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It is assumed that the central part of Junggar underwent continuous deposition from the Mesozoic to Cenozoic, but few data are available from deep well to support this hypothesis. The tectonic settings of the late Paleozoic central region have been used to focus on the folded mountain belts around the Junggar Basin. In this study, petro-geochemical and lithological characters of drilling samples in Upper Carboniferous-Lower Permian of the Central Junggar Basin were discussed, through core and thin section identification, major and trace element analyses. The results reveal the following: (1) Brown tuff is present in various layers of these well, suggesting a eruption environment around sea/lake; (2) the volcanic rocks in the study area are mainly included alkali-basalts, andesites and small amounts of dacite. Most samples characterized by high alkali that likely erupted from thickened crust, (3) suggesting a continental tectonic setting, and the Central Junggar Basin was part of a continental tectonic setting during the late Paleozoic. These results suggest that there may be a more ancient continental basement below the Carboniferous volcanic rocks. Keywords: Volcanic rocks, Geochemistry, Continental basement, Tectonic settings, Upper Carboniferous-Lower Permian, Junggar Basin

By using data such as lithology, thin sections, sedimentary structure, particle size, logging facies signs, mercury intrusion, porosity and permeability from 34 wells, 11 types of sedimentary microfacies were divided in this study. Upon analysis, sedimentary microfacies exert significant control on reservoirs, and high quality reservoirs are primarily developed with the following sedimentary microfacies: gray sandy conglomerate in underwater distributary channels microfacies of fan delta fronts sub-facies, river-estuary dams and gray sandstones of distal bars on the front edge of the fan delta that have strong hydrodynamic conditions and good stability. Relatively good reservoirs are primarily distributed in the braided channel in fan-delta plains with brown sandy conglomerates, main channel of underwater distributary channels on the front edge of the fan delta with gray conglomerates and underwater distributary channel ends on the front edge of the fan delta with gray fine sandstones. With the stable tectonic background, Triassic sedimentary microfacies in the Mahu sag control the distribution and development of reservoirs. Therefore, sites of high quality reservoirs can be predicted by sedimentary microfacies, and this study provides guidance for oil and gas exploration. Keywords: Microfacies, Reservoir, Mahu sag, Junggar Basin

Field outcrop observation, drilling core description, thin-section analysis, SEM analysis, and geochemistry, indicate that Dixi area of Carboniferous volcanic rock gas reservoir belongs to the volcanic rock oil reservoir of the authigenic gas reservoir. The source rocks make contact with volcanic rock reservoir directly or by fault, and having the characteristics of near source accumulation. The volcanic rock reservoir rocks mainly consist of acidic rhyolite and dacite, intermediate andesite, basic basalt and volcanic breccia: (1) Acidic rhyolite and dacite reservoirs are developed in the middle-lower part of the structure, have suffered strong denudation effect, and the secondary pores have formed in the weathering and tectonic burial stages, but primary pores are not developed within the early diagenesis stage. Average porosity is only at 8%, and the maximum porosity is at 13.5%, with oil and gas accumulation showing poor performance. (2) Intermediate andesite and basic basalt reservoirs are mainly distributed near the crater, which resembles the size of and suggests a volcanic eruption. Primary pores are formed in the early diagenetic stage, secondary pores developed in weathering and erosion transformation stage, and secondary fractures formed in the tectonic burial stage. The average porosity is at 9.2%, and the maximum porosity is at 21.9%: it is of the high-quality reservoir types in Dixi area. (3) The volcanic breccia reservoir has the same diagenetic features with sedimentary rocks, but also has the same mineral composition with volcanic rock; rigid components can keep the primary porosity without being affected by compaction during the burial process. At the same time, the brittleness of volcanic breccia reservoir makes it easily fracture under the stress; internal fracture was developmental. Volcanic breccia developed in the structural high part and suffered a long-term leaching effect. The original pore-fracture combination also made volcanic breccia reservoir more easily leached by fresh water or groundwater, leading to secondary erosion pores. Volcanic rock weathering obviously has control on reservoir properties, and while the thickness of the weathering crust is 200–300 m, the properties of volcanic rock reservoir are the best. This is attributed mainly to the period during and after the volcano eruption, in which tectonism made the brittle volcanic rock develop a large number of fractures and micro cracks. This has led to the increased permeability of volcanic rock reservoir, the weathering and leaching effect of volcanic rock diagenetic late phase (which also formed lots of secondary pores), and greatly improved reservoir conditions. The overlying Permian Wutonggou formation mudstone provided high-quality cap rock for oil and gas accumulation.

Accurate evaluation of the heavy metal contamination caused by oil spills is more urgent than that of organic pollution since heavy metals are toxic and persistent. This study applies bulk geochemical parameters and hydrocarbon compositions to explore heavy metal contamination caused by oil spills. The contents of six heavy metals (Cu, Pb, Zn, Cr, Ni, and Co), total organic carbon, aliphatic hydrocarbons, and grain size were measured in 50 subsurface sediment samples obtained from an area affected by oil spills in the Bohai Sea. The values of the contamination factor (CF), the geo-accumulation index (Igeo), and the enrichment factor (EF) indicate moderate contamination with the six investigated heavy metals at most of the sampling sites. Riverine inputs, oil spills, and airborne dust are the three main sources of the heavy metals, and oil spills are the significant source of heavy metal contamination in the areas. The distributions of the mean grain size (Mz) and the contents of unresolved complex mixture (UCM) and Cr suggest that crude oil migrates from deep hydrocarbon reservoirs through geological faults and seeps through coarse-grained sediments until it reaches fine-grained sediments. The spilled oil contributes appreciable amounts of heavy metals to the sediments at the oil-contaminated sites. At these sites, the heavy metals from oil spills overprinted on those contributed by terrigenous materials, which are the predominant source of metals in the subsurface sediments in the areas affected by oil spills.

The sedimentary rocks of the Dishuiquan Formation represent an important potential source for volcanic rock reservoirs and record the transition of the depositional environment from marine to terrestrial during paleo-Junggar oceanic subduction. The source rock potential and paleoenvironment of mudstones from Dishuiquan Formation in Eastern Junggar, were determined by organic petrography, Rock-Eval, molecular and stable carbon (δ 13 C) analyses. TOC, S 2 , and hydrogen index (HI) values suggest a fair to good organic richness in mudstone samples from the C-2 well. Moreover, an early mature to mature state for all the samples is inferred based on the Rock-Eval and biomarker parameters. The maceral composition, molecular geochemistry and carbon isotopic results for kerogen reveal that all the mudstone samples are characterized by a mixed organic matter assemblage (Types II–III) with relatively high percentages of terrigenous organic matter. The low to intermediate values of Pr/Ph and the high abundances of β-carotene and gammacerane indicate the presence of a dysoxic, reducing, high-salinity sedimentary environment during the deposition of the Dishuiquan Formation. Numerous parameters derived from the organic geochemical analyses indicate that the terrigenous organic matter increased with decreasing salinity and oxidation in the sedimentary environment. This study concludes that a warm, wet climate provided a continuous fluvial input of terrigenous plant debris and fresh water. The organic geochemical data, combined with the tectonic setting, reveal a restricted, semi-closed marine depositional environment during the deposition of the Dishuiquan Formation in the early Carboniferous.

This study investigates the mechanism of dolostone formation and establishes a dolomitization model in the Permian strata on the northwestern margin of Junggar Basin, China. Dolomitic rock samples are collected from the Permian Fengcheng Formation in Urho area and then characterized by petrological, mineralogical, carbon and oxygen isotope, and trace element geochemical analyses. Results show that the major types of dolomitic rocks include dolomitic mudstone, dolomitic siltstone, dolomitized tuffaceous siltstone, and dolomitized tuffaceous mudstone. The dolomitized rocks are dominated by euhedral or subhedral powder- and fine-crystal dolomites formed by replacement lacustrine argilla-calcareous and siliceous (tuffaceous) components and commonly filled with residual and late calcite cements. The parameters of dolomitic rocks show great variations, including the V/Ni ratio (1.02–4.88), Sr content (95.9–783.6 μg/g), Mg/Ca ratio (0.68–5.13), degree of ordering (0.39–1.00), δ18OPDB (−14.8‰ to 3.2‰), and δ13CPDB (−1‰ to 5.2‰). The dolomitic rocks have multi-stage origins and were formed in a semi-closed continental brackish-saltwater bay with weak hydrodynamic processes, deep water bodies, and relatively quiet conditions. In the Permian depositional stage, a combination of complex tectonic activities, fault development, hot subtropical climate, and frequent volcanic activities provided not only Mg2+ source for dolomitization but also channels for rapid flow and seepage of Mg-rich fluids. The origins of dolostones in the study area include penecontemporaneous dolomitization, burial dolomitization, and hydrothermal dolomitization. This study lays a foundation for further studies on dolomite formation and dolomite reservoir, and provides effective methods for researching complex dolostone (tuffaceous, shale and silty dolomite) formation.

This paper presents petrology, mineralogy, and elemental geochemistry research on diagenesis, formation environment, and source material of the Upper Ganchaigou Formation of clastic rocks in the Eboliang III structural belt on the northern margin of the Qaidam basin. Point-line contacts of particles and directional alignment of feldspars show relatively intense compaction. Clays have high content with mean up to 35.03 % of total cement content, mainly consisting of illite, chlorite, and mixed-layer illite–smectite. Carbonate cements contain large amounts of calcite and little dolomite. Carbon and oxygen isotope composition of carbonate cement present δ13C values between −6.8 and −4.0 ‰ (mean −5.0 ‰) and δ18O values between −11.1 ‰ and −5.4 ‰ (mean −8.7 ‰). According to δ13C and δ18O calculations, ancient salinity Z values are distributed between 108.34 and 114.89 (mean 112.77), and the formation temperature of carbonate cement is between 43.36 and 77.84 °C (mean 62.30 °C). From the analysis of major elements, trace elements, and organic carbon, the diagenetic stage of the Upper Ganchaigou Formation is regarded as the B period of the early diagenesis stage or the A period of the middle diagenesis stage. The sedimentary environment is evolved from dry and cold freshwater and brackish water to warm and wet freshwater during deposition of the Upper Ganchaigou Formation.

Late Paleozoic magmatic rocks (including basic dykes, basaltic andesite, rhyolite, keratophyre and syenite-porphyry with minor tuff) are widespread in the western margin of the East Junggar terrane. In-situ zircon U–Pb dating and Hf isotope analyses were carried out for these magmatic rocks from the Baijiangou and Zhangpenggou localities of East Junggar, integrating with geochemical data, to investigate their tectonic evolution as well as crustal accretionary process of this region in the Late Paleozoic. Inherited zircons from basic dykes range in age from 435 Ma to 300 Ma. The Zhangpenggou rhyolite and keratophyre have typical arc-like geochemical signatures and were formed in the Early Carboniferous (332 Ma and 336 Ma, respectively), suggesting they are products of subduction-related magmatism. The Baijiangou rhyolites were formed in the Late Carboniferous (315 Ma and 323 Ma) and their formation ages are similar to those of the syenite-porphyries (307 Ma and 312 Ma). The Hf model ages and the formation ages of zircons from these magmatic rocks are alike, with positive e Hf (t) values vary from + 0.7 to + 16.6, implying that voluminous growth of juvenile crust happened in the East Junggar terrane during the Late Paleozoic. The absence of Precambrian inherited zircons in basic dykes indicates the lack of Precambrian basement beneath the East Junggar terrane. Taking geochronological studies on regional ophiolites into account, the East Junggar terrane is considered as a Devonian–Carboniferous oceanic island arc which has been continuously accreted to the southern active margin of the Siberian Craton since the Early Carboniferous.

By analyzing the composition of n-alkane and macroelements in the surface sediments of the central South Yellow Sea of China, we evaluated the influencing factors on the distribution of organic matter. The analysis indicates that the distribution of total organic carbon (TOC) was low in the west and high in the east, and TOC was more related to Al2O3 content than medium diameter (MD). The composition of n-alkanes indicated the organic matter was mainly derived from terrestrial higher plants. Contributions from herbaceous plants and woody plants were comparable. The comprehensive analysis of the parameters of macroelements and n-alkanes showed the terrestrial organic matter in the central South Yellow Sea was mainly from the input of the modern Yellow River and old Yellow River. However, some samples exhibited evident input characteristics from petroleum sources, which changed the original n-alkanes of organic matter in sediments.

In this paper, the diurnal dynamics of photosynthetic rate (Pn) and transpiration rate ( Tr) of four years planted alfalfa under dry farming, as well as those of photosynthetic active radiation (PAR) , CO2 concentration in field ( Ca ) , relative humidity (RH) and air temperature ( Ta) were measured, and the relationships between the diurnal dynamics of Pn, Tr and climatic factors were analyzed by correlation coefficient, path coefficient, and decision coefficient analyses. The results showed that T. had the greatest effect on the diurnal dynamics of Pn , while RH, PAR and C, affected P,, mainly through their acting on Ta PAR had the greatest effect on the diurnal changes of Tr, and RH, Ta and Ca affected Tr indirectly by acting on PAR. For the characteristics of photosynthesis and transpiration, PAR was the primary determining factor, and Ta was the main limiting factor.