摘要:

摘要:

摘要:A new partial specimen of Zhenyuanopterus from the Lower Cretaceous Yixian Formation of Beipiao city, Liaoning Province is described. This specimen is slightly larger than half the size of the holotype. Although it is not complete, it provides new information on Zhenyuanopterus both in taxonomy and ontogeny: the total number of the caudal vertebrae is 15; the forelimb is more robust than the hindlimb; the growth rate of the humerus and femur is constant, and their ratio is about 1. Compared with the holotype, the scapula and coracoid grow faster than the humerus and the femur. The scapula and coracoid may slow their growth rate after a certain ontogenetic stage. The pectoral girdle, robust forelimb and weak hindlimb of the new material (XHPM1088) together with data from the holotype of Zhenyuanopterus indicate that this taxon spent less time on land than in the sky or other ecological niches such as forests and cliffs.

摘要:A nearly complete right maxillary or left dentary tooth (NHMG 10858) from the Lower Cretaceous Xinlong Formation of the Napai Basin, Fusui County, Guangxi, southern China, is described. The tooth is large in size, with a CBL of 37 mm. Given the geological age and its crown morphology, including the size, it is most likely that the tooth belongs to a carcharodontosaurid. The recovered specimen represents one of the largest theropod teeth hitherto reported from the Early Cretaceous of Asia.

摘要:Based on a new nearly naturally preserved skull and four cervical vertebrae of the pterosaur Feilongus sp. from the lower Cretaceous Jiufotang Formation of Beipiao, western Liaoning province, northeastern China, the diagnosis of Feilongus is amended. The revised diagnosis notes long, curved, needle-shaped teeth that are confined to the jaw far anterior to the nasoantorbital fenestra; posterior teeth that are slightly smaller than the anterior teeth; cervical vertebrae elongated with a ratio of length to width greater than 5; tooth number of about 78; and two cranial sagittal crests.

摘要:Although the evidence of insect oviposition on plant organs has been reported from the late Paleozoic to the Miocene, record from the middle Jurassic is still blank. This paper reports a significant evidence of insect oviposition on plant leaf from the middle Jurassic for the first time. The ovipositional scar is distributed on the abaxial surface of Sphenobaiera leaf (Ginkgoales) from the middle Jurassic Daohugou Formation of Inner Mongolia, China. A new ichnospecies Paleoovoidus venustus sp. nov. is described. The scar is elliptic to oval, arranged in longitudinal rows between leaf veins with almost regular distance, with its long axis paralleling to the leaf venation. This discovery adds new information to the morphology of insect endophytic oviposition probably produced by Odonata existed in a terrestrial ecosystem ~165 Ma ago. The new materials also provide important data for the study of insect reproductive biology, plant-insect interaction and coevolution, as well as understanding the paleoclimate and palaeoenvironment during that time in northeast China.

摘要:A new species, Cimbrophlebia rara sp. nov., in the family Cimbrophlebiidae (Mecoptera) is described and illustrated. This specimen was collected from the Early Cretaceous Yixian Formation at Liutiaogou in Inner Mongolia, China. This is the first record of a cimbrophlebiid from the Jehol biota. A key to all species of Cimbrophlebia is given. A preliminary review of published taxa data indicates that from the Middle Jurassic to the Early Cretaceous, Mecoptera became less diverse and less abundant in northeastern China at familiar level (from 11 to 6), generic level (from 32 to 8) and specific level (from 44 to 14).

摘要:Abundant conodont elements have been recovered from the Hwajeol Formation, to allow five zones to be erected: Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus, Cordylodus proavus, and Fryxellodontus inornatus-Monocostodus sevierensis-Semiacontiodus lavadamensis zones, in ascending order. More confident biozones are recognized in the Sesong Slate and lower Hwajeol Formation in the Makgol section, a part of the southern limb of the Baekunsan syncline, Taebaeksan Basin, Korea, especially focusing on the conodont biostratigraphic boundary of two units, and the subdivision potential of the previous “Proconodontus Zone”, lowermost biozone of the Hwajeol Formation. Similarly, only a few conodont elements recovered from upper 14.5 m interval, namely the Furongian portion of the Sesong Slate, in the Makgol section did not allow erection of a biozone. Nevertheless, this part of the unit plus the basal 2.5 m interval of the Hwajeol Formation is characterized by the occurrence of Prooneotodus rotundatus (Druce and Jones), Teridontus nakamurai (Nogami), Phakelodus elongatus (An) and Phakelodus tenuis Müller. This interval marks the early Furongian “Prooneotodus rotundatus Zone”. The rest of the measured section yielded relatively abundant conodonts, so three conodont biozones are proposed, based on the successive appearance of key species: Proconodontus tenuiserratus, Proconodontus posterocostatus, and Proconodontus muelleri zones, in ascending order, and thus allowing subdivision of the previous “Proconodontus Zone”. The four conodont biozones are correlated with the relevant biozones of North and South China, and North America.

摘要:Based on the palynological data from Well Ta-19-36 and Well Ta-19-37 in the Ta’nan Sag, and Well Ta-22-1 and Well Ta-21-1 in the Bayin Gobi Sag, a spore-pollen assemblage from the Damoguaihe Formation is named as Cicatricosisporites minutaestriatus - Aequitriradites spinulosus - Protopinus sp. assemblage in the Tamutsag Basin, Mongolia. The assemblage is characterized by abundant gymnosperm pollen and diverse fern spores, counted 46.35%–65.57% and 34.43%–52.58% in percentage respectively. Among the gymnosperm pollen, Pinuspollenites sp. (2.66%–16.94%), Protopinus sp. (0–11.38%) and Protopicea sp. (0–10.81%) are dominant; and Alisporites sp., Cerebropollenites sp., Podocarpidites sp., and Abietineaepollenites sp. are common. Some important elements, such as Chasmatosporites sp., Callialasporites prominulus, Parvisaccites sp., Parcisporites sp., Jiaohepollis cf. annulatus, J. bellus, J. verus, Polycingulatisporites sp., Schizaeoisporites certus, Classopollis annulatus are seen. Within the fern spores, Osmundacidites wellamanii (0.85%–4.93%), Appendicisporites sp. (0–4.45%), Baculatisporites comaumensis (0.80%–2.87%), Cicatricosisporites sp. (0.51%–2.66%), C. minor (0–2.14%), Foraminisporis asymmetricus (0–2.40%), Aequitriradites sp. (0–2.19%) and Cyathidites minor (0–2.13%) are dominant; and some specie of Densoisporites, Cooksonites, Impardecispora, Pilosisporites, Schizaeosprites, Fixisporites, Leptolepidites, Trilobosporites, Kuylisporites, Klukisporites, Hsuisporites, Couperisporites, Maculatisporites are seen. The angiosperm pollen are rare in the assemblage, characterized by Clavatipollenites sp. (0–0.80%) and Songipollis sp. (0–0.27%). The geological age of the Damoguaihe Formation is assigned to Hauterivian – Barremian of Early Cretaceous according to the palynological data, due to the fact that there existed a lot of diverse spores of the family Schizaeaceae and prosperous gymnosperm saccat pollen which the corpus and sacci are differentiated completely, and the presence of early angiosperm pollen of Clavatipollenites. However, the zircon U-Pb isotopic dating of the volcanic rocks in the Nantun Formation indicated that the overlying strata of the Nantun Formation, i.e. the Damoguaihe Formation must be younger than 127.0±2.0–137.9±1.5 Ma. This is consistent with the palynological data. Furthermore, the vegetation reconstructed on the palynological data of the Damoguaihe Formation is conifer forest with shrubs and grassland, belonging to the semi-humid or humid middle to south subtropical climate. Moreover, three new species, namely Biretisporites punctatus sp. nov., Chasmatosporites reticulates sp. nov. and Concentrisporites contractus sp. nov. are described here.

摘要:Extensive mass transport deposits (MTDs), which form a significant component of the stratigraphic record in ancient and modern deep water systems, mostly distributed in the continental margin of ocean basins worldwide. To date, no large-scale MTDs have been found in Chinese terrestrial basins. Based on integrated analysis of the seismic, drilling, core and logging data, this article report MTDs have been found in Songliao terrestrial basin (SLTB), Northeast China. During the depositional period of the Upper Cretaceous Qingshankou Formation, slope break of lacustrine basins was an ideal discharge place for gravity depositions. Regional sedimentary study of MTDs reveals that Cretaceous-age MTDs in SLTB were deposited in slope-break environments by slide, slump and debris flow, and MTDs were mixed with little turbidite simultaneously. Besides the massive aspect, key features of MTDs are the common presence of deformational structures or soft-sedimentary deformation, floating shale clasts, boudins, microfaults, distortion beddings, rotated sand debris. Detailed mapping of two three-dimensional (3-D) seismic surveys acquired in Yingtai (YT) and Haituozi (HTZ) areas reveals that MTDs are characterized by chaotic, mounded, and transparent seismic reflection. Growth fault, slope gully and geomorphology of the slope break greatly influenced the sedimentary process and external geometry of MTDs, and as a consequence, MTDs in SLTB exhibit classic fan-like geometry and some special (non-fan-like) external geometry. Furthermore, fan-like MTDs can be divided into three subcategories, including isolated fan, mother-son fan and stacked fan. Non-fan-like MTDs can be divided into two subcategories, strip-like MTDs and faulted-pit MTDs. A new sedimentary model has been built for MTDs in SLTB. MTDs have become a new exploration and development target in the SLTB.

摘要:In the Langshan region, northwestern China, marked multi-stage intraplate deformation events have occurred since the Mesozoic, including (1) northeast-striking ductile left-lateral strike slip during the Middle-Late Triassic, which is closely related to the collision between the North China and the Yangtze plates; (2) top-to-the-southeast thrust with northwest-southeast trending maximum compression during the Late Jurassic; (3) nearly eastward detachment during the Early Cretaceous; (4) top-to-the-northwest thrust with northwest-southeast trending maximum compression during the Late Cretaceous and Early Cenozoic; (5) northeast-striking brittle left-lateral strike slip with nearly north-south trending maximum compression; and (6) northwest-southeast extension during the Middle-Late Cenozoic. All these deformation events belong to the intraplate deformation across the entire Central Asian region and respond to the tectonic events along the plate boundaries or deep tectonics. The structures developed in early events in the crust were the most important factors controlling the later deformation styles, and few new structures have later developed. Based on previous research and our results, the paleostress inversion in the Langshan region shows that the Mesozoic intraplate deformations in the study region mainly resulted from the tectonic events from the Paleo-Pacific region and have no or a weak relation to the Tethys region. During the Late Jurassic, the maximum compression from the Mongolia-Okhotsk region cannot be excluded. The Langshan region is the bridge between southern Mongolia and the western Ordos tectonic belt and is thus important to understand the nature and relationship between both regions.

摘要:A succession of 5 FIA trends (foliation intersection or inflection axes in porphyroblasts) preserved in high temperature-low pressure regime PreCambrian rocks in the Texas Creek, Arkansas River region reflected by the fold axial plane traces and schistosity data in this region. Similar fold axial plane trace data measured in Palaeozoic rocks in Chester Dome, Vermont, which is high temperature to medium pressure regime, only preserve the effects of the youngest FIAs of the all 5 FIA sets that obtained in this region. The other three FIA sets have no equivalent fold axial planes. This difference from shallow to deeper orogenic regimes reflects decreasing competency at greater pressure with collapse and unfolding of earlier formed folds. The greater overlying load of rocks has tended to flatten all but the very largest early-formed structures, preserving only those folds that were more recently developed.

摘要:Albitite often accompanies with various metal and gem mineral deposits and a large number of occurrences have been reported globally, including the South Qinling orogen, China. The Xiaozhen copper deposit is a typical deposit in the North Daba Mountain area of the South Qinling orogen whose distribution is controlled by albitite veins and fractures. As there are few studies on the petrogenesis of albitite in Xiaozhen copper deposit, this paper focuses on the petrogenesis of albitite and its mineralization age. Detailed fieldwork and mineral microscopic observations initially suggest that albitite from the Xiaozhen copper deposit is igneous in origin. Further zircon trace element geochemistry studies indicate that these zircons have high Th/U ratios (>0.5), low La content, high (Sm/La)N and Ce/Ce* values, and a strong negative Eu anomaly, which are commonly seen in magmatic zircons. The chondrite–normalized rare earth element (REE) patterns are consistent with magmatic zircons from throughout the world, and they fall within or near the field of magmatic zircons on discriminant diagrams. The calculated average apparent Ti–in–zircon temperature for young zircons is 780°C, consistent with magmatic zircon crystallization temperatures. Therefore, zircon geochemistry indicates that the albitite origin is magmatic. SIMS U–Pb dating on nine magmatic zircons yielded a concordia age of 154.8±2.2 Ma, which represents the formation of albitite and the metallogenic age. More importantly, it is consistent with the ages of Yanshanian magmatism and metallogenesis in the South Qinling orogen, so formation of the Xiaozhen copper deposit may be a closely related geological event.

摘要:The cored sediments sampled by R/V Marion Dufrense in the active margin off southwestern Taiwan on the east side of the Manila Trench are mostly muds consisting mainly of quartz, feldspar, illite, chlorite + kaolinite with a trace amount of montmorillonite. The cored sediments have higher Fe, Ti, Cr, Cs, Li, Ni, and V but lower Ca, Na, Mn, Hf, Nb, Sr, Ta, U and Zr contents when compared with the upper continental crust (UCC, Taylor and McLennan, 1985). The Eu/Eu* ratios of the sediments averaging 0.69 indicate that the recycling effect on the Eu anomaly may be minor and the contribution of mafic source rock was unimportant, which can also be depicted in the La-Th-Sc plot (Cullers, 1994) showing a “mixed origin” close to the felsic end member. The chemistry of the cored sediment can be explained by a mixing model designed by Ho and Chen (1996) with four end members i.e., greywacke, shale, quartzite and limestone, which are widely distributed in the Cenozoic formations of southern Taiwan with greywacke as the dominant contributor followed by shale.

摘要:The Gol-e-Zard Zn-Pb deposit is one of several sediment-hosted Zn-Pb deposits found in the central part of the Sanadaj-Sirjan Zone, known as the Isfahan-Malayer belt, western Iran. Mineralization occurs in Upper Triassic to Jurassic phyllites and meta-sandstones. Sphalerite and galena are the most abundant metallic ores, with minor chalcopyrite. Calcite and quartz are the main gangue minerals. Fissure filling, replacement textures and especially mineralized faults, suggest an epigenetic stage in the Gol-e-Zard deposit formation. Geochemical studies of mineralized rocks show high concentrations of Zn, Pb and Cu, (Zn and Pb > 10000 ppm and Cu average 3000 ppm). LREE enrichment (LREE>HREE, La/Lu average 1.44) and positive Eu anomalies (Eu/Eu*>1 average 1.67) indicate reducing conditions during the deposition of deposit. However, some samples do not display negative Ce anomalies, which indicate that localized oxidizing conditions are also present. This study indicates that the Gol-e-Zard deposit formed due to circulating hydrothermal fluids in a marine environment. A SEDEX-type genesis, which is defined by circulating hydrothermal fluids through sediments in a marine environment, and syngenetic precipitation of Zn and Pb sulphides, is suggested for the Gol-e-Zard deposit. Emplacement of some granitoid intrusions such as the Aligudarz granitoid intrusion remobilized mineralizing fluids and metamorphosed the Gol-e-Zard deposit.

摘要:The Sanchahe quartz monzonite intrusion is situated in the middle segment of the North Qinling tectonic belt, Central China mainland, and consists chiefly of sanukitoid–like and granodioritic-monzogranitic rocks. The sanukitoid–like rocks are characterized by quartz monzonites, which display higher Mg# (55.0–59.0), and enrichments in Na2O+K2O (7.28–8.94 %), Ni (21-2312 ppm), Cr (56-4167 ppm), Sr (553-923 ppm), Ba (912-1355 ppm) and LREE ((La/Yb)N=9.47–15.3), from negative to slightly positive Eu anomalies (δEu=+0.61 to +1.10), but also depletion in Nb, Ta and Ti. The granodioritic-monzogranitic rocks diaplay various Mg# of 6.00-53.0, high Na2O+K2O (7.20–8.30%), Sr (455–1081 ppm) and (La/Yb)N (27.6–47.8), with positive Eu anomalies (δEu=1.03–1.57) and depleted Nb, Ta and Ti. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) zircon U-Pb isotopic dating reveals that the sanukitoid-like rocks were emplaced at two episodes of magmatism at 457±3 Ma and 431±2 Ma, respectively. The monzogranites were emplaced at 445±7Ma. Sanukitoid–like rocks have their εHf(t) values ranging from +0.3 to +15.1 with Hf–depleted mantle model ages of 445 to 1056 Ma, and the monzogranite shows its εHf(t) values ranging from ?21.6 to +10.8 with Hf–depleted mantle model ages of 635 to 3183 Ma. Petrological, geochemical and zircon Lu–Hf isotopic features indicate that the magmatic precursor of sanukitoid–like rocks was derived from partial melting of the depleted mantle wedge materials that were metasomatized by fluids and melts related to subduction of oceanic slab, subsequently the sanukitoid magma ascended to crust level. This emplaced mantle magma caused partial melting of crustally metamorphosed sedimentary rocks, and mixing with the crustal magma, and suffered fractional crystallization, which lead to formations of quartz monzonites. However, the magmatic precursor of the granodioritic-monzogranitic rocks were derived from partial melting of subducted oceanic slab basalts. Integrated previous investigation for the adackitic rocks in the south of the intrusion, the Sanchahe intrusion signed that the North Qinling tectonic zone was developed in an early Paleozoic transitionally tectonic background from an island arc to back–arc.

摘要:Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(–Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni–Mn–V–Ti (Factor 1), Mg–Al–Zn (Factor 2), and Ga–Co (Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(–Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(–Cu) deposits may be related to felsic magmatism.

摘要:The SEM-EDX technique was applied to investigate Au, and Cu+Sn alloyed grains in the mineralization of the Um Shashoba mine for achieving further understanding of occurrences, internal structures and microchemistry of Au and Cu alloys and associated minerals, and mineralization type. This study is aiming at the genetic history of ore-bearing fluid events, geochemical evaluation and exploration significance. The results showed that the mineralization could be considered as a single major episode generated by metamorphic mesothermal solution rich in sulfides and unsaturated respect to Au. It was differentiated into many stages; started with formation of auriferous pyrite that was pseudomorphed by secondary hematite, limonite and goethite. Three phases of Au alloy were precipitated, and Cu+Sn and Ag-rich alloys were produced respectively and followed by deposition of two generations of barren pyrite. Calcite and ankerite were crystalized, surrounded and partially replaced some of early formed minerals. Finally, barren muscovite recrystallized around and inside both later formed carbonate minerals that were free of any sign of Au in their structures. The processes of deformation, recrystallization, annealing, dissolution, remobilization and re-precipitation played the most important roles in the genetic history of the mineralization.

摘要:An extinct hydrothermal barite-silica chimney from the Franklin Seamount of the Woodlark Basin, in the southwestern Pacific Ocean, was investigated for mineral distribution and geochemical composition. Six layers on either side of the orifice of a chimney show significant disparity in color, mineral assemblage and major element composition. Electron microscope (SEM) images reveal that the peripheral wall of the chimney is composed of colloform silica, suggesting that incipient precipitation of silica-saturated hydrothermal fluid initiated the development of the chimney wall. Intermediate layers, between the exterior wall and the inner fluid-orifice, dominate with barite and sulfides. Low Sr-to-Ba ratios (SrO/BaO = 0.015–0.017) indicate restricted fluid-seawater mixing, which causes relatively high-temperature formation of the intermediate layers. Whereas the innermost layer bordering the chimney orifice is characterized by more silica and a higher Sr-to-Ba ratio (SrO/BaO = 0.023), could have formed due to a paragenetic shift from a high-temperature active phase to a cooler waning stage of formation. A paragenetic shift is also probably responsible for the change in mineral formation mechanism that resulted in the textural variation of barite and colloform silica developed during different growth phases of this barite-silica chimney.

摘要:The distributions of lipids in surface and subsurface sediments from the northern South China Sea were determined. The n-alkanes were in bimodal distribution that is characterized by a centre at n-C16–n-C20 with maximum at C18 (or C19) and n-C27–n-C31 as well as at C29 (or C31). The short-chain alkanes suffered from significant losses due to their slow deposition in the water column, and their presence with a slight even carbon predominance in shallow seafloor sediments was ascribed mainly to the direct input from the benthos. The long-chain alkanes with odd predominance indicate transportion of terrigenous organic matter. Immature hopanoid biomarkers reflect the intense microbial activity for bacteria–derived organic matter and the gradual increase of maturity with burial depth. Abundant n-fatty acid methyl esters (n-FAMEs) that are in distributions coincident with fatty acids were detected in all samples. We proposed that the observed FAMEs originated from the methyl esterification of fatty acids; methanol production by methanotrophs and methanogenic archaea related to the anaerobic oxidation of methane, and sulfate reduction provided an O–methyl donor for methylation of fatty acids. The CH4 released from hydrate dissociation at oxygen isotope stage II of Cores ZD3 and ZS5, which had been confirmed by the occurrence of negative δ13C excursion and spherical pyrite aggregates, could have accelerated the above process and thus maximized the relative content of FAMEs at ZD3-2 (400–420 cm depth) and ZS5-2 (241–291 cm depth).

摘要:The impact of CO2 sequestration on the host formation is an issue occurring over geologic time. Laboratory tests can provide important results to investigate this matter but have limitations due to a relatively short timeline. Based on literature review and core sample observation, naturally occurred geological phenomena, stylolites are studied in this paper for understanding CO2 sequestration in deep carbonate formations. Stylolites are distinctive and pervasive structures in carbonates that are related to water-assisted pressure solution. Pressure solution involving stylolitization is thought to be the main mechanism of compaction and cementation for many carbonates. In parallel, CO2 sequestration in carbonate formation involves extensive chemical reactions among water, CO2 and rock matrix, favoring chemical compaction as a consequence. An analogue between stylolites and CO2 sequestration induced formation heterogeneity exists in the sense of chemical compaction, as both pressure solution in stylolites and CO2 enriched solution in CO2 sequestration in carbonate formations may all introduce abnormal porous regions. The shear and/or tension fractures associated with stylolites zones may develop vertically or sub-vertically; all these give us alert for long-term safety of CO2 sequestration. Thus a study of stylolites will help to understand the CO2 sequestration in deep carbonate formation in the long run.

摘要:In this study uranium and thorium contents and depositional characteristics of ?ay?rhan bituminous shales (?BS), west of Ankara (central Anatolia), are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H?rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of ?BS (1.83/2.62 ppm) are much lower than averages of UC, NASK and PAAS (uranium: 2.70/2.66/3.10 ppm; thorium: 8.50/12.30/14.60 ppm). Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of ?BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites (e.g. gneiss, schist) which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals (e.g. autunite, torbernite) which occur in granite, gneiss and schist. ?BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements.

摘要:This paper reviews the current progress and problems in the study of microbialites and microbial carbonates. Microbialites and microbial carbonates, formed during growth of microbes by their calcification and binding of detrital sediment, have recently become one of the most popular geological topics. They occur throughout the entire geological history, and bear important theoretical and economic significances due to their complex structures and formative processes. Microbialites are in place benthic microbial buildups, whereas microbial carbonates can be classified into two categories: stabilized microbial carbonates (i.e., carbonate microbialites, such as stromatolites and thrombolites) and mobilized microbial carbonates (i.e., microbial carbonate grains, such as oncoids and microbial lumps). Various texture, structures, and morphologies of microbialites and microbial carbonates hamper the systematic description and classification. Moreover, complex calcification pathways and diagenetic modifications further obscure the origin of some microbialites and microbial carbonates. Recent findings of abundant sponge spicules in previously identified “microbialites” challenge the traditional views about the origins of these “microbialites” and their implications to reef evolution. Microbialites and microbial carbonates did not always flourish in the aftermath of extinction events, which, together with other evidences, suggests that they are affected not only by metazoans but also by other geological factors. Their growth, development, and demise are also closely related to sea-level changes, due to their dependence on water depth, clarity, nutrient, and sunlight. Detailed studies on microbialites and microbial carbonates throughout geological history would certainly help understand causes and effects of major geological events as well as the co-evolution of life and environment.

摘要:The chemical and isotopic characteristics of the water and suspended particulate materials (SPM) in the Yangtze River were investigated on the samples collected from 25 hydrological monitoring stations in the mainsteam and 13 hydrological monitoring stations in the major tributaries during 2003 to 2007. The water samples show a large variation in both δD (?30‰ to ?112‰) and δ18O (?3.8‰ to ?15.4‰) values. Both δD and δ18O values show a decrease from the river head to the Jinsha Jiang section and then increase downstream to the river mouth. It is found that the oxygen and hydrogen isotopic compositions of the Yangtze water are controlled by meteoric precipitation, evaporation, ice (and snow) melting and dam building. The Yangtze SPM concentrations show a large variation and are well corresponded to the spatial and temporal changes of flow speed, runoff and SPM supply, which are affected by the slope of the river bed, local precipitation rate, weathering intensity, erosion condition and anthropogenic activity. The Yangtze SPM consists of clay minerals, clastic silicate and carbonate minerals, heavy minerals, iron hydroxide and organic compounds. From the upper to lower reaches, the clay and clastic silicate components in SPM increase gradually, but the carbonate components decrease gradually, which may reflect changes of climate and weathering intensity in the drainage area. Compared to those of the upper crust rocks, the Yangtze SPM has lower contents of SiO2, CaO, K2O and Na2O and higher contents of TFe2O3 and trace metals of Co, Ni, Cu, Zn, Pb and Cd. The ΣREE in the Yangtze SPM is also slightly higher than that of the upper crust. From the upper to lower reaches, the CaO and MgO contents in SPM decrease gradually, but the SiO2 content increases gradually, corresponding to the increase of clay minerals and decrease of the carbonates. The δ30SiSPM values (?1.1‰ to 0.3‰) of the Yangtze SPM are similar to those of the average shale, but lower than those of the granite rocks (?0.3‰ to 0.3‰), reflecting the effect of silicon isotope fractionation in silicate weathering process. The δ30SiSPM values of the Yangtze SPM show a decreasing trend from the upper to the middle and lower reaches, responding to the variation of the clay content. The major anions of the river water are HCO3?, SO42?, Cl?, NO3?, SiO44? and F? and the major cations include Ca2+, Na+, Mg2+, K+ and Sr2+. The good correlation between HCO3- content and the content of Ca2+ may suggest that carbonate dissolution is the dominate contributor to the total dissolved solid (TDS) of the Yangtze River. Very good correlations are also found among contents of Cl?, SO42?, Na+, Mg2+, K+ and Sr2+, indicating the important contribution of evaporite dissolution to the TDS of the Yangtze River. High TDS contents are generally found in the head water, reflecting a strong effect of evaporation in the Qinghai-Tibet Plateau. A small increase of the TDS is generally observed in the river mouth, indicating the influence of tidal intrusion. The F? and NO3? contents show a clear increase trend from the upstream to downstream, reflecting the contribution of pesticides and fertilizers in the Chuan Jiang section and the middle and lower reaches. The DSi shows a decrease trend from the upstream to downstream, reflecting the