The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs c...The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold.Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials.The Re-Os isotopic data of four pyrite samples construct an isochron,yielding a weighted average age of 226±17 Ma(mean square weighted deviation=1.7),which is considered the main mineralization age.A dioritic porphyrite vein sample,showing weaker mineralization,was also dated using the SHRIMP zircon UPb isotopic method to constrain the youngest metallogenic age of the ore deposit,because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field,but also the main ore bodies.The dioritic porphyrite sample yields a weighted mean ^(206)Pb/^(238)U age of 221±3 Ma,which is slightly younger than the Re-Os isotopic isochron age of the pyrites,considered as the upper age limit of the mineralization,namely the ending age of the mineralization.The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma-related fluid,and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle.The Erlihe Pb-Zn deposit and associated dioritic porphyrite vein,important records of Qinling tectonic-magmatism-mineralization activities,were formed during the Triassic collisional orogeny processes.展开更多
The Jinniu Basin in southeast Hubei,located at the westernmost part of middle-lower val-ley of the Yangtze River,is one of the important vol-canic basins in East China. Volcanic rocks in the Jin-niu Basin are distribu...The Jinniu Basin in southeast Hubei,located at the westernmost part of middle-lower val-ley of the Yangtze River,is one of the important vol-canic basins in East China. Volcanic rocks in the Jin-niu Basin are distributed mainly in the Majiashan Formation,the Lingxiang Formation and the Dasi Formation,consisting of rhyolite,basalt and basaltic andesite,(trachy)-basalt and basaltic trachy-andesite and (trachy)-andesite and (trachy)-dacite and rhyolite respectively,in which the Dasi volcanism is volumet-rically dominant and widespread. The Dasi volcanic rocks were selected for SHRIMP zircon U-Pb dating to confirm the timing of volcanism. The results indi-cate that there exist a large amount of magmatic zir-cons characterized by high U and Th contents in the volcanic rocks. The concordia ages for 13 points are 128 ± 1Ma (MSWD = 3.0). On account of the shape of zircons and Th/U ratios,this age is considered to represent the crystallization time of the Dasi volcan-ism. The volcanic rocks in the Dasi,Majiashan and Lingxiang Formations share similar trace elementand REE partition patterns as well as Sr-Nd isotopic compositions. In combination with the regional geol-ogy,it is proposed that the southeast Hubei volcanic rocks were formed mainly during the Early Creta-ceous,just like other volcanic basins in middle-lower Yangtze valley. A lithospheric extension is also sug-gested for tectonic regime in this region in the Cre-taceous Period.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
The Dabao Formation in the South Qinling Orogenic Belt was previously regarded as Ordovician in age and consists of clastic matrix and blocks of siltstone,limestone,chert,and volcanic rocks.However,some Middle Devonia...The Dabao Formation in the South Qinling Orogenic Belt was previously regarded as Ordovician in age and consists of clastic matrix and blocks of siltstone,limestone,chert,and volcanic rocks.However,some Middle Devonian corals,conodonts,and other fossil fragments within the limestone blocks were discovered in recent field investigations,indicating that the Dabao Formation was formed during late Paleozoic.Combined with other regional geological data,the Dabao Formation in the Southern Qinling Orogenic Belt is considered to be a late Paleozoic or early Mesozoic accretionary complex.展开更多
基金supported by the National Scientific and Technological Support Program of China (grant no:2006BAB01A11)
文摘The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold.Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials.The Re-Os isotopic data of four pyrite samples construct an isochron,yielding a weighted average age of 226±17 Ma(mean square weighted deviation=1.7),which is considered the main mineralization age.A dioritic porphyrite vein sample,showing weaker mineralization,was also dated using the SHRIMP zircon UPb isotopic method to constrain the youngest metallogenic age of the ore deposit,because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field,but also the main ore bodies.The dioritic porphyrite sample yields a weighted mean ^(206)Pb/^(238)U age of 221±3 Ma,which is slightly younger than the Re-Os isotopic isochron age of the pyrites,considered as the upper age limit of the mineralization,namely the ending age of the mineralization.The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma-related fluid,and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle.The Erlihe Pb-Zn deposit and associated dioritic porphyrite vein,important records of Qinling tectonic-magmatism-mineralization activities,were formed during the Triassic collisional orogeny processes.
基金supported by the National Natural Science Foundation of China(Grant 40434011)China Geological Survey Project of the Ministry of Land and Resources(Grant 1212010535804).
基金supported by the National Science Foundation of China (project 40872147/40472119)the basic outlay of scientific research work from the Ministry of Science and Technology of China(project 2006BAB01A11)the Geological Survey Project of China(project 12120100782003-13)
基金Acknowledgements The authors would like to thank Southeast Hubei Geological Party and No.4 Geological Party of Hubei Province, and Hubei Geological Survey Institution for help during the field investigation. Chen Fukun, Li Sunrong, Feng Jiayi, Hu Jing, Qiu Yi, Tao Hua and Chen Zhenyu are thanked for their assistance during major and trace element and Sr-Nd isotope and SHRIMP analyses. Comments and discussion given by Wan Yusheng, Li Jianwei and Yang Zhusen were very helpful in improving and clarifying the manuscript. Two anonymous reviewers have provided detailed suggestions, critical comments, which led to considerable improvement and modification of this manuscript. This work was jointly supported by the National Natural Science Foundation of China （Grant Nos. 40434011 and 40402011）, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences （Grant Nos.GPM40504）, State Key Laboratory of 0re Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences （Grant Nos. 200402）, the Chinese Geological Survey Bureau （Grant Nos. 20031020081） and Postdoctoral Science Foundation.
文摘The Jinniu Basin in southeast Hubei,located at the westernmost part of middle-lower val-ley of the Yangtze River,is one of the important vol-canic basins in East China. Volcanic rocks in the Jin-niu Basin are distributed mainly in the Majiashan Formation,the Lingxiang Formation and the Dasi Formation,consisting of rhyolite,basalt and basaltic andesite,(trachy)-basalt and basaltic trachy-andesite and (trachy)-andesite and (trachy)-dacite and rhyolite respectively,in which the Dasi volcanism is volumet-rically dominant and widespread. The Dasi volcanic rocks were selected for SHRIMP zircon U-Pb dating to confirm the timing of volcanism. The results indi-cate that there exist a large amount of magmatic zir-cons characterized by high U and Th contents in the volcanic rocks. The concordia ages for 13 points are 128 ± 1Ma (MSWD = 3.0). On account of the shape of zircons and Th/U ratios,this age is considered to represent the crystallization time of the Dasi volcan-ism. The volcanic rocks in the Dasi,Majiashan and Lingxiang Formations share similar trace elementand REE partition patterns as well as Sr-Nd isotopic compositions. In combination with the regional geol-ogy,it is proposed that the southeast Hubei volcanic rocks were formed mainly during the Early Creta-ceous,just like other volcanic basins in middle-lower Yangtze valley. A lithospheric extension is also sug-gested for tectonic regime in this region in the Cre-taceous Period.
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 National Natural Science Foundation of China (Grant Nos. 40602026, 40772137)the Basic Outlay of Scientific Research Work from the Ministry of Science and Technology of China (Grant No. J0720)+1 种基金Key Projects in the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period (Grant No. 2006BAB01A11)the Geological Survey Project of China (Grant No. 1212010611807)
文摘The Dabao Formation in the South Qinling Orogenic Belt was previously regarded as Ordovician in age and consists of clastic matrix and blocks of siltstone,limestone,chert,and volcanic rocks.However,some Middle Devonian corals,conodonts,and other fossil fragments within the limestone blocks were discovered in recent field investigations,indicating that the Dabao Formation was formed during late Paleozoic.Combined with other regional geological data,the Dabao Formation in the Southern Qinling Orogenic Belt is considered to be a late Paleozoic or early Mesozoic accretionary complex.
