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	JOPC 2018 Vol.20 Number 1
	2018, Vol.20 Num.1
	Online: 2018-02-01

	MAGMATIC-HYDROTHERMAL EXHALATIVE SEDIMENTARY ROCKS LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY PAST AND PRESENT GEOGRAPHIC ENVIRONMENTS AND HUMAN CIVILIZATION

MAGMATIC-HYDROTHERMAL EXHALATIVE SEDIMENTARY ROCKS

	1	Zheng Rong-Cai, Wen Hua-Guo, Li Yun, Chang Hai-Liang

		Compositions and texture of lacustrine exhalative rocks from the Lower Cretaceous Xiagou Formation in Qingxi sag of Jiuxi Basin, Gansu
		The widely developed laminated, fine-grained sedimentary rocks of the Lower Cretaceous Xiagou Formation in Qingxi sag of Jiuxi Basin, Gansu Province are rich in ankerite,albites,barites,zeolites and pyrites,and are poor in fluorites,tremolites,halites and clastic chalcopyrites,galenas and sphalerite. The hydrothermal minerals and favorable hydrocarbon conditions have been attracting the attention of many sedimentary geologists and petroleum geologists. In previous studies,most geologists believed that these fine-grained sedimentary rocks were associated with the volcanic activity,or were the products of volcanic material alteration. However, through a systematic study on the geological background,compositions,rock textures,rock structures,inclusions and geochemical features,we believed that these fine-grained sedimentary rocks were the lacustrine white-smoke type exhalative rocks. Six kinds of hydrothermal mineral assemblages were identified,including: Ⅰ albites-ankerites(or ankerites-albites),Ⅱ barites-albites-ankerites,Ⅲ Analcime-albite-ankerites,Ⅳ quartz-albite-ankerites,Ⅴ dickite-ankerites and Ⅵ the single ankerite. Three main types of rock textures were identified,including: ① the microcrystalline textures,②the intraclastic structure and ③ the halite pseudocrystal textures. Four common types of primary sedimentary structures were divided,including: ① the laminated and banded structures,② the network vein filling structures,③ vortical nozzle structures and ④ the syngenetic deformation bedding structures. On the basis of the rock composition,textures and structures,we have identified four occurrence types of exhalative rocks were identified,including the network vein filling type,the water bursting type,the basin deposition and the regional diffusion type. In addition, we establish the sedimentary model of the lacustrine “white smoke type” exhalative rock was established,and explored the significance of this kind of exhalative rock.
		2018 Vol. 20 (1): 1-18 [Abstract] ( 1087 ) [HTML 1KB] [PDF 7027KB] ( 432 )

	19	Zhong Da-Kang, Yang Zhe, Sun Hai-Tao, Zhang Shuo

		Petrological characteristics of hydrothermal-sedimentary rocks:A case study of the Lower Cretaceous Tengger Formation in the Baiyinchagan Sag of Erlian Basin, Inner Mongolia
		In the Baiyinchagan Sag of Erlian Basin,Inner Mongolia,there is a set of hydrothermal-sedimentary rocks occurred in the Tengger Formation and Duhongmu Formation of the Lower Cretaceous. In order to classify hydrothermal-sedimentary rocks,the mineral compositions,textures,structures and mineral assemblages were analyzed by studying the drilling cores,microscopes,field emission scanning electron microscope(FE-SEM),total rock X-ray diffraction,and electron probe analysis(EPMA). The rocks are displayed dark-grey,grey and grey-brown colors. The mineral compositions of rocks are complex and diverse. Dolomite and zeolite(natrolite and analcime)are main rock-forming minerals,and pyrite,magnesite,siderite and barite are secondary minerals,which are mixed with muddy terrestrial sediments composed of clay minerals,quartz,and plagioclase. The textures of hydrothermal-sedimentary rocks can be divided into four types and structures can be divided into nine,which differentiate them from normal lacustrine depositions like carbonate and terrestrial clastic rocks. According to the contents of dolomite,zeolite and terrestrial sediment(marked by 90%,75%,50%,25% and 10%),the hydrothermal-sedimentary rocks are generally divided into argillaceous dolostone,zeolite-bearing dolomitic mudstone and zeolite rock,of which the two formers are major types of hydrothermal-sedimentary rocks in study area. This research would provide an case study to analyze hydrothermal-sedimentary rocks and build depositional model in other basins,as well as enrich theoretical knowledge of sedimentology.
		2018 Vol. 20 (1): 19-32 [Abstract] ( 688 ) [HTML 1KB] [PDF 44544KB] ( 376 )

	33	Zhang Shuai, Liu Yi-Qun, Jiao Xin, Zhou Ding-Wu, Zhang Xu, Lu Shen-Tong, Zhou Ning-Chao

		Sedimentary environment and formation mechanisim of dolomitic rocks in the Middle Permian Lucaogou Formation,Jimusar Depression, Junggar Basin
		The Middle Permian Lucaogou Formation of Jimusar Depression,Junggar Basin is characterized by lacustrine fine-grained dolomitic sediments,which are composed of silt-sized to mud-sized terrigenous clasts,tuff clasts,carbonate and hydrothermal minerals. This paper is aimed to understand the sedimentary environment and formation mechanism of dolomitic rocks by studying their petrological,mineralogical and geochemical features. Petrological-mineralogical and major and trace element characteristics of the dolomitic rocks suggest the study area was a shallow salty lake formed under an arid climate during the Middle Permian,and was characterized by intense regional volcanism and active mantle-derived hydrothermal in the basin. The dolomites in the dolomitic rocks mainly present as euhedral-subhedral micritic crystals,forming fine lamination or mixing with other compositions,while fine-crystalline dolomites can only be found occasionally. The micritic dolomites,with low order degrees(0.46)and homogeneous compositions,are usually surrounded by laminations. The fine-crystalline dolomites are featured by well-developed metasomatic relict texture and thereby should be the product of diagenesis. Both two kinds of dolomites have high strontium and low magnesium contents,while fine-crystalline dolomites have higher contents of iron and manganese than that of micritic dolomites. The micritic dolomites have a low δ¹⁸O_PDB(av.-4.72‰). The forming temperature,54.61℃ to 186.46℃,is calculated from the δ¹³C_PDB(av. 8.79‰)of micritic dolomites might be resulted from the gigantic buried organic matter of Lucaogou Formation and metabolic activities of methanogens. In conclusion,the micritic dolomites are contemporaneous-penecontemporaneous protodolomite. Magnesium ion was supplied by the salty lake water,tuff materials as well as mantle-dervied hydrothermal fluid. The dynamic barrier of dolomite formation was broken by the high temperature brought from hydrothermal fluid and the metabolic activities of methanogens.
		2018 Vol. 20 (1): 33-48 [Abstract] ( 757 ) [HTML 1KB] [PDF 9348KB] ( 463 )

	49	Liu Yi-Qun, Zhou Ding-Wu, Nan Yun, Jiao Xin, Li Zhe-Xuan, Li Hong, Zhou Xiao-Hu

		Permian mantle-derived carbonatite originated exhalative sedimentary rocks in North Xinjiang
		In the Permian Lucaogou epoch, an underfilled intracontinental rift basin was developed in the North Xinjiang, which yields an important source rock of the Lucaogou Formation. A new series of sedimentary rocks that are laminated, thin bedded, carbonate rick and mantle-derived were observed in the source rock and termed as Exhalative Sedimentary Rocks (ESR). The carbonatite ESR in this paper include two types, Effusive Rocks and Explosive Rocks. The thickness of carbonatite Explosive Rocks ranges from 0.5~4 cm. Fine-grained calcite clasts distribute dispersedly in black matrix with various sizes and shapes and display normal grading. The calcite carbonatite originated Effusive rocks are characterized by 2~4 mm laminae and 2~3 cm thin bed, and are intercalated within oil-bearing sedimentary tuffs and tuffaceous dolostones. The calcites represent granular mosaic and zonal structure; homogenization temperatures of fluid inclusions reaches to 435℃. C-O and Sr-Nd isotope compositions indicate the calcite in canbonatite ESR was originated from mantle yet has been largely influenced by interaction with lake water. This study shows that the carbonatite ESR are the product of interaction between mantle-derived carbonatite melt/fluid and fresh lake water.
		2018 Vol. 20 (1): 49-63 [Abstract] ( 710 ) [HTML 1KB] [PDF 7724KB] ( 465 )

LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	65	Cai Juan-Juan, Cui Xiao-Zhuang, Lan Zhong-Wu, Wang Jian, Jiang Zhuo-Fei, Deng Qi, Zhuo Jie-Wen, Chen Feng-Lin, Jiang Xin-Sheng

		Onset time and global correlation of the Cryogenian glaciations in Yangtze Block, South China
		It's well known that the Jiangkou and Nantuo glaciations are two remarkable Cryogenian glaciations in South China. However,their precise onset time and global correlations remain undecided. In this study,detrital zircon LA￣ICP￣MS U-Pb dating was performed on the glacial diamictites from the basal part of the Chang'an and Nantuo Formations in the southeastern Yangtze Block. The new results show that detrital zircon grains from the Chang'an Formation give a concentrated ²⁰⁶Pb/²³⁸U age range of 958 to 717 Ma with distinct peaks at 720,753,805 and 848 Ma. The youngest age population yields a weighted mean of 719.6±6.1 Ma,representing the maximum depositional age of the Chang'an Formation. Detrital zircon grains from the Nantuo Formation has a main ²⁰⁶Pb/²³⁸U age range between 987 and 649 Ma,with distinct peaks at 650,720,753,803,823 and 848 Ma. The youngest age population gives a weighted mean of 649.3±6.2 Ma,representing the maximum depositional age of the Nantuo Formation. Taking into account the available age data,it is suggested that the Jiangkou glaciation was most likely initiated at ca.715 Ma,which is synchronous with the Sturtian glaciation in other blocks such as Tarim,Arabia-Nubia and Laurentia;the Nantuo glaciation was probably initiated later than 650 Ma,synchronous with the Marinoan glaciation in other blocks such as Siberia, Australia and Laurentia. Furthermore,detrital zircon U-Pb age spectrums and CL images indicate that sediments of the Chang'an and Nantuo Formations in the Yangtze Block were mainly derived from the underlying Neoproterozoic magmatic and sedimentary rocks,indicative of the intensive Neoproterozoic severe exaration and episodic tectonic-thermal events. The Cryogenian exaration in the Yangtze Block should be the response to the breakup of the Rodinia supercontinent prior to the termination of the global Marinoan glaciation.
		2018 Vol. 20 (1): 65-86 [Abstract] ( 881 ) [HTML 1KB] [PDF 3298KB] ( 494 )

	87	Meng Qi, Huang Heng, Yan Jia-Xin, Chen Fa-Yao

		Sedimentary evolution of the Middle Permian carbonate platform margin in southern Guizhou and its palaeo-oceanographic implications
		South China,part of Eastern Tethys,developed a huge carbonate platform in the Permian. During the Maokouin Subepoch of the Middle Permian,the carbonate platform experienced a transition from its prosperity to shrink. The southern Guizhou was located at the southern margin of the carbonate platform. It is a good area for discussing the controlling factors of platform evolution by analysis of stratigraphic structure and its variation. In this study,we selected the typical Nashui and Moyang sections of Luodian,southern Guizhou and studied on their carbonate factory by analyzing rock types and skeletal association statistics. As a result,15 rock types,5 sedimentary facies and 6 skeletal associations are recognized by field and indoor research. The carbonate factory features of the skeletal associations were also rebuilt. The results show that a distinct transition from tropical,shallow and warm water factory to tropical,deep and cool water factory occurred starting from the late Kuhfengian in the southern Guizhou,manifested as the beginning occurrence of deep water sediments in the upper Kuhfengian Stage. This transition was widespread from the Kuhfengian to the early Lengwuan in South China,manifested as the shrink of the carbonate platform and the drowning of the platform margin. The late Kuhfengian of the Middle Permian to the Wuchiapingian of the Late Permian was a significant turning point of global geological history where the photosynthetic organisms suffered heavy losses and the marine ecological environment deteriorated sharply. The drastic change of the carbonate factory was related to the inhibition or destruction of the shallow tropical carbonate factory.
		2018 Vol. 20 (1): 87-103 [Abstract] ( 826 ) [HTML 1KB] [PDF 17823KB] ( 371 )

	105	Zou Guang-Jun, Liang En-Yun, Zhang Xiao-Yang, Ling Yue-Xin, Xiong Miao

		Sedimentological characteristics and lithofacies palaeogeography of the Early Ordovician in northwestern Hunan Province
		Xiangxibei area refers to the northwestern Hunan Province mainly, Taoyuan, Yuanling, Huaihua cities. Lithofacies have been investigated, on the basis of the key Lower Ordovician sections collected during the field mapping projects. The lithofacies palaeogeography maps of the Tremadocian and Floian ages are presented here. The lithofacies palaeogeographic analyses suggest that there was a palaeo-uplift in areas of Zhangjiajie-Guzhang-Jishou, which shows the significant difference in lithofacies between both sides of the palaeo-uplift. The Tongzi and Honghuayuan Formations were formed on carbonate platform facies in the northwestern of palaeo-uplift,including six types of subfacies, including restricted-platform,open-platform,platform edge,marginal reef of platform,platform slope and shollow sea shelf. The Baishuixi/Panjiazui and Qiaotingzi sormations were formed on the shelf in the southeastern of palaeo-uplift,including two types of facies(i.e. ,mixed shelf and clastic shelf). Results from this work improve the understanding of the Early Ordovician,and provide important information for evaluation of geological prospecting in the area.
		2018 Vol. 20 (1): 105-118 [Abstract] ( 729 ) [HTML 1KB] [PDF 8908KB] ( 467 )

	119	Zhong Jian-Hua, Cao Meng-Chun, Ni Liang-Tian, Sun Ning-Liang, Liu Chuang, Hao Bing, Yang Guan-Qun, Song Guan-Xian, Ge Yu-Zhu

		Situation of study and development tendency of sandy dykes
		In recent years,sandy dykes have been attracted lots of attention and the research has intensified on sandstone intrusion processes and products because of their potential commercial significance. The paper focuses on five aspects about situation of study and development tendency of sandy dykes: geometry, component, genesis, classification and geological significance. Despite of some previous work,more problems are waiting to be solved in China,considering the complexity of sandy dykes and internationally research degree. Based on the abundant source of sandy dykes in China,we should analyze the typical cases and discuss the dynamic mechanism and relationship with seismicity,which offers basic materials to enrich and complete sedimentary theories.
		2018 Vol. 20 (1): 119-132 [Abstract] ( 1145 ) [HTML 1KB] [PDF 34676KB] ( 511 )

	133	Wu Bing, Jin Xin, Shi Zhi-Qiang, Nereo Preto, Du Yi-Xing

		Characteristics and geological significance of corrosion karst at the top of Middle Triassic in northwestern Sichuan Basin
		The corrosion karst at the top of the Middle Triassic was widely found at the Jinhe section in Shifang and in most parts of the Sichuan Basin. With the recent field studies,we identified this karst surface in the Triassic sections at Hanwang Guanyinya in Mianzhu,Huanglianqiao and Ma'antang in Jiangyou along the northwest margin of the Sichuan Basin. The karst yielded in top Tianjingshan Formation and its origin is thought to be related to strong tectonic activity and global sea-level fall that resulted in long-time exposure of the Middle Triassic. The main forms of the karst are as follows: (1)exposed erosion and discontinuous sedimentary surfaces,(2)solution channels, solution fractures and associated carbonate and terrigenous clastic fillings,(3)exposed clay layer,and(4)karst breccia. The exposed erosion and discontinuous sedimentary surfaces are most typical of birdeye structures or stromatactis,and at the Hanwang Guanyinya section in Mianzhu, they are most developed. The fillings of solution channels and fractures are mainly carbonate and terrigenous debris,commonly developed at the Ma'antang section in Jiangyou,Hanwang Guanyinya section in Mianzhu and Jinhe section in Shifang. The related dissolution joints and dissolution ditches are nearly vertical,with different widths and depths,and are filled with carbonate breccia,sparite, dolomite or terrigenous clay. The exposure soil is mainly confined to Huanglianqiao section in Jiangyou where two sets of exposure soils,about 5~20 cm thick each,contain iron minerals and the overlying and underlying intervals are dark gray limestone deposited in a lagoon paleoenvironment. The karst breccia is most common at Hanwang Guanyinya section in Mianzhu,with a maximum breccia size of up to 15×20 cm. The angular karst breccia is surrounded by dark carbonate matrix rich in mud and organic matter. The discovery of the corrosion-type karst at or near the top of the Tianjingshan Formation can provide the basis for regional stratigraphic isochronous correlation. In addition,the paleo-karst oil/gas accumulations can be formed in the carbonate rocks at the upper Tianjingshan and Leikoupo Formations with dissolution pores and fractures as the main storage space.
		2018 Vol. 20 (1): 133-146 [Abstract] ( 750 ) [HTML 1KB] [PDF 6885KB] ( 405 )

	147	Wang Meng-Shi, Zhang Zhi-Jie, Zhou Chuan-Min, Yuan Xuan-Jun, Lin Min-Jie, Liu Yin-He, Cheng Da-Wei

		Lithological characteristics and origin of alkaline lacustrine of the Lower Permian Fengcheng Formation in Mahu Sag, Junggar Basin
		The Lower Permian Fengcheng Formation,as favourable source rock in the Junggar Basin,has been the target for petroleum exploration. Due to its deep burial depth,complicated lithology and few global analogs,the evaluation of the petroleum potential of Fengcheng Formation is still at its rudimentary stage. This study discusses the characteristics of alkaline minerals,geological background,origin of alkaline lakes and its forming processes through methods including core description,thin section observation,SEM,X-ray diffraction analysis,TOC content measurements,inclusion temperature test,geochemical analysis,etc. the results suggest: (1)the Fengcheng Formation can be categorized into five rock types,among which,alkaline rock is the most distinguished lithofacies type of alkaline lakes and reedmergnerite is generally related to volcanic eruption or hydrothermal activities;(2)five rock associations are recognized in the Fengcheng Formation. From near-source to lake center,they are type Ⅴ of alluvial-fluvial facies,type Ⅲ and Ⅳ of shallow shoreface to lacustrine facies,respectively;type Ⅰ and Ⅱ of deep-semideep lacustrine facies,respectively. Type Ⅰ and Ⅲ are typical alkaline rock associations with favourable source rock potential;(3)the formation of alkaline lake is primarily controlled by volcanic activities and climate,where the former supply the Na-rich fluids,and the latter salinized the freshwater lake and facilitate the final formation of alkaline lake.
		2018 Vol. 20 (1): 147-162 [Abstract] ( 809 ) [HTML 1KB] [PDF 28817KB] ( 314 )

PAST AND PRESENT GEOGRAPHIC ENVIRONMENTS AND HUMAN CIVILIZATION

	163	Mo Dong-Po, Zhu Li-Dong, Li Feng-Quan, Ye Wei, Qiao Shu-Jie, He Jun-Jie, Wang Tian-Yang, Zhang Wei-Hong

		Chroma characteristics and its Holocene environmental record of Borehole XYC in the downstream area of Cao'e River,Zhejiang Province
		The Borehole XYC is located in the downstream area of the Cao'e River which is in the south bank of the Qiantang River. Based on the analysis of chroma,particle size and total organic carbon(TOC) of 1717 samples,the chromaticity characteristics and environmental significance of the drilling sediments were mainly discussed,and the characteristics of environmental change in the area were documented in combination with a chronological framework. The preliminary conclusions are as follows: (1)The drilling deposits show characteristics of high brightness, low yellowness and low redness. In the vertical direction,the chromaticity fluctuats markedly of Layers ① and ②,and the chroma changes steadly from Layer ③ to lower part of ⑧. However,the fluctuation amplitude of chromaticity changes from the upper part of Layer ⑧ to Layer ⑨ is enhanced again,and it presents the characteristics of fluctuation,stability and re-fluctuation eventually. (2)High brightness values brightness correlates well with sand and TOC content. The stronger the deposition power is,the higher the sand content is and the higher brightness value brightness is;while the higher of the TOC content,the lower of the brightness value. The values of low yellowness,saturation and TOC content have a good negative correlation,and also have a good indication of the humid climate and sea level changes. (3)The chromaticity and its variation process indicates a damp or subaqueous environment,and to some extent,it responds to the sea level change in the area and change process of sedimentary facies between fluvial facies,tidal-flat facies,neritic facies and limnetic facies. During 9690-9107cal a BP,the fluvial deposits were developed,the hydrodynamic changes were unstable,and the climate is dry,the TOC content is low,brightness is high,while the values of yellowness and redness are low. During 9107—8613 cal a BP,the values of yellowness and saturation were reduced,the climate was damp,the brackish water shellfish and benthic foraminifera, mainly including Ammonia beccarii vars., emerged,all of these indicates that transgression occurred in the study area and gradually changed from a low tidal flat to a high tidal environment. During 8932-7330 cal a BP,the values of yellowness and saturation are lowest,the climate was more humid,accompanied by the normal salinity of Elphidium advenum and a small amount of Globigerina spp., Globorotalia spp. and other planktonic foraminifera,the sea further rose into a shallow sea environment. During 8932-7330 cal a BP,the values of yellowness and saturation are increased,the sea level fell and the climate became dry,into the limnetic environment,and the peat was developed.
		2018 Vol. 20 (1): 163-174 [Abstract] ( 831 ) [HTML 1KB] [PDF 1640KB] ( 404 )

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