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Jin C.-S.,Oil and Gas Survey | Xu X.-H.,Sinopec | Li G.,CAS Qingdao Institute of Oceanology | Liang J.-S.,China National Offshore Oil Corporation | And 2 more authors.
Geology in China | Year: 2015

Based on the newly acquired and reprocessed seismic data, in combination with drilling data, gravity and magnet inversion and onshore and offshore correlation, the authors studied the geological characteristics of Mesozoic and Cenozoic strata in southern East China Sea Shelf Basin. With sedimentary center in the east, the Mesozoic strata of great thickness are distributed extensively over such uplift areas as Taibei, Guanyin and Yandang. The Cenozoic strata are thicker in the east and west than in the central part in the study area. The southern East China Basin was a marginal depression basin in Mesozoic, with a western boundary of Jurassic on the east side of Yandang uplift, and that of Cretaceous on the west side of Oujiang Sag. More marine facies marks were found in drilling analysis, which shows that the transgression from south to north and from east to west happened in Jurassic, and that from east to west occurred in Cretaceous, in consideration of surrounding sedimentary environments. Source rocks of Lower Jurassic, Lower Cretaceous, Paleocene, Eocene, Oligocene and Miocene are well developed in the study area, so there exists a great hydrocarbon potential in the study area. Source

Wang B.,Research Center for Tibetan Plateau Geology | Wang L.,Research Center for Tibetan Plateau Geology | Xu J.,CAS Guangzhou Institute of Geochemistry | Chen L.,Research Center for Tibetan Plateau Geology | And 4 more authors.
Geological Bulletin of China | Year: 2015

A high pressure metamorphic (HP) and ultrahigh pressure metamorphic (UHP) belt is exposed in Baxoi, Amdo and Pengco areas along the middle-eastern Bangongco-Nujiang suture zone (BNSZ). However, the similar HP-UHP metamorphic rocks have not discovered in the western section of BNSZ. In this paper, the authors first report the high-pressure granulite (probably retrograde eclogite) at Dongco area in the western section of the BNSZ. Dongco high-pressure granulite occurs in lenticular, stratoid and massive forms in plagioclase amphibolites and metamorphic gabbros. Based on the intensive study of petrology and mineralogical geochemistry, the authors hold that the HP granulite was made up of the early mineral assemblage of garnet (Grt)+clinopyroxene (Cpx) + plagioclase (Pl) (mostly saussuritized) and the late massive retrograde mineral assemblages amphibole (Hb)+plagioclase (Pl). Garnets in high-pressure granulites are surrounded by plagioclase which forms the corona. LA-ICP-MS zircon U-Pb dating yielded the age of original rock from the high-pressure granulite of 254±2 Ma, indicating that the opening time of Bangong Co-Nujiang River oceanic basin can be traced to the Late Permian. Geological temperature pressure indicator shows that the temperature-pressure conditions of high-pressure granulite phase are 780~900℃, 13~16 kPa, while those of retrogressive metamorphic amphibolite phase are 430~480℃, 4.5~5.2 kPa, respectively, suggesting that the high-pressure granulites were most likely the product of granulite facies (even eclogite facies) high pressure metamorphism of the Bangong Co-Nujiang River Tethyan oceanic crust. The discovery of Dongco high pressure granulites shows that a high-pressure metamorphic belt might exist within the BNSZ, and might have been formed by the deep subduction of the Bangong Co-Nujiang River Tethyan Ocean. Further study of the high-pressure granulites is of great significance for recognizing the deep subduction process, continent-continent collision orogeny and the tectonic evolution of BNSZ in the Tibetan Plateau. ©, 2015, Science Press. All right reserved. Source

Xu X.,Wuhan University | Li Y.,Wuhan University | Xue D.,Fujian Institute of Geological Survey | Xie M.,Southeastern Fujian Geology Party of Fujian Province | And 3 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2014

Multi-stage Late Mesozoic magmatism and structural deformation related to the subduction of Paleo-Pacific plate occurred in the coast of Fujian Province, southeastern China. Extensional deformation in Quanzhou area presents high-angular normal faults and low-angular normal faults or detachment faults. The extensional deformation developed in NW-striking extensional setting. Zircon U-Pb geochronological data in this study suggest that Late Jurassic (~155 Ma), middle Early Cretaceous (130-125 Ma), late Early Cretaceous (~109 Ma) and early Late Cretaceous magmatic rocks outcrop in Quanzhou area. The comprehensive analyses of cutting relations and geochronological data of magmatic rocks show that the sinistral ductile strike-slip of the Changle-Nan'ao shear zone occurred in 130-120 Ma, whereas the dextral brittle shear developed between 120 Ma and 100 Ma. The angular variations of subduction for the Paleo-Pacific plate underneath the South China led to the development of the Late Mesozoic orogenic belt in the coast of Fujian Province. This orogen commenced at the beginning of Early Cretaceous and terminated in the latest Early Cretaceous, which is marked by the extensive NW-striking extensional structures. The transform from syn-orogen compression to post-orogen extension occurred at ~120 Ma. Source

Wang H.-Q.,CAS Institute of Tibetan Plateau Research | Wang H.-Q.,Chinese Academy of Sciences | Wang H.-Q.,University of Chinese Academy of Sciences | Ding L.,CAS Institute of Tibetan Plateau Research | And 16 more authors.
Gondwana Research | Year: 2015

As the boundary thrust between India and Asia in southern Tibet, the Zhongba-Gyangze Thrust (ZGT) emplaced the Yarlung Zangbo Suture Zone (YZSZ) units in the hanging wall southward onto Tethyan Himalaya sequences (THS) of the northern Indian continental margin in the footwall. Detailed field investigation, electron backscatter diffraction (EBSD) analysis, detrital zircon U-Pb geochronology and 40Ar-39Ar thermochronology were conducted to understand the evolution of the ZGT in Sangsang area, central southern Tibet. The shear zone of ZGT is located within the sedimentary-matrix mélange of YZSZ that is mainly composed of matrix of blueschist with meta pelagic-hemipelagic siliceous and siliciclastic rocks and blocks of basalt, limestone and sandstone. Penetrative F1 foliation and kink band structure were recorded within the matrix both on outcrop and under microscope. Strong lattice preferred orientation (LPO) fabric initiated by the low-temperature (350-450°C) (010)[001] slip system was detected by EBSD in the sodic amphiboles of the blueschist. The 40Ar-39Ar ages of the phengites from blueschist and sericites from the phyllite in the shear zone indicate that the activity of ZGT occurred between 71 and 60Ma. In the THS, a newly documented younger unit preserving detrital zircons from the southern Asian margin lies above the Triassic-Cretaceous sequences that carries only detrital zircons from the Indian continent. This unit is dated to be ~61Ma by the detrital zircon ages, similar to the Sangdanlin Formation and representing the Yarlung Zangbo Foreland Basin (YZFB) system. The ZGT had probably been active due to the initial India-Asia collision and acted as the frontal thrust controlling the development of YZFB. © 2015 International Association for Gondwana Research. Source

Qu C.,Wuhan University | Qu C.,University of Naples Federico II | Qi S.,Wuhan University | Yang D.,Wuhan University | And 7 more authors.
Journal of Geochemical Exploration | Year: 2015

Surface soil samples from farmlands in Ningde were analyzed for 20 organochlorine pesticides (OCPs) with the aim of elucidating contamination profiles, distribution characteristics, influencing factors and carcinogenic risks of these compounds in this hilly region. The total concentrations of OCPs ranged from 3.66 to 658.42ng/g, with a mean of 78.83ng/g. HCHs, DDTs and Endosulfans were the predominant contaminants in agricultural soils. The residual levels of OCPs on vegetable farmlands were significantly higher than those of corresponding counterparts on paddy farmlands, mainly attributed to variations in pesticide application and OCP degradation in the soils. Potential source analysis traced the occurrence of high residual levels of DDTs and HCHs to historical applications. Spearman correlation analysis pointed to TOC as a significant variable controlling OCP distribution, and artificial influences possibly contributed to the fate of OCPs in the soils. The OCP contamination levels in the agricultural soils based on national standards are generally considered safe for crop production, but they however, pose significant carcinogenic risks to exposed populations based on the calculated results of the incremental lifetime cancer risk (ILCR) parameters. © 2014 Elsevier B.V. All rights reserved. Source

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