Zircon LA-ICP-MS U-Pb geochronology and geochemical analyses are undertaken for the garnet-bear-ing muscovite monzogranite in Yitong area, central Jilin Province. The formation age and petrogenesis of the granite are ...Zircon LA-ICP-MS U-Pb geochronology and geochemical analyses are undertaken for the garnet-bear-ing muscovite monzogranite in Yitong area, central Jilin Province. The formation age and petrogenesis of the granite are determined, and the regional tectonic background is discussed. Zircons from the granite are euhe-dral-subhedral in shape, and display fine-scale oscillatory growth zoning, indicating a magmatie origin. LA- ICP-MS zircon U-Pb dating result indicates that the garnet-bearing muscovite monzogranites formed in the mid-dle Triassic （243 Ma ）. The garnet-bearing muscovite monzogranites have high SiO2 （SiO2 = 74.1%- 76.49% ）, rich aluminum （A1203 = 14.47%-14.68% ） and alkali （ NazO ＋ K20 = 4.31%-7.9% ）, low Fe203T and MgO （MgO =0.1%-0. 13% , Fe203T =0.46%-1.02% ）. The ratio of CaO/Na20 is between 0.17--0. 21. The garnet-bearing muscovite monzogranites in Yitong region are relatively enriched in light rare earth elements （LREEs） and large ion lithophile elements （LILEs） , and depleted of heavy rare earth elements （HREEs） and high field strength elements （HFSEs）. They are characterized by high Sr and Ba, poor Rb and Y, and negative Eu abnormally （δEu =0.48-0.62） , with Rb/Sr 〈 1. The εHf（t） values and TDM2 of zircons range from ＋ 6. 10 to ＋ 8.00 and from 725 Ma to 814 Ma, respectively. The above features indicate that gar- net-bearing muscovite monzogranites in Yitong area were derived from partial melting of metasedimentary rock. These granites have high Sr/Y ratios, which suggest they formed in a thickened continental crust. Combined with the coeval granitic rocks in central Jilin Province, we suggested that a significant eollisional and thickening event took place during the Middle Triassic.展开更多
Based on the results of four regional geological surveys of 1: 50000 including Shulan County map in Jilin,taking Shulan area as the study area,the authors re-delineated the rock type assemblages,e.g. metamorphic rhyol...Based on the results of four regional geological surveys of 1: 50000 including Shulan County map in Jilin,taking Shulan area as the study area,the authors re-delineated the rock type assemblages,e.g. metamorphic rhyolite,metamorphic tuffaceous breccia lava,sericite-quartz schist and tremolite altered rock,etc.,and the structural contacts between them. With the help of in-situ LA-ICP-MS U-Pb dating for zircons,it is concluded that the zircon crystallization ages of the metamorphic rhyolite,the metamorphic andesitic tuff breccia lava and the tremolite altered rock are 339. 1 ± 1. 3 Ma( n = 27,MSWD = 0. 78),351. 8 ± 1. 7 Ma( n = 21,MSWD = 0.82),and 362.0±1.8 Ma( n = 43,MSWD = 2.2) respectively. The metamorphic complex is actually a set of tectonic melange which comprises the rocks in different types,sources,times,or tectonic settings,and was formed by tectonism.展开更多
Using the radius of gyration from fractal theory, this paper describes the calculation of fractal dimensions for the four tiers of central places in the Jilin Central Urban Agglomeration(JCUA), Jilin Province, China a...Using the radius of gyration from fractal theory, this paper describes the calculation of fractal dimensions for the four tiers of central places in the Jilin Central Urban Agglomeration(JCUA), Jilin Province, China and the structural characteristics of each tier: 1) the 1st tier central place, Changchun Proper(not including Shuangyang District), provides the most service functions and has the most stable primate position; 2) the 2nd tier central places, Jilin Proper, Siping Proper, Liaoyuan Proper and Songyuan Proper have unclear statuses and do not provide certain functions; 3) the 3rd tier central places comprise 23 county-level cities, counties and urban districts(including Shuangyang District of Changchun), exhibiting a dense spatial structure that agrees with theory; 4) the 4th tier contains the largest number of central places(248 designated towns), but they are loosely distributed. In this study, a spatial image of the JCUA was created, based on vectorized data of the urban settlement distribution, which was then modified and abstracted to create a hexagonal network covering the JCUA. Compared to the traditional central place model, the modified spatial image conforms to the K = 3 principle. In reality, however, the growth of some 3rd tier central places should be increased with the cities being upgraded to the 2nd tier so as to overcome that tier′s functional deficiency. The loose distribution in the 4th tier should also be changed. This apparent anomaly can be explained by the fact that the classic hexagon model used to describe the way market areas layout does not exist in the real world. However, this should not be viewed as an obstacle to using central place theory. If its assumptions are properly applied, it can still assist research into the spatial structure of regions.展开更多
The Ordovician Changtu Fauna is recently discovered in the Xia' ertai and Hulan Groups in northernLiaoning-central Jilin. The fauna, containing 10 genera and 14 species (including 3 new genera, 9 new speciesand an...The Ordovician Changtu Fauna is recently discovered in the Xia' ertai and Hulan Groups in northernLiaoning-central Jilin. The fauna, containing 10 genera and 14 species (including 3 new genera, 9 new speciesand an unidentified species), is closely related in evolution with the Early Cambrian Qinghezhen Fauna. Thediscovery of this fauna is significant to the study on the age of the strata, Ordovician biostratigraphy and geo-logical evolution of the tectonostratigraphical terrane on the northern margin of the Sino-Korean plate.展开更多
基金Supported by National Basic Research Program of China(No.41572043)
文摘Zircon LA-ICP-MS U-Pb geochronology and geochemical analyses are undertaken for the garnet-bear-ing muscovite monzogranite in Yitong area, central Jilin Province. The formation age and petrogenesis of the granite are determined, and the regional tectonic background is discussed. Zircons from the granite are euhe-dral-subhedral in shape, and display fine-scale oscillatory growth zoning, indicating a magmatie origin. LA- ICP-MS zircon U-Pb dating result indicates that the garnet-bearing muscovite monzogranites formed in the mid-dle Triassic （243 Ma ）. The garnet-bearing muscovite monzogranites have high SiO2 （SiO2 = 74.1%- 76.49% ）, rich aluminum （A1203 = 14.47%-14.68% ） and alkali （ NazO ＋ K20 = 4.31%-7.9% ）, low Fe203T and MgO （MgO =0.1%-0. 13% , Fe203T =0.46%-1.02% ）. The ratio of CaO/Na20 is between 0.17--0. 21. The garnet-bearing muscovite monzogranites in Yitong region are relatively enriched in light rare earth elements （LREEs） and large ion lithophile elements （LILEs） , and depleted of heavy rare earth elements （HREEs） and high field strength elements （HFSEs）. They are characterized by high Sr and Ba, poor Rb and Y, and negative Eu abnormally （δEu =0.48-0.62） , with Rb/Sr 〈 1. The εHf（t） values and TDM2 of zircons range from ＋ 6. 10 to ＋ 8.00 and from 725 Ma to 814 Ma, respectively. The above features indicate that gar- net-bearing muscovite monzogranites in Yitong area were derived from partial melting of metasedimentary rock. These granites have high Sr/Y ratios, which suggest they formed in a thickened continental crust. Combined with the coeval granitic rocks in central Jilin Province, we suggested that a significant eollisional and thickening event took place during the Middle Triassic.
基金Supported by projects of China Geological Survey(Nos.DD20160049,12120114029101)
文摘Based on the results of four regional geological surveys of 1: 50000 including Shulan County map in Jilin,taking Shulan area as the study area,the authors re-delineated the rock type assemblages,e.g. metamorphic rhyolite,metamorphic tuffaceous breccia lava,sericite-quartz schist and tremolite altered rock,etc.,and the structural contacts between them. With the help of in-situ LA-ICP-MS U-Pb dating for zircons,it is concluded that the zircon crystallization ages of the metamorphic rhyolite,the metamorphic andesitic tuff breccia lava and the tremolite altered rock are 339. 1 ± 1. 3 Ma( n = 27,MSWD = 0. 78),351. 8 ± 1. 7 Ma( n = 21,MSWD = 0.82),and 362.0±1.8 Ma( n = 43,MSWD = 2.2) respectively. The metamorphic complex is actually a set of tectonic melange which comprises the rocks in different types,sources,times,or tectonic settings,and was formed by tectonism.
基金Under the auspices of National Natural Science Foundation of China(No.41201162)
文摘Using the radius of gyration from fractal theory, this paper describes the calculation of fractal dimensions for the four tiers of central places in the Jilin Central Urban Agglomeration(JCUA), Jilin Province, China and the structural characteristics of each tier: 1) the 1st tier central place, Changchun Proper(not including Shuangyang District), provides the most service functions and has the most stable primate position; 2) the 2nd tier central places, Jilin Proper, Siping Proper, Liaoyuan Proper and Songyuan Proper have unclear statuses and do not provide certain functions; 3) the 3rd tier central places comprise 23 county-level cities, counties and urban districts(including Shuangyang District of Changchun), exhibiting a dense spatial structure that agrees with theory; 4) the 4th tier contains the largest number of central places(248 designated towns), but they are loosely distributed. In this study, a spatial image of the JCUA was created, based on vectorized data of the urban settlement distribution, which was then modified and abstracted to create a hexagonal network covering the JCUA. Compared to the traditional central place model, the modified spatial image conforms to the K = 3 principle. In reality, however, the growth of some 3rd tier central places should be increased with the cities being upgraded to the 2nd tier so as to overcome that tier′s functional deficiency. The loose distribution in the 4th tier should also be changed. This apparent anomaly can be explained by the fact that the classic hexagon model used to describe the way market areas layout does not exist in the real world. However, this should not be viewed as an obstacle to using central place theory. If its assumptions are properly applied, it can still assist research into the spatial structure of regions.
文摘The Ordovician Changtu Fauna is recently discovered in the Xia' ertai and Hulan Groups in northernLiaoning-central Jilin. The fauna, containing 10 genera and 14 species (including 3 new genera, 9 new speciesand an unidentified species), is closely related in evolution with the Early Cambrian Qinghezhen Fauna. Thediscovery of this fauna is significant to the study on the age of the strata, Ordovician biostratigraphy and geo-logical evolution of the tectonostratigraphical terrane on the northern margin of the Sino-Korean plate.
