Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P
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2016, 90(5):1560.
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2016, 90(5):1561.
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TANG Biao , HAN Meng , XU Qingqing , JIN Jianhua
2016, 90(5):1561-1571.
Abstract:Machilus maomingensis Jin et Tang, sp. nov. from the Eocene Youganwo Formation of the Maoming Basin, South China, is studied in detail from the perspective of the leaf architecture and the excellently preserved cuticle. The leaf margin is entire, the primary venation is pinnate; 6 to 8 secondary veins are present and the major secondary venation is eucamptodromous. Stomata are paracytic and occur on the lower epidermis. Trichome bases are unicellular. Oil cells are present in the upper epidermis. The new fossil species described has features of the Lauraceae, particularly of the extant genus Machilus Rumphius ex Nees, and it is most similar to Machilus chinensis (Bentham) Hemsley, an extant species distributed in southern China and Vietnam. Hence, Machilus maomingensis sp. nov. is inferred to live in a warm and humid climate. The discovery of the present fossil indicates that Machilus has existed in South China from at least the Eocene.
Aram BAYET-GOLL , Paul M. MYROW , Guillermo F. ACE?OLAZA , Reza MOUSSAVI-HARAMI , Asadollah MAHBOUBI
2016, 90(5):1572-1597.
Abstract:The Lower Ordovician Shirgesht Formation in central Iran is composed of siliciclastic and carbonate rocks deposited in diverse coastal and marine shelfal environments (tidal flat, lagoon, shoreface, offshore-shelf and carbonate ramp). Five facies associations contain diverse ichnofossil assemblages that show distinct proximal to distal trends formed in a wide range of physical-chemical conditions. The ethological groups of trace fossils in the Shirgesht Formation reflect a gradient of depositional stress conditions across a wave-influenced shoreline and shelf. Deposits of wave-influenced environments make up a significant component of the geological record of shallow marine settings, and the ability to determine paleoenvironments in detail in such successions is critical for reconstruction of depositional histories and sequence-stratigraphic interpretation.The Cruziana ichnofacies of the study shows highly diverse suites that record the establishment of a benthic community under stable conditions and a long-term colonization window. The Skolithos ichnofacies recognized is a low diversity opportunistic ichnocommunity suite that resulted from colonization after tempestite deposition in a stressed environment. The strata record an onshore to offshore replacement of the Cruziana ichnofacies (with abundant feeding traces of deposit-feeders) by the Skolithos ichnofacies (dominated by suspension-feeders and predators). A transitional zone between the two ichnofacies coincides with the offshore-transition/distal lower-surface deposits. The distribution of ichnofacies, the diversity and range of ethological characteristics reflected by the ichnogenera, and the wide range of wave-dominated coastal facies demonstrate the potential to use individual trace fossils and ichnofacies for significantly refined palaeoenvironmental analysis of wave-dominated coastal settings, particularly in Ordovician successions.
ITO Tsuyoshi , FENG Qinglai , MATSUOKA Atsushi
2016, 90(5):1598-1610.
Abstract:The Permian planktonic distribution is not well known, in contrast to other fossil distributions of nekton and benthos. Radiolaria are representative microfossils of plankton in the Permian palaeocean. This study compares both correlated radiolarian occurrences (Pseudotormentus De Wever et Caridroit and Quadriremis Nazarov et Ormiston) in literature data from the Pacific Rim and quantitative data from the Liuhuang and Gujingling sections in South China. Pseudotormentus distributions are concentrated in the Panthalassa, whereas Quadriremis occurrences are distributed over both the Panthalassa and the Palaeotethys. The uneven distribution of Pseudotormentus seems to have been controlled by a difference in the oceanic basins, indicating the presence of faunal differences in Permian planktonic microorganisms between the Panthalassa and the Palaeotethys. In other words, this study infers the provincialism of Permian planktonic microorganisms. The uneven distribution is explainable by a hypothesis that Pseudotormentus was strongly affected by a Panthalassan equatorial current.
WANG Ye , WANG Yue , DU Wei , WANG Xunlian
2016, 90(5):1611-1628.
Abstract:The abundance and diversity of macrofossils in the Ediacaran have attracted much attention. The upper Doushantuo macrobiotas in South China, including the Miaohe biota from Hubei and the Wenghui biota from Guizhou, are mainly preserved as the carbonaceous compressions and dominated by macroscopic algae and metazoans. Here, we describe 10 genera and 10 species (including 6 new genera and species) of macrofossils from the Wenghui biota. At present, the Wenghui biota yields macrofossils in more than 31 genera and 33 species, excluding those given no image and established on a few unascertained specimens. Based on the occurrence and distribution of macrofossils in both Miaohe and Wenghui areas, the middle-late Ediacaran (back shales of the upper Doushantuo Formation) in South China can be subdivided into two assemblage biozones in biostratigraphy: (i) the Protoconites–Linbotulitaenia–Eoandromeda–Anomalophton assemblage biozone characterized by abundant and diverse macrofossils and by the ranges of Protoconites, Linbotulitaenia and Anomalophton; and (ii) the Baculiphyca–Gesinella–Cucullus–Beltanelliformis assemblage biozone characterized by the acme of the longer macrofossils Baculiphyca and Gesinella, and by few shorter and discoidal macrofossils.
LIU Yunhuan , ZHANG Yanan , SHAO Tiequan , TANG Hanhua , JIANG Kaituo , WANG Qi , CHEN Cheng , DONG Junyan , LIANG Yongchun , DAI Jun , XUE Jiaqi
2016, 90(5):1629-1636.
Abstract:Maikhanellids are a distinct group of Cambrian Fortunian small shelly fossils by the cap-shaped profiles and scaly shell ornamentation. According to the individual shell shape and ornamentation feature types of 50 maikhanellids fossils which were collected from Xixiang botia, we confirmed the family Maikhanellidae content of six genera, which are Maikhanella, Ramenta, Purella, Ramentoides, Yunnannopleura and Mediata. Unlike the halkieriid animals whose shells and spicules are articulated on different body parts, maikhanellids were presumably yielded by siphogonuchitid spicules penetrating the intermediate matrix (the "spicule shell" hypothesis), and this is the reason that some researchers treated maikhanellids and co-occurring siphogonuchitids as synonyms. The affinities of Maikhanellids and siphogonuchitids remain debatable. Here, we report three dimensionally phosphatized maikhanellid shells and siphogonuchitid spicule bundles from the Cambrian Fortunian small shell faunas of South China. They differ from all the previously reported maikhanellids and siphogonuchitids, and may represent new types. The intact and smooth surface underneath the partially preserved scales of the shells challenges the "spicule-shell" hypothesis. The present siphogonuchitid spicules differ from the maikhanellid scales in size, morphology, and .arrangement pattern, thus the spicules might not be derived from the shells. Whether the shells and spicule bundles were articulated on different body parts of the same animals remains unknown.
SUN Ya , LIU Jianxin , TANG Youcai , CHEN Jiawei , ZHOU Keping , CHEN Bo
2016, 90(5):1637-1652.
Abstract:We applied the finite frequency tomography method to S wave data recorded by 350 broadband stations beneath the South China Block (SCB) and its surroundings from earthquakes occurring between July 2007 and July 2010, to better understand upper mantle deformation. Differential travel-times in the pair of stations with appropriate weighting for each station are used in the inversion. Our results are consistent with previous tomography that show a high velocity anomaly beneath the Sichuan basin and a high velocity anomaly in the transition zone beneath the Yangtze Craton. However, the resolution of mantle heterogeneity provides new insight into the tectonic framework of subduction of Burmese lithosphere in the west part of the study region and subduction of oceanic lithosphere in the east. In the subduction realm, west of 107oE, a significant fast S-wave anomaly is located on the southeast of Sichuan Basin. East of 107oE, and two narrow and discontinuous fast S-wave anomalies occur at a depth of 400–600 km beneath the middle of the South China block overlain by the pronounced low S-wave anomalies at a depth of 100 and 400 km. If the fast anomalies located in the mantle transition zone represent stagnant slabs, their fragmented nature may suggest that they could be produced by different episodes of subduction beneath western Pacific island and the above slow velocity anomaly may associated with the back-arc regions of ongoing subduction. In addition, tomography also reveals an anomalously high S-wave velocity continental root extends eastward to a depth 400 km beneath the eastern Sichuan Basin. This anomaly may be related to eastern extrusion of Indian lithosphere associated with the collision of India and Eurasia. Moreover, our results also show large slow anomalies beneath the Red River fault region connected to deeper anomalies beneath the South China Fold Belt and South China Sea. All these observations are consistent with the scenario that the South China block has been built by both of subduction of Paleo-pacific plate and eastward subduction of Burma microplate.
BUI Hoang Bac , NGO Xuan Thanh , Yungoo SONG , Tetsumaru ITAYA , Koshi YAGI , KHUONG The Hung , NGUYEN Tien Dung
2016, 90(5):1653-1663.
Abstract:Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes. This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province, Vietnam. The fault gouge samples were separated into three grain-size fractions (<0.1 μm, 0.1–0.4 μm and 0.4–1.0 μm). The results show that the K-Ar age values decrease from coarser to finer grain fractions (24.1 to 19.2 Ma), suggesting enrichment in finer fraction of more-recently grown authigenic illites. The timing of the fault movement are the lower intercept ages at 0% detrital illite (19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma). In combination with previous geochronological data, this result indicates that the metamorphism of the Day Nui Con Voi (DNCV) metamorphic complex took place before ca. 26.8 Ma. At about 26.8 Ma–25 Ma, the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone (RR-ASFZ). During brittle deformation, the DNCV slowly uplifted, implying weak movement of the fault. This brittle deformation might have lasted for ca. 5 Ma.
2016, 90(5):1664-1678.
Abstract:A thrust belt formed in the basin along the eastern margin of Pamir. The thrust belt is about 50 km wide, extends about 200 km, and includes three compressive structures from south to north: the blind Qipan structural wedge and Qimugen structural wedge, and the exposed Yengisar anticline. The thrust belt displays a right-stepping en echelon pattern. The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge, and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline. Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt, recording the deformation sequence of the thrust belt. The depth of the Cenozoic growth strata decreases from south to north. The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation (N2a), the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation (Q1x), and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation (Q1x). Combined with magnetostratigraphic studies in the western Tarim basin, it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward. The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation, suggesting that the thrust belt was formed in a transpressional tectonic setting.
YANG Xin , XU Xuhui , ZHANG Zhongpei , LIU Yifeng , ZHANG Jibiao , LIU Xingwang , XIONG Ping , ZHENG Jianjing
2016, 90(5):1679-1698.
Abstract:Western Yunnan is composed of several extruded continental microblocks that were generated by the oblique collision between the Indian and Asian continents during the Cenozoic. In this study, the magmatic and tectonic frameworks of western Yunnan in the Cenozoic were analyzed based on geochemistry, Sr–Nd–Pb isotopes, and apatite/zircon fission track dating. Magmatism during the Cenozoic in western Yunnan was then divided into three distinctive episodes: alkali granite rocks produced from 55 to 46 Ma were derived from the anatexis of crustal materials; bimodal igneous rocks formed between 37 and 24 Ma were possibly derived from an EMII mantle with a contribution from continental materials; and intermediate–basic volcanic rocks produced in the Tengchong microblocks since ~16 Ma are considered to be generated by the partial melting of the upper mantle that was induced by the pulling apart of the dextral Gaoligong strike–slip fault system. Moreover, fission track analysis of apatite and zircon indicates that the regional crustal uplift in western Yunnan possibly began at ~34 Ma, with accelerated annealing occurring at ~24 Ma, ~13 Ma, and ~4 Ma. During the past 24 Ma, the average denudation rate was ~0.32 mm/yr for the faulted block controlled by the Chongshan–Lancang River fault. However, crustal uplift has been relatively gentle in places lacking influence from strike–slip shear zones, with an average denudation rate of ~0.2 mm/yr. Combined with strike–slip shear and block rotation in the Cenozoic, the tectonic evolution of western Yunnan since ~45 Ma can thus be divided into four stages occurring at 45–37 Ma, 37–24 Ma, 24–13 Ma, and 13–0 Ma.
Christopher BAIYEGUNHI , Oswald GWAVAVA
2016, 90(5):1699-1712.
Abstract:Gravity modelling was carried out along five profiles that traverse the Eastern Cape Province of South Africa in order to determine the depositional surface and isochore thickness of the Ecca sediments. Gravity models of the subsurface rock density reveal that the Ecca Group has a maximum vertical thickness of about 3215 ± 160 m. The maximum depositional surface (elevation) above sea level for the Ecca sediments is about 500 m, whilst the depth below sea level reaches about 10000 m. Correlation of the isochore thickness maps with the depositional surfaces shows that the sediments in the basement highs were subsided, deformed, eroded and deposited in the basement lows. The basement highs served as the source area(s) for the sediments in the basement lows, thus basement highs are characterized with thin sediment cover whilst the lows have thick sediment cover.
ZHOU Liyun , WANG Yu , HEI Huixin , ZHOU Xiaohui
2016, 90(5):1713-1742.
Abstract:Magma mingling has been identified within the continental margin of southeastern China. This study focuses on the relationship between mafic and felsic igneous rocks in composite dikes and plutons in this area, and uses this relationship to examine the tectonic and geodynamic implications of the mingling of mafic and felsic magmas. Mafic magmatic enclaves (MMEs) show complex relationships with the hosting Xiaocuo granite in Fujian area, including lenticular to rounded porphyritic microgranular enclaves containing abundant felsic/mafic phenocrysts, elongate mafic enclaves, and back-veining of the felsic host granite into mafic enclaves. LA-ICP-MS zircon U-Pb analyses show crystallization of the granite and dioritic mafic magmatic enclave during ca. 132 and 116 Ma. The host granite and MMEs both show zircon growth during repeated thermal events at ~210 Ma and 160?180 Ma. Samples from the magma mingling zone generally contain felsic-derived zircons with well-developed growth zoning and aspect ratios of 2?3, and mafic-derived zircons with no obvious oscillatory zoning and with higher aspect ratios of 5?10. However, these two groups of zircons show no obvious trace element or age differences. The Hf-isotope compositions show that the host granite and MMEs have similar εHf(t) values from negative to positive which suggest a mixed source from partial melting of the Meso-Neoproterozoic with involvement of enriched mantle-derived magmas or juvenile components. The lithologies, mineral associations, and geochemical characteristics of the mafic and felsic rocks in this study area indicate that both were intruded together, suggesting Early Cretaceous mantle–crustal interactions along the southeastern China continental margin. The Early Cretaceous magma mingling is correlated to subduction of Paleo-Pacific plate.
WANG Hejing , YUAN Lei , WANG Ling , ZHOU Zhao , AN Jiali
2016, 90(5):1743-1753.
Abstract:This study uses illite crystallinity, chlorite crystallinity, illite polytypes, the b0 cell-dimension of K-white mica, clay mineral assemblages and mineral geothermo-geobarometers to investigate the overprint of diagenesis and metamorphism on the Meso-Neoproterozoic and the Lower Paleozoic along the profile Yueyang-Linxiang in northeastern Hunan Province, China. Illite crystallinity Kübler index (KI) of the <2μm fractions ranges from 0.225 to 0.485°Δ2θ while chlorite crystallinity árkai index (AI) ranges from 0.244 to 1.500°Δ2θ. This indicates that the Meso-Neoproterozoic and the Lower Paleozoic along the profile Yueyang-Linxiang were overprinted with diagenesis and anchi- to epimetamorphism. Peak metamorphic temperature is estimated with the IV site chlorite geothermometer roughly at 360°C. The b0 cell dimension values of illites (K-mica) range from 0.9002 to 0.9054 nm and, on average, at 0.9030 nm for the Meso-Neoproterozoic. Based on cumulative frequency curves of illite (K-mica) b0 cell dimension, the peak metamorphic pressure of the Meso-Neoproterozoic along the profile Yueyang-Linxiang is derived of an intermediate pressure type. Most illites occur in the 2M1 polytype and some of them in a mixture of 2M1+1M types especially those in the Paleozoic. This result partly agrees with the conclusion of the lower greenschist and greenschist facies of the Lengjiaxi and Banxi Groups. However, it is not agreed with the sedimentary cover from the Sinian to the Lower Paleozoic or from the Banxi Group to the Lower Paleozoic. Crustal thickening due to “collision” between the Yangtze and Cathaysia blocks led to an increase in the thickness of the Meso-Neoproterozoic to ca. 14 km and resulted in a temperature increase in those rocks due to burial. The very low grade to low grade metamorphism overprinting the Meso-Neoproterozoic implies that the so called “Chiangnania or Jiangnan orogen” was no relative with the “Grenvillian orogeney; instead, it might be a continuous amalgamation product between the Yangtze and Cathaysia blocks.
BIAN Chunjing , XU Jiuhua , CHEN Deping , ZHANG Hui , CHENG Xihui
2016, 90(5):1754-1767.
Abstract:The Wulasigou Cu–Pb–Zn deposit, located 15km northwest of Altay city in Xinjiang, is one of many Cu–Pb–Zn polymetallic deposits in the Devonian Kelan volcanic-sedimentary basin in southern Altaids. Two mineralizing periods can be distinguished: the marine volcanic sedimentary Pb–Zn mineralization period, and the metamorphic hydrothermal Cu mineralization period, which is further divided into an early bedded foliated quartz vein stage (Q1) and a late sulfide-quartz vein stage (Q2) crosscutting the foliation. Four types of fluid inclusions were recognized in the Q1 and Q2 quartz from the east orebodies of the Wulasigou deposit: H2O–CO2 inclusions, carbonic fluid inclusions, aqueous fluid inclusions, and daughter mineral-bearing fluid inclusions. Microthermometric studies show that solid CO2 melting temperatures (Tm,CO2) of H2O–CO2 inclusions in Q1 are from ?62.3°C to ?58.5°C, clathrate melting temperatures (Tm,clath) are from 0.5°C to 7.5°C, partial homogenization temperatures (Th,CO2) vary from 3.3°C to 25.9°C (to liquid), and the total homogenization temperatures (Th,tot) vary from 285°C to 378°C, with the salinities being 4.9%–15.1% NaCl eqv. and the CO2-phase densities being 0.50–0.86 g/cm3. H2O–CO2 inclusions in Q2 have Tm,CO2 from ?61.9°C to ?56.9°C, Tm,clath from 1.3°C to 9.5°C, Th,CO2 from 3.4°C to 28.7°C (to liquid), and Th,tot from 242°C to 388°C, with the salinities being 1.0%–15.5% NaCl eqv. and the CO2-phase densities being 0.48–0.89 g/cm3. The minimum trapping pressures of fluid inclusions in Q1 and Q2 are estimated to be 260–360 MPa and 180–370 MPa, respectively. The δ34S values of pyrite from the volcanic sedimentary period vary from 2.3‰ to 2.8‰ (CDT), and those from the sulfide-quartz veins fall in a narrow range of ?1.9‰ to 2.6‰ (CDT). The δD values of fluid inclusions in Q2 range from ?121.0‰ to ?100.8‰ (SMOW), and the δ18OH2O values calculated from δ18O of quartz range from ?0.2‰ to 8.3‰ (SMOW). The δD–δ18OH2O data are close to the magmatic and metamorphic fields. The fluid inclusion and stable isotope data documented in this study indicate that the vein-type copper mineralization in the Wulasigou Pb–Zn–Cu deposit took place in an orogenic-metamorphic enviroment.
LI Bo , ZHOU Jiaxi , LI Yingshu , CHEN Aibing , WANG Ruixue
2016, 90(5):1768-1779.
Abstract:The Yinchanggou-Qiluogou Pb-Zn deposit, located in the western Yangtze Block, southwest China, is hosted by the Upper Sinian Dengying Formation dolostone. Ore bodies occur in the Qiluogou anticline and the NS- and NNW-trending faults. Sulfide ores mainly consist of sphalerite, pyrite, galena and calcite, with subordinate dolomite and quartz. Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt% Zn and 6.89wt% Pb. The δDH2O-SMOW and δ18OH2O-SMOW values of fluid inclusions in quartz and calcite samples range from ?68.9‰ to ?48.7‰ and 7.3‰ to 15.9‰, respectively, suggesting that H2O in the hydrothermal fluids sourced from metamorphic water. Calcite samples have δ13CPDB values ranging from ?6.2‰ to ?4.1‰ and δ18OSMOW values ranging from 15.1‰ to 17.4‰, indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates. The δ34SCDT values of sulfide minerals range from 5.5‰ to 20.3‰, suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40, 15.66 to 15.76 and 38.25 to 38.88, respectively. The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone. This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks. The ore geology and C-H-O-S-Pb isotopic data suggest that the Yinchanggou-Qiluogou deposit is an unusual carbonate-hosted, strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.
LI Wei , XIE Guiqing , ZHU Qiaoqiao
2016, 90(5):1780-1794.
Abstract:The Chengchao iron deposit, the largest high-grade skarn iron deposit in southeastern Hubei Province, contains considerable amounts of magnetite and by-product anhydrite. To obtain better understanding of the ore-formation process, this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization. The results indicate that the δ34S values (ranging from 14.0‰ to 17.6‰) of pyrites formed from the two stages have no obvious differences, suggesting that they were not derived from a single magmatic sulfur source. The δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰, similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt (MLYRB). The Pb isotopic compositions of the pyrites of both stages are homogeneous, with values of 208Pb/204Pb, 207Pb/204Pb, and206Pb/204Pb being 38.006–38.257, 15.523–15.556, and 17.806–18.052, respectively, indicating a mixed crust-mantle source. The He-Ar results exhibit different compositions of the two stages: the 3He/4He (R/Ra) and 40Ar/36Ar values for the early-stage pyrite are 0.46–0.63 and 311–322, respectively, whereas the values for late-stage pyrite are 0.23–0.34 and 305–361, respectively. Both stages of pyrites indicate the multiple sources of the ore-forming fluids, with decreasing amount of magmatic water and increasing amount of modified meteoric water(MASW) during fluid evolution. The Triassic evaporites played an important role in the mineralization process.
WANG Kun , HU Suyun , LI Wei , LIU Wei , HUANG Qingyu , MA Kui , SHI Shuyuan
2016, 90(5):1795-1808.
Abstract:Using analyses of the lithology, sequences, paleoenvironment, and tectonic setting, the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified. The lithological characteristics of the Lower Member, Middle Member, and Upper Member were analyzed and classified. Before the use of carbon, oxygen, and strontium isotopes in the analysis, all of the geochemical data were tested for validity. On the basis of the Z values obtained from carbon and oxygen isotopes, the paleoenvironments of the three members were elucidated. Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea. Middle Member developed in a semi-enclosed to normal marine environment with many rivers. Upper Member was formed in a normal marine environment. The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation, forming a relatively enclosed depositional setting. Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks; these paleogullies can be identified. On the basis of a comprehensive analysis, we propose that the Huanglong Formation developed in a platform system. Four microfacies were identified: supratidal flat, dolostone flat, grain shoal, and shelf microfacies. The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation, while the supratidal flat and shelf microfacies developed very few high-quality reservoirs. The paleogullies, in which increased amounts of grain shoal microfacies developed, controlled the distribution of high-quality reservoirs.
LI Cunlei , CHEN Panpan , LIU Jianmei , Fu Hongtao , ZHANG Jinliang , XIE Jun
2016, 90(5):1809-1820.
Abstract:Overlapping gravity accumulation bodies were formed on the northwestern steep slope of the Shuangyang Formation in the Moliqing fault depression of northeast China. This study analyzed in detail the spatial distribution of the lithofacies and lithofacies associations of these accumulation bodies based on more than 600 m of core sections, and summarized 12 major types of lithofacies and three types of lithofacies associations: (1) the proximal zone consists of gravelly debris flows dominated by alluvial channel conglomerates; (2) the middle zone is dominated by various gravity flow deposits and traction flow deposits; and (3) the distal zone is dominated by mudstones with intercalations of sandy debris and turbidites. Combining with the grain size cumulative probability curves analysis, we determined the transformation of debris flows to sandy debris flows and to turbidity currents in the slope zone of the basin margin, and further proposed a lacustrine slope apron model that is characterized by (1) an inconstant multiple source (line source), (2) an alternation of gravity flow deposits and traction flow deposits dominated by periodical changes in a source flood flow system, and (3) the transformation of sandy debris flow deposits into distal turbidity current deposits. This sedimentary model may be applicable to other fault depressions for predicting reservoir distribution.
WU Songtao , ZOU Caineng , ZHU Rukai , YAO Jingli , TAO Shizhen , YANG Zhi , HAI Xiufen , CUI Jingwei , LIN Senhu
2016, 90(5):1821-1837.
Abstract:The Upper Triassic oil accumulations in the Ordos Basin is the most successful tight oil play in China, with average porosity values of less than 10% and permeability values below 1.0 mD. This study investigated the geological characteristics and origin of the tight oil accumulations in the Chang 6 member of the Upper Triassic Yanchang Formation in the Shanbei area based on over 50, 000 petrological, source-rock analysis, well logging and production data. The tight oil accumulation of the Chang 6 member is distributed continuously in the basin slope and the centre of the basin. The oil-water relationships are complex. Laumontite dissolution pores are the most important storage spaces, constituting 30%–60% of total porosity and showing a strong positive relationship with oil production. The pore-throat diameter is less than 1 μm, and the calculated critical height of the oil column is much larger than the tight sand thickness, suggesting that the buoyancy was probably of limited importance for oil migration. The pressure difference between the source rocks and sandstone reservoirs is inferred to have provided driving force for hydrocarbon migration. Two factors of source-reservoir configuration and laumontite dissolution contributed to the formation of the Chang 6 tight oil accumulations. Intense hydrocarbon generation and continuous sand bodies close to the hydrocarbon kitchen are the foundation for the large-scale oil distribution. Dissolution of feldspar-laumontite during the process of organic matter evolution generated abundant secondary pores and improved the reservoir quality.
LI Fucheng , ZHANG Yang , JIA Xiaofeng , LI Xufeng , JIA Xiaoleng , GUO Shengxiu
2016, 90(5):1838-1851.
Abstract:This work established an evaluation index system based on a comprehensive analysis of those factors affecting the suitability of CO2 geological storage. This evaluation index system includes three evaluation index layers of geological safety, storage scale and social economy, nine evaluation index sub-layers, and 28 evaluation index factors, and adopts the analytic hierarchy process (AHP) and index overlay methods. Taking the Xining Basin in northwest China as an example, we conducted comprehensive analysis of geological conditions and performed quantitative evaluation based on this evaluation index system, which indicates that the Shuangshu depression of the Xining Basin is comparatively suitable for CO2 geological storage. It is suggested that this evaluation index system and the evaluation method proposed in this study are suitable for most continental sedimentary basins in China and should be widely applied.
2016, 90(5):1852-1864.
Abstract:The Upper Permian Dalan Formation and the Lower Triassic Kangan Formation in the Persian Gulf area are mainly composed of shallow marine facies limestone and dolomite. Two subsurface-cored intervals were investigated in order to understand the original mineralogy and paleoceanic conditions. The decreasing trend of Sr concentration in these deposits shows that aragonite was precipitated during the Late Permian and then gradually changed to calcite toward the Permian–Triassic boundary (PTB). The dissolution rate of aragonite decreased from 60 m below the PTB toward the boundary, with the only exception at 10 m below the Permian-Triassic Boundary (PTB) due to the Permian–Triassic unconformity in this region. The increasing trend of Mg/Ca ratio in a global scale at the end-Permian time shows that the interpreted variation of mineralogy does not result from the change of this ratio. The increasing pCO2 and decreasing pH are considered to be the main controlling factors. The increase of Ca2+ at the end-Permian time due to the input of meteoric waters is too little to fully compensate this effect. A local maximum of the Si content just at the PTB confirms the input of runoff waters.
Aftab Alam KHAN , Mustaffa Kamal SHUIB
2016, 90(5):1865-1886.
Abstract:Genesis of the so-called Bentong–Raub Suture of Malay Peninsula does not fit to the model of subduction-related collision. It has evolved from transpression tectonics resulting closure and exhumation of the inland basin which underwent extensive back-arc extension during Triassic. Crust having similar thickness (average ~35 km) below entire Malay Peninsula nagate collision of two separate continental blocks rather supports single continental block that collided with South China continental block during Permo-Triassic. Westward subduction of intervening sea (Proto South China Sea) below Malay Peninsula resulted in widespread I- and S-Type granitization and volcanism in the back-arc basins during Triassic. Extensive occurrence of Permo-Triassic Pahang volcanics of predominantly rhyolitic tuff suggest its derivation from back-arc extension. Back-arc extension, basin development and sedimentation of the central belt of the peninsula continued until Cretaceous. A-Type granite of metaluminous to peraluminous character indicates their emplacement in an intraplate tectonic setting. Malay Peninsula suffered an anticlockwise rotation due to the rifting of Luconia–Dangerous Grounds from the east Asia in the Late Cretaceous–Early Tertiary. Extensive ductile and brittle deformation including crustal segmentation, pull-apart fracturing and faulting occurred during the closure and exhumation of the basins developed in the peninsula during Late Cretaceous–Early Tertiary. Crustal shortening in the central belt of the peninsula has been accomodated through strike-slip displacement, shearing and uplift.
2016, 90(5):1887-1902.
Abstract:As a milestone of the entire energy industry, unconventional resources have inevitably swept the world in the last decade, and will certainly dominate the global oil and gas industry in the near future. Eventually, the “unconventional” will become “conventional”. Along with the rapid development, however, some issues have emerged, which are closely related to the viability of unconventional resources development. Under the current circumstances of low crude oil and gas price, coupled with the prominent environmental concerns, the arguments about the development and production of unconventional resources have been recently heated up. This work introduced the full-blown aspects of unconventional resources especially shale reservoirs, by discussing their concepts and definitions, reviewing the shale gas and shale oil development history and necessity, analyzing the shale plays’ geology and petroleum systems with respects to key hydrocarbon accumulation elements and mechanisms, and summarizing the technology resolution. This study also discussed the relevant key issues, including significant estimation uncertainty of technically recoverable resources, the equivocal understanding of complex geology preventing the production and technologies implementation optimization, the difficulties of experiences and technologies global expanding, and the corresponding risks and uncertainties. In addition, based on the latest production and exploration data, the future perspective of the unconventional resources was depicted from global unconventional resources assessments, technology development, and limitations constraining the development.
2016, 90(5):1903.
Abstract:
2016, 90(5):1907.
Abstract:
LI Shan , CHUNG Sunlin , Simon A. WILDE , WANG Tao , XIAO Wenjiao , GUO Qianqian
2016, 90(5):1907-1908.
Abstract:
JIA Xiaohui , WANG Xiaodi , TANG Gongjian , YANG Wenqiang , NIU Zhijun
2016, 90(5):1913-1914.
Abstract:
DENG Qi , WANG Jian , CUI Xiaozhuang , WANG Zhengjiang , SHI Meifeng , MA Long
2016, 90(5):1917-1918.
Abstract:
PENG Bo , LIU Chenglin , LI Zongxing , MA Yinsheng , CAO Jun , WANG Bing , ZHANG Xu
2016, 90(5):1919-1920.
Abstract:
LIANG Jiaju , XU Fanghao , YUAN Haifeng , XIAO Yao , LIANG Feng , BAI Chenggang
2016, 90(5):1921-1922.
Abstract:
2016, 90(5):1925-1925.
Abstract:
ZHANG Daolai , LIU Na , YIN Ping , ZHU Zhigang , LU Jingfang , LIN Xuehui , ZHANG Yuanyuan , MENG Xianwei
2016, 90(5):1926-1926.
Abstract:
Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P