Formation of Liaohe Group, or to Early Cambrian Beidagou Formation of Qinghezhen Group, or Middle-Late Proterozoic Shenjiapu Formation-Complex of Kaiyuan Group-complex. Dating the zircons from the dacite with schistosity is 2 506 Ma in method of U-Pb (SHRIMP). This evidence indicates the rocks may be referred to Late Permian in age. Discovery of the rocks is significant to re-recognize stratigraphic property of "Liaohe Group", regional geotectonic location and revolution of orogenic zone in Qinghe valley of the northern Liaoning.
文摘The Sipu region of North Guangxi is located in the southwest of the "Jiangnan Ancient Land",where there are developed the oldest stratum in southern China,the Proterozoic Sipu Group,and there are also largely ex-posed mafic intrusive rocks,mafic volcanic rocks and copper-nickel sulfide deposits.Both mafic intrusive rocks and volcanic rocks are rich in MgO(6.52%-26.39%),but poor in K2O(0.05%-1.00%) and TiO2(0.33%-0.89%).They are also rich in trace elements such as Rb and Ba while poor in Ta,Nb and the like.Both of them have medium con-tents of rare-earth elements,30.26×10-6-126.71×10-6,in which LREEs are slightly rich with ΣLREE/ΣHREE of 1.35-2.46,δEu 0.79-1.33,displaying weak or no δEu anomaly,with the same geochemical features.The right-inclined distribution patterns and the features show that magma would be formed at the comagmatic un-diagenetic stage.All studies show that mafic intrusive rocks and volcanic rocks are the products of the same source region evolving in different stages and times.The copper-nickel sulfide deposits are characterized by liquation,crys-tallization and fractionation of mafic rocks,and have some interrelations with mafic intrusive rocks and volcanic rocks with respect to magmatic genesis.
基金the Key Project of the Chinese Academy of Sciences(Grant No.KZ951-A1-404) the Key Project(Grant No KZCX1-07)under the Knowledge-Innovation Program of the ChineseAcademy of Sciences.
文摘Samples were systematically collected from metamorphic basic volcanic rocks in the Jiehekou and Xiyupi areas on both sides of the L黮iang Mountains, Shanxi Province and analyzed for their major elements, trace elements and rare earth elements (REE). The geochemical charac-teristics of their major, trace and rare-earth elements indicated that the metamorphic basic volcanic rocks in this area were emplaced in the tectonic environment like a modern continental rift. Sm-Nd and Rb-Sr isotope chronological studies demonstrated that the Jiehekou Group metamorphic basic volcanic rocks were formed during the 2600-Ma crust/mantle differentiation event, and were trans-formed by granulite facies metamorphism during the late Neo-Archaean period (2500 Ma ?, mak-ing the Sm-Nd systematics of the rocks reset. During the late Paleoproterozoic period (1800 Ma ? the Rb-Sr systematics of the rocks were disturbed again in response to the L黮iang movement. Since the extent of disturbance was so weak that the Sm-Nd systematics was not affected, the age of 1600 Ma obtained from this area seems to be related to local magmatic activities within the craton. Research results lend no support to the idea that the L黮iang Group was formed during the Archaean. Instead, it should be formed during the Proterozoic.
文摘The volcanic rocks of the Xiong'er Group occur widely in the southern part of the North China Craton, which mark the beginning of the cover in the southern part of the North China Craton. The age of the volcanic rocks is thus crucial to understand the tectonic regime and evolutionary history of the North China Craton in the Proterozoic age. Zircons from five volcanic rocks and intrusions were dated by U-Pb SHRIMP method. The results indicate that the Xiong'er Group formed in 1.80--1.75 Ga of Paleo-Proterozoic. Since the Xiong'er Group formed earlier than the Changcheng System, the earliest rocks in the Changcheng System is therefore assumed to be formed in 1.75 Ga. A thermal-tectonic event of ca. 1.84 Ga is indicated by new zircon U-Pb SHRIMP ages in the southern part of the North China Craton. The volcanic rocks of the Xiong'er Group thus represent the initial magmatism of the Paleo-Proterozoic breakup of the North China Craton. Numerous inherited zircons in the volcanic rocks mainly formed in ～2.20 Ga, indicating that the source magma of the volcanic rocks may be derived from the ～2.20 Ga crust, or from a mantle magma with significant contamination of the ～2.20 Ga crust.
文摘This paper briefly introduces the right Proterozoic geological sections of both the Linjiawan Formation,Cangshuipu Group and the Hengluchong Formation,Banxi Group in Hunan Province,China,respectively;in detail compares their main characteristics such as bed lithology,diagenetic epoch and position in the Proterozoic;and demonstrates the Linjiawan Formation,Cangshuipu Group is congruent objectively with Hunan’s Proterozoic stratigraphic sequence;as well as notes it is significant to further study and to discuss the division and correlation of the molasse－ volcanic formation at Cangshuipu,Yiyang City,Hunan.
基金Supported by China Geological Survey (Grant No. 200313000055)Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0546)the National Natural Science Foundation of China (Grant No. 40621002)
文摘Whether or not Grenvillian orogeny occurred in South China still remains highly controversial because high-quality,discriminating data are lacking,and therefore,the key to resolve this matter is to find datable volcanic and/or sedimentary rocks related to Grenvillian orogeny. Such rocks are apparently present in the Fuliangpeng Member from the lower-middle part of Kunyang Group in central Yunnan; here the unit is more than 100 m thick and consists of andesitic ignimbrite,tuffite,terrigeous clastic rocks and carbonates. These volcanic rocks,developed south of the Sibao fold-thrust belts,represent the earliest calc-alkaline volcanic activity in late Precambrian time from central Yunnan and are coeval with both a change in sedimentary facies from detritus to carbonates and the beginning of seismite development elsewhere. Two samples for SHRIMP analysis were collected from this volcanic unit. Sample G3-29-2,from the bottom of Fuliangpeng Member,is an ignimbrite,and about 100 zircon crys-tals recovered from it have euhedral shapes and display relatively simple sector zonation under cathodoluminescent (CL) imaging,suggesting a magmatogenic origin. Twenty-five of the zircons were analyzed and a weighed-mean U-Pb age of 1032±9 Ma was obtained. Sample G3-29-3 from uppermost part of Fuliangpeng Member is a tuffite,and many rounded,evidently detrital zircons were recovered. Nine of these zircons were analyzed,and the oldest single-grain U-Pb zircon age is 1938±26 Ma,im-plying that Paleoproterozoic basement developed in Cathaysia. The dating result,combined with the geotectonic research on the Fuliangpeng Member,leads us to conclude that late Mesoproterozoic orogenic volcanic activity occurred in the western part of South China,and that the related collision of Yangtze and Cathaysian cratons was an integral part of the assembly of Rodinia.
基金supported by the National Natural Science Foundation of China (Grant No. 40972041)
文摘Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing'an-Mongolian Orogenic Belt(XMOB).Zircon U-Pb ages of eight volcanic rocks from the Budate Group and two basement granites in the Hailar Basin were reported in this study.The dating results indicated that the formation of these volcanic rocks was consistent with the emplacement of Late Paleozoic basement granite in age(356-290 Ma),i.e.,Early Carboniferous to Early Permian rather than Early Mesozoic.Combined with regional geology,it was concluded that the Budate Group is the component of the basement of the Hailar Basin,and these volcanic rocks were formed at an active continental margin,which is related to the closure of the Hegen Mountains suture zone.The captured Neoproterozoic zircons(814-873 Ma) were probably derived from the Neoproterozoic basement materials in the Ergun Block,implying the close genetic relationships between the Ergun Block(including the Hailar Basin) and the Siberian Block.
文摘YANGBA Formation of Bikou Group is located in south Qinling, a famous orogenic belt separating Chinesecontinent into two parts: North China plate and Yangzi plate. The Yangba Formation comprises the maficand felsic volcanic rocks formed in an ancient seafloor environment during the Proterozoic era. The suitesof mafic and felsic volcanic rocks are petrochemically divided into tholeiite and calc-alkaline dacite, respectively, showing characteristics of bimodal volcanic rock mainly by lithology and major element content, and a lack of typical intermediate rocks. These signatures indicate that the volcanic rocks of YangbaFormation were generated in rift tectonics setting. The tholeiites of Yangba Formation are similar in trace element content to mid-ridge basalt, displaying a slight depletion to enrichment in light rare earth elements (LREE’s) (La/Yb_n = 0.6-1.4), slightfractionation between LREE (La/Sm_n =0.55-1.14) and HREE (Gd/Lu_n = 1.09-1.50), and relative flat patterns in whole. The decoupling of Eu to its neighboring elements in two samples likely indicates an effect of fractional crystallization in magma evolution. The La-La/Sm, Ni-La, Ni-Th, Ni-Ta,and Ni-Hf diagrams all support a conclusion that the mafic rocks are generated by partial melting pro-
