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Braided delta is an important reservoir of oil and gas which is enriched in sand with good physical properties. Consequently, study of its sedimentary characteristics and sedimentary sequence has important guiding significance for the oil and gas exploration. In this study, sedimentary model and stratigraphy sequence for Wulabo Formation are established through outcrop measure, analysis of microfacies and sedimentary characteristics in southern margin of Junggar Basin. The results show that the main subfacies of Wulabo Formation is braided delta plain and front, the microfacies is delta plain distributary channel, subaqueous interdistributary channel, subaqueous distributary channel, mouth bar etc. The sandbody in braided delta front is significant reservoir for oil and gas since it has fine particle size, well sorting and rounding. Through lithofacies division, Wulabo Formation can be divided into 8 typical lithofacies and 4 typical litho-facies combination. The grain size probability cumulative of distributary channel is made up of saltation and suspension, moreover, the saltation of subaqueous distributary channel can be divided into two sections and the grain size probability cumulative of mouth bar is composed of multiple sections which is more complicated.Based on the study of sedimentary characteristics, lithofacies and grain size, the braided river delta depositional model of Wulabo Formation is established, which can provide guidance for oil and gas exploration in this area. [ABSTRACT FROM AUTHOR]

Located between the Tarim, Kazakhstan, and Siberian plates, the West Junggar terrane is a key component of the Paleozoic Central Asian Orogenic Belt (CAOB) with widespread late Paleozoic igneous rocks. In this paper, we report petrological, geochronological, and geochemical data for selected granitoids from the West Junggar. Based on geochronology, the I-type and A-type granites were formed predominantly at 347.9-319.0 Ma and at 321.4-290 Ma respectively. The early-stage I-type granites are characterized by low SiO2, Na2O, and K2O contents with Na2O/K2O ratios > 1 and are metaluminous to weakly-peraluminous. They are enriched in large ion lithophile elements (LILE) and in Sr but depleted in high field strength elements (HFSE), with (87Sr/86Sr)i ratios of 0.7028-0.7044 and εNd(t) values varying from + 5.74 to + 7.76. The late-stage I-type granites are characterized by low contents of Si2O and K2O and relatively high contents of FeO, MgO, and Na2O with Na2O/K2O ratios > 1, and are metaluminous to weakly-peraluminous. They are also enriched in LILE and depleted in HFSE with Eu anomalies, (87Sr/86Sr)i ratios of 0.703-0.704, and εNd(t) values varying from + 5.20 to + 8.00. The A-type granites have high SiO2 contents, high K calc-alkaline-shoshonitic affinities, positive εNd(t) values (5.76-7.77), and low initial 87Sr/86Sr ratios (0.7017-0.7045). Along with reported Sr-Nd isotopic data and regional geologic evidence the Early Carboniferous I-type granites are interpreted as products of partial melting of trapped oceanic crust triggered by underplated mantle wedge-derived basaltic magma; the Late Carboniferous-Early Permian I-type granites as derivatives of partially melted trapped oceanic crust; and the A-type granites as resulting from partial melting of trapped juvenile oceanic crust in an extensional regime. The A-type granitoids with high positive εNd(t) values and high Zr-saturation temperatures could be genetically related to a mantle plume or a regional-scale mantle upwelling in the CAOB. [ABSTRACT FROM AUTHOR]