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Hu L.,Wuhan University | Cawood P.A.,University of St. Andrews | Cawood P.A.,University of Western Australia | Du Y.,Wuhan University | And 3 more authors.
Journal of Asian Earth Sciences | Year: 2015

Upper Permian to Lower Triassic siliciclastic succession in the Shiwandashan Basin, South China, accumulated in response to a Permo-Triassic orogeny (often referred to as the Indosinian orogeny). The petrology, geochemistry and geochronology of this succession, along with north and northwest-directed paleocurrent indicators, reveal an evolving provenance related to erosion and reworking of Precambrian, Early Paleozoic and Permian to Early Triassic units exposed to the south of the basin. The Upper Permian to Lower Triassic sandstones within the basin are quartz dominated, which along with their high Th/Sc and Zr/Sc ratios indicate a multi-cycled source. Sandstone clasts in the Upper Permian conglomerates display age patterns similar to nearby Silurian strata. Other clast types (limestone, mudstone and cherts) are from the Early Paleozoic strata within or adjoining the basin. Detrital zircon age spectra of the strata display prominent age groups at 1200-800. Ma, 650-500. Ma and 460-420. Ma, and are inferred to have been derived from basement units similar to those exposed in the Yunkai Massif to the south and southeast of the Shiwandashan Basin and/or from reworking of the Paleozoic units around the basin. The Lower Triassic strata also contain 260-240. Ma zircons that were likely derived from magmatic rocks located to the south of the basin. The Late Permian marks a significant change in the paleogeography of the Shiwandashan Basin from an older deep marine chert succession to a terrestrial to shallow marine environment receiving an influx of clastic detritus related to uplift and erosion to the south of the basin. The Lower Triassic units within the basin record a further pulse of sediment influx including detritus derived from approximately syn-sedimentary magmatic activity. Yunkai Massif, located in the southeast of the basin, underwent uplift in Late Permian and provided majority detritus for the basin in the Late Permian to Early Triassic. Integration of provenance data with regional geological information, magmatic and metamorphic records to the south of the Shiwandashan Basin suggests the basin was converted from a pre-Late Permian deep marine extensional basin to a Late Permian to Early Triassic foreland basin. Conversion to a foreland basin reflected collision between the South China and Indochina blocks. © 2014 Elsevier Ltd.

Chen M.H.,Chinese Academy of Geological Sciences | Huang Z.Z.,Guangxi Academy of Geophysical Exploration | Li B.,Guangxi Academy of Geophysical Exploration | Huang H.W.,General Academy of Geological Survey of Guangxi
Acta Petrologica Sinica | Year: 2012

The Shedong tungsten and molybdenum deposit in Cangwu County, Guangxi is a quartz-skarn type deposit related to granitoids.Major granitoids are comprised of Caledonian granodiorite, granodiorite-porphyry and Late Yanshanian granite porphyry in mineral district. Caledonian granodiorite and granodiorite-porphyry dominantly exhibit low Si, K, high Na, Al and basic components, thus can be classified to the normal calc-alkaline granite with strongly peraluminous. The rocks are characterized by low REE contents, high LREE/HREE ratios, weakly Eu depletion (SEu =0.62 ∼0.70) , depletion of Ti, Nb, Ta, enrichment of Th, U, Pb, Zr, Hf, low Rb/Sr ratio (0.78) , obviously enrichment of W, Mo, Cu.Geochemical evidences indicate that early Caledonian granodiorite ( -porphyry) are I-type granite, and formed in compression tectonic setting of early collision stage in intra-continent orogenic belt, and associated with W, Mo, Cu mineralization. Late Yanshanian granite porphyry dominantly exhibit high Si, K, low Na, Ca and basic contents, can be defined as the high-moderate potassium calc-alkaline granite with strong peraluminous. The rock is characterized by relative high REE contents, low LREE/HREE ratios, strong Eu depletion (δEu = 0.03 ∼0.06) , depletion of Ti, Ba, K, Eu, more enrichment of Th, U, Sm, Dy, Y, Ho, Yb, Lu, high Rb/Sr ratio (7.56) , clearly enrichment of Sn, Bi, thus it is assigned to Late Yanshanian S-type granite evolved well, and formed in intraplate extension tectonic setting of post-collision, and is related to Sn, Au mineralization.

Yang J.,Wuhan University | Cawood P.A.,University of St. Andrews | Cawood P.A.,University of Western Australia | Du Y.,Wuhan University | And 3 more authors.
Sedimentary Geology | Year: 2012

Whole-rock geochemistry and zircon trace element and U-Pb age data for Late Permian-early Middle Triassic volcanogenic sedimentary rocks in SW China show a change from Large Igneous Province to subduction-related sources immediately before the Permian-Triassic boundary. Zircons from Late Permian samples give identical within-error ages to the adjoining Emeishan Large Igneous Province (LIP). The bulk-rock geochemistry of these Late Permian units shows no depletion in high field strength elements and is similar to the high-titanium basalts of the Emeishan. Six samples of latest Permian-earliest Triassic tuff and two earliest Middle Triassic tuffs samples yield U-Pb zircon ages at of ~. 252. Ma and ~. 247. Ma, respectively. These tuffs and interstratified volcanogenic sedimentary rocks show significant depletion in high field strength elements, akin to magmatic arc-related rocks. Zircons from the tuffs have Nb/Hf, Th/Nb and Hf/Th ratios similar to those from arc/orogenic-related settings and distinct from the zircons from the Late Permian samples which display within-plate/anorogenic characteristics. Our data demonstrate that there is a compositional change of the volcanogenic sediments across the Permian-Triassic boundary in South China. © 2012 Elsevier B.V.

Yu W.,Wuhan University | Wang R.,General Academy of Geological Survey of Guangxi | Zhang Q.,General Academy of Geological Survey of Guangxi | Du Y.,Wuhan University | And 2 more authors.
Journal of Geochemical Exploration | Year: 2014

Two types of bauxite deposits have been discovered in the Fusui area, Guangxi Province, South China. The original Permian bauxite occurs on the unconformity between the Middle Permian Maokou Formation and the Upper Permian Heshan Formation. The Salento-type (or karstic accumulational) bauxite is composed of the Quaternary incompact sediments that transformed from the original Permian bauxite. Samples were collected from two drilling cores and two profiles in study area, and field observations and mineralogical and geochemical analyses are integrated to reconstruct the metallogenic process from the original Permian bauxite to the Quaternary Salento-type bauxite. In the Permian lateritization and bauxitization, alkali metals and alkali earth metals are preferentially dissolved and removed from the parent rocks due to the intense chemical weathering; other major elements from the original profile are also depleted, as shown by the mass-change calculation result. Elements with a low mobility (e.g., Ti, Zr, Cr, Nb and V) are positively correlated with Al. When the bauxite deposit is affected by the modern groundwater system in the near-surface environment, the elements in the deposit display varied mobility due to the leaching intensity and the drainage conditions. After the bauxite ore horizons are exposed in the surface environment, impurities (primarily Fe and Si) are removed from the profiles, and Al is enriched; the clay minerals (kaolinite and chlorite) in the ores convert into aluminum minerals (boehmite and diaspore). When the exposed original bauxite orebodies break down and accumulate as bauxite gravel in the modern karstic depressions, the Salento-type bauxite deposits appear, and the ore quality is further improved. The intensity of the leaching process and the drainage conditions are the most important factors that control the ore quality during the ore-forming process that converts the original bauxite into the Salento-type bauxite. © 2014 Elsevier B.V.

Huang H.,Wuhan University | Huang H.,Chengdu University of Technology | Du Y.-S.,Wuhan University | Yang J.-H.,Wuhan University | And 4 more authors.
Lithos | Year: 2014

The Linghao Formation is composed of interbedded clastic and basaltic rocks in the Napo region of Youjiang Basin, Southwest China. The basalts are geochemically divided into low-Ti and high-Ti groups. Relative to the high-Ti group, the low-Ti group exhibits lower Ti/Y ratios, higher ratios of Th/Nb and Th/La, more significant negative Nb-Ta anomalies and lower εNd(t) values (-7.26 to +0.29). The high-Ti group is characterized by primitive mantle normalized OIB-like incompatible element patterns. These geochemical signatures are also comparable to those of the Emeishan high-Ti and low-Ti basalts in Southwest China, respectively, and support a view that both of the low-Ti and high-Ti basalts at Napo are part of the Emeishan large igneous province (ELIP). The geochemical features imply that the high-Ti basalts could have been generated by low degree of melting of the garnet peridotite, whereas the low-Ti basalts may be derived from an EMII-like source. All clastic rocks exhibit no Nb-Ta anomalies on primitive mantle normalized elemental diagrams. Detrital zircons from clastic rocks yield U-Pb ages of ~260Ma and have a geochemical affinity to within-plate-type magmas, implying a sedimentary source dominated by the ELIP. Most clastic rocks from the upper part of the Linghao Formation show higher TiO2 contents and lower ratios of Al2O3/TiO2, Th/Sc, and Zr/Sc than those from the lower part. The former were related to the Emeishan high-Ti basaltic rocks, whereas the latter may have mixed felsic source compositions. In terms of chemostatigraphic correlation, we propose that the eruption of the ELIP may be more complex than previously thought and a prolonged and punctuated history of ELIP formation may exist in the Youjiang Basin. © 2014 Elsevier B.V.

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