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摘要:A new species, Tsuga nanfengensis sp. nov. (Pinaceae), is described on the basis of lignified fossil wood from the late Miocene of the Xianfeng Basin, central Yunnan, southwestern China. Detailed observation of the fossil wood specimens show the following characteristics: distinct growth rings, absence of resin canals, uniseriate bordered pits in the radial wall of tracheids, ray tracheids and piceoid and cupressoid cross-field pits. These features indicate similarities to the wood of extant Tsuga canadensis, T. chinensis, and T. dumosa. According to the fossil record, Tsuga was present in Xundian County during the Miocene. Today Tsuga is drought intolerant, preferring wet conditions with no extant species growing naturally in Xundian County. The presence of Tsuga in the Miocene of Xundian County indicates a humid climate consistent with previous palaeoclimatic reconstructions showing a wetter and probably shorter dry season in the Miocene, relative to the present day. Therefore, the change in the local climate such as increasing aridity through the Miocene might explain the local extinction of Tsuga from central Yunnan.

摘要:In Europe, fossil fruits and seeds of Rhodoleia (Hamamelidaceae) have been described from the Upper Cretaceous to the Miocene, whereas no fossil record of Rhodoleia has been reported in Asia, where the modern species occur. Herein, 21 fossil leaves identified as Rhodoleia tengchongensis sp. nov. are described from the Upper Pliocene of Tengchong County, Yunnan Province, Southwest China. The fossils exhibit elliptic lamina with entire margins, simple brochidodromous major secondary veins, mixed percurrent intercostal tertiary veins, and looped exterior tertiaries. The leaf cuticle is characterized by pentagonal or hexagonal cells, stellate multicellular trichomes, and paracytic stomata. The combination of leaf architecture and cuticular characteristics suggests that the fossil leaves should be classified into the genus Rhodoleia. The fossil distributions indicate that the genus Rhodoleia might originate from Central Europe, and that migrated to Asia prior to the Late Pliocene. Additionally, insect damage is investigated, and different types of damage, such as hole feeding, margin feeding, surface feeding, and galling, are observed on the thirteen fossil leaves. Based on the damage frequencies for the fossil and extant leaves, the specific feeding behavior of insects on Rhodoleia trees appears to have been established as early as the Late Pliocene. The high occurrence of Rhodoleia insect herbivory may attract the insect-foraging birds, thereby increasing the probability of pollination.

摘要:The present paper reports two new species of Buxus from the Oligocene Ningming Formation of Guangxi, South China, on the basis of several compressed fossil leaves. Buxus ningmingensis sp. nov. is characterized by an elliptic to ovate shape; pinnate venation with marginal secondary, long hairs on the adaxial side of the midvein base; and amphistomatic, anomocytic stomata with a prominent outer ring. All of these characteristics suggest a closest af?nity to the living Buxus microphylla subsp. sinica. Another new species identi?ed as Buxus preaustro-yunnanensis sp. nov. is characterized by the diagnostic formation of its admedially branched tertiaries, the trunks of which are often strongly thickened by sclereides. This species is most similar to the extant Buxus austro-yunnanensis. The co-occurrence of Buxus ningmingensis sp. nov. and Buxus preaustro-yunnanensis sp. nov. suggests that these two Buxus lived during the Oligocene under a warm, tropical to subtropical climate, similar to the current climate of Ningming. Our ?ndings provide the earliest fossil evidence of Buxus leaves with detailed illustrations of leaf architectural and cuticular features. The occurrence of these two species indicates that Buxus began to diversify in Guangxi no later than the Oligocene.

摘要:We describe new material of three-dimensionally phosphatized small shelly fossils Acanthocassis and Xinlispina gen. nov. from the Fortunian Stage (early Cambrian) of southern Shaanxi and northern Sichuan Provinces. The new materials allow description of the delicate morphology of these skeletons, and also their skeletogenesis. Acanthocassis and Xinlispina have comparable morphological features: a main branch and radially arranged sub-branches. They differ from each other in many details, e.g., the presence of a single central branch only in Xinlispina, and the presence of small nodes only in Acanthocassis. Acanthocassis cannot be a naked anthopolyp or hydropolyp because of the more-or-less stiffened cuticle and the absence of a mouth. Acanthocassis and Xinlispina differ from coeval sponge spicules and chancelloriid sclerites and rosettes of crossed pedicellariae of echinoderms, and might be cuticular ornaments of animals of unclear affinities. They occur in the first small shelly fossil assemblage zone, and could be adopted as auxiliary fossils for biostratigraphic correlation in southern China.

摘要:Four new species of three genera in the family Cimbrophlebiidae, Telobittacus decorus sp. nov., Bellicimbrophlebia heteroneura sp. nov., Cimbrophlebia amoena sp. nov., and Cimbrophlebia gracilenta sp. nov., are described and illustrated based on eleven well-preserved fossil specimens. These specimens were collected from the latest Middle Jurassic Jiulongshan Formation of Daohugou, Inner Mongolia, China. This is the first record of the genus Cimbrophlebia in the Jurassic extending its age from the Lower Cretaceous to the Middle Jurassic. Due to same venational characters, we propose that an undescribed fossil specimen of Cimbrophlebiidae from the Jurassic of Germany is attributed to C. gracilenta sp. nov. Our new findings demonstrate an evolutionary trend of venational change from 185 to 50 Ma that the level of the bifurcation of Rs is gradually moving toward the base of wing in reference to the bifurcation of M.

摘要:As an important part of South China Old Land, the Jiangnan Orogenic Belt plays a significant role in explaining the assembly and the evolution of the Upper Yangtze Block and Cathaysia, as well as the structure and growth mechanism of continental lithosphere in South China. The Lengjiaxi and the Banxi groups are the base strata of the west section of the Jiangnan Orogenic Belt. Thus, the research of geochronology and tectonic evolution of the Lengjiaxi and the Banxi groups is significant. The maximum sedimentary age of the Lengjiaxi Group is ca. 862 Ma, and the minimum is ca. 822 Ma. The Zhangjiawan Formation, which is situated in the upper part of the Banxi Group is ca. 802 Ma. The Lengjiaxi Group and equivalent strata should thus belong to the Neoproterozoic in age. The Jiangnan Orogenic Belt consisting of the Lengjiaxi and the Banxi groups as important constituents is not a Greenville Orogen Belt (1.3 Ga–1.0 Ga). The Jiangnan Orogenic Belt is a recyclic orogenic belt, and the prototype basin is a foreland basin with materials derived from the southwest and the sediments belong to the active continental sedimentation. By combining large amounts of dating data of the Lengjiaxi and the Banxi groups as well as equivalent strata, the evolutionary model of the western section of the Jiangnan Orogenic Belt is established as follows: Before 862 Ma, the South China Ocean was subducted beneath the Upper Yangtze Block, while a continental island arc was formed on the side near the Upper Yangtze Block. The South China Ocean was not closed in this period. From 862 Ma to 822 Ma, the Upper Yangtze Block was collided with Cathaysia; and sediments began to be deposited in the foreland basin between the two blocks. The Lengjiaxi Group and equivalent strata were thus formed and the materials might be derived from the recyclic orogenic belt. From 822 Ma to 802 Ma, Cathaysia continued pushing to the Upper Yangtze Block, experienced the Jinning-Sibao Movement (Wuling Movement); as result, the folded basement of the Jiangnan Orogenic Belt was formed. After 802 Ma, Cathaysia and the Upper Yangtze Block were separated from each other, the Nanhua rift basin was formed and began to receive the sediments of the Banxi Group and equivalent strata. These large amounts of dating data and research results also indicate that before the collision of the Upper Yangtze Block with Cathaysia, materials of the continental crust became less and less from the southwest to the east in the Jiangnan Orogeneic Belt; only island arc and neomagmatic arc were developed in the eastern section. Ocean-continent subduction or continent-continent subduction took place in the western and southern sections, while intra-oceanic subduction occurred in the eastern section. Comprehensive analyses on U-Pb ages and Hf model ages of zircons, the main provenance of the Lengjiaxi Group is Cathaysia.

摘要:The Xiaojiang fault is a major active left-lateral fault along the southeastern margin of the Tibetan Plateau. The largest historical earthquake in Yunnan Province, with a magnitude 8 and a mean coseismic left-lateral displacement of ~ 6.9 m, occurred on the western branch of the Xiaojiang fault. Studying this fault is important in understanding current deformation and kinematic characteristics of the Tibetan Plateau. Activities and stretches have been well undertaken on the Xiaojiang fault, while paleoseismic research work is always the weak link on this fault. To investigate the paleoseismic history and large earthquake activity of the Xiaojiang fault, we opened a large trench at the northern edge of Caohaizi sag pond on the western branch of the Xiaojiang fault. Six paleoseismic events have been identified, and named E1 through E6 from the oldest to the youngest. Charcoal and woods are abundant, 20 samples were dated to constrain the ages of the paleoseismic events at 40?000–36?300?BC, 35?400–24?800?BC, 9?500?BC–AD 500, AD 390–720, AD 1120–1620 and AD 1750–present. We associate the youngest event E6 with the 1833 M8 earthquake. Events E4, E5 and E6 show a continuous record of the western strand of the Xiaojiang fault in the late Holocene, with a average recurrence interval of 370–480 yr. Large earthquake recurrence in the late Holocene is far less than the recurrence of 2000–4000 yr posed in previous studies. Thus, the seismic hazard on the Xiaojiang fault should be reevaluated. Furthermore, the irregular recurrence of large earthquakes on the Xiaojiang fault and other faults in the Xianshuihe-Xiaojiang system, indicates the uneven southeastward extrusion of the Sichuan-Yunnan block along the southeastern margin of the Tibetan Plateau.

摘要:On the basis of field observations of the structures of three profiles from the Linshu region, deformation characteristics and the tectonic background of the Yishu fault belt in the Late Cretaceous–Early Cenozoic have been discussed in detail. Three structural profiles, whose deformations consist mainly of earlier transpressional faults and later normal faults, were developed for the Mengtuan Formation of the Lower Cretaceous Dasheng Group. Typical positive flower structures, duplex structures, and break-through faults were found in these profiles. On the basis of analyses of the structural deformation and previous geochronological studies, it was concluded that the earlier transpressional faults of the profiles were triggered by the sinistral transpression of the Yishu fault belt in the Late Cretaceous–Early Paleogene, and that the later normal faults, formed during the Late Paleogene–Neogene extension, truncated the earlier transpressional faults. With consideration of the tectonic evolution of the Tan-Lu fault belt and the different drift directions of the Pacific plate since the Cretaceous, we suggest that the major tectonic events of the Late Cretaceous–Neogene in eastern China were mainly controlled by the subduction of the Pacific plate.

摘要:It seems to be progressively recognized that the stress of the India-Asia convergent front can be transferred rapidly through the southern and central Tibetan lithosphere to the northern Tibet, hence leading to the crustal thickening deformation there during or immediately after the onset of the India-Asia collision (ca. 55 Ma). This study focuses on the late Cenozoic deformation and tectonic uplift of the northern Tibet and Tian Shan area. Detailed compilations of a variety of proxy data from sediments and bedrocks suggest that the northern Tibet and Tian Shan area underwent one stage of approximately synchronous widespread contractile deformation since 25–20 Ma, which seemed to decrease at circa 18 Ma as revealed by low-temperature thermochronological data. The latest Oligocene-early Miocene was also significant basin-forming episodes when many intermontane subbasins began to receive syntectonic sedimentation in the northeastern Tibet. Subsequently, the other phase of compressional deformation began to encroach more widely into the northern Tibet and Tian Shan area in episodic steps or continuously from 16–12 Ma to present.

摘要:This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelectron spectroscopy (XPS). A revolutionary discovery is that the uranium not only exists in the forms of tetravalent and hexavalent uranium oxides, but also occurs in the form of native uranium. This is the first discovery of the existence of native uranium in nature. It greatly helps to reveal the origin of hydrothermal mineralization of uranium, and also has great significance for studying the thermal energy, formation and evolution of the earth.

摘要:The Duocaima carbonate-hosted Pb-Zn deposit is a newly found large deposit in the southern area of Qinghai Province. In this paper, the characteristics, genesis, significance to Pb-Zn mineralization of the widely developed breccias, and the ore-forming process have been carefully studied based on geological documentation of drilling holes, microscopic observations of petrography and microstructure and some stable isotope measurements. Based on the compositions of the clast and matrix, the breccias can be classified into three types: limestone clasts cemented by marl; limestone clasts with fine-grained calcareous materials; and limestone clasts cemented by hydrothermal calcite. The mineralization in the first type of breccia is weak, whereas it is strong in the latter two types of breccias. According to the locations of occurrence and structural characteristics of the breccias along with the relationship between the breccias and mineralization, part of the limestone clasts that are cemented by marl and outcrop in the contact zone between the Wudaoliang Formation (Nw) and the underlying Jiushidaoban Formation (Pj) are attributed to synsedimentary fault-genetic breccia, whereas the last of the limestone clasts that are cemented by marl and developed in the Jiushidaoban Formation (Pj) are attributed to the breccia generated by karst cave collapse; the limestone clasts with fine-grained calcareous materials and the limestone clasts cemented by hydrothermal calcite are attributed to breccia formed by hydrothermal dissolution. The breccia formed by karst collapse had consistently evolved for a long period of time, while the breccias with other origins were formed around the period of mineralization (i.e., about or slightly later than 20–16 Ma). The breccia generated by karst cave collapse and hydrothermal dissolution are somewhat related; the formation of the breccia from karst cave collapse provided open space for the later mineralization and reaction between hydrothermal fluids and host rocks, and the subsequent strong dissolution by hydrothermal fluids transformed some of the breccia formed earlier by karst cave collapse. Meanwhile, carbonate host rocks with breccias and brecciaed mineralization can be a potential sign of Mississippi Valley Type (MVT) deposits and important indicators for regional mineral exploration. The δ13CV-PDB, δ18OV-SMOW, and 87Sr/86Sr values of hydrothermal calcite in the Duocaima deposit range from 4.3‰ to 7.1‰, 14.9‰ to 20.1‰, and 0.707494 to 0.708185, respectively; the δ13CV-PDB, δ18OV-SMOW, and 87Sr/86Sr values of the host limestones of the Jiushidaoban Formation range from 3.6‰ to 5.3‰, 18.0‰ to 20.5‰, and 0.707372 to 0.707945, respectively. The δ13CV-PDB and 87Sr/86Sr values of hydrothermal calcite and limestone are similar, indicating single sources of C and Sr in this deposit, with the likely source being the limestone of the Jiushidaoban Formation. The minor scattering of the δ18OV-SMOW values suggests that different O isotope fluids underwent the isotope exchange reaction. The C-O-Sr isotope characteristics indicate that the host limestones experienced a dissolution and precipitation process during mineralization, which is beneficial to improving the porosity of host rocks and promoting the precipitation of metal sulfides. The δ34SV-CDT value of the breccia-type mineralization sulfides ranges from ?30.4‰ to ?0.3‰; that is, the δ34SV-CDT value is negative with considerable variation, illustrating that during the breccia-type mineralization process, the bacteriogenic reduction of sulfates provided the vast majority of sulfur, whereas the thermochemical reduction of sulfates was relatively unimportant. The brecciation that occurred as a result of karst cave collapse was mainly generated by the dissolution of groundwater; however, the brecciation related to hydrothermal dissolution and mineralization processes were caused by mixing of different fluids.

摘要:The Tongshankou Cu-Mo deposit, located in southeast Hubei province, is a typical skarn–porphyry type ore deposit closely related to the Tongshankou granodiorite porphyry, characterized by a high Sr/Y ratio. Detailed in situ analyses of the trace elements and U–Pb and Lu–Hf isotopes in zircons from the Tongshankou granodiorite porphyry were performed. Scarcely any inherited zircons were observed, and the analyzed zircons yielded highly concordant results with a weighted mean 206Pb/238U age of 143.5 ± 0.45 Ma (n=20, mean square weighted deviation was 0.75), which was interpreted to represent the crystallization age of the Tongshankou granodiorite porphyry. The chondrite-normalized rare-earth element pattern was characterized by a slope that steeply rises from the light-group rare-earth elements (LREE) to the heavy-group rare-earth elements (HREE) with a positive Ce-anomaly and inconspicuous Eu-anomaly, which was coincident with the pattern of the zircons from the Chuquicamata West porphyry, Chile. The analyzed zircons also had relatively low 176Hf/177Hf ratios of 0.282526–0.282604. Assuming t=143 Ma, the corresponding calculated initial Hf isotope compositions (εHf(t)) ranged from ?5.6 to ?2.9. The results of the in situ analysis of trace elements and U–Pb and Lu–Hf isotopes in zircons from the Tongshankou granodiorite porphyry suggest that a deep-seated process involving a thickened-crust/enriched-mantle interaction may play an important role in the generation of high Sr/Y-ratio magma and potentially in the generation of porphyry Cu-Mo systems.

摘要:We report geochemical data, SHRIMP zircon ages and Hf-in-zircon isotopic compositions for Cenozoic granitoids from major fault systems in the Tethyan belt in western Yunnan Province, southwestern China. Four magmatic pulses occurred in the Paleogene, namely at ca. 57 Ma, ca. 50 Ma, 45–40 Ma, and 38–34 Ma. Early magmatism of this episode (57–50 Ma) produced S-type granites whose zircons yielded εHf(t) values of ?5.0 to ?0.3. In contrast, late magmatism of this episode reflects heterogeneous sources. Zircons from a granite porphyry along the Ailaoshan-Red River fault system have slightly positive εHf(t) values suggesting derivation from relatively young crust and/or a juvenile source. However, zircons from a granite along the Gaoligong fault system have strongly negative εHf(t) values and suggest derivation from a Paleoproterozoic crustal source. The composition of the granitoids varies with age (from ca. 57 Ma to ca. 34 Ma) from peraluminous to metaluminous and also suggests a change from syn-collisional to late-orogenic tectonic setting. A new tectonic model, impacting lithospheric wedge (ILW) is shown for the origin of Paleogene granitoids in this paper.

摘要:Hydrogen gas accelerates hydrocarbon generation, but little is known about its distribution and origin in petroliferous basins, which has hindered the further exploration. Taken the Jiyang Depression in eastern China as an example, this study collected natural gas from different tectonic units, and analyzed various geochemical characters including gas contents, and carbon and hydrogen isotopic composition. The result shows that: (1) hydrogen gas is widespread distributed, but its content is very low, which typically ranges from 0.01% to 0.1% in this region; (2) the ratios of H2/3He, indicative of the origins of hydrogen gas, suggest that mantle-derived hydrogen is dominant. Even in tectonically stable areas absent with deep fluid activities, there is also mantle-derived; (3) the isotopic composition of hydrogen falls in the range of –798‰ to –628‰ (relative to VSMOW standard). In areas with deep-derived fluids, the hydrogen gas has a similar isotopic composition with the previously documented deep-sourced gas, with lighter isotopic composition. In contrast, hydrogen gas has a heavier isotopic composition in relatively stable areas. The isotopic signatures suggest that there is a mixture of mantle- and crust-derived hydrogen gas in the relatively stable area, which is consistent with the H2/3He ratios. Therefore, it is clear that the hydrogen gas has a much wider distribution than found in the deep-derived fluid area, resulting in a much broader area with hydrogenating effect for resource rock. This understanding will provide new insights for hydrocarbon generation research and resource assessment in petroliferous basins.

摘要:Gas-bearing deposits in the Lower Mingyuefeng Formation of Paleogene, Lishui Sag, East China Sea Shelf Basin consist of shoreface sandstones of the highstand systems tract (HST) and transgressive systems tract (TST), and deltaic sandstones of the lowstand systems tract (LST) and falling stage systems tract (FSST). Detailed petrographic observations suggest that the diagenetic features and related evolution of these deposits cannot be simply characterized and demonstrated in the depth domain. However, the occurrence of diagenetic minerals systematically depends on the studied interval within the HST, TST, LST, and FSST; therefore, diagenesis in this region can be better constrained when studied in the context of the depositional environments and sequence stratigraphic framework. The eogenetic processes in such settings include: (1) microcrystalline siderite precipitated as concretions in almost all environments and systems tracts, which inhibited further mechanical compaction; (2) grain dissolution and kaolinitization occurred in shoreface HST sandstones and deltaic LST and FSST sandstones; (3) glaucony was locally observed, which did not clearly reflect the controls of facies or sequence stratigraphy; and (4) cementation by pyrite aggregates occurred in the shoreface HST sandstones and deltaic LST sandstones. The mesogenetic diagenesis includes: (1) partial conversion of kaolinite into dickite in deltaic LST sandstones, and minor chlorite cementation in deltaic FSST sandstones; (2) transformation of kaolinite into illite and quartz cementation in deltaic LST and FSST sandstones; (3) frequent precipitation of ankerite and ferroan calcite in shoreface TST sandstones and early HST sandstones, forming baffles and barriers for fluid flow, with common calcite in shoreface HST sandstones as a late diagenetic cement; and (4) formation of dawsonite in the deltaic LST and FSST sandstones, which is interpreted to be a product of the invasion of a CO2-rich fluid, and acts as a good indicator of CO2-bearing reservoirs. This study has thus constructed a reliable conceptual model to describe the spatial and temporal distribution of diagenetic alterations. The results may provide an entirely new conceptual framework and methodology for successful gas exploration in the continental margins of offshore China, thus allowing us to predict and unravel the distribution and quality evolution of clastic reservoirs at a more detailed and reliable scale.

摘要:The hydrocarbon potential of the Hangjinqi area in the northern Ordos Basin is not well known, compared to the other areas of the basin, despite its substantial petroleum system. Restoration of a depth-converted seismic profile across the Hangjinqi Fault Zone (HFZ) in the eastern Hangjinqi area shows one compression that created anticlinal structures in the Late Triassic, and two extensions in ~Middle Jurassic and Late Early Cretaceous, which were interrupted by inversions in the Late Jurassic–Early Early Cretaceous and Late Cretaceous, respectively. Hydrocarbon generation at the well locations in the Central Ordos Basin (COB) began in the Late Triassic. Basin modeling of Well Zhao-4 suggests that hydrocarbon generation from the Late Carboniferous–Early Permian coal measures of the northern Shanbei Slope peaked in the Early Cretaceous, predating the inversion in the Late Cretaceous. Most source rocks in the Shanbei Slope passed the main gas-migration phase except for the Hangjinqi area source rocks (Well Jin-48). Hydrocarbons generated from the COB are likely to have migrated northward toward the anticlinal structures and traps along the HFZ because the basin-fill strata are dipping south. Faulting that continued during the extensional phase (Late Early Cretaceous) of the Hangjinqi area probably acted as conduits for the migration of hydrocarbons. Thus, the anticlinal structures and associated traps to the north of the HFZ might have trapped hydrocarbons that were charged from the Late Carboniferous–Early Permian coal measures in the COB since the Middle Jurassic.

摘要:The northeastern Tibetan Plateau is located at the convergence of the Asian winter and summer monsoons and westerlies; thus, this area has witnessed historic climate changes. The Xunhua basin is an intermontane basin on the northeastern margin of the Tibetan Plateau. The basin contains more than 2000 m of Cenozoic fluvial–lacustrine sediments, recording a long history of climate and environmental changes. We collected the mid-Miocene sediments from the Xunhua basin and used palynological methods to discuss the relationship between aridification in the interior of Asia, global cooling, and uplift of the Tibetan Plateau. Based on the palynological analysis of the Xigou section, Xunhua basin, the palynological diagram is subdivided into three pollen zones and past vegetation and climate are reconstructed. Zone I, Ephedripites–Nitraridites–Chenopodipollis–Quercoidites (14.0–12.5 Ma), represents mixed shrub–steppe vegetation with a dry and cold climate. In zone II, Pinaceae–Betulaepollenites–Ephedripites–Chenopodipollis–Graminidites (12.5–8.0 Ma), the vegetation and climate conditions improved, even though the vegetation was still dominated by shrub–steppe taxa. Zone III, Ephedripites–Nitrariadites–Chenopodipollis (8.0–5.0 Ma), represents desert steppe vegetation with drier and colder climate. The palynological records suggest that shrub–steppe dominated the whole Xigou section and the content gradually increased, implying a protracted aridification process, although there was an obvious climate improvement during 12.5–8.0 Ma. The aridification in the Xunhua basin and surrounding mountains during 14.0–12.5 Ma was probably related to global cooling induced by the rapid expansion of the East Antarctic ice-sheets and the relatively higher evaporation rate. During the 12.5–8.0 Ma period, although topographic changes (uplift of Jishi Shan) decreased precipitation and strengthened aridification in the Xunhua basin on leeward slopes, the improved vegetation and climate conditions were probably controlled by the decrease in evaporation rates as a result of continuous cooling. From 8.0 to 5.0 Ma, the rapid development of the desert steppe can be attributed to global cooling and uplift of the Tibetan Plateau.

摘要:There have been divergent opinions on whether Conophyllia develops synapticulae and dissepiments since its erection in 1849, with different views existing on the morphology of columella in Conophyllia. This paper presents a comprehensive review of Conophyllia, and revises the diagnosis according to new material from the Renacuo area of Gêrzê, Tibet. The revised diagnosis emphasises the following features: solitary coral; abundant radial elements subequal in thickness, lateral faces with granules and synapticulae; parietal, papillar or incompact columella, a few species lacking in columella; developed dissepiments. Individuals of Conophyllia have laminar septa of Triadophyllum type in earlier ontogenetic stages, while their septa in later ontogenetic stages are more fenestrate. The geological and geographical distribution of this genus is discussed, with five species of Conophyllia from the Renacuo area of Gêrzê, Tibet being described and illustrated, including one new species and two in open nomenclatue.

摘要:The Upper Carboniferous Zhanjin Formation has attracted much attention from geoscientists for containing glacial–marine diamictite and cold-water fauna typified by the bivalve Eurydesma. The presence of this Formation has provided important evidence for determining the northern border of Gondwana. Previous researchers have classified those strata north of Niangrong Co in the Gêrzê region as part of the Zhanjin Formation based on the presence of glacial–marine diamictite, although the absence of biological fossil evidence has defied clear age determination. Our field investigations first discovered large quantities of corals, sponges and bryozoans. All coral fossils were identified as belonging to the Hexacorallia subclass including 13 genera and 25 species, primarily including Conophyllia guiyangensis Deng et Kong, Coryphyllia regularis Cuif, Cuifia columnaris Roniewicz, Distichophyllia norica Frech, Distichophyllia gigas Vinassa de Regny, Pamiroseris rectilamellosa Winkler, Retiophyllia clathrata Emmrich, and Retiophyllia paraclathrata Roniewicz. Extensive biostratigraphic correlations show that the hexacorallia should belong to the Late Triassic, thereby negating the presence of the Zhanjin Formation in the study area. Based on analyses of sedimentary facies and detailed study of the glacial–marine diamictite as supposed by earlier researchers, the limestone blocks and gravels within the facies are slope facies olistostromes and waterway sediments from lime slurry debris flows in the submarine fan rather than primary sedimentary products. Among them, lenticular sandstone should be sequentially distributed waterway sand bodies, indicating that the strata have no glacial–marine diamictite. In addition, the rocks containing the mentioned fossils are just limestone blocks from olistostromes, and limestone gravels from waterways of submarine fans. Such a result further negates the presence of the Zhanjin Formation in the study area, and indicates that the age of the studied strata should be youner than the Late Triassic. Through regional stratigraphic comparisons and the study of tectonic settings of the strata, the sedimentary characteristics of the subject strata, including lithology, lithofacies and fossils, are confirmed to be similar to the widely distributed Sêwa Formation in this region. We thus infer that the strata belong to the Middle–Lower Jurassic Sêwa Formation. This finding is important for both studying paleogeography of Tibet and determining the northern boundary of Gondwana.

摘要:The Wenchuan earthquake has altered the crustal motion characteristics in the eastern margin of the Tibetan Plateau and adjacent regions. Using discontinuous GPS survey data for 2008–2012, the velocity field for the Eurasia reference framework has been obtained, and the general trend of contemporary crustal motion after the occurrence of the Wenchuan earthquake has been studied. In addition, using the velocity field, the block movement velocity has been estimated by least-squares fitting. Furthermore, the properties and displacement rates of main faults have been obtained from the differences in velocity vectors of the blocks on both sides of the faults. The results reveal that there are no obvious changes in the general characteristics of crustal motion in this area after the Wenchuan earthquake. The earthquake mainly changed the rate of the movement of the Chuan-Qing block and caused variation in the movement direction of the South China block. The effect of the earthquake on faults is mainly reflected in variations in fault displacement velocity; there is no fundamental change in the properties of fault activity. The displacement rates of the Xianshuihe fault decreased by 3–4 mm/a, the Longmenshan fault increased by 9–10 mm/a, and the northern segment of the Anninghe fault increased by approximately 9 mm/a. Furthermore, the displacement rates of the Minjiang, Xueshan, Huya, Longquanshan, and Xinjin faults increased by 2–3 mm/a. This implies that the effects of the Wenchuan earthquake on crustal movement can mainly be observed in the Chuan-Qing, South China, and N-Chuan-Dian blocks and their internal faults, as well as the Xianshuihe and Longmenshan faults and the northern section of the Anninghe fault. The reason for this is that the Wenchuan earthquake disturbed the kinematic and dynamic balance in the region.

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摘要:The distribution and formation mechanisms of typical identified seismites are analyzed based on various factors from plate tectonic positions, types of sedimentary basins and properties of seismogenic faults to focal mechanisms. Especially, structural styles, reserved positions, activity times, formation mechanisms and dynamics of soft-sediment deformation structures triggered by seismic activity are systematically analyzed. According to the genetic types of seismites, we propose 5 categories, including liquefied deformation, thixotropic deformation, hydroplastic deformation, superimposed gravity driving deformation and brittle deformation. Further, based on the main genetic types, composition of sediments and deformation styles, we draw up 35 secondary classifications. To determine paleo-seismic sequences in different times, activities of seismogenic faults, high-resolution tectonic events in one main tectonic movement and paleo-tectonic settings, and to understand the inducing mechanisms of paleo-earthquakes and ecologic environment evolution, researching on seismites are of great significance. Combing multiple approaches to identify the paleoearthquake records, simulating experiments on various soft-sediment deformation structures triggered by different magnitudes of shocking, dating precisely on paleo-seismic events, impacting on paleogeography and biological environment and on energy and resources domain are the frontiers of paleoseismic research.

摘要:China has abundant reserves of magnesite, making it the world’s leading source of this strategic mineral. Sparry magnesite is the main type of magnesite deposit, and is easy to exploit. It occurs mainly as the sedimentary-metamorphic type. Production is centred on eastern Liaoning Province, where a world-class large to super large magnesite ore processing and production facility has been developed. Hydrothermal metasomatic deposits, associated with ultramafic complexes and eluvial deposits produced by weathering, are two other important types found in China. The Western section of the Bangonghu-Nujiang metallogenic belt is an important target region for prospecting lake-sedimentary magnesite deposits. Based on a systematic analysis of material from 62 magnesite production areas, this study investigated the metallogeny of magnesite and delineated 13 magnesite metallogenic belts. Maps were produced showing metallogenic regularities in magnesite deposits, the metallogenic system of the magnesite deposits, and the distribution of the metallogenic belts of Chinese magnesite deposits. It provides a theoretical basis for forecasting the location of potential magnesite resources in China. Finally, it explores some key scientific issues, including the formation processes of ultra magnesite ore-concentrated areas, and their sources of magnesium.

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