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Hu F.,Wuhan University | Chen J.,Wuhan University | Sun S.,Hubei Geological Survey
Energy Education Science and Technology Part A: Energy Science and Research

Soil geochemical analysis is a common prospecting method in mining areas. The chemical prospecting data of mining areas is not in line with a normal distribution law and thus a good effect is difficult to obtain if it is processed using a conventional geochemical processing method. In this paper, the geochemical data of the soil in mining areas was studied and analyzed using the multi-fractal “C-A” model to make the element fractal dimensions comparatively fractal, indicating the fractal dimension of the ore-forming elements was less than 2 and the multi-fractal dimensions of the associated elements were similar. Based on the fractal dimension, the directional minerals as well as the related ore-forming elements were quickly determined and also the local anomalies area was smaller compared with the traditional method, so that the principle of the maximum ore-bearing rate within the minimum area was more effectively embodied. This will be of guiding significance for the future work in mining areas. © Sila Science. All rights reserved. Source

Liu B.,Yangtze University | Ma C.-Q.,Wuhan University | Guo Y.-H.,Wuhan University | Xiong F.-H.,Chengdu University of Technology | And 2 more authors.

Although numerous Paleo-Tethyan ophiolites with mid-oceanic ridge basalts (MORB) and/or oceanic-island basalt (OIB) affinities have been reported in the central Tibetan Plateau (CTP), the origin and tectonic nature of these ophiolites are not well understood. The petrogenesis, mantle sources and geodynamic setting of the mafic rocks from these ophiolites are unclear, which is the main reason for this uncertainty. In this paper, we present new geochronological, mineralogical and Sr-Nd isotopic data for the Chayong and Xiewu mafic complexes in the western Garzê-Litang suture zone (GLS), a typical Paleo-Tethyan suture crossing the CTP. Zircon LA-ICP-MS U–Pb ages of 234 ± 3 Ma and 236 ± 2 Ma can be interpreted as formation times of the Chayong and Xiewu mafic complexes, respectively. The basalts and gabbros of the Chayong complex exhibit enriched MORB (E-MORB) compositional affinities except for a weak depletion of Nb, Ta and Ti relative to the primitive mantle, whereas the basalts and gabbros of the Xiewu complex display distinct E-MORB and OIB affinities. The geochemical features suggest a probable fractionation of olivine ± clinopyroxene ± plagioclase as well as insignificant crustal contamination. The geochemical and Sr-Nd isotopic data reveal that the Chayong mafic rocks may have been derived from depleted MORB-type mantle metasomatized by crustal components and Xiewu mafic rocks from enriched lithospheric mantle metasomatized by OIB-like components. The ratios of Zn/Fet, La/Yb and Sm/Yb indicate that these mafic melts were produced by the partial melting of garnet + minor spinel-bearing peridotite or spinel ± minor garnet-bearing peridotite. We propose that back-arc basin spreading associated with OIB/seamount recycling had occurred in the western GLS at least since the Middle Triassic times, and the decompression melting of the depleted MORB-type asthenosphere mantle and partial melting of sub-continental lithosphere were metasomatized by plume-related melts, such as OIB s, which led to the generation of the Chayong and Xiewu mafic melts. © 2016 Source

Du Q.,Chengdu Institute of Geology and Mineral Resources | Du Q.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | Wang Z.,Chengdu Institute of Geology and Mineral Resources | Wang Z.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | And 7 more authors.
Precambrian Research

The Yangtze Block is an important component in reconstructing the Proterozoic tectonic evolution of South China within the Rodinia supercontinent. The geochronology and paleoenvironment of the Liantuo Formation in the Yangtze Block are still highly controversial. An integrated approach of facies analysis, paleogeography and geochronology provides new insights into understanding the sedimentology and paleogeography of the formation. Here, results are presented from a detailed U-Pb zircon examination of geochronology and paleoenvironment of the Liantuo Formation in the Yangtze Block. The formation was deposited in the period of ca. 790-730. Ma, which coeval with the development of the Wuqiangxi Formation in the middle-upper part of the Banxi Group. The top of the Liantuo Formation gives a U-Pb age of 736. ±. 5.8. Ma, which signifies an onset time of the Sturtian glaciation as ca. ≤730. Ma. The zircon U-Pb ages reveal magmatic events that were correlated with Neoproterozoic continental growth indicating that the Rodinia initiated rifting occurred at ca. 824. Ma and extensive rift-related magmatism took place at ca. 780. Ma in the northern Yangtze Block. Moreover, these results provide geochronological and petrologic evidence that confirms the stratigraphic framework of the Nanhuan System, thereby promoting a better understanding of the Neoproterozoic tectonic development of South China. © 2013 Elsevier B.V. Source

Liu R.,Wuhan University | Li J.-W.,Wuhan University | Bi S.-J.,Wuhan University | Hu H.,Wuhan University | Chen M.,Hubei Geological Survey
International Journal of Earth Sciences

In this paper, we present zircon U-Pb age and Hf isotope data to document the significance of magma mixing in the formation of Late Jurassic granitoid intrusions in the eastern Qinling Orogen, China. The Muhuguan granitoid pluton from this orogen consists of monzogranite and lesser biotite granite and granodiorite, all containing abundant hornblende-rich cumulates, dioritic xenoliths, and mafic magmatic enclaves (MMEs). The monzogranite and granodiorite are intruded by a number of lamprophyre dykes. Both a cumulate and a dioritic xenolith samples have concordant zircon U-Pb ages of ca. 161 ± 1 Ma, but possess contrasting Hf isotopic compositions. The cumulate has more radiogenic zircon Hf isotopes with negative ε Hf(t) values (-7.9 to -2.5) and T DM1 ages of 0.9-1.1 Ga, indicating its derivation likely from basaltic rocks of the Neoproterozoic to early Paleozoic Kuanping Group in the area. The dioritic xenolith has much lower zircon ε Hf(t) values of -19.5 to -8.8 and T DM2 ages of 2.4-1.7 Ga, consistent with a juvenile Paleoproterozoic crust source presumably represented by the metabasic rocks of the Qinling Group in the area. Individual samples of the monzogranite, MME, and a lamprophyre dyke have U-Pb ages of 150 ± 1, 152 ± 1, and 152 ± 1 Ma, respectively, demonstrating coeval mafic and felsic magmatism in the Late Jurassic. The lamprophyre dyke has homogeneous, highly negative zircon ε Hf(t) values (-29.8 to -24.8) and Archean T DM2 ages (3.0-2.7 Ga), and its genesis is interpreted as partial melting of an ancient enriched subcontinental mantle source. Zircons from the fine-grained MME show a large range of ε Hf(t) between -29.1 and -9.8, overlapping values of the monzogranite and lamprophyre dyke samples. Zircon U-Pb age and Hf isotopes of the MMEs are consistent with their formation by mixing of crustal- and enriched mantle-derived magmas. The main group of zircons from the monzogranite has ε Hf(t) values (-17.9 to -9.3) and T DM2 ages (2.3-1.8 Ga) that are compatible with the dioritic xenoliths, indicating that the former was produced by partial melting of Paleoproterozoic crustal source with involvement of mantle-derived magmas. Mafic magmatism revealed from the Muhuguan pluton indicates that the eastern Qinling Orogen was dominated by lithospheric extension during the Late Jurassic. Compilation of existing geological and geochronological data suggests that this extensional event started in Late Jurassic (ca. 160 Ma) and persisted into the Early Cretaceous until ca. 110 Ma. The Jura-Cretaceous extension may have resulted from the late Mesozoic westward subduction of the Pacific plate beneath the East Asian continental margin. © 2013 Springer-Verlag Berlin Heidelberg. Source

Tang R.,Wuhan University | Lu X.,Wuhan University | Cao X.,Wuhan University | Mei W.,Wuhan University | And 3 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences

Weilasituo and Bairendaba are two large-scale silver polymetallic deposits, discovered in the western slope of the south and central sections of Great Hinggan Mountains in recent years. This study focuses on identifying and analyzing the mineral associations and occurrence of silver minerals using scanning electron microscopy-energy dispersive spectrometry and electron microprobe. The analyses suggest that mineral associations change from tungstate and oxide, to diatomic sulphide, to simple sulphide, to antimony sulfosalt mineral, to antimonide with decreasing temperature based on the microscopy observations. The silvers contained in the ore occur in several forms, including mainly visible silver minerals, followed by the lattice silver (isomorphous substitution) and sub-micron inclusion silver. The mineral sequence of visible silver's formation is Ag-bearing tetrahedrite-argentian tetrahedrite-freibergite-diaphorite- freieslebenite-pyrargyrite-dyscrasite. Ag occurs in lattice of chalcopyrite, bornite, chalcocite, pyrite and galena in isomorphism in small amount, and also as the microscopic wrappage in galena. The results, combined with the characteristics of mineral association and fluid inclusions in different mineralizing stages, indicate that W and Sn are transported as wolframic acid and tungstate at the early high-temperature meta-acid oxidizing environment, while Zn2+, Pb2+, Cu+ and other metalions are transported as chloride complexes. After wolframite's precipitation and the changes of metallogenetic fluid physical and chemical condition, the metallogenetic environment becomes slightly alkaline and reductive, and Zn2+, Cu+ and other metalions form HS- complexes. The continuous drop of temperature and water-rock interaction lead to the separation of Zn2+, Cu+ with HS- to form pyrrhotite, sphalerite etc.. In late phases, Ag+ can combine Sb3+, Cu+, Pb2+, Sb3-, S2- etc., which results in multiple silver antimony sulfide minerals, boulangerite etc.. Source

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