Generation and accumulation of Quaternary shallow gas in eastern Qaidam Basin, NW China

1INTRODUCTION SHALLOW(MOSTLYBIOGENIC)GASACCOUNTSFOROVER20%OFTHEWORLD’SDISCOVEREDGASRESERVES(RICEAND CLAYPOOL,1981;CLAYPOOLANDKAPLAN,1974),AND REPRESENTSONEOFTHEUNCONVENTIONALENERGYSOURCES THATINCREASINGLYATTRACTTHEATTENTIONOFPETROLEUMGEOL OGISTS.NUMEROUS…     

Selenium enrichment in Carboniferous Shales,Britain and Ireland: Problem or opportunity for shale gas extraction?

The Carboniferous Bowland Shale in England, and its correlatives in Ireland, contain anomalously high concentrations of trace elements, including selenium (Se), molybdenum (Mo) and arsenic (As). High levels of these elements reflect high sulphur contents as these elements occur as trace constituents of pyrite. Anomalous Se in particular may have a volcanic provenance, from contemporary volcanic activity and/or drainage from Ordovician volcanogenic sulphide deposits. Following concern over the release of Se and As into groundwater during shale gas extraction in the US, the potential fate of Se and As during any future shale gas extraction from the Bowland Shale merits attention. It is at least an environmental issue that must be managed, but at best it could be an opportunity for extraction of Se in an environmentally sensitive manner.     

Discussion on “sandwich” structures and preservation conditions of shale gas in the South Yellow Sea Basin

In order to make a breakthrough in Mesozoic-Paleozoic shale gas exploration in the South Yellow Sea Basin, a comparison of the preservation conditions was made within the Barnett shale gas reservoirs in the Fortworth Basin, the Jiaoshiba shale gas reservoirs in Sichuan Basin and potential shale gas reservoirs in Guizhou Province. The results show that the “Sandwich” structure is of great importance for shale gas accumulation. Therein to, the “Sandwich” structure is a kind of special reservoir-cap rock assemblage which consist of limestone or dolomite on the top, mudstone or shale layer in the middle and limestone or dolomite at the bottom. In consideration of the Mesozoic-Paleozoic in the Lower Yangtze, and Laoshan Uplift with weak Paleozoic deformation and thrust fault sealing on both flanks of the Laoshan Uplift, a conclusion can be drawn that the preservation conditions of shale gas probably developed “Sandwich” structures in the Lower Cambrian and Permian, which are key layers for the breakthrough of shale gas in the South Yellow Sea. Moreover, the preferred targets for shale gas drilling probably locate at both flanks of the Laoshan Uplift.     

The geochemistry of platinum group elements in marine oil shale—A case study from the Bilong Co oil shale,northern Tibet,China

The Bilong Co oil shale zone is located in the South Qiangtang depression. This zone, together with the Shengli River-Changshe Mountain oil shale zone in the North Qiangtang depression, northern Tibet plateau, represents the potentially largest marine oil shale resource in China. Seventeen samples including oil shale and micritic limestone were collected from the Bilong Co oil shale area to determine the concentrations, distribution patterns, occurrences and origins of platinum group elements (PGEs) in marine oil shale. The oil shale samples from the Bilong Co area exhibit very low total PGE contents ranging from 1.04 to 2.96 ng/g with a weighted mean value of 1.686 ng/g, while the micritic limestone samples from the Bilong Co area exhibit a little lower PGE value ranging from 0.413 to 1.11 ng/g. PGEs in oil shale samples are characterized by high contents in Pd (average 0.79 ng/g), Os (average 0.123 ng/g) and Pt (average 0.644 ng/g) compared with Ru (average 0.068 ng/g), Rh (average 0.033 ng/g) and Ir (average 0.026 ng/g). The highest values for individual PGEs are not uniformly distributed in the section. Clearly, the PGEs are generally enriched in the oil shale samples near the boundary between micritic limestone and oil shale.The individual PGEs in oil shale samples from the Bilong Co area exhibit various modes of occurrence. Ruthenium and Pt occur mainly in pyrite, while Pd is associated mainly with organic matter and Mg-minerals. Rhodium and Os are controlled mainly by pyrite and organic matter. Iridium is present mainly in other Fe-bearing minerals, rather than pyrite. The PGEs in the Bilong Co oil shale are mainly of seawater origin and possibly influenced by terrigenous supply.     

The petrologic characteristics of carbonaceous shale and its significance of shale (las. Lucaogou formation,southern junggar basin北大核心CSCD

In the margin of southern Junggar basin, there is a potential of shale gas with the upper Permian l.uoaogou Formation. For a detailed understanding and evaluation with the shale gas geological characteristics of l.uoaogou Formation, the petrologic characteristics of the carbonaceous shale was researched, and the results show that: ( 1 ) in l.ucaogou Formation, the mean value of the brittle mineral percentages of the upper member, the middle member and the lower member are all more than 50%, but it is the highest in the middle member, and it is second in the lower member. At the same time, in the lower member, the mean value of the brittle mineral percentages is significantly lower than the upper and middle members; (2)the main brittle mineral in each member are quartz+feldspar, and there is a same change rule between the quartz+feldspar content and the total brittle mineral, that is; The quartz + feldspar content is the highest in the middle member, followed with the lower member, and it is obviously low in the upper member; (3 )from the lower member to the upper member, the content of carbonate in the carbonaceous shale are gradually reduced; (4) the clay mineral content of the carbonaceous shale of the upper member is far higher than the lower and middle members. And the clay mineral in each member are mainly constituted with illite and illite/Mongolia inter layer; ( 5 ) in the northern margin of the western part of the Bogda Mountain, south Junggar Basin, the brittle mineral content of the carbonaceous shale generally present as a decreasing trend from west to east to Fu Rang.     

Petrogenesis and W-Mo fertility indicators of the Gaojiabang “satellite” granodiorite porphyry in southern Anhui Province,South China

The Gaojiabang W-Mo mineralized granodiorite porphyry occurs as a “satellite” intrusion on the northern margin of the Qingyang-Jiuhua pluton in southern Anhui Province, South China. The geology, mineral and whole-rock geochemistry of the granodiorite porphyry is I-type and formed from a reduced melt. The Gaojiabang mineralized granodiorite porphyry was derived from the transition zone between the lower crust and upper mantle, and underwent high-degree fractional crystallization during emplacement. There is no obvious genetic relationship between the granodiorite porphyry and the granodiorite pluton of the Qingyang-Jiuhua plutonic complex. The key characteristics of the W-Mo mineralized Gaojiabang granodiorite porphyry include: 1) small volume (<0.5 km³), 2) an abundance of hornblende (>5 vol%), 3) low ∑REE concentrations (145.50–159.46 ppm) accompanying weak negative Eu anomalies (0.85–0.94), 4) high differentiation-indices degree and water contents, and 5) low oxygen fugacity. These criteria can be used to identify potential W-Mo mineralized intrusions in southern Anhui Province, South China.     

Pyrite characteristics and shale gas significance of the Niutitang Formation in Cengong area,Guizhou ProvinceSCIEI北大核心CSCD

黄铁矿特征研究可为页岩沉积环境恢复与页岩气富集保存规律预测提供依据。以贵州岑巩地区岑页1井牛蹄塘组为研究对象,基于岩心、薄片、扫描电镜及微量元素、硫同位素地球化学,确定牛蹄塘组页岩沉积环境及页岩气富集地质条件。研究表明,牛蹄塘组页岩黄铁矿发育为草莓状、自形-半自形及他形(主要为胶状他形)三种形态,不同形态的黄铁矿形成于不同沉积环境,草莓状黄铁矿形成于缺氧还原环境,自形-半自形黄铁矿形成于贫氧环境,胶状他形黄铁矿指示沉积过程有热液活动的参与。测试井牛蹄塘组整体处于较开放的沉积水体,上段为含氧-贫氧环境,硫同位素整体变轻且发生负漂;中段为较缺氧环境,硫同位素跨度大且发生正漂;下段为还原性更强的沉积环境,硫同位素小幅度负漂。黄铁矿含量与有机质富集密切相关,与黄铁矿有关的孔隙为页岩气吸附、保存及运移提供载体,且草莓状黄铁矿指示的缺氧硫化环境更利于有机质保存。研究工作系统梳理了黄铁矿对牛蹄塘组页岩沉积环境及储层页岩气富集的指示作用,为页岩气勘探提供指示。     

Organochlorine pesticides in marine environment of Quanzhou Bay, Southeast China

As one of the most important buildup of persistent organic pollutants （POPs）, organochlorine pesticides （OCPs） have received more and more attention. Samples including sediments, water and marine products were collected. In the lab, nineteen types of organochlorine pesticides were tested using GC-ECD following US-EPA 8080A method. In the top sediments, the concentration of HCHs was 0.1-3.08 ng/g and the concentration of DDTs was 3.53-75.83 ng/g. In the bottom sediments, the concentration of HCHs was 0.1-3.59 ng/g and the concentration of DDTs was 1.56-81.68 ng/g. The concentration ranges of HCHs and DDTs in sea water were 1.31-9.96 ng/L and 0.78-6.51 ng/L, respectively. And the concentration ranges of HCHs and DDTs in land surface water were 7.04-14.08 ng/L and 3.82-9.66 ng/L, respectively. The residual levels of HCHs and DDTs in marine product samples ranges from 0.1 to 0.6 ng/g and from 0.57 to 85.02 ng/g, respectively. In this thesis, discussions of DDTs and HCHs in sediment, water and marine product samples were made. The following are the main results and conclusions： A general decreasing trend was found from the inner to outer sectors of the Bay for both sediment and water samples. The distribution of OCPs depends greatly on the different properties pertaining to them. The topography, redox, hydrodynamic condition as well as other factors also play an important role in controlling the distribution and fate of OCPs.     

Geochronology and geochemistry of Mesozoic mafic–ultramafic complexes in the southern Liaoning and southern Jilin provinces,NE China: Constraints on the spatial extent of destruction of the North China Craton

LA–ICP–MS zircon U–Pb ages, geochemical and Sr–Nd–Pb isotope data are presented for mafic–ultramafic complexes from the southern Liaoning–southern Jilin area with the aim of determining the nature of the Mesozoic lithospheric mantle and to further constrain the spatial extent of destruction of the North China Craton (NCC). The complexes consist of olivine-websterite, gabbro, dolerite, and gabbro-diorite. Zircons from the complexes show typical zoning absorption, are euhedral–subhedral in shape, and yield high Th/U ratios (1.23–2.87), indicating a magmatic origin. Zircon U–Pb age data indicate that they formed in the Early Cretaceous (129–137 Ma). Geochemically, they have SiO₂ = 44.3–49.8%, MgO = 6.8–26.5%, Cr = 102–3578 ppm, and Ni = 31–1308 ppm, and are characterized by enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depletion in high field strength elements (HFSEs) and heavy rare earth elements (HREEs), as well as a wide range of Sr–Nd–Pb isotopic compositions [(⁸⁷Sr/⁸⁶Sr)i = 0.70557–0.71119; ε_Nd (t) = ?5.4 to ?20.1; (²⁰⁶Pb/²⁰⁴Pb)i = 15.13–17.85; Δ7/4 = ?11.49 to 16.00; Δ8/4 = 102.64–203.48]. Compared with the southern Liaoning mafic–ultramafic rocks, the southern Jilin mafic–ultramafic rocks have high TiO₂ and Al₂O₃ contents, high ε_Nd (t) values, low (La/Yb)_N values, low initial ⁸⁷Sr/⁸⁶Sr ratios, and low radiogenic Pb isotopic compositions. These findings indicate that the primary magmas of the southern Jilin complexes were derived from lithospheric mantle that was previously metasomatized by a melt derived from the delaminated ancient lower crust, whereas the primary magmas of the southern Liaoning complexes originated from partial melting of a lithospheric mantle source that was previously modified by melt derived from the broken-off Yangtze slab. Therefore, the lateral extent of the NCC destruction should include the southern Liaoning–southern Jilin area.     

The impact of over 100 years of wildfires on mercury levels and accumulation rates in two lakes in southern California,USA

In southern California, USA, wildfires may be an important source of mercury (Hg) to local watersheds. Hg levels and Hg accumulation rates were investigated in dated sediment cores from two southern California lakes, Big Bear Lake and Crystal Lake, located approximately 40-km apart. Between 1895 and 2006, fires were routinely minimized or suppressed around Big Bear Lake, while fires regularly subsumed the forest surrounding Crystal Lake. Mean Hg concentrations and mean Hg accumulation rates were significantly higher in Crystal Lake sediments compared to Big Bear Lake sediments (Hg levels: Crystal Lake 220 ± 93 ng g⁻¹, Big Bear Lake 92 ± 26 ng g⁻¹; Hg accumulation: Crystal Lake 790 ± 1,200 μg m⁻² year⁻¹, Big Bear 240 ± 54 μg m⁻² year⁻¹). In Crystal Lake, the ratio between post-1965 and pre-1865 Hg concentrations was 1.1, and several spikes in Hg levels occurred between 1910 and 1985. Given the remote location of the lake, the proximity of fires, and the lack of point sources within the region, these results suggested wildfires (rather than industrial sources) were a continuous source of Hg to Crystal Lake over the last 150 years.     

Mobility and accumulation of selenium and its relationship with other heavy metals in the system rocks/soils–crops in areas covered by black shale in Korea

The purpose of this study is to investigate the enrichment level and dispersion patterns of Se and associated elements in rocks, soils and crops which were collected in the Dukpyung and the Chubu areas covered with black shales of the Okchon Group in Korea. Rock and soil samples were analyzed for Se including multiple elements by ICP, ICP-MS and INAA, and crop samples by INAA. Soil pH and loss-on-ignition (LOI) were also measured.     

Mesozoic–Cenozoic stress field magnitude in Sichuan Basin,China and its adjacent areas and the implication on shale gas reservoir: Determination by acoustic emission in rocks

The Sichuan Basin is one of the vital basins in China, boasting abundant hydrocarbon reservoirs. To clarify the intensity of the tectonic stress field of different tectonic episodes since the Mesozoic and to identify the regional dynamic background of different tectonic movements in the Sichuan Basin and its adjacent areas, the characteristics of the acoustic emission in rocks in different strata of these areas were researched in this paper. Meanwhile, the tectonic stress magnitude in these areas since the Mesozoic was restored. The laws state that the tectonic stress varied with depth was revealed, followed by the discussion of the influence of structural stress intensity on structural patterns in different tectonic episodes. These were conducted based on the paleostress measurement by acoustic emission method and the inversion principle of the stress fields in ancient periods and the present, as well as previous research achievements. The results of this paper demonstrate that the third episode of Yanshanian Movement (Yanshanian III) had the maximum activity intensity and tremendously influenced the structural pattern in the study area. The maximum horizontal principal stress of Yanshanian III varied with depth as follows: 0.0168 x + 37.001 (MPa), R² = 0.8891. The regional structural fractures were mainly formed in Yanshanian III in Xujiahe Formation, west Sichuan Basin, of which the maximum paleoprincipal stress ranging from 85.1 MPa to 120.1 MPa. In addition, the law stating the present maximum horizontal principal stress varies with depth was determined to be 0.0159 x+10.221 (MPa), R²=0.7868 in Wuling Mountain area. Meanwhile, it was determined to be 0.0221 x+9.4733 (MPa), R²=0.9121 in the western part of Xuefeng Mountain area and 0.0174 x+10.247 (MPa), R²=0.8064 in the whole study area. These research results will not only provide data for the simulation of stress field, the evaluation of deformation degree, and the prediction of structural fractures, but also offer absolute geological scientific bases for the elevation of favorable shale gas preservation.     

Late Quaternary marine deposition in New South Wales and southern Queensland — An evolutionary model

From new data on coastal and continental shelf morphology, sediments, stratigraphy and chronology, it is possible to formulate a general model of late Quaternary marine sedimentation, for New South Wales and southern Queensland. This model integrates various factors influencing deposition in coastal and shelf environments, in relation to glacio‐eustatic sea level oscillations.

The model involves several components, including (i) very slow to negligible continental margin subsidence during the Quaternary, (ii) an inherited geomorphic framework; (iii) oscillations of sea level of c 100 m amplitude every 100 000 years, with interglacial high sea levels being close to present and only the Last Interglacial being significantly higher; and (iv) a wave climate that induces a potential south to north littoral sand transport at all sea level positions.

Terrigenous sediment that is moved from the hinterland through embayments to the shelf is either stored as barrier, estuarine or inner shelf deposits, or lost to depositional sinks on the continental slope or into coastal dune fields. Over many glacial‐interglacial cycles, sand has been progressively moved northward and has accumulated in vast aeolian sand deposits in southern Queensland. Littoral sand transport was especially effective during sea levels lower than present. The relatively shallow and lower gradient shelf north of Newcastle (33°S) has encouraged preservation at the coast of a wide range of depositional morphologies, including Pleistocene barriers, whereas the steeper southern shelf has induced net sediment loss seawards and shoreline erosion, excpt in the Holocene. To account for Holocene barrier development in the southern region, the model invokes reworking of sand deposits stranded high on the inner shelf at the end of the Pleistocene Epoch. These were in disequilibrium with Postglacial marine processes that operated at a lower level of the sea than did those during the Last Interglacial maximum.     

Heavy metals contamination and assessment in gas station dust of Xi’an,a mega-city of China

The dust samples from 30 gas stations located in Xi’an are analyzed for Mn, Ni, Co, Cr, Cu, Cd, Pb and Zn by using atomic absorption spectrometry. The concentration, spatial distribution, source and the contamination levels provide scientific basis for urban planning and environmental renovation in Xi’an. The results indicate that the mean values of Ni, Cr, Co, Cu, Pb, Zn and Cd in the dust are 1.15, 1.19, 8.13, 3.94, 4.42, 5.09 and 15.62 times higher than the corresponding background values of Shaanxi soil, respectively. The high concentration of heavy metals is located in the inner and second ring road of Xi’an, China. Furthermore, the contents of metals in the south are higher than in the north. In addition, the concentrations of the gas station dust metals in the west are higher than in the east, particularly in the southwest. Three main sources of heavy metals of gas station dusts are identified in Xi’an. Mn and Ni mainly originate from a natural source; Cr, Cu, Pb, Cr and Zn mainly originate from traffic flow; and Co is mainly from industrial sources. The results of the potential ecological risk assessment indicate that the potential ecological risk index (RI) of Co is moderate; Cd is very high ecological risk, and the other analyzed metals belong to low ecological risk. The mean RI value of eight heavy metals in the gas station dusts from Xi’an is considerable ecological risk.     

Re–Os age of non-mineralized black shale from the Kupferschiefer, Poland, and implications for metal enrichment

Six samples of non-mineralized black shale from a Kupferschiefer section in the northern part of the Polish Zechstein Basin (Zdrada IG-8 drill hole: 1026.16–1026.90 m) were studied for Re–Os isotopes and selected major and trace elements. These black shales, averaging 5.82 wt.% C_org and 1.69 wt.% S_tot, display very low base metal values (up to 106 ppb Cu, 792 ppb Pb, and 144 ppb Zn) and have abundances of 64–1376 ppb Re and 0.37–1.25 ppb Os, with a ¹⁸⁷Os/¹⁸⁸Os ratio of 6.95–22.5. The regression of all Re–Os data yields an age of 247 ± 20 Ma, which is within the range of uncertainties of previous Rb–Sr and K–Ar geochronological studies. The scatter in the Re–Os data can be explained in terms of fluctuations in sedimentary conditions, i.e., restricted basin with terrestrial influence.     

Methane adsorption in the low–middle-matured Neoproterozoic Xiamaling marine shale in Zhangjiakou,Hebei

The adsorption capacity of high–over-matured shale has been widely investigated, but the adsorption capacity and the main factors influencing low–middle-matured, type II kerogen-containing, and organic-rich marine shale have been rarely explored. This research conducts organic geochemistry, mineralogical composition, adsorption isotherm tests to reveal the adsorption and main influencing factors of the different geochemistry characteristics, mineralogical compositions, temperature and pressure conditions of the low–middle-matured Neoproterozoic Xiamaling marine shale in Zhangjiakou, Hebei. The investigated shale is in a low–middle maturity stage, contains type II kerogen and is rich in organic matter. The results show that the total organic carbon (TOC) content of the Xiamaling shale is positively correlated with the methane adsorption capacity, which is the most important influencing factor on the adsorptive property of shale. The methane adsorption capacity first decreases to the minimum value as the temperature reaches 360°C equivalent Ro (EqRo = 1.0%), then increases and reaches the maximum value at 620°C (EqRo = 3.28%) and finally decreases again as the temperature rises at the last simulation stage. The mineral components exhibit an insignificant influence on the methane absorbability because of organic-matter coatings. The TOC-normalised methane adsorption capacity is positively correlated with the illite–smectite and clay-mineral contents but shows no significant correlation with brittle minerals, such as quartz. Soluble organic matter and kerogen caused the methane dissolution and adsorbtion, respectively. The strong dissolution property of the soluble organic matter is the most important cause of the larger adsorption capacity of the original shale compared with that of the residual samples. Moreover, the methane adsorption capacity of the Xiamaling shale decreases with increasing temperature, and increases with pressure below the critical pressure but decreases exceeding the critical pressure.     

Study on indium occurrence state and enrichment patterns in the Xianghualing Sn-Pb-Zn orefield in southern HunanSCIEI北大核心CSCD

In作为一种分散元素,通常极难形成独立矿床,而主要以伴生组分的形式赋存在锡多金属矿床中。香花岭矿田蕴藏着丰富的Sn、Pb、Zn等矿产资源,是我国潜在的In资源基地,但目前该矿田中In的赋存状态、分布规律及成矿潜力尚不清楚。鉴于此,本文以香花岭矿田3个典型锡多金属矿床(新风、铁砂坪、茶山)为研究对象,在野外地质及矿相学观察的基础上,采用ICP-MS、EPMA和LA-ICP-MS开展了全岩地球化学和闪锌矿元素地球化学研究。结果表明,In主要以类质同象的形式富集在闪锌矿中,可能的替代方式为In^(3+)+Cu^(+)2←→Zn^(2+)。不同矿床中In的富集程度明显不同,其中,新风最富In(平均品位213.7g/t),其次为茶山,而铁砂坪最贫In。发现当闪锌矿中Cd含量介于5000×10^(-6)~7000×10^(-6)区间时,对应的In含量最高(>1000×10^(-6))。3个矿床的闪锌矿均富集Fe、Mn、In等高温元素,显著亏损Ga和Ge等低温元素。通过对比发现,这些闪锌矿与典型中高温岩浆-热液矿床(如远端矽卡岩型矿床)中闪锌矿的元素地球化学特征相似,应用闪锌矿地质温度计估算的结晶温度为345~372℃,且新风闪锌矿温度略高。闪锌矿中In的含量主要受温度控制,越靠近岩体、温度越高的闪锌矿越富In。结合前人资料,估算香花岭矿田伴生In资源量超过15000t,潜在经济价值巨大,应予以回收利用。     

Geological and geochemical characteristics of the Middle–Lower Jurassic shales in the Kuqa Depression,Tarim Basin: an evaluation of shale gas resources

Middle–Lower Jurassic terrigenous shales constitute a set of significant hydrocarbon source rocks in the Kuqa Depression of the Tarim Basin. Until recently, however, most investigations regarding this set of hydrocarbon source rocks have mainly focused on conventional oil and gas reservoirs, and little research has been conducted on the formation conditions of shale gases. This research, which is based on core samples from nine wells in the Kuqa Depression, investigated the geological, geochemical, mineralogical and porosity characteristics of the shales, analysed the geological and geochemical conditions for the formation of shale gases, and evaluated the shale gas resource potential. The results show that the distribution of the Middle–Lower Jurassic shales is broad, with thicknesses reaching up to 300–500 km. The total organic carbon (TOC) content is relatively high, ranging from 0.2 to 13.5 wt% with a mean of 2.7 wt%. The remaining hydrocarbon generative potential is between 0.1 and 22.34 mg/g, with a large range of variation and a mean value of 3.98 mg/g. It is dominated by type III kerogen with the presence of minor type II₁ kerogen. The vitrinite reflectance values range from 0.517 to 1.572%, indicating the shales are in a mature or highly mature stage. The shales are mainly composed of quartz (19–76%), clay (18–68%) and plagioclase (1–10%) with mean contents of 50.36 wt%, 41.42 wt%, and 3.37 wt%, respectively. The pore spaces are completely dominated by primary porosity, secondary porosity and microfractures. The porosity is less than 10% and is mainly between 0.5 and 4%, and the permeability is generally less than 0.1 mD. These results classify the shale as a low-porosity and ultra-low-permeability reservoir. The porosity has no obvious correlation with the brittle or clay mineral contents, but it is significantly positively correlated with the TOC content. The maximum adsorbed gas content is between 0.82 and 8.52 m³/t with a mean of 3.37 m³/t. In general, the shale gas adsorption content increases with increasing the TOC content, especially when the TOC content is greater than 1.0%. The volumetric method, used to calculate the geological resources of the Middle–Lower Jurassic shales in the Kuqa Depression, shows that the geological resources of the Middle and Lower Jurassic shales reach 667.681 and 988.115 × 10⁹ m³, respectively with good conditions for the formation of shale gas and good prospects for shale gas exploration.     

Jurassic Tectonic Revolution in China and New Interpretation of the “Yanshan Movement”

With acquisition and accumulation of new data of structural geological investigations and high-resolution isotopic dating data, we have greatly improved our understanding of the tectonic events occurring in eastern China during the period from the Late Jurassic to Early Cretaceous and may give a new interpretation of the nature, timing and geodynamic settings of the “Yanshan Movement”. During the Mid-Late Jurassic （165±5 Ma）, great readjustment of plate amalgamation kinematics took place in East Asia and the tectonic regime underwent great transformation, thus initiating a new tectonic regime in which the North China Block was the center and different plates converged toward it from the north, east and southwest and forming the “East Asia convergent” tectonic system characterized by intracontinental subduction and orogeny. As a consequence, the crustal lithosphere of the East Asian continent thickened considerably during the Late Jurassic, followed immediately by Early Cretaceous substantial lithospheric thinning and craton destruction featured by drastic lithospheric extension and widespread volcano-magmatic activities, resulting in a major biotic turnover from the Yanliao biota to Jehol Biota. Such a tremendous tectonic event that took place in the continent of China and East Asia is the basic connotation of the “Yanshan Movement”. In the paper, according to the deformation patterns, geodynamic settings and deep processes, the “Yanshan Movement” is redefined as the Late Jurassic East Asian multi-directional plate convergent tectonic regime and its associated extensive intracontinental orogeny and great tectonic change that started at -165±5 Ma. The substantial lithospheric attenuation in East China is considered the post-effect of the Yanshanian intracontinental orogeny and deformation.     

Geochemistry of Gneiss-Granulite transformation in the “incipient charnockite” zones of southern India

Summary Upper amphibolite facies gneisses in the southern Indian Shield show local transformation into veins, clots and patches of orthopyroxene-bearing dry granulites (incipient charnockites). Depending upon the protolith composition, these desiccated zones are classified into ortho- and para-charnockites and have developed within rocks of distinct mineralogy and chemistry at different time intervals through the structurally-controlled influx of carbon dioxide-rich fluids. Our geochemical investigations at five critical quarry sections indicate that the incipient charnockites have undepleted chemistry and very low K/Rb values. In the paracharnockite localities, where granulite formation is characterized by consumption of garnet, biotite and quartz to produce orthopyroxene, loss of Rb and Ba and enrichment of Ti are observed. In contrast, the orthocharnockite localities show marked LILE enrichment with gain of K, Rb and Ba and loss of CaO, suggesting extensive replacement of plagioclase in the gneisses by K-feldspar in the charnockite through K-Na-Ca exchange reactions with influxing carbonic fluids. The marked depletion in Fe, Mg, Ti and P in these rocks correlates with progressive dissolution of hornblende, biotite, magnetite and accessory apatite. Our study indicates that gneiss to granulite transformation, even if on a local scale, is not an isochemical phenomenon, but attended by distinct element mobilities, although they are contrastingly different from the geochemical trends in some regional high grade terrains.

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Geochemie von Gneiss-Granulit-Übergängen in den Incipient Charnockite Zonen von Süd-Indien

Zusammenfassung Gneise der oberen Amphibolit-Fazies im Südteil des Indischen Schildes zeigen lokal Umwandlungen in Adern, and unregelmäßigen Bereichen von orthopyroxen-führenden trockenen Granuliten (Incipient Charnockites). In Abhängigkeit von der Zusammensetzung des Ausgangsgesteins werden diese Zonen in Ortho- und Paracharnockite eingeteilt. Sie entwickelten sich in Gesteinen von charakteristischer mineralogischer und chemischer Zusammensetzung zu verschiedenen Zeit-Intervallen durch die tektonisch kontrollierte Zufuhr von kohlendioxid-reichen Fluiden. Unsere geochemischen Untersuchungen an fünf strategisch ausgewählten Steinbruchen zeigen, daß die Incipient Charnockite eine nicht verarmte chemische Zusammensetzung und sehr niedrige K/Rb Werte haben. In den Paracharnockit-Lokalitäten, wo Granulitbildung charakterisiert wird durch das Verschwinden von Granat, Biotit und Quartz, aus denen Orthopyroxene gebildet werden, ist Verlust von Rb und Ba und Anreicherung an Ti zu beobachten. Im Gegensatz dazu zeigen die Orthocharnockite eindeutige LILE Anreicherung mit Zunahme von K, Rb, und Ba und Verlust von Ca0. Dies weist auf extensiven Ersatz von Plagioklas in den Gneisen durch K-Feldspat in den Charnockiten durch K-Na-Ca Austausch-Reaktionen mit zugeführten C0₂-Fluiden hin. Die deutliche Verarmung an Fe, Mg, Ti und P in diesen Gesteinen wird mit zunehmender Auflösung von Hornblende, Biotit, Magnetit und akzessorischem Apatit erKlärt. Unsere Untersuchungen zeigen, daß die Gneis-Granulit Transformation auch im lokalen Maßstab nicht ein isochemisches Phänomen ist, sondern durch charakteristische Elementtransporte charakterisiert wird. Diese unterscheiden sich jedoch deutlich von den geochemischen Trends, die in einigen regional-metamorphen high grade terrains zu beobachten sind.[/p]