Abstract:Exploration results reveal that the northern slope of South China Sea (SCS) is a favorable area for gas hydrate accumulation and hence has huge energy resources potential. Based on the results of gas hydrate exploration conducted in northern SCS and geological background of gas hydrate reservoir in the study area, the authors analyzed the conditions of temperaturepressure stability, gas source supply, migration conduction system and reservoir for gas hydrate accumulation in northern SCS. Moreover, the accumulation models of gas hydrate reservoir in Shenhu, the western slope of South China Sea areas and the northeastern slope of South China Sea areas were discussed as well. The results show that the diffusion gas hydrate reservoir is mainly accumulated in Shenhu area, while the western slope of South China Sea area is dominated by the leakage type of reservoir. On the northeastern slope of South China Sea area, gas hydrate accumulation is complex and is characterized by both diffusion and leakage types.

Abstract:During the Miocene, there were a number of reefs developed in the Beikang Basin, which constitute potential for hydrocarbon exploration. The high-resolution seismic data and numerous well drilling data have provided an opportunity to understand the evolution of reefs in the study area. Six types of reefs were identified, i.e., point reef, platform-edge reef, block reef, bedded reef, pinnacle reef, and atoll reef, and their development could be divided into four stages. In early Miocene, a few point reefs small in size initiated in this basin and they flourished in the early middle Miocene and mainly developed around the Central Uplift and Eastern Uplift. However, the reefs began to wither in the late middle Miocene in response to a rapid relative sea level rise which was caused by the loading subsidence. Since late Miocene, with the continuous rising of the relative sea level, many reefs formerly developed around the Central Uplift and Eastern Uplift have been submerged and only some atoll reefs have survived around the islands on the Eastern Uplift. Additionally, the numerous reefs which are little influenced by later diagenesis are favorable reservoirs for hydrocarbon exploration. The match relation of regional hydrocarbon rock, dredged system and the distribution of reefs indicates that the west of Central Uplift and the east of Eastern Uplift seem to be the favorable exploration zones for the hydrocarbon exploration of reefs in the Beikang Basin.

Abstract:With the consumption and decreasing of the worldwide resources of petroleum and natural gas, the exports from various countries are working hard to find a new kind of substitute energy. Undoubtedly, a new hope in the future is probably attributed to the resource of gas hydrate following its discovery, exploration, development and utilization. For the significant strategies and economic benefits of gas hydrate, many developed countries and developing countries, such as United States, Japan, India, South Korea, Germany, Norway and China, have arranged it under the key national projects and invested enormous capital on the marine surveys and exploitation tests. In this review, the authors concisely describe the histories and current situations of gas hydrate in the main countries, with the emphasis placed on the national projects with the exploration extents, development situations, national investments and strategic deployments for gas hydrate. The authors also discuss the current progresses with which experts are most concerned. The authors divide those countries into 3 types:(1) United States. It has accumulated huge geological data and material supported by research institutions and ODP explorations in the early stage, but recently it somewhat reduces the investments on surveys and exploitation tests mainly because of the commercial success of shale gas revolution. In spite of such a situation, it still has great interest in theories and techniques of gas hydrate mainly focusing on the comprehensive subjects, and waits the opportunity to venture again once the market opportunity is ready. (2) China, Japan, India, South Korea. Due to the limits of domestic energy structures and preserve capacities, they hold an extremely active position on the development of gas hydrate with huge national investments on marine drilling expeditions. In particular, China and Japan have gained a great momentum in the marine exploitation tests, quite possibly being the first nations with full commercial operations. (3) Germany, Norway. As the traditional European industrial countries, they focus on improving gas hydrate exploitation techniques, for instance, the technology of CO₂-CH₄ replacement, paying much attention on environmental assessment supported by their solid industrial technical groundwork. They are the representatives of Greenpeace in the subject of gas hydrate and maybe provide a new opportunity in the later energy times for gas hydrate development.

Abstract:The deep-sea sediments rich in rare earth elements discovered in recent years in the Pacific and Indian Ocean basin are a potential rare earth mineral resource. The metalliferous sediments, zeolite clay and pelagic clay are thought to be the main types of REY-rich sediments with high total REY(REE+Y) content (400×10^-6-2000×10^-6, the highest up to 6600×10^-6) and heavy rare earth content (HREE). The HREE values of the sediments are nearly twice as abundant as those in the southern Chinaion-absorption-type deposits. Previous chemical and mineral studies suggest that Fe/Mn oxide and oxyhydroxide precipitated from hydrothermal activities is the main host of the REY in the metalliferous sediments, while phosphate whose chemical composition is equivalent to apatite (such as fish debris) is the main carrier of rare earth elements in the zeolite clay and pelagic clay. The NASC-normalized REE patterns of deep-sea sediments are similar to those of seawater, indicating that the rare earth elements of the sediments were taken up from ambient seawater. REY were mainly enriched at the early diagenetic stage of apatite without differentiation. Many achievements have been made about the rare earth elements in deep-sea sediments in recent years. However, the enrichment mechanisms of rare earth elements in deep-sea sediments and influencing factors still need further study. China has been the dominant producer of REE and hosts the most known global reserves. In order to safeguard China's right in the competition for REE in the international seabed and safeguard China's benefit, it is very necessary and critical to search for and evaluate potential marine REE resources.

Abstract:Cobalt-rich crusts constitute another deep-sea sedimentary solid mineral resource discovered after oceanic polymetallic nodule. Cobalt-rich crusts are distributed on the seafloor of the Pacific Ocean, the Atlantic Ocean and the Indian Ocean. It is estimated that the amount of dry crust resources in the three oceans is (1081.1661~2162.3322)×10⁸ t. Survey of the cobalt-rich crust by various countries in the world began in the early 1980s. So far, 4 countries, i.e., Japan, China, Russia and Brazil, have signed a cobalt-rich crust exploration contract with the International Seabed Authority. The application of cobalt-rich crusts mining area submitted by South Korea was also approved by International Seabed Authority in 2016. Cobalt-rich crusts can be divided into plate curst, gravel-like crust and nodule-like crust according to their shapes. Cobalt-rich crusts are usually three-layer structure in the macro. Upper layer is called bright coal seam layer, intermediate layer is called loose layer, and bottom layer is called relatively loose layer. Microscopically, cobalt-rich crusts are mainly characterized by such structures as columnar structure, callenia structure, plaque structure, and laminar structure. The minerals of cobalt-rich crusts are mainly authigenic iron and manganese minerals, which include vemadite, todorokite, amakinite, akaganeite, feroxyhyte, goethite, and so on. Cobalt-rich crusts are rich in Mn, Fe, Co, Ni, Cu, Pb, Zn as well as REEs and PGEs. The content of Co of cobalt-rich crusts is particularly significant. The average content of Co in cobalt-rich crusts from the Pacific Ocean is the highest in the three large oceans in the world. Formation process of cobalt-rich crusts is extremely slow. Only several millimeters of crust can be formed in one million years. Studies show that cobaltrich crusts from the West Pacific Ocean were formed as early as Eocene to early Miocene. It's generally accepted that the cobaltrich crust is hydatogenic. Co, Fe, Mn and other metal elements in crusts originate from sea water. In addition, studies have shown that microorganisms play a very important role in the formation of cobalt-rich crusts. The distribution and characteristics of cobaltrich crust are affected by such factors as topography, water depth, substrate rocks type, hydrochemical characteristics of seawater, latitude and longitude. Cobalt-rich crusts are formed on the slope of seamount and island and submarine highland above the depth of carbonate compensation and below oxygen minimum zone, with the water depth of 800~2500m. West and Central Pacific seamounts are considered to be the main production area of cobalt-rich crusts in the world.

Abstract:The first successful case for exploration oil in New China was the discovery of the Daqing oil field in 1958. The discovery of the Daqing oil field subverted the concept that oil can only be formed in marine strata, and proved that oil field could also be formed in continental strata. Besides, in the exploration of Daqing oil field advanced geophysical methods were adopted to carry out strategic regional investigation, and the geophysical work was no longer confined to front basins with oil seepage.
In the upcoming oil exploration, we should create a common perspective that oil is generated in the mantle, and hence the work should expand to the whole lithosphere.
According to thermodynamics, methane is the sole hydrocarbon which can be stably living under the standard temperature and pressure condition; straight-chain alkanes hydrocarbons can be formed only under the condition pressure > 30 kbar and temperature > 700℃ (corresponding to a depth about 100 km). Therefore, both marine oil generation theory or terrestrial oil generation theory cannot hold the water. In fact, oil is generated in the mantle, and then migrate to marine basins or terrestrial basins for accumulation of petroleum.
Geophysical methods play an important role in prospecting for deep oil reservoir. Many petroleum geologists have considered that the low velocity-low resistivity layer is closely related to oil reservoir. Besiders, researchers have found that, under the known oil fields, there frequently exists asthenospheric matter. Asthanosphric matter is active and can penetrate mantle matter to form a mushroom cloud in the mantle.
Based on seismic tomography and regional geological environtal condition, the authors put forward three perspective regions for oil exploration:
(1) The East Asia-West Pacific Oceanic low-velocity region. There are three zones which were formed in MesozoicCenozoic period and are different in depth, extent and shape. From west to east, they are Songliao-North China -SE China coastal continental rift zone; Japan Sea-Yellow Sea-East Sea-South China Sea marginal sea rift zone, and Shikoku Sea basin-Parece Vela Sea basin -Papua New Guinea marine rift zone
(2) East Tetisi mantle uprifting region:The East Tetisi mantle uprifting region consists of Lanping basin, Simao basin and Chuqiong basin in Southwest China. This region originally had the richest oil and gas reservoirs in the world, but its structures were severely destroyed under the extrusion of the Indian block
(3) The deep faults in Xinjiang region:The Xinjiang region formed a series of synformal and antiformal structures under the extrusion of the Indian block, and hence deep oil may migrate upward to the surface through deep faults. According to satellite gravity, the authors hold that Bayan-Ovoo-Xining discontinuous zone, Naomaohu-Mangnai discontinuous zone, Yutian-Keriya Hu discontinuous zone, and Alma-Ata-Taxkorgan discontinuous zone are favorable areas for oil exploration.

Abstract:The lithology of the 3rd Member of Liushagang Formation in eastern Wushi sag of Beibuwan Basin is relatively complex, with significant differences in sedimentary characteristics, rapid lateral changes and poor connectivity. The study of sediment sources and sedimentary facies is controversial, and the oil and gas exploration and reserves calculation have long been constrained by sedimentary facies study and its distribution regularity. In this paper, based on the core observation and fine description, combined with the logging, seismic and analytical data, the authors analyzed the sedimentary facies type and distribution characteristics of the 3rd Member of Liushagang Formation. It is concluded that the sediment sources of the 3rd Member of Liushagang Formation were from the high terrain in the north, and the transgressive fan delta was developed in this area, with larger sandbody thickness, narrow sedimentary facies, and fast sedimentary facies changes. The delta front can be further divided into four kinds of sedimentary microfacies, i.e., underwater distributary channel, channel dam, sandy sand, and shunt bay. Based on the sand-containing contours compiled by the combination of well and seismic survey, combined with the logging plane facies, seismic facies and seismic reflection structure, the sedimentary microfacies plane profile of the study area was drawn comprehensively, and the sedimentary characteristics of the 3rd Member of Liushagang Formation in the study area were determined. Finally, the fan delta deposition model in this area was established, which provides reference for oil and gas exploration and development and reserve calculation of the 3rd Member of Liushagang Formation in eastern Wushi sag, Beibuwan Basin.

Abstract:The Jurassic source rocks have long been one of the research hotspots, but the Carboniferous-Permian source rocks' capability of hydrocarbon generation has not aroused much attention due to the scattered distribution in Qiangtang Basin. Organic geochemical characteristics of carbonate rock and mudstone samples from eight sections in the Carboniferous-Permian strata of Qiangtang Basin were analyzed for the organic matter abundance, types and thermal evolution. The authors found that source rocks, including carbonate rock and mudstone, were influenced by the evolution of sedimentary environment. The carbonate source rocks might have been the micrite limestone of the carbonate platform, and the mudstone source rocks were mainly the dark mudstone of delta and slope facies and tuffaceous mudstone. The organic carbon content of Carboniferous-Permian mudstone is higher, suggesting hydrocarbon-generative potential; most sections have moderate to high content of organic carbon except Rejuechaka section which has no or poor source rock. Kemo section and Gongri section have mainly reached the standard of mid-good hydrocarbon source rock. However, the Carboniferous-Permian carbonate rock shows a lower content of organic carbon, with no or poor source rock. The type of organic matter of Carboniferous-Permian carbonate rock is mainly Ⅱ₁, but the type of organic matter of Carboniferous-Permian mudstone is mainly Ⅱ₂ and Ⅲ. The degree of thermal evolution of Carboniferous Permian source rock is generally high, and all the source rocks, except for the Kemo areas where the source rock is at the mature stage, are mostly in the high mature and over-mature stage. Such a situation is very favorable for the generation of natural gas and has a good prospect of natural gas exploration.

Abstract:Luoyu Group and Ruyang Group are cropped out extensively along the southern margin of the North China Craton (NCC), and are mostly composed of sandstone with minor shale and dolostone. Based on field investigation along Luoyukou and Yangpo Village section, Ruzhou City, Henan Province, a few interbedded tuff layers were found in the upper part of the Luoyukou Formation. By means of LA-MC-ICPMS zircon U-Pb dating, the ages of the volcanic eruption, 1638±9 Ma and 1634±10 Ma from Luoyukou Village and Yangpo section, were respectively obtained. These data mean that Luoyukou Formation was formed during Mesoproterozoic Changcheng period rather than during Meso-Neoproterozoic Jixian period and Qingbaikou period as previously held. According to the new dating data, the Luoyu Group and Ruyang Group which conformably underlies Luoyu Group ought to belong to the Mesoproterozoic Changcheng period, because Luoyukou Formation is at the uppermost part of Luoyu Group. This discovery has great significance for Meso-Neoproterozoic stratigraphic redivision and correlation in the NCC, and for the study of the relationship between the tectonic evolution history of the Late Paleoproterozoic to Early Mesoproterozoic geological records in the NCC and the breakup of the Columbia Supercontinent as well as for the evolution of the early life on the Earth.

Abstract:Late Paleozoic intermediate-acid granitoids are widely distributed in the East Section of East Kunlun, but the records of basic magmatism are very insufficient. Alasimu mafic rocks on the southern margin of the arc magmatic rock belt in northern East Kunlun Mountains was selected as the study objective so as to provide a new basis for the research on the Late Paleozoic magmatic evolution of the east section of East Kunlun Mountains. LA-ICP-MS zircon U-Pb analysis yielded the crystallization age of 241±1Ma, suggesting that Alasimu Mafic rocks were formed in the Middle Triassic. All the rock samples are characterized by relatively low TiO₂ (0.17%-0.37%, averagely 0.25%) and high Mg^# (72.94%-77.32%, averagely 74.95%) and high Al₂O₃ (13.08%-23.20%, averagely 18.9%), enrichment of large ion lithophile elements (LILE:Sr, Rb, Ba), apparent depletion of high field strength elements (HFSE, Nb, Ta, Zr and Hf). MgO shows some correlation with Fe₂O₃^T, TiO₂, Ni and Co in the diagram of Harker, which reveals some degree of fractional crystallization of olivine and Ti-Fe oxide. Alasimu mafic rocks have similar chemical composition to island arc basalts, and they formed earlier than the collision and post-collision time of tectonic-magmatic activity. Combined with regional studies, the authors hold that Alasimu gabbro rocks ought to be the latest magmatism records in the East Kunlun region related to Middle Triassic Paleo Tethys oceanic crust subduction, which indicated that the tectonic transition from ocean subduction to collisional orogeny might have commenced in Middle Triassic.

Abstract:The Indosinian Qianui copper polymetallic deposit discovered in recent years is located in the central and southern segment of the eastern Geza porphyry belt of southern Yidun arc in Southwest China. A large number of indo-Chinese large-size ore deposits were formed in the metallogenic area, which is hence an important polymetallic belt in China. In this paper, the authors studied the ages of the Qiansui quartz diorite porphyry with zircon LA-ICP-MS U-Pb dating method and obtained the formation age of the copper mineralized quartz diorite porphyry of 220.3±0.66 Ma (MSWD=0.99). Geochemical characteristics indicate that Qiansui ore-bearing quartz diorite porphyry is characterized by rich Na (K₂O/Na₂O=0.05-1.42, averagely 0.86), metaluminous nature (0.82-1.19, averagely 1.07), enrichment of light rare earth elements (LREE, Ba, Th, U, Sr), obvious REE fractionation (La_N/Yb_N=19.6 -28.8), enrichment of large ion lithophile elements (LILE, Ba, Th, U, Sr), and depletion of high field strength elements (HFSF, Ta, Nb, Ce, P, Ti). The rock belongs to typical I-type granite. The ore-forming process of Qiansui metallogenic rock body occurred in the late Indosinian, and the trace element characteristics, tectonic background and isotopic characteristics of the orebearing porphyry suggest that Qiansui rock was formed in an island arc environment, and that its formation was probably related to the subduction of oceanic crust in Indosinian.The study of geochemical characteristics and petrogenetic age of Qiansui reveals the fixed formation age of Qiansui and the time limit of Ganzi-Litang oceanic crust subduction orogeny, suggesting that Pulang and Hongshan copper deposits were the products of the evolution of magma structure in the same period. The results obtained by the authors have important significance for the study of Gezan island arc tectonic magmatic evolution and petrogenetic mineralization.

Abstract:Aimed at exploration of provenance and basin-mountain coupling relationship in southwestern Ordos Basin, the authors selected detrital zircons from the first member of Shanxi Formation and the eighth member of Shihezi Formation of the late Paleozoic in southwestern Ordos Basin and conducted LA-ICP-MS detrital zircon U-Pb isotope analysis. The result reveals that the 105 analytical points of the magma-genetic detrital zircons yielded four age groups:(1) The first group which ranges from 260 to 340Ma accounting for 21.9% of the total analytical points, indicating that the provenance might have come from the North Qinling orogenic belt and the West Qinling orogenic belt; (2) The second group which ranges from 370 to 470 Ma accounting for 24.8% of the total analytical points, suggesting that the provenance was mainly derived from the North Qinling orogenic belt, the West Qinling orogenic belt and the North Qilian orogenic belt; (3) The third group which ranges from 1600 to 2000 Ma accounting for 32.4% of the total analytical points, implying that the provenance might have come from the North Qinling orogenic belt and the North Qilian orogenic belt; (4) The last group which ranges from 2300 to 2600 Ma accounting for 15.2% of the total analytical points, indicating that the provenance was derived from the North Qinling orogenic belt, the West Qinling orogenic belt, the North Qilian orogenic belt and the crystalline basement of the North China plate. This study indicates that the provenance of southwestern Ordos Basin had multiple origins:the North Qinling orogenic belt, the West Qinling orogenic belt, the North Qilian orogenic belt and the crystalline basement of the North China plate, mainly from the North Qinling orogenic belt and the North Qilian orogenic belt. The Paleozoic detrital zircons have also proved that the southwestern Ordos Basin passive continental margin was developed during the Ordovician, then it evolved into continent-continent collisional orogenic belt during the Silurian-Devonian, and finally gradually evolved into a sedimentary basin during the Carboniferous-Permian period.

Abstract:The study of the composition and evolution of the Precambrian metamorphic series such as Xinghudukou Group in northeastern Da Hinggan Mountains is critical for determining the tectonic attribute of Ergun massif and Xing'an block, and thus is one of the hotspots of recent studies of northern Da Hinggan Mountains. Based on the U-Pb dating results of the detrital zircons from two-mica-quartz schist and the magmatic zircons from migmatite, the authors hold that the Xinghuadukou Group in the Shihuiyao-Mingzhi Mountain of northern Heihe area is not the Precambrian metamorphic rock, but is a tectonic complex composed of early Paleozoic sedimentary (or metamorphic) rocks and Late Paleozoic magmatic rocks. The dating results of the magmatic core of detrital zircons from two-mica-quartz schist show 7 age groups mainly, i.e., 401-427 Ma, 442-448 Ma, 473-517 Ma, 639-714 Ma, 757-818 Ma, 896-933 Ma and 1704-1751 Ma, in which the 473-517 Ma group exhibits most obvious peaks of detrital zircons and is consistent with the early Paleozoic magma event such as the island arc volcanic rock from the Duobaoshan Formation, and the other age groups have also been reported in many places in northern Da Hinggan Mountains. These characteristics suggest that the provenance was complex, composed of not only Proterozoic rocks but also Paleozoic rocks, with the early Paleozoic magmatic rocks being the main source. So the protolith age of the two-mica-quartz schist is the Paleozoic and might be sfter 416 Ma, as shown by the minimum peak age of detrital zircons. The considerable Proterozoic detrital zircons from the schist suggests that there indeed exists Precambrian basement in Ergun massif or Xing'an blocks. The migmatite outcropped in the Mingzhi Mountain is the mylonitized granite actually caused by the dynamic metamorphism, and it has a ²⁰⁶Pb/²³⁸U weighted average age of (304.5±3.1)Ma, which reflect the granite formed during the Late Carboniferous. The granite was part of the estern margin granite belt in of Xing'an blocks during the late Paleozoic.

Abstract:Located in the eastern part of Northeast China, the Wandashan area mainly consists of basalts, cumulates, (ultra)basic lavas, silicalite and pelites. It contains the only succession of Mesozoic marine facies sedimentary strata in eastern China, known as the Hyperplasia Complex. Mineral resources are rich, and 1 medium-sized deposit and 4 small deposits have been discovered in this area. In addition, it shows more ore potential. Based on the 1:200000 geochemical data of stream sediments in Wandashan area, the authors carried out the correlation analysis, cluster analysis, factor analysis, single element anomaly analysis and combination analysis of 16 kinds of ore-forming elements. The analytical results show that Au, Ni, Cr, Bi, Hg have lots of high points, strong discreteness, favorable geological and geochemical conditions, and strong metallogenic potential. Au mineralization is mainly related to acidic magmatic rocks, and Ni, Cr mineralization is related to the (ultra)basic magma liquation. Combined with geology, tectonics, geophysical exploration and ore deposits (ore spots), the authors selected four metallogenic prospective areas:258 highland gold metallogenic prospective area, Baliqiao -Xianrentai copper -nickel -tungsten -tin metallogenic prospective area, Sipingshan-358 highland gold-silver metallogenic prospective area, and Yuejinshan-Xianfengbeishan gold-silver-copper-iron metallogenic prospect area. These metallogenic prospective areas provide the scientific basis for the deployment of ore-prospecting work and the study of regional metallogenic regularity of the Wandashan area.

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