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Wu P.,Nanjing University | Gao C.,Nanjing University | Chen F.,Anhui Geological Survey | Yu S.,University of Minnesota
Journal of Environmental Sciences (China) | Year: 2016

Lakes are an important component of terrestrial carbon cycling. As the trend of eutrophication in many lakes continues, the mechanisms of organic carbon (OC) burial remain unclear. This paper aims to understand the distribution of OC and the effect of trophic level changes on OC burial in Chaohu Lake, a shallow eutrophic lake located in the lower reaches of the Yangtze River, SE China. Two hundred and one surface sediment samples (0-20cm) and 53 subsurface samples (150-200cm) from the lake were collected. The OC accumulation rates (OCARs) are relatively low, with an average of 10.01g/m2/year in the surface sediments. The spatial distribution of the OCARs is similar to that of allochthonous OC. The difference in total phosphate (TP) content between the surface and subsurface sediments (δTP) is significantly correlated with the autochthonous OC, suggesting that TP loading is a critical limiting nutrient for the lake's primary productivity. It is concluded that allochthonous OC is the dominant source of total OC in surface sediments compared to autochthonous OC. The primary productivity of Lake Chaohu increased due to increasing nutrient loading. However, the autochthonous OC contributed 11% of the total OC in the surface sediments. This could be ascribed to strong mineralization in the water column or surface sediments. © 2016.

L Q.,Chinese Academy of Geological Sciences | Yan J.,Chinese Academy of Geological Sciences | Shi D.,Chinese Academy of Geological Sciences | Dong S.,Chinese Academy of Geological Sciences | And 3 more authors.
Tectonophysics | Year: 2013

Five intersecting reflection seismic profiles were shot over the Lu-Zong volcanic basin, one of the seven ore districts in the middle and lower Yangtze River Metallogenic Belt in east China. The seismic data reveal diversified reflective patterns in the upper crust, which are interpreted as horsts and grabens in general. The middle crust presents both thrust related structures and boudinage and pinch-and-well structure on different profiles, suggesting a strong structural heterogeneity, which developed due to a change from compressional to extensional movement. Below the central part of a volcanic basin, the lower crust shows an obvious reflective anisotropy both at the crust-mantle and the brittle-ductile transition in the crust. This feature may be explained by magma system emplaced along a NE-trending fault or weak zone at different depths. The Tan-Lu fault zone is present as a northwest-dipping fault extending to the middle crust. The lower crust beneath the Tan-Lu fault and peripheries is possibly of Dabie affinities. The Lu-Zong volcanic basin is clearly defined as an asymmetric graben with master faults on both the east and north flanks. A contrasting reflection character suggests a division of the basin into northern and southern parts separated by a concealed fault. The relatively thin volcanic sequences, inferred to be 800-1000. m in thickness, cover Triassic and Paleozoic sequences at depth, that provide an exploration target in the northern part for deep porphyry and skarn deposits. The dominant deformation reflects NW-SE-oriented compression and extension formed during the Yanshanian orogenic episode. The contraction deformation is characterized by thrust faults with imbrication of crustal slices, whereas the extension deformation is featured by normal faults, regional detachments and basins. Underplating of mantle-derived magma and a multi-layer magma intrusion model are proposed to explain both seismic features and the NE-striking Lu-Zong volcanism and igneous intrusions in the region. © 2013 Elsevier B.V.

Qin Y.,Chinese Academy of Geological Sciences | Wang D.,Institute of Mineral Resources | Wu L.,Anhui Geological Survey | Wang K.,Anhui Geological Survey | Mei Y.,Yichang Institute of Geology and Mineral Resources
Acta Geologica Sinica | Year: 2010

Dongyuan W deposit is a newly-found large-scale scheelite deposit, which is also the biggest one in south of Anhui province. The discovery of the Dongyuan W deposit set the direction for mineral exploration and laid groundwork for further exploration. This paper preliminarily analyzed regional structural background and metallogenic controlling factors, firstly obtained U-Pb age of zircon by using SHRIMP. The results showed that ore-forming age of the granite-porphyry in the Dongyuan porphyry W deposit is 148. 6 ±1. 8 Ma (n = 16, MSWD=1. 5), and the granite porphyry rock was product of late Jurassic magmatic movement. The results also suggested that the regional tungsten mineralization might extend from South China to the Middle and Lower Reach of the Yangtze River.

Lan X.-Y.,Geological Exploration Technologies Institute of Anhui Province | Du J.-G.,Anhui Geological Survey | Yan J.-Y.,Chinese Academy of Geological Sciences | An M.,Geological Exploration Technologies Institute of Anhui Province | And 7 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015

Three-dimensional geological modeling is an important way to realize the breakthrough of deep mineral exploration. This method is based on the three-dimensional modeling of ore-controlling geological bodies, which can directly describe the spatial, genetic and evolutionary relationship between the ore controlling factors. At present, the 3D modeling mainly uses geological data; while in the absence of drilling and other known information, it is difficult to construct a reliable 3D geological model. In order to overcome the disadvantages of poor accuracy and low reliability of conventional 3D geological modeling, we propose an effective method based on the prior information. In this approach, a series of sections obtained by the 2.5D interactive inversion, combined with the sections of 3D physical property inversion, are employed to correct the process of building a 3D geological model. Using this method, the 3D geological model of the Tongling ore concentration area is successfully established, that objectively describes the 3D spatial characteristics of strata, fractures and rock mass. Through the interactive analysis of the 3D model, we draw the following conclusions. 1) The important ore-controlling formations (C-P-T2) of the Tongling area are mainly distributed in the syncline and volcanic-covered area with intense deep magmatic activity, which will greatly expand the prospecting space in the Tongling area. 2)The traditional five orefield intrusive rocks are characterized by having a composite rock, especially with the pyroxene diorite symbiosis mineral iron copper-based, and the gold mines is closely related to the intermediate-acid intrusive rocks. This inference, if established, will have a significant impact on selection of the Tongling area prospecting target. 3) Nappe structure is well developed in the Tongling area, the early Paleozoic basement in the Muzhen sag region and the Daigongshan anticline in the NW edge of the Nanling basin are the product of a regional nappe structure. 3D physical property inversion reveals that the Tongling area intrusive rocks have deep-middle-shallow triple structure, which provides some evidence for the thrusting cause of the Tongling terrane, and also we can look for another “Tongling” outside the Tongling area. © 2015, Science Press. All right reserved.

Xia B.,Sun Yat Sen University | Xia B.,CAS Guangzhou Institute of Geochemistry | Cai Z.,Sun Yat Sen University | Zhang Y.,CAS Guangzhou Institute of Geochemistry | And 6 more authors.
Acta Geologica Sinica | Year: 2010

Shiguan migmatite of Yuexi County is part of former North Dabie Complex. The zircon SHRIMP U-Pb dating shows: the first metamorphism occurred at 232 Ma, equivalent to early period of Late Triassic, and the second metamorphic at 207 Ma, equivalent to late period of Late Triassic. Magmatic detrital zircons with well developed rhythmic zoning constitutes the core of the composite zircon and have the ages of ages of 560, 444, 394, 378 and 331 Ma respectively, suggesting that protolith was not magmatic rock instead of sedimentary rock. Research also shows that the Shiguan migmatite of the North Dabie has gone through two metamorphisms: (1) ultra-high pressure metamorphism at the time of 232 Ma (n = 5, mean age) and 2) retrograde metamorphism at 207 Ma. The two ages of metamorphism are consistent with the time of ultrahigh-pressure metamorphic and retrograde metamorphism in Sulu region.

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