2018 Vol.1(3)

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Original Articles
“Source-Diagenesis-Accumulation” enrichment and accumulation regularity of marine shale gas in southern China
Gang-yi Zhai, Yu-fang Wang, Zhi Zhou, Guo-heng Liu, Yu-ru Yang, Juan Li
2018, 1(3): 319-330. doi: 10.31035/cg2018059
[Abstract](163) [FullText HTML] (38) [PDF 6883KB](17)
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After the breakthrough of shale gas exploration and development in the Ordovician Wufeng Formation (Fm.) and Silurian Longmaxi Fm. of Chongqing Jiaoshiba area, Changning-Weiyuan area, etc. in Sichuan basin, a series of discovery and breakthrough were obtained by China Geological Survey in the Cambrian Niutitang Fm. and Sinian Doushantuo Fm. shale of the areas with complicated structure outside Sichuan basin. Based on the understanding of the law of shale gas enrichment in Longmaxi Fm. in the basin, this paper puts forward three elements of the formation and enrichment of shale gas, which are the " Source”, the " Diagenesis” and the " Accumulation”, after deeply studying the law shale gas enrichment and accumulation in Sinian-Cambrian reservoir of the complex structure area outside the basin. The " Source” means the sedimentary environment and petrological characteristics of organic shale. The " Diagenesis” means the basin tectonic subsidence and hydrocarbon generation and expulsion process of organic matter. The " Accumulation” means the tectonic uplift and shale gas preservation. It is proposed that the Sinian-Cambrian and Ordovician-Silurian black shale series in the middle and upper Yangtze region of southern China were both formed in the deep-water shelf environment of rift trough and foreland basin respectively. The dessert intervals were formed in the strong reduction environment under transgressive system tract. The shale lithology belongs to calcium-siliceous and charcoal-siliceous respectively. Based on the summary of structural evolution in Yangtze area, the correlation of structural burial depth with shale diagenesis and the coupling evolution of organic matter with pore structure are discussed. Combining with structural styles, the preservation conditions of shale gas are discussed. Five types of shale gas reservoir control models are further described. Two types of future exploration directions, which are reverse fault syncline and paleo-uplift margin in complex structural area outside the basin, are proposed.
The geothermal formation mechanism in the Gonghe Basin: Discussion and analysis from the geological background
Yan-fang Feng, Xiao-xu Zhang, Bo Zhang, Jiang-tao Liu, Yang-gang Wang, De-long Jia, Li-rong Hao, Zhao-yu Kong
2018, 1(3): 331-345. doi: 10.31035/cg2018043
[Abstract](141) [FullText HTML] (34) [PDF 6537KB](19)
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The Gonghe Basin, a Cenozoic down-warped basin, is located in the northeastern part of the Qinghai-Xizang (Tibetan) Plateau, and spread over important nodes of the transfer of multiple blocks in the central orogenic belt in the NWW direction. It is also called " Qin Kun Fork” and " Gonghe Gap”. The basin has a high heat flow value and obvious thermal anomaly. The geothermal resources are mainly hot dry rock and underground hot water. In recent years, the mechanism of geothermal formation within the basin has been controversial. On the basis of understanding the knowledge of predecessors, this paper proposes the geothermal formation mechanism of the " heat source–heat transfer–heat reservoir and caprock–thermal system” of the Gonghe Basin from the perspective of a geological background through data integration-integrated research-expert, discussion-graph, compilation-field verification and other processes: (1) Heat source: geophysical exploration and radioisotope calculations show that the heat source of heat in the basin has both the contribution of mantle and the participation of the earth's crust, but mainly the contribution of the deep mantle. (2) Heat transfer: The petrological properties of the basin and the exposed structure position of the surface hot springs show that one transfer mode is the material of the mantle source upwells and invades from the bottom, directly injecting heat; the other is that the deep fault conducts the deep heat of the basin to the middle and lower parts of the earth's crust, then the secondary fracture transfers the heat to the shallow part. (3) Heat reservoir and caprock: First, the convective strip-shaped heat reservoir exposed by the hot springs on the peripheral fault zone of the basin; second, the underlying hot dry rock layered heat reservoir and the upper new generation heat reservoir and caprock in the basin revealed by drilling data. (4) Thermal system: Based on the characteristics of the " heat source-heat transfer-heat reservoir and caprock”, it is preliminarily believed that the Gonghe Basin belongs to the non-magmatic heat source hydrothermal geothermal system (type II21) and the dry heat geothermal system (type II22). Its favorable structural position and special geological evolutionary history have given birth to a unique environment for the formation of the geothermal system. There may be a cumulative effect of heat accumulation in the eastern part of the basin, which is expected to become a favorable exploration area for hot dry rocks.
The evolution of the Huangling uplift and its control on the accumulation and preservation of shale gas
Shu-jing Bao, Gang-yi Zhai, Zhi Zhou, Shu-fang Yu, Ke Chen, Yu-fang Wang, Hao Wang, Yi-min Liu
2018, 1(3): 346-353. doi: 10.31035/cg2018052
[Abstract](131) [FullText HTML] (23) [PDF 6129KB](17)
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There are plenty of Sinian and Cambrian potential shale gas resources in South China, which is characterized by high thermal evolution degrees, poor drilling performances and only occurs in local areas. Taking the principle " high to find low” is the key issue to achieving a breakthrough in older shale. China Geological Survey drilled in the periphery of the Proterozoic basement, i.e. the Huangling anticline, in the western Hubei, and Hannan paleocontinent in the southern Shanxi. It received high-quality gas-bearing shale with relatively low Ro in the in Lower Cambrian Niutitang formation and Sinian Doushantuo formation. Based on geological conditions of shale gas reservoirs in the Huangling anticline, this paper puts forward the new model named " Control over reservoirs by periphery of basement” about shale gas accumulation, suggesting that the shale deposited in a deepwater continental shelf in the periphery of the basement is characterized by shallow burial, a short burial time, stable tectonics, relatively low thermal evolution degrees, and shale gas reservoirs in a good condition. The shale of the Sinian-Cambrian strata deposited in deepwater continental shelves in the periphery of Chuanzhong paleo-uplift in Sichuan, Hannan paleocontinent in the southern Shanxi, Huangling anticline in western Hubei and Jiangnang-Xuefeng paleo-uplift in Hunan and Guizhou province have good shale gas exploration potential.
Ordovician sequence stratigraphy and correlation in the Middle-Upper Yangtze region, South China
Chuan-shang Wang, Xiao-feng Wang, Xiao-hong Chen, Zhi-hong Li, Xu-bing Li
2018, 1(3): 354-366. doi: 10.31035/cg2018041
[Abstract](117) [FullText HTML] (21) [PDF 6350KB](10)
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The precise correlation of the Ordovician successions in different facies is difficult due to the complex changes of the tecto-paleogeography in South China. Based on previous studies, the authors recognized 10 3rd grade sequences, i. e., Osq1 to Osq10 in ascending order, by the integrated study of chronostratigraphy, biostratigraphy as well as the analysis on the sedimentary facies. The authors are confident to correlate the Ordovician successions precisely in different facies in an isochronous stratigraphic framework with the application of the method of sequence stratigraphy and correlation.
Multi-factor sensitivity analysis on the stability of submarine hydrate-bearing slope
Liang Kong, Zhen-fei Zhang, Qing-meng Yuan, Qian-yong Liang, Yao-hong Shi, Jin-qing Lin
2018, 1(3): 367-373. doi: 10.31035/cg2018051
[Abstract](140) [FullText HTML] (29) [PDF 5645KB](13)
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There are many factors affecting the instability of the submarine hydrate-bearing slope (SHBS), and the interaction with hydrate is very complicated. In this paper, the mechanical mechanism of the static liquefaction and instability of submarine slope caused by the dissociation of natural gas hydrate (NGH) resulting in the rapid increase of pore pressure of gas hydrate-bearing sediments (GHBS) and the decrease of effective stress are analyzed based on the time series and type of SHBS. Then, taking the typical submarine slope in the northern South China Sea as an example, four important factors affecting the stability of SHBS are selected, such as the degree of hydrate dissociation, the depth of hydrate burial, the thickness of hydrate, and the depth of seawater. According to the principle of orthogonal method, 25 orthogonal test schemes with 4 factors and 5 levels are designed and the safety factors of submarine slope stability of each scheme are calculated by using the strength reduction finite element method. By means of the orthogonal design range analysis and the variance analysis, sensitivity of influential factors on stability of SHBS are obtained. The results show that the degree of hydrate dissociation is the most sensitive, followed by hydrate burial depth, the thickness of hydrate and the depth of seawater. Finally, the concept of gas hydrate critical burial depth is put forward according to the influence law of gas hydrate burial depth, and the numerical simulation for specific submarine slope is carried out, which indicates the existence of critical burial depth.
Petrogenesis of the microcrystalline-dioritic enclaves from Jiuling granitoids in the eastern segment of Jiangnan Orogen and constraints on magma source materials
Zheng Duan, Guang-fu Xing, Sheng-bing Liao, Ping-li Chu, Wen-cheng Huang, Yan-hui Zhu, Xu-jie Shu, Chang-bo Li
2018, 1(3): 374-391. doi: 10.31035/cg2018042
[Abstract](105) [FullText HTML] (19) [PDF 6476KB](14)
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Numerous dark enclaves with different shapes are found in Jiuling Neoproterozoic granitoids. Precise LA-ICP-MS U-Pb dating was conducted on zircons extracted from two microcrystalline enclave samples, yielding crystallization ages of 822.6±5.8 Ma and 822.2±6.2 Ma, respectively. The consistent ages within analytical errors with the host granitoids suggested that they were the products of the same magmatism. The microcrystalline-dioritic enclaves commonly show plastic forms and contain similar plagioclase megacrysts to the host rocks, and both of the enclaves and host granitoids showed a complex composition and structural imbalance in plagioclases. Furthermore, the apatites with a euhedral acicular shape occurred widely in the microcrystalline-dioritic enclaves. All of these petrographic features above imply magma mixing is involved in their diagenesis. The enclaves and host granitoids show a marked zircon trace element difference and Hf isotopic signatures without correlation in zircon trace element pairs but form their own system between enclaves and host granitoids. Additionally, most of the zircons show extremely high εHf (t) with εHf (t) =3.54−11.94 from the southern samples, andεHf (t) =1.0−9.09 from the central region. Some zircons with the higherεHf (t) are similar to the zircons from the juvenile island arc in the eastern segment of Jiangnan Orogen. Integrated geological and Hf isotopic characteristics suggest microcrystalline-dioritic enclaves were derived from the partial melting process of the Mesoproterozoic crust which enriched juvenile island arc materials and mixed with the granitic magma that remelted from the Mesoproterozoic continental crust which relatively enriched ancient sediments and mixed with the host granitoid in diagenesis.
Review Articles
Progress in the investigation of potash resources in western China
Mian-ping Zheng, Xian-hua Hou, Yong-sheng Zhang, En-yuan Xing, Hong-pu Li, Hong-wei Yin, Chang-qing Yu, Ning-jun Wang, Xiao-lin Deng, Zhao Wei, Zhong-ying Miao, Jia-ai Zhong, Fan Wang, Fu Fan, Xue-fei Zhang, Xu-ben Wang, Tu-qiang Liu, Wei-gang Kong
2018, 1(3): 392-401. doi: 10.31035/cg2018046
[Abstract](128) [FullText HTML] (29) [PDF 18500KB](13)
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Through the study of the geological conditions of potash deposits in China from recent years, a new understanding of potash theories has arisen that appropriate Chinese geological features. Important progress and substantial breakthroughs have been gained in the direction and management of potash prospecting: (1) Important breakthroughs in continental potassium prospecting: The "Quaternary gravel type deep potassium rich brine metallogenic model in western Qaidam" ensures Quaternary deep potassium rich brine prospecting will grow new KCl resources by 350 Mt, providing a resource guarantee for meeting the Chinese demand for sylvite. (2) The Marine facies potash prospecting shows good prospects: the determination of the new type of Triassic polyhalite potash ore deposits in Sichuan provide an important scientific basis for the establishment of exploration planning and the selection of exploration target areas for polyhalite minerals in the Sichuan Basin; The "two-storey potash deposits model" in southwestern Yunnan has been confirmed, which indicates prospects for the exploration of potash in the deeper Marine facies in southwestern Yunnan are likely to be successful. The discovery of a high concentration of rich bromite salt and potash salt in the Paleogene of the Kuqa depression and the southwestern Tarim region provides strong support for the likelihood large-scale potash deposits exist in these regions.
Cretaceous terrestrial deposits in China
Ke Cao
2018, 1(3): 402-414. doi: 10.31035/cg2018045
[Abstract](139) [FullText HTML] (23) [PDF 6575KB](10)
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As an important part of an epidermic system, terrestrial deposits can provide a good record of major geological events in the Cretaceous epidemic system. This article is a review of the geological background, paleogeography, paleoclimate, basin evolution and sedimentary characteristics in China through the Cretaceous period, in order to provide a comprehensive understanding for interested researchers. During the Berriasian-Hauterivian age, red-mainly fluvial and shallow lacustrine deposition developed under arid and semi-arid climates in westen China when eastern China had been occupied by the " East Plateau”. During the Barremian-Albian, age coal-bearing depositions occurred to the north of the Yanshan Mountain under the wet and warm climate. However, mainly red fluvial and shallow lacustrine depositions prevailed in most of the south to the Yanshan Mountain except basins where seawater could enter and caused mostly green depositions. During the Cenomanian-Santonian age, high land uplift took place in northwestern China. Mainly red deposition with developed alluvial plains occupied southwestern China and South China when the Songliao Basin was filled by black deep lacustrine mud shale caused by transgression. Mainly red deposition under an arid and semi-arid climate occupied all basins in China during the Campanian-Maastrichtian age.
Exploration and research progress on ion-adsorption type REE deposit in South China
Deng-hong Wang, Zhi Zhao, Yang Yu, Jing-jing Dai, Mao-chun Deng, Ting Zhao, Li-jun Liu
2018, 1(3): 415-424. doi: 10.31035/cg2018022
[Abstract](107) [FullText HTML] (23) [PDF 6176KB](15)
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Since 2011, certain advances have been made through the resource investigation, metallogenesis research, mining supervision and environmental protection of ion-adsorption type rare earth element (REE) deposit in South China. Firstly, some progress has been made in REE prospecting in Jiangxi, Guangdong, Guangxi and Yunnan. REE deposits are not only found within the weathering crusts of granites and felsic volcanic rocks, but also within the weathering crusts of epimetamorphic rocks and basic magmatic rocks. Secondly, the methods of exploration, delineating ore bodies and calculation of reserves have been improved, which intuitively reflect the thickness, REE composition and value of weathering crust. Thirdly, the relationship between REEs and weathering degree and the rule of distribution, migration and enrichment of REEs in the weathering profile was summarized through the analysis of big data, which can predict the metallogenetic horizon of REEs. Fourthly, a method for quick, accurate and dynamic investigation of the REE deposit has been established by using high resolution remote sensing technology. Finally, the relation between the production status of REE mines and water pollution has been revealed based on long-term hydrochemical monitoring data of rivers and wells in mines and surrounding areas.
Geological characteristics, metallogenic regularities and the exploration of graphite deposits in China
Li Sun, Cui-ping Xu, Ke-yan Xiao, Yu-sheng Zhu, Ling-ya Yan
2018, 1(3): 425-434. doi: 10.31035/cg2018044
[Abstract](184) [FullText HTML] (37) [PDF 6626KB](14)
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The demand for graphite resources has been increasing due to its extensive use. Graphite deposits in China are mainly distributed in Heilongjiang, Innner Mogolia, Sichuan, Shanxi and Shandong, characterized by "one old & one new" and "many in east & few in west". There are mainly three genetic types, including regional metamorphic type, contact metamorphic type and hydrothermal type. Here we provide a summary of the metallogenic regularity and 15 metallogenic belts in China based on the study of the geology of national graphite deposits. In recent years, great progress has been made in the research of genesis, mineral exploration and evaluation on graphite deposits, which indicate great potential for graphite resource in China. The authors suggest that the research on geochronology, ore sources, the genesis of crystalline graphite and exploration for hydrothermal graphite in China should be heightened.
An overview of the resources and environment conditions and major geological problems in the Yangtze River economic zone, China
Yue-hua Jiang, Liang-jun Lin, Li-de Chen, Hua-yong Ni, Wei-ya Ge, Hang-xin Cheng, Gang-yi Zhai, Gui-ling Wang, Yi-zhong Ban, Yuan Li, Ming-tang Lei, Cheng-xuan Tan, Jing-wen Su, Quan-ping Zhou, Tai-li Zhang, Yun Li, Hong-ying Liu, Ke Peng, Han-mei Wang
2018, 1(3): 435-449. doi: 10.31035/cg2018040
[Abstract](176) [FullText HTML] (30) [PDF 31017KB](22)
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Focusing on the Yangtze River economic zone, the previous geological researches are systematically summarized, resources and environment conditions and major geological problems which are needing to be concerned in land planning and construction are studied. The results show that the resource conditions of cultivated land, shale gas, geotherm, lithium and so on are superior in the Yangtze River economic zone, and the resources and environment conditions are conducive to develop the modern agriculture, clean energy industry and strategic emerging industries. 3×1013 m2 farmlands without heavy metal pollution are concentrated; there are three national level shale gas exploration and development bases with explored reserves of 5.441×1011 m3; geothermal availability is 2.4×109 t of standard coal each year, equivalent to 19% of the amount of coal in 2014; Asia's largest energy lithium metal ore deposit is found. In some parts of Yangtze River economic zone, there are some major geological problems such as active faults, karst collapse, ground subsidence, landslide-collapse-debris flow, affecting the river-crossing channels, high-speed railway, urban agglomeration and green ecological corridor planning and construction. Those problems should be concerned, and the relevant suggestions and countermeasures are put forward. Meanwhile, the ideas to further support the development of the Yangtze River economic zone are put forward.
Research Advances
Land submerged to carbonate platform by conodonts: paleoenvironment reconstruction of the western Gangdese in Tibet during Triassic
Zhan-sheng Ji, Jian-xin Yao, Gui-chun Wu, Qian Sun, Qiu-yuan Shi, Hao Li, Ji-fu He, Shao-wen Zhang
2018, 1(3): 450-452. doi: 10.31035/cg2018053
[Abstract](122) [FullText HTML] (53) [PDF 5431KB](19)
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Features of micro-fabric and the genetic study of Triassic deep polyhalite in the Guang'an area, central Sichuan Basin
Da-xing Gong, Bo Hui, Jia-yun Zhou
2018, 1(3): 453-454. doi: 10.31035/cg2018038
[Abstract](137) [FullText HTML] (26) [PDF 5358KB](12)
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News and Highlights
Introduction of the Beijing SHRIMP Center (National Science and Technology Infrastructure)
2018, 1(3): 455-456. doi: 10.31035/cg2018039
[Abstract](35) [FullText HTML] (33) [PDF 5260KB](6)
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International Union of Geodesy and Geophysics: 27th General Assembly Conference
2018, 1(3): 457-458. doi: 10.31035/cg2018037
[Abstract](32) [FullText HTML] (28) [PDF 5173KB](5)
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