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Abstract:An incomplete dinosaur skeleton, including a partial skull, recently discovered from the Lower Jurassic Lufeng Formation of Yunnan, China, is here reported. Apart from its small size, little anatomical evidence supports, a priori, the non-adult status of this new sauropodomorph specimen but osteohistological analyses suggest that it is a fast-growing juvenile. This specimen represents only the second occurrence of a juvenile non-sauropodan sauropodomorph in the Lufeng Basin. The anatomy of the new specimen does not match that of other Lower Jurassic immature specimens; although cranial material is preserved, it does not display the diagnostic characters of early sauropodomorphs from the same horizon, namely Lufengosaurus, Yizhousaurus and Yunnanosaurus. Our phylogenetic analysis places the new specimen in a position relatively distant from other Chinese sauropodomorphs, and corroborates the anatomical evidence showing it is not referable to any known species already excavated in Yunnan. This result is interpreted with caution considering that ontogeny affects phylogenetic reconstruction. A thorough comparison with adult forms, taking into account ontogeny-related characters, suggests that this Lufeng juvenile might represent a previously unknown species of early sauropodomorph.

Abstract:Discovery of the remains of belemnites referred to the Hibolithes sp.from the Jurassic–Cretaceous Pedawan Formation in Sarawak,on the island of Borneo (Malaysia) comprises four fragments of belemnite rostra.The specimens are characterized by multiple fractures and vein filling.Two fragments measuring about 130 mm are relatively intact,with only part of the alveolar region missing;a third piece represents the middle part of a rostrum,and the fourth specimen is too fragmentary to be assigned to any specific part of the rostrum.Based on specimen characteristics,a Tithonian–Hauterivian age is plausible.The sedimentary succession that yielded the belemnite material comprises thick shale that reflects the Te division of Bouma sequence.The occurrence of a Hibolithes taxon in the uppermost Jurassic to lowermost Cretaceous Pedawan Formation sediments in Borneo reflects a near to global palaeobiogeographic distribution of this genus.

Abstract:Nummulites multiplicutiospiralis n.sp.is described and illustrated for both generations from a claystone of Lutetian age in the Middle Eocene Qarara Formation, Maghagha,Nile valley,Egypt.Previously considered to be Nummulites gizehensis,we describe this form as a new species based on diameter of the test and protoconch sizes,septal shape and granulations.The primary feature of this species is spiral multiplication,seen in spiral section.The species is also characterized morphologically by lenticular to flat tests with rounded periphery,wrinkled to broadly meandering septal filaments and few granules on the periphery in microspheric forms.The granules are spirally arranged on the septal filaments in megalospheric forms.Chambers are longer than high and the spire is irregular.The new taxon belongs to the Nummulites partschi Group,Subgroup N.gizehensis.Reflexive coiling in the spiral may develop through ontogeny as in N.rollandi,the species which was considered to be an index species in the southern Tethys (Boukhary et al.,1982 and Boukhary et al.2010).The characters of the new species,as well as its retrogenesis and reflexive coiling,should be further studied in general in Nummulites spp.,to understand the importance of such characters phylogenetically.

Abstract:The provenance and paleogeography of the Upper Triassic deep-sea flysch Langjiexue Group (LG) of the Shannan Terrane in the northeastern Himalaya orogen,south of Yarlung Zangbo,have been disputed in recent years since its affinity to the Tethys Himalaya was suspected during the early 2000s.Based on the earlier discoveries of the Upper Permian–Triassic basalts and mafic dykes from the LG and of coeval detrital zircons from the Qulonggongba Formation (QF) in shallow shelf sediments of the Tethys Himalaya,the previous viewpoints on the basin and tectonics of the LG have been recently rejected.We compared the two units of the Upper Triassic,and our results reveal a number of differences,discrepancies, and inconsistencies in the debate,raising crucial questions on the postulation and provenance model of the remote Gondwanide Orogen for the LG.It is suggested that more observations and evidence are needed to further improve the paleogeographic understanding and relationship of the two units.

Abstract:The calibration of sedimentary rock absolute dates is one of the difficulties in sedimentological and stratigraphic research.Since strontium (Sr) resides in seawater much longer (≈106 a) than the seawater intermixing time (≈103 a),the Sr isotopic composition of global seawater is uniform at any time and results in a stable system throughout geological history,based on which a global Sr isotope composition dating database has been established for age-calibration of marine strata.The Permian stratigraphic sections in the northern part of the Upper Yangtze block,southern China,record continuous marine sediments with clear stratigraphic boundaries and is suitable for stratigraphic dating of Sr isotopes.Based on sampling and Sr isotopic compositions of Permian carbonate strata in the northern part of the Upper Yangtze,a Permian Sr isotope evolution curve was established. According to the basic principles of Sr isotope stratigraphy,the global Strontium isotope age database can be used to calibrate the Permian stratigraphic dates in the northern Upper Yangtze.The results show that the Sr isotope evolution curves for the marine carbonate rocks in the Permian stratigraphic section of the Upper Yangtze present a decreasing trend from the mid-Qixia stage (P2) to the mid-Wujiaping stage (P3),and then rise from the middle Wujiaping stage to the end of Changxing stage (P3).When the Permian Sr-isotope evolution curve is compared with the global Sr isotope evolution curve in the northern Upper Yangtze,the two are consistent in their long-term evolutionary trend,indicating that Permian global geological events are important controlling factors for the composition and evolution of Sr isotopes. The 87Sr/86Sr value decreased gradually in the background of large-scale regressions at the turn of middle to late Permian period,revealing that the Emeishan basalt eruption occurred near the Maokou/Wujiaping boundary (GLB).Sr-isotope stratigraphy dating was performed on the boundaries of the Qixia Formation/Maokou Formation,Maokou Formation/Wujiaping Formation (GLB),Wujiaping Formation/Changxing Formation (WCB) and the Permian/Triassic (PTB) using the Global Strontium Isotope Age Database.The results are 270.4 Ma,261.2 Ma,254.5 Ma and 249.7 Ma,respectively. Based on this,the eruption age of the Emeishan basalts is defined at about 261.2 Ma.,which is more coincident with that acquired from other previous dating methods on the eruption age of the Emeishan basalts,and therefore proves that the application of Sr isotopic stratigraphy to dating marine sedimentary units is an effective method.

Abstract:The Xiaotian–Mozitan Shear Zone (XMSZ) is the boundary of the Dabie High-grade Metamorphic Complex (DHMC) and the North Huaiyang Tectonic Belt.It was deformed in ductile conditions with a top-to-NW/WNW movement.Geothermometers applied to mineral parageneses in mylonites of the shear zone give a temperature range of 623–691°C for the predeformation and 515–568°C for the syndeformation,respectively, which indicates a retrograde process of evolution.A few groups of zircon U-Pb ages were obtained from undeformed granitic veins and different types of deformed rocks in the zone.Zircons from the felsic ultramylonites are all magmatic,producing a weighted mean 206Pb/238U age of 754 ± 8.1 Ma,which indicates the time of magmatic activities caused by rifting in the Neoproterozoic.Zircons from the granitic veins,cutting into the mylonites,are also of magmatic origin,producing a weighted mean 206Pb/238U age of 130 ± 2.5 Ma,which represents the time of regional magmatic activity in the Cretaceous.Zircons from the mylonitic gneisses are of anatectic-metamorphic origins and are characterized by a core-mantle interior texture,which yielded several populations of ages including the Neoproterozoic ages with a weighted mean 206Pb/238U age of 762 ± 18 Ma, similar to that of the felsic ultramylonites and the Early Cretaceous ages with a weighted mean 206Pb/238U age of 143 ± 1.8 Ma,indicating the anatectic metamorphism in the Dabie Orogenic Belt (DOB).Based on integrated analysis of the structure,thermal conditions of ductile deformation and the contact relations of the dated rocks,the activation time of the Xiaotian–Mozitan Shear Zone is constrained between ~143 Ma and 130 Ma,during which the DOB was undergoing a transition in tectonic regime from compression to extension.Therefore,the deformation and evolution of this shear zone plays an instrumental role in fully understanding this process.This research also inclines us to the interpretation of it as an extensional detachment,with regard to the tectonic properties of the shear zone.It may also be part of a continental scale extension in the background of the North China Block’s cratonic destruction,dominated by the subduction and roll-back of the Paleo-Pacific plate,but more detailed work is needed in order to unravel its complicated development.

Abstract:The Kabr El-Bonaya mafic–ultramafic intrusion is exposed along the southeastern border of the Sinai Peninsula and the northernmost segment of the Arabian-Nubian Shield (ANS).It occurs as an elliptical intrusive body that is located along the major NE–SW trending fracture zones that prevail in the Kid metamorphic complex. The ultramafic rocks in the complex comprise ultramafic cumulates of peridotites (dunite, harzburgite and wehrlite) and pyroxenite.These rocks are generally unmetamorphosed and have intrusive contacts with the country rock.Mineral chemistry and whole-rock chemical compositions of these ultramafic rocks are mostly consistent with those of residual mantle peridotites from refractory supra-subduction tectonic settings.Based on the variations of the major elements,the studied ultramafic rocks are consistent with those of a supra-subduction zone mantle,as it seems to have melted at 1–2 GPa and 1300–1450°C.Linear variations of Al2O3, CaO,V and Ni with MgO,coupled with incompatible and rare-earth-element depletion and mineral compositions,suggest prior events of partial melting in both wehrlites and harzburgites. The LREE enrichment in the harzburgite,as well as the development of Cr-rich spinel,is consistent with a history of melt–peridotite interaction. The calculated (Sm/Yb)N variations for the studied peridotites indicate a general increase in the addition of fluids with an increasing degree of melting from the wehrlite (~13–15 wt% of fluid) in the source,after initial spinel peridotite melting to the harzburgite (~20–25 wt% of fluid) in the same source,which is contrary to normal abyssal peridotites.The estimated equilibration temperature ranges from 1214 to 1321°C for the studied wehrlites and from 1297 to 1374°C for harzburgites.The Mg-rich nature of the analysed olivines from the studied ultramafic rocks (Fo = 81.41 to 91.77) reflect their primary composition and are similar to olivines in Alaskan-type ultramafic rocks.The Fo content of the analyzed olivines decrease slightly from the dunite to the harzburgite to the wehrlite and to pyroxenite,reflecting a fractional crystallization trend.The high Cr# and very low TiO2 contents (0.03–0.12 wt%) of the Cr-spinels from the studied peridotites are mostly consistent with modern highly refractory fore-arc peridotites,indicating that these peridotites developed in a supra-subduction zone environment.

Abstract:In view of the importance of mafic dyke swarms and their contribution to current scientific problems relating to South China,herein,we present the findings of studies on twenty–five representative mafic dykes cropping out in Hunan Province and Guangxi Zhuang Autonomous Region,within the southern Wuling Mountain gravity lineament,China.These results include new zircon LA-ICP-MS U-Pb age,whole rock geochemical,Sr-Nd-Pb isotopic,and zircon Hf isotopic data for these dykes.The dykes formed between 131.5 ± 1.2 and 121.6 ± 1.1 Ma,and have typical doleritic textures.They fall into the alkaline and shoshonitic series,are enriched in light rare earth elements (LREE),some large ion lithophile elements (LILE;e.g.,Rb,Ba,and Sr),Th,U,and Pb,and are depleted in Nb,Ta,Hf,and Ti.Moreover,the dolerites have high initial 87Sr/86Sr ratios(0.7055–0.7057),negativeεNd(t) and zircon εHf(t) values(?14.8 to ?11.9,?30.4 to ?14.9),and relatively constant initial Pb isotopic ratios (that are EM1-like,16.77–16.94,15.43–15.47,and 36.84–36.92 for 206Pb/204Pb,207Pb/204Pb,and 208Pb/204Pb,respectively).These results indicate that the dykes were likely derived from magma generated through low-degree partial melting (1.0%–10%) of an EM1-like garnet–lherzolite mantle source.The parental magmas fractionated olivine,clinopyroxene,plagioclase,and Ti-bearing phases with negligible crustal contamination,during ascent and dyke emplacement.Several possible models have been proposed to explain the origin of Mesozoic magmatism along the Wuling Mountain gravity lineament.Herein we propose a reasonable model for the origin of these mafic dykes,involving the collision between the paleo-Pacific Plate and South China,which led to subsequent lithospheric extension and asthenosphere upwelling,resulting in partial melting the underlying mantle lithosphere in the Early Cretaceous,to form the parental magmas to the WMGL mafic dykes,as studied.

Abstract:The Qilian Block (QB) is a Precambrian micro-continent located in the northeastern Qinghai–Tibet Plateau. Prevalent Lower Paleozoic granitic magmatic rocks crop out in the QB.A new integrated study of zircon U-Pb ages and systematic whole-rock geochemical data for the Xindian,Dongjiazhuang and Xiaogaoling granites in the eastern segment of the QB constrains their emplacement ages,petrogenesis,and regional evolutionary history.U-Pb dating reveals that the Xindian granite was emplaced 454 Ma, and both the Dongjiazhuang and Xiaogaoling granites were emplaced ca.440 Ma.Geochemical study shows that all granites belong to the high-K calc-alkaline to shoshonitic series and are S-type granites formed by partial melting of continental crust,mainly metagraywacke. We infer that these ca.454–445 Ma granites formed in a syn-collisional setting during the continental collisional between the Qaidam and Qilian blocks.

Abstract:The Abu Dabbab albite granite (ADAG),in the central Eastern Desert of Egypt,hosts the most significant rare metal ore deposit in the northern part of the Neoproterozoic Arabian-Nubian Shield.Here,we report detailed field,petrographic,mineralogical and geochemical investigation of the ADAG,an isolated stock-like granitic body with sharp intrusive contacts against metamorphic country rocks,probably emplaced at about 600 Ma.The fine-grained porphyritic upper unit is a preserved remnant of the shallowly-emplaced apex of the magma chamber,whereas the medium-grained lower unit crystallized at deeper levels under subvolcanic conditions.The peraluminous leucocratic ADAG shares common geochemical characteristics with post-collisional intraplate A-type magmas.In addition to the conspicuous enrichment in Na2O,the ADAG is remarkable for its anomalous concentrations of Ta,Nb,Li,Hf,Ga,Sn,Zn and heavy rare-earth elements.Nb-Ta minerals in the ADAG are mixed with Fe-Mn oxides,forming black patches that increase in abundance toward of the base of the intrusion.Columbite-tantalite,cassiterite and wolframite are the most important ore minerals.Pronounced negative Eu anomalies (Eu/Eu* = 0.10–0.24) reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interaction.The ADAG was most likely generated by partial melting of the juvenile middle crust of the ANS as the geotherm was elevated by erosional uplift following lithospheric delamination and it was emplaced at the intersection of lineations of structural weakness.Although formation of the ADAG and its primary enrichment in rare metals are essentially due to magmatic processes,late-stage metasomatism caused limited redistribution of rare metals.Fluid-driven subsolidus modification was limited to the apex of the magma chamber and drove development of greisen,amazonite, and quartz veins along fracture systems.

Abstract:The central part of South Mongolia,located to the north of the Solonker Suture,is a key region for studying the late Paleozoic tectonic evolution of the Central Asian Orogenic Belt (CAOB).Voluminous late Paleozoic granitic rocks,especially of Carboniferous age,were intruded in this area.However,these granitoids have not been well studied and there is a lack of precise ages and isotopic data.This has hampered our understanding of the tectonic evolution of southeastern Mongolia,and even the entire CAOB.In this paper,we provide new U-Pb isotopic ages and geochemical analyses for these Carboniferous granites.One granite from the Ulaanbadrakh pluton yielded a zircon U-Pb age of 326 Ma,which indicates emplacement in the Early Carboniferous,and three other granites from the Khatanbulag region gave zircon U-Pb ages of 316 Ma,315 Ma,and 311 Ma,which indicate emplacement in the Late Carboniferous.The Early Carboniferous granite has SiO2 contents of 70.04–70.39 wt% and K2O + Na2O contents of 6.48–6.63 wt%,whereas the Late Carboniferous granites have more variable compositions (SiO2 = 65.29–77.91 wt% and K2O + Na2O = 5.30–7.27 wt%).All the granites are weakly-peraluminous I-types that are relatively enriched in U,Th, K,Zr,Hf,and LREEs.The whole rock Sr-Nd and zircon in situ Lu-Hf isotope analyses for the Early Carboniferous granite gave positive values of εNd(t) (2.87) and εHf(t) (4.31–12.37) with young Nd (TDM = 860 Ma) and Hf (TDMc = 1367–637 Ma) two-stage model ages,indicating derivation from juvenile crustal material.In contrast,the Late Carboniferous granites had more diverse values of εNd(t) (–4.03 to 2.18) and εHf(t) (–12.69 to 5.04) with old Nd (TDM = 1358–1225 Ma) and Hf (TDMc = 2881–1294 Ma) depleted mantle two-stage model ages, suggesting derivation from remelting of Precambrian basement.Based on the existing results,the tectonic setting of the Late Carboniferous granites in the central part of South Mongolia is known for its diversity,and this paper believes that the tectonic background of the carboniferous granite records the tectonic transition from a continental-margin-arc to a post-collisional extensional setting during the Late Carboniferous–Permian.

Abstract:A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China.W-Mo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks,and the ore bodies are structurally controlled by NW–SE- and NNE–SSW-striking faults.Evidence for magmatism in the area is widespread and is dominated by intermediate–felsic intrusives or apophyses,such as the Dongjiangkou,Yanzhiba,Lanbandeng,and Sihaiping granitic bodies.Quartz-vein-type mineralization and fault-controlled skarn-type mineralization dominate the ore systems,with additional enrichment in residual deposits.At present,there are few or insufficient studies on(1)the age of mineralization,(2)the relationship between intermediate–felsic granite and W-Mo mineralization,(3)the source of ore-forming materials,and(4)the metallogenic and tectonic setting of the mineralized area.In this paper,we present geochronology results for numerous intrusive granitic bodies in the South Qinling tectonic belt.U-Pb zircon geochronology of the Lanbandeng monzogranite and Wangjiaping biotite monzogranite yields ages of 222.7 ± 2.3 and 201.9 ± 1.8 Ma,respectively.In contrast to the Late Triassic age of the Lanbandeng monzogranite,the age of the newly discovered Wangjiaping biotite monzogranite places it at the Triassic–Jurassic boundary.Re-Os molybdenite geochronology on the Qipangou W-Mo deposit yielded a model age of 199.7 ± 3.9 Ma,indicating the deposit formed in the early Yanshanian period of the Early Jurassic.Granitoid intrusions in the mineralized area are characterized by composite granite bodies that crystallized at ca.240–190 Ma.While there were multiple stages of intrusion,most occurred at 210–220 Ma,with waning magmatic activity at 200–190 Ma.The Re-Os age of molybdenite in the region is ca. 200–190 Ma, which may represent a newly discovered period of W-Mo metallogenesis that occurred during the final stages of magmatism.The heat associated with this magmatism drove ore formation and might have provided additional ore-forming components for metallogenesis (represented by the Wangjiaping biotite monzogranite).Ore materials in the mineralized area were derived from mixed crustal and mantle sources.Enrichment of the region occurred during intracontinental orogenesis in the late Indosinian–Yanshanian,subsequent to the main Indosinian collision.At this time,the tectonic environment was dominated by extension and strike-slip motion.

Abstract:Petrological,mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield, northern Ordos Basin,North China, define their characteristics,ore genesis and economic interest.Based on the crystalline size,two different types of kaolinite rocks,cryptocrystalline and grainy, were identified under the microscope.XRD data show that kaolinite is the predominant mineral,associated with boehmite,magnesite,anatase,pyrite,diaspore and calcite. However,high boehmite content (mean 70%) shows up in the middle layers.Kaolinite minerals present homogeneous shape and a good crystallinity (HI = 0.96–1.26). Geochemical studies show that the SiO2/Al2O3 molar ratio of kaolinite is close to the theoretical value,and the contents of Na2O,K2O,CaO,MgO are less,suggesting a strong chemical weathering environment. The REE and Eu anomalies show a close relationship between kaolinite and the Yinshan Oldland granite. A Ce anomaly reflects a continental sedimentary environment with shallow water.A temperature range of 26.7–34℃ was calculated on the basis of the isotopic signatures (δ18O,δD) of the kaolinite rocks.All these data indicate that the formation of the kaolinite is caused mainly by the dissolution,coagulation,precipitation and recrystallization of aluminosilicate clastics in acidic conditions.The formation of boehmite in the middle layers indicates that the source rocks have changed.Boehmite is mainly formed by dehydration and compaction of an aluminum-rich colloid which transported into peat swamp during diagenesis.In addition,it formed by desiliconization of kaolinite under acidic conditions.Due to its high kaolinite content (up to 90%) and low iron mineral content (less than 1%),and good crystallinity,kaolinite deposits occurred at Haerwusu surface mine probably have great economical value in the future.

Abstract:The Gas Hure Salt Lake (GHSL) in the northwestern Qaidam Basin,western China,is rich in boron (B) resources,but its B-resource origin is hardly known.Hydrochemical compositions and B isotope characteristics of different waters were collected around the GHSL,including the river water,stream water,spring water,salt-lake brine, intercrystalline brine,well water,drilling brine,and solar pond brine.The hydrochemical signatures suggest that silicates,carbonates and evaporates are the main B-bearing rocks during the water dynamic.The reservoir estimation of B resources shows that the Kulamulekesay River (KLMR) and the Atekan River (ATKR) contribute annually 18.3 tons and 22.84 tons of B,respectively,with a total amount of 11.72 × 104 tons of B during the past 5.7 ka.In comparison with the known B reservoir (32.96 × 104 tons) in the GHSL,a significant amount of B in the GHSL was probably recharged from deep fluids and sediments around the GHSL.The B concentration and B-enrichment degree are shaped by the evaporation process,which are highly elevated at the carnallite and bischofite stages.

Abstract:Sedimentary chert phases from the Archean to the present are widely used to trace sedimentary environments and tectonic settings. Recently,chert nodules occurring within carbonates have been the subject of possible hydrothermal or biogenic origin,in lieu of a diagenetic origin.However,chert nodules from a vast cratonic basin represent extremely rich silica accumulations but less noted is how they respond to submarine hydrothermal activity (and/or surface siliceous organism productivity). The links between the cratonic-type chert depositions and environmental changes regarding cratonic evolution need to be revisited at a large temporal-spatial scale. The chert nodules are widespread throughout the Lower Permian Taiyuan Formation in the North China Craton (NCC).Several Taiyuan chert-rich successions across the NCC have been selected to study possible links between chert deposition and cratonic evolution in scenario of partial cratonic activation of the northern NCC margin during the Late Paleozoic.Based on stratigraphic correlation,the chert nodules are ubiquitously,evenly distributed throughout the Taiyuan Formation at a large craton-basin scale from the northern to southern interior NCC.Petrological results,elemental abundances,together with silicon and oxygen isotopic compositions of chert samples infer significant hydrothermal contributions for the silica accumulations. Therefore, the cratonic-scale chert depositions of hydrothermal origin infer a giant and remote silica reservoir,linking to the large igneous province and magmatism in the NCC northern margins.The Taiyuan chert nodules could be unique marine sedimentary archives recording the Late Paleozoic NCC partial activation,which also generated continental records of igneous rocks,bauxites and tuffs.The strong tectonics of the northern margin,south-dipping topography and northward transgression of the Early Permian NCC facilitated the chert deposition on the shallow marine platform in the cratonic interior.

Abstract:The micro-nano pore structure of conglomerate in the Lower Karamay Formation of the Xinjiang Oilfield,Junggar Basin,northern China is characterized to predict its impact on fluid reserves and seepage.Authigenic clay minerals are mainly kaolinite (67%),followed by an illite/smectite mixed layer (18%),illite (10%),and chlorite (5%).For kaolinite,pore throats between 0–200 nm are dominant,accounting for 90% of the total pore throats.For illite/smectite mixed layer,pore throats also between 0–200 nm account for nearly 80%,while pore throats between 200-500 nm only account for 15%.For illite, pore throats below 100 nm account for about 80%,while pore throats in the range of 100–500 nm only account for 20%.For chlorite,most throats are below 200 nm.The pore roundness of illite is the highest,while the pore roundness of chlorite is relatively lower.The lower limits of the dynamic and static pore throat radii are 42.128 nm and 72.42 nm,respectively.The theoretical contribution rates of the illite/smectite mixed layer,kaolinite,illite and chlorite to storage/seepage are 60%/45.86%,52.72%/38.18%,37.07%/28.78% and 32.97%/26.3%, respectively.Therefore,the contribution rates of clay minerals in the study area are as follows: illite/smectite mixed layer,kaolinite,illite and chlorite.

Abstract:Fine-grained sedimentary rocks often contain hydrocarbon and mineral resources.Compared with coarse-grained sedimentary rocks,fine-grained sedimentary rocks are less studied.To elucidate the lithofacies and pore structure of lacustrine fine-grained rocks,the 340.6 m continuous core of Cretaceous Qing-1 Member from five wells in the southern central depression of the Songliao Basin was analyzed using X-ray diffraction,Rock-Eval pyrolysis,low-temperature nitrogen adsorption,high-pressure mercury injection,argon ion polishing-field emission scanning electron microscopy,and laser scanning confocal microscopy.Based on mineral compositions,organic matter abundance and sedimentary structure,lacustrine fine-grained rocks in the study area were divided into ten lithofacies,with their spatial distributions mainly influenced by tectonic cycle,climate cycle and provenance.Furthermore,pore structure characteristics of different lithofacies are summarized.(1)The siliceous mudstone lithofacies with low TOC content and the laminated/layered clay-bearing siliceous mudstone lithofacies with medium TOC content have the highest proportion of first-class pores (diameter > 100 nm),making it the most favourable lithofacies for the accumulation of shale oil and shale gas.(2)The massive clay-bearing siliceous mudstone lithofacies with low TOC content has the highest proportion of second-class pores (diameter ranges from 10 to 100 nm),making it a favourable lithofacies for the enrichment of shale gas.(3) The massive clay-bearing siliceous mudstone lithofacies with high TOC content has the highest proportion of third-class pores (diameter < 10 nm),making it intermediate in gas storage and flow.Laser confocal oil analysis shows that the heavy component of oil is mainly distributed in the clay lamina,while the light part with higher mobility is mainly concentrated in the silty lamina.

Abstract:To investigate pore characteristics and the factors controlling lacustrine shales,geochemical,mineralogical and petrophysical experiments were performed on 23 shale samples from the Qingshankou Formation of the Songliao Basin,China.A comparison of mercury injection capillary pressure (MICP) and low-temperature N2 adsorption pore-size distribution showed that MICP has a higher pore-size distribution (PSD) line in its overlapping pore diameter range,which may be elevated by the higher pressure of MICP.Therefore,in the overlapping range,low-temperature N2 adsorption data were preferred in pore characterization.Negative correlations were observed between pore volumes and TOC content,indicating organic matter pores are not well-developed in the studied samples.This may be related to their low grade of maturity and type I kerogens.There existed negative relationships between pore volumes and S1,which illustrated that liquid hydrocarbons occupied some pore space.Micropore volume had a better correlation with S1 than mesopore and macropore volumes,which suggests that liquid hydrocarbons preferentially occur in micropores.No obvious relationships between pore volumes and quartz or feldspar were observed,while pore volumes increased with the increasing clay mineral content.These relationships indicate that intraparticle pores in clay minerals represent the principal pore type.

Abstract:The Qilian permafrost of the South Qilian Basin (SQB) has become a research focus since gas hydrates were discovered in 2009.Although many works from different perspectives have been conducted in this area,the origin of gas from gas hydrate is still controversial.Molecular composition and carbon isotope of 190 samples related to gas hydrates collected from 11 boreholes allowed exploration of genetic type,thermal maturity, biodegradation,as well as gas-source correlation of alkane gases from gas hydrates and free gases.Results indicate that alkane gases biodegraded after the formation of natural gas.According to differences in carbon isotopes of methane and their congeners (CH4,C2H6,C3H8),the thermal maturity (vitrinite reflectance,VRo) of most alkane gases ranges from 0.6% to 1.5%,indicating a mature to high mature stage.The thermal maturity VRo of a small part of alkane gas (in boreholes DK5 and DK6) is higher than 1.3%,indicating a high mature stage.Alkane gases were mainly produced by secondary cracking,consisting of crude oil-cracking gases and wet gases cracking to dry gases.Genetic types of alkane gases are primarily oil-type gases generated from shales and mudstones in the upper Yaojie Formation of Jurassic,with less coal-type gases originated from the mudstones in the Triassic Galedesi Formation and the lower Yaojie Formation of Jurassic.Carbon dioxides associated with alkanes from gas hydrates and free gases indicate the thermal decomposition and biodegradation of organic matter.The origins of natural gases from gas hydrates and free gases shed light on the evaluation of petroleum resource potential,deeply buried sediments,and petroleum resource exploration in the SQB.

Abstract:Turbidite sandstones have become increasingly significant in hydrocarbon exploration.Carbonate cementation occur commonly in turbidite reservoirs developing within the Paleocene lacustrine basins,Northeastern China.This study utilizes core data,thin section data and production data to investigate the interaction between the carbonate cementation and hydrocarbon charge within turbidite reservoirs in the Niuzhuang Sub-sag of the Dongying Sag,Bohai Bay Basin, East China.The results reveal that the carbonate cementation is mainly developed at the top and bottom of the turbidite sandbodies,and even forms carbonate cement shells.Three stages of hydrocarbon accumulation are identified based on fluid inclusion analysis: stage I(27.5–24.6 Ma),stage II(14.0–5.0 Ma),and stage III(5.0–0 Ma).The interaction between the carbonate cementation and hydrocarbon charge has significant controls on the formation of a turbidite reservoir.The temporal relations and intensity relations between the two factors should be considered significantly.Moreover,hydrocarbon charge during the early stage can inhibit the carbonate cementation, favoring the hydrocarbon accumulation in turbidite reservoirs.Many deep-lacustrine turbidite sandbodies surrounded by source rocks with abnormal high pressure,are also favorable for hydrocarbon accumulation.These results suggest that some deeply buried turbidite sandbodies with similar geological settings have high potential for hydrocarbon exploration.

Abstract:To tackle the problem that wells that are deployed in a specific pattern based on the requirements of gas reservoir development are not suitable for gas storage,we have conducted concentrically circular injection and production simulation experiments for gas storage,discovered the existence of a threshold radius,denoted by Rt, and derived the expression for Rt.Based on the analysis and discussion results,we propose a strategy for deploying gas storage wells in specific patterns.The expression for Rt shows that it is affected by factors such as the gas storage gas production/injection time,the upper pressure limit,the lower pressure limit,the bottomhole flow pressure at the ends of injection and production,the and permeability. The analysis and discussion results show that the Rt of a gas storage facility is much smaller than the Rt for gas reservoir development.In the gas storage facilities in China,the Rt for gas production is less than the Rt for the gas injection, and Rt increases with the difference in the operating pressure and with permeability K.Based on the characteristics of Rt,we propose three suggestions for gas storage well pattern deployment:(1)calculate Rt according to the designed functions of the gas storage facility and deploy the well pattern according to Rt;(2) deploy sparser,large-wellbore patterns in high-permeability areas and denser,small-wellbore patterns in high-permeability areas;and (3)achieve the gas injection well pattern by new drilling,and the gas production well pattern through a combination of the gas injection well pattern and old wells.By assessing a gas storage facility with a perfect well pattern after a number of adjustments,we found that the Rt of the 12 wells calculated in this paper is basically close to the corresponding actual radius,which validates our method.The results of this study provide a methodological basis for well pattern deployment in new gas storage construction.

Abstract:A large number of lacustrine sedimentary records indicate that global warming is the main factor leading to significant changes in diatom communities in lakes of the northern hemisphere.However,due to the intensification of human activities since 1850,some scholars have emphasized that the increasing lake trophic level may be the main reason for the changes in diatom communities.The debate is ongoing.In order to avoid falling into the complex relationship between diatom changes and the seasonal cycle that characterizes lakes in mid and high latitudes,we chose a lake located at a low latitude,where the relationship between diatoms and temperature is not indirect but direct.The diatom record spans the past ca.100 years and reveals that the abundance of Aulacoseira granulata increased from 1900 until 1985, replacing the previously dominant Aulacoseira ambigua.These changes are in agreement with the increasing trend in global temperature.Since 1985,the percentages of the small-celled Discostella stelligera and the benthic diatom Navicula heimansioides have increased,while Aulacoseira granulata has decreased.This latest shift is caused by further global warming.We conclude that warming is the main factor leading to changing diatom communities in Douhu Lake.

Abstract:n-Alkanes are widely used in paleoenvironmental reconstructions.However,our understanding of changes in the distribution of n-alkanes with climatic and environmental factors remains unclear in arid/semi-arid regions.We sampled 26 surface sediments from three climatic zones across the southwestern Tibetan Plateau to evaluate the sensitivity of chain length distributions of n-alkanes to climatic and environmental parameters.Our observations demonstrate that average chain length (ACL), proportion of aquatic macrophyte (Paq),carbon preference index (CPI) and ratio of the contents of nC27 and nC31 (nC27/nC31) are all sensitive to hydroclimatic conditions.In contrast to commonly-adopted assumptions,the correlations between these indices and hydrological parameters are not always good,which indicates that the interpretation of n-alkane indices is special on the southwestern Tibetan Plateau.These might be related to the vegetation characteristics and seasonality of biological activity,and need to be considered in paleoclimatic reconstruction.The impact of seasonal precipitation on n-alkanes indices was also evaluated.

Abstract:The‘twin cities’district of Rawalpindi–Islamabad is among the most endangered seismic regions in Pakistan,with the seismic hazard assessed (0.32 g)to intensity IX MMI for a 475-year return period. A seismic hazard map for Rawalpindi–Islamabad is presented herein,based on 85 shear-wave velocity (VS) profiles obtained through geophysical H/V measurements and from the geological map of the region.Relationships between the average top thirty-meter shear-wave velocities (VS30) and surficial geological units have been determined.The peak ground acceleration (PGA) maps for 150,475 and 2475-year return periods were converted into a seismic intensity map. Intensity increments for different soils were used to compute PGA values for 150,475 and 2475-year return periods.Sites located on softer ground experienced a higher degree of damage from moderate earthquakes.Due to the presence of soft clay or lique?able soil and lateral spreading,a few locations may be classified as hybrid sites class C and D.This map is a critical step in facilitating code-based site classification and seismic design throughout Rawalpindi–Islamabad.Although the seismic hazard map based on seismic intensities is no longer used in engineering geology,it is still important in seismological analysis and for civil protection purposes.

Abstract:Ground subsidence is an emerging geological hazard in Baotou,Inner Mongolia.Four areas of Baotou with relatively large subsidence range and rate were selected for analysis.Focusing on investigation of ground subsidence using PS-InSAR technology,a total of 43 frames of ALOS PALSAR images yielded a SAR data span from December 2006 to January 2011,allowing ground subsidence scope,subsidence velocity,time-series deformation to be obtained.Major causes and influencing factors of the ground subsidence are closely related to soft soil consolidation and compaction and the decrease in the level of groundwater caused by increased development and utilization of groundwater.

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