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Jin L.,Hubei University | Jin L.,No1 Institute Of Geology And Mineral Resource Exploration Of Shandong Province | Zhou H.,Hubei University | Zhou H.,State Key Laboratory of Geological Processes and Mineral Resources | And 3 more authors.
Geotectonica et Metallogenia | Year: 2015

The Serteng Formation outcrops in the south part of the East Kunlun consisting mainly of metaclastic rocks, which experienced the regional metamorphism and contact metamorphism. From the bottom up, the sedimentary facies of the Serteng Formation are deepwater turbidite, shallow water sediment, and coastal-shallow water sedimentary, which constitute a regressive sequence. The sedimentary characteristics of the Serteng Formation indicate that it was formed during the closure of the Proto-Tethys. The ever existing controversy about the formation time of the Serteng Formation is primarily due to the absence of fossil. We expect to provide some valuable information about the provenance and stratigraphic formation time of the Serteng Formation through detrital zircon U-Pb dating. We have obtained five age ranges, such as >2500 Ma, 2300~2600 Ma, 1600~1800 Ma, 800~1200 Ma, and 421~600 Ma. The existence of zircon grains with ages older than 2500 Ma may indicate the existence of ancient crystalline basement in the East Kunlun. The rest age ranges indicate the source regions of the Serteng Formation have experienced complex multi-phase geological events, which corresponding to the Early Paleoproterozoic, Late Paleoproterozoic, Late Mesoproterozoic, Early Neoproterozoic and Early Paleozoic tectono-magmatic events, respectively. The paleocurrent direction abstracted from cross bedding indicates the clastics in the Serteng Formation are mainly from the north adjacent regions. Comparing the detrital zircon ages from the Serteng Formation with the adjacent stratigraphic units, we conclude that the Baishahe Group, Xiaomiao Group, Wanbaogou Group, granite formed during early Neoproterozoic tectono-magmatic event, and the evolution of the Proto-Tethys are the mainly provenance of the Serteng Formation. Combining the youngest zircon age 421±7 Ma and the age of rocks which intrude the Serteng Formation, we narrow the formation time of the Serteng Formation to 421~413 Ma. Furthermore, the Serteng Formation recorded the subduction to closure history of the Proto-Tethys in the East Kunlun, so we can use the stratigraphic formation to constraint the closure time of the Proto-Tethys in the East Kunlun. ©, 2015, Science Press. All right reserved.

Liu C.-H.,Chinese Academy of Geological Sciences | Liu C.-H.,Shandong Institute of Geological Survey | Zhang G.-H.,Chinese Academy of Geological Sciences | Wang W.,No1 Institute Of Geology And Mineral Resource Exploration Of Shandong Province | And 4 more authors.
Acta Geoscientica Sinica | Year: 2014

In regional groundwater vulnerability assessment, the impact factors are multiple and complex, and hence it is difficult to determine the evaluation system and the weights of factors objectively. This problem has affected the credibility of the assessment results. Selecting the Northern Shandong Plain as the study area, the authors used innovative overlay and index method. The conventional DRASTIC model was improved and converted into DRITCS model to evaluate groundwater vulnerability. The evaluation factors of DRITCS model included the groundwater depth, integrated lithology of the aeration zone, thickness of clay layer with the thickness of a single layer over 0.5 m within 2 m of land surface, aquifer thickness, permeability coefficient, and net recharge. A key factor in groundwater vulnerability assessment was determined reasonably, which represented the changes of the clay layer in the aeration zone. The DRITCS model was used to evaluate the groundwater vulnerability in northern Shandong plain as an example and was verified by nitrogen pollution status of the study area. The verification of groundwater vulnerability assessment results of northern Shandong plain indicates that the proposed method can reflect objectively the spatial differences and regional distribution characteristics of groundwater vulnerability caused by phase transition of the basin. It is proved that the DRITCS Model has good practicability.

Wang J.,Hubei University | He B.,CAS Guangzhou Institute of Geochemistry | Jin L.,Hubei University | Jin L.,No1 Institute Of Geology And Mineral Resource Exploration Of Shandong Province
Geotectonica et Metallogenia | Year: 2015

The Xingzi Group is located in the core of the Xingzi metamorphic dome, which experienced multistage metamorphism within which an amphibolites facies metamorphism was dated at 142.6±1.5 Ma. Field observations show that the metamorphism may have been related to the Mesozoic magmatism in the study area, but the available ages of the Mesozoic intrusions are all later than that of the Xingzi Group's peak metamorphic time. In order to locate the possible the heat source for the metamorphism, we analyzed the zircons from the deformed pegmatite dikes that emplaced at the end of the Mesozoic magmatism. There are three kinds of zircons in the pegmatite dikes. The first kind of zircons show core-rim structure. The cores of the zircons are magmatic origin with weighted average age of 824±13 Ma, and were likely inherited from the Neoproterozoic Guanyinqiao granite, whereas the rims are metamorphic overgrowth which were dated at about 142 Ma. The second kind of zircons are magmatic origin showing simple internal structure, and are dated at 140.5±1.7 Ma. The age of the magmatic zircons indicates that the Mesozoic magmatic activity in the study area should not be latter than 140.5±1.7 Ma. Moreover, this age is consistent with the peak metamorphic time of the Xingzi Group. We thus consider that the Mesozoic magmatism caused the metamorphism of the Xingzi Group. In addition, the deformation of the pegmatite should be postdate its emplacement, we propose the deformation event in the study area maybe take place simultaneously with the magmatism. The third kind of zircons are hydrothermal in origin, commonly characterized by sponge texture, high content of U, and yielding U-Pb ages of about 123 Ma. ©, 2015, Science Press. All right reserved.

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