And 6 more authors.
Tectonophysics | Year: 2017
The Mesozoic strata, within the Bangong-Nujiang suture zone in central Tibet, recorded critical information about the subduction-accretion processes of the Bangong-Nujiang Ocean prior to the Lhasa-Qiangtang collision. This paper reports detailed field observations, petrographic descriptions, sandstone detrital zircon U-Pb ages and Hf isotopic analyses from an accretionary complex (preserved as Mugagangri Group) and the unconformably overlying Shamuluo Formation near Gaize. The youngest detrital zircon ages, together with other age constraints from literature, suggest that the Mugagangri Group was deposited during late Triassic-early Jurassic, while the Shamuluo Formation was deposited during late Jurassic-early Cretaceous. Based on the differences in lithology, age and provenance, the Mugagangri Group is subdivided into the upper, middle and lower subunits. These units are younging structurally downward/southward, consistent with models of progressive off-scrapping and accretion in a southward-facing subduction complex. The upper subunit, comprising mainly quartz-sandstone and siliceous mud/shale, was deposited in abyssal plain environment close to the Qiangtang passive margin during late Triassic, with sediments derived from the southern Qiangtang block. The middle and lower subunits comprise mainly lithic-quartz-sandstone and mud/shale, containing abundant ultramafic/ophiolitic fragments. The middle subunit, of late Triassic-early Jurassic age, records a transition in tectono-depositional setting from abyssal plain to trench-wedge basin, with sudden influx of sediments sourced from the central Qiangtang metamorphic belt and northern Qiangtang magmatic belt. The appearance of ultramafic/ophiolitic fragments in the middle subunit reflects the subduction initiation. The lower subunit was deposited in a trench-wedge basin during early Jurassic, with influx of Jurassic-aged zircons originating from the newly active southern Qiangtang magmatic arc. The lower subunit records the onset of arc magmatism related to the northward subduction of the Bangong-Nujiang Ocean. The Shamuluo Formation, comprising mainly lithic-feldspar-sandstone with limestone interlayers, was deposited in a post-collisional residual-sea or pre-collisional trench-slope basin, with sediments derived entirely from the Qiangtang block. © 2017 Elsevier B.V.
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.
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.
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.
AIM: To explore the association between molybdenum levels and risk of gastric cancer by comparing environmental molybdenum levels between a high and a low incidence area of gastric cancer. METHODS: Samples of soil, earth, paddy, surface water, drinking water, and hair, serum and urine of residents were collected from a high and a low incidence area of gastric cancer. Atomic emission spectrometry and oscillopolarography were applied to detect the contents of molybdenum in the above samples. Nonparametric rank sum test was used for statistical analysis. RESULTS: There is a significant difference in environmental molybdenum content between the high and low incidence areas of gastric cancer (P < 0.01). The median molybdenum contents in soil, bottom mud and rice were significantly higher in the low than in the high incidence area of gastric cancer (2.57 mg/kg vs 0.50 mg/kg, 3.53 mg/kg vs 0.71 mg/kg, 1.04 mg/kg vs 0.54 mg/ kg, all P < 0.01). The median molybdenum contents in soil and low mud in the low incidence area of gastric cancer were fve times as high as those in the high incidence area. The molybdenum contents in the hair, serum and urine of residents in the low incidence area were significantly higher than those in the high incidence area (0.11 mg/kg vs 0.05 mg/kg, 8.42 μg/L vs 3.17 μg/L, 0.13 mg/L vs 0.04 mg/L, all P < 0.001). CONCLUSION: High incidence of gastric cancer is probably related to insufficient intake of molybdenum.
LA-ICP-MS zircon U-Pb dating was carried out for Dongshan metamorphic rocks in Fujian Province. Their ages obtained are 176.8 Ma, 203 Ma, 230 Ma, 1320 Ma and 1810 Ma respectively, Among them, the 176.8 Ma is the age of magmatic zircon in volcanic-sedimentary rocks, representing the formation age of the sedimentary rock; 203 Ma and 230 Ma represent Late Triassic granitoids; 1320 Ma and 1810 Ma represent the metamorphic basement age of metamorphic rocks. The geochemical data indicate that these metamorphic rocks have poor Si and high Al, Fe, K and are characterized by low Co, Ni, V content and high Ba, Rb, Zr, Hf, U, Th, La values, exhibiting crust source features; relatively high REE content, slight enrichment of LREE, indistinct fractionation between LREE and HREE, and weak negative Eu anomaly all indicate that sources of the metamorphic rocks might have been mantle-crust and granitoids of I series. The Qingyingshan Formation seems to have been the early Jurassic product of the marine-terrigenous facies at the rifting stage, accompanied by volcanism.