1988 Vol. 6, No. 1
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1988, 6(1): 1-12.
Abstract:
The flysch trace fossils described in this paper including 15 ichnogenera and 20 ichnospecies,Were collected from the Permian--Triassic strata in the Guoluo and Yushu regions, southern Qinghai, thses two places have been most abundant in trace fossils of Nereites facies in China up to now.All trace fossils are well-preserved,and with quite abundant varieties. Among them, the Pascichnia and Agrichnia are predominant with a few Fodinichnia, but common shallow Domichnia and Cubichnia are absent, so it's proved that these trace fossils developed in turbidites of deep-sea slope environments. The fossil sites are just located on the Maxin-Xiugou conve-rgent joint zone in Guoluo and near the crustal consumption zone between the Tanggula Plate and Bay an kela Plate, of Yushu.The following fossils are described in this paper,such as,Chondrites, Impona}glphus,Helicolithus,Helminthopsis, Hel- minthoida, Nereites, Neonereites, Lophoctenum, Megagrapton, Paleodictyon, Protop-alondictyon, Phycosiphon, Plaaolites, Spirophycus and Sublorenzinia.
The flysch trace fossils described in this paper including 15 ichnogenera and 20 ichnospecies,Were collected from the Permian--Triassic strata in the Guoluo and Yushu regions, southern Qinghai, thses two places have been most abundant in trace fossils of Nereites facies in China up to now.All trace fossils are well-preserved,and with quite abundant varieties. Among them, the Pascichnia and Agrichnia are predominant with a few Fodinichnia, but common shallow Domichnia and Cubichnia are absent, so it's proved that these trace fossils developed in turbidites of deep-sea slope environments. The fossil sites are just located on the Maxin-Xiugou conve-rgent joint zone in Guoluo and near the crustal consumption zone between the Tanggula Plate and Bay an kela Plate, of Yushu.The following fossils are described in this paper,such as,Chondrites, Impona}glphus,Helicolithus,Helminthopsis, Hel- minthoida, Nereites, Neonereites, Lophoctenum, Megagrapton, Paleodictyon, Protop-alondictyon, Phycosiphon, Plaaolites, Spirophycus and Sublorenzinia.
1988, 6(1): 21-28.
Abstract:
The explorations for the sedimentary environment of Lower Tertiary in the North Jiangsu petroliferous basin are different. No consistent conclusion exists in these explroations. In order to f urther study the environment mentioned above, the approach used in this paper can avoid the conf usion of multisources of hydrocarbons and indicate directly the salinities of waters in which the carbonate deposits. In this study, the sedimental environment of this basin is defined by using the inorganic compounds in the sedimentary environment the δ13C and δ18O values for and other important evidences to identify the paleoenvironment and paleoclimate of Tertiary in the North Jiangsu basin. A diagram based on δ13C and δ18O values for members and formations of the basin is compared with Mook's Diagram (by Mook, 1971)of the δ13C / δ18O retionship and thesalinities in differnet waters.(Figs. 1,2).The comparison shows that most of the values fall in the area of lacustrine and fluvial environments in Mook's Diagram,only parts of the values of members Ef2 and Ef2 fall in the vicinity of marine environment. Another approach used in this study is the formula of Z datum (by Keith,1964),by which we can distinguish the marine-limestone from freshwater limestone.The calculated Z data of most members (Et, Ef1,Ef3 and Es1)are less than 120, only the data of members Ef2 and Ef4 are a little more than 120. Therefore they can be defined as a mixed type of limestone. Thirdly,the result, obtained bythe comparison of the δ13C values measured of this area with the δ18O for different environments defined by Degens, is good coincident with the results obtained above. Based on the above reasons, it can be concluded that the sedimentary paleoenvi-ronment of the basin is dominated by Iacustrine-fluvial facies. Only the intermittent marine transgressions during the two depositional periods of Ef2 and Ef4 resulted in the increase of salinities and the δ13C / δ18O values deviated from nonmarine environm-ent, but the values haven't reached the normal marine environment. It belongs to amixed sedimentary environment. The estimation for paleotemperature of the basin during the early Tertiary period is based on two approaches.One is the revised Craig Formula (1965).By the Craig Formula,the claculated mean annual paleotemperature of the basin is 21℃.The other is York's least square method (1969). Plotting the coordinates of calculated δ13C and δ18O values by using York's least square method on Mook's diagram for te-mper ature range (1971),we can obtain that the mean annual paleotemperature during that time is about 20 C.The two results agree with each other. Thirdly,according to the zonation of torrid zone and subtropical zone from "China's Vegetation" The paleoclimate of the basin during the early Tertiary should belong to south subtropi-cal zone. Thus,the mean annual paleotemperature at that time is estimated to be 21℃. The conclusions hereinabove also show good agreement with the evidences of paleontology.The fossils found in this area, such as calcareous super-microscopic fossils, ostracoda,foraminifera and spore-pollens, have fully confirmed the conclu-sions discussed in this paper.
The explorations for the sedimentary environment of Lower Tertiary in the North Jiangsu petroliferous basin are different. No consistent conclusion exists in these explroations. In order to f urther study the environment mentioned above, the approach used in this paper can avoid the conf usion of multisources of hydrocarbons and indicate directly the salinities of waters in which the carbonate deposits. In this study, the sedimental environment of this basin is defined by using the inorganic compounds in the sedimentary environment the δ13C and δ18O values for and other important evidences to identify the paleoenvironment and paleoclimate of Tertiary in the North Jiangsu basin. A diagram based on δ13C and δ18O values for members and formations of the basin is compared with Mook's Diagram (by Mook, 1971)of the δ13C / δ18O retionship and thesalinities in differnet waters.(Figs. 1,2).The comparison shows that most of the values fall in the area of lacustrine and fluvial environments in Mook's Diagram,only parts of the values of members Ef2 and Ef2 fall in the vicinity of marine environment. Another approach used in this study is the formula of Z datum (by Keith,1964),by which we can distinguish the marine-limestone from freshwater limestone.The calculated Z data of most members (Et, Ef1,Ef3 and Es1)are less than 120, only the data of members Ef2 and Ef4 are a little more than 120. Therefore they can be defined as a mixed type of limestone. Thirdly,the result, obtained bythe comparison of the δ13C values measured of this area with the δ18O for different environments defined by Degens, is good coincident with the results obtained above. Based on the above reasons, it can be concluded that the sedimentary paleoenvi-ronment of the basin is dominated by Iacustrine-fluvial facies. Only the intermittent marine transgressions during the two depositional periods of Ef2 and Ef4 resulted in the increase of salinities and the δ13C / δ18O values deviated from nonmarine environm-ent, but the values haven't reached the normal marine environment. It belongs to amixed sedimentary environment. The estimation for paleotemperature of the basin during the early Tertiary period is based on two approaches.One is the revised Craig Formula (1965).By the Craig Formula,the claculated mean annual paleotemperature of the basin is 21℃.The other is York's least square method (1969). Plotting the coordinates of calculated δ13C and δ18O values by using York's least square method on Mook's diagram for te-mper ature range (1971),we can obtain that the mean annual paleotemperature during that time is about 20 C.The two results agree with each other. Thirdly,according to the zonation of torrid zone and subtropical zone from "China's Vegetation" The paleoclimate of the basin during the early Tertiary should belong to south subtropi-cal zone. Thus,the mean annual paleotemperature at that time is estimated to be 21℃. The conclusions hereinabove also show good agreement with the evidences of paleontology.The fossils found in this area, such as calcareous super-microscopic fossils, ostracoda,foraminifera and spore-pollens, have fully confirmed the conclu-sions discussed in this paper.
1988, 6(1): 39-49.
Abstract:
At present, cement of clastic rocks in interior basins has been considered an important factor affecting the accumulation of oil and gas. The author systemtically researches this problem by studying the Lower Cretaceous in the Jiuxi Basin. The results show that the cement, depending on its sedimentary environment, has two types of cementintergrowthing-combination namely rich in iron and poor in iron. In the sedimentary system of iron-rich alluvial fan, a lot of cement is formed around iron, such as ferruginous, calcareous and argillaceous mixed cement; ferrodolomite, gypsum, silica and ferruginous layer. But in the sedimentary system of iron-poor river or lake, a lot of cement is formed around carbonate, for example, argillaceous and calcite, argillaceous and ferruginous mixed cement, ankerite, dolomite, calcite, and ankerite layer. The horizontal distribution of cement is divided into three zones: mixed cement zone, ferromagnesian cement zone and diagenetic zone. Argillaceous and ferruginous cement in interior basins is formed during early diagenetic buried stage, and a series of changes of clay minerals in argillaceous cement occur with their buried depth, but the depth at which clay minerals such as kaolinite, montmorillonite, chlorite changeinto illite is different owing to the difference of geothermal gradient. The study that ferruginous, magnesian and calcareous carbonate form calcite, ferrocalcite, dolomite and ankerite cement minerals is a very interesting and worthwhile subject. So far, only a small quantity of the reports regarding this subject of interior basins have been published. However, it has been found that in the Jiuxi Basin there are lots of ankerites and dolomites, which are in the ferromagnesian cement and distribute widely. Most of them are automorphic crystals: a few of them are allotriomorphic crystals. The same result is got by staining in thin section, infra-ree absorption spectrum and X-ray diffraction analysis. In the Jiuxi Basin, there are lots of thin layers of ferruginous, magnesian and calcareous carbonate both in well and outcrop area. Usually, the carbonate thin layers are composed of one, two or three kinds of intergrowth minerals of the four kinds of minerals mentioned above and they have quite close origin relations. During early diagenetive buried stage, calcites formed earliest are replaced by Mg, Fe anions to form dolomite, ankerite and ferrocalcite minerals. During late diagenetic stage, mineral autogeny and recrystallization take place and result in the formation of allatriomorpjic ankerite and dolomite. If there are spaces, autogenetic dolomite rhombohedron can be formed within biological cavity; however, autogenic and bright ankerite crystals can be formed in pore space of sandstone. According to the studies of other people by electron microscope, there are some dissolution pores, intergranular pores and intercrystal pores within solomite. Dolomite rocks and dolomite crystal cement are very useful for the reservoir of oil and gas. It has been confirmed that dolomite rocks and ferromagnesian cementation zones in the Jiuxi Basin are of high yield oil-porducing zones.
At present, cement of clastic rocks in interior basins has been considered an important factor affecting the accumulation of oil and gas. The author systemtically researches this problem by studying the Lower Cretaceous in the Jiuxi Basin. The results show that the cement, depending on its sedimentary environment, has two types of cementintergrowthing-combination namely rich in iron and poor in iron. In the sedimentary system of iron-rich alluvial fan, a lot of cement is formed around iron, such as ferruginous, calcareous and argillaceous mixed cement; ferrodolomite, gypsum, silica and ferruginous layer. But in the sedimentary system of iron-poor river or lake, a lot of cement is formed around carbonate, for example, argillaceous and calcite, argillaceous and ferruginous mixed cement, ankerite, dolomite, calcite, and ankerite layer. The horizontal distribution of cement is divided into three zones: mixed cement zone, ferromagnesian cement zone and diagenetic zone. Argillaceous and ferruginous cement in interior basins is formed during early diagenetic buried stage, and a series of changes of clay minerals in argillaceous cement occur with their buried depth, but the depth at which clay minerals such as kaolinite, montmorillonite, chlorite changeinto illite is different owing to the difference of geothermal gradient. The study that ferruginous, magnesian and calcareous carbonate form calcite, ferrocalcite, dolomite and ankerite cement minerals is a very interesting and worthwhile subject. So far, only a small quantity of the reports regarding this subject of interior basins have been published. However, it has been found that in the Jiuxi Basin there are lots of ankerites and dolomites, which are in the ferromagnesian cement and distribute widely. Most of them are automorphic crystals: a few of them are allotriomorphic crystals. The same result is got by staining in thin section, infra-ree absorption spectrum and X-ray diffraction analysis. In the Jiuxi Basin, there are lots of thin layers of ferruginous, magnesian and calcareous carbonate both in well and outcrop area. Usually, the carbonate thin layers are composed of one, two or three kinds of intergrowth minerals of the four kinds of minerals mentioned above and they have quite close origin relations. During early diagenetive buried stage, calcites formed earliest are replaced by Mg, Fe anions to form dolomite, ankerite and ferrocalcite minerals. During late diagenetic stage, mineral autogeny and recrystallization take place and result in the formation of allatriomorpjic ankerite and dolomite. If there are spaces, autogenetic dolomite rhombohedron can be formed within biological cavity; however, autogenic and bright ankerite crystals can be formed in pore space of sandstone. According to the studies of other people by electron microscope, there are some dissolution pores, intergranular pores and intercrystal pores within solomite. Dolomite rocks and dolomite crystal cement are very useful for the reservoir of oil and gas. It has been confirmed that dolomite rocks and ferromagnesian cementation zones in the Jiuxi Basin are of high yield oil-porducing zones.
1988, 6(1): 58-69.
Abstract:
The mid-seventies is the period of full bloom in delta sedimentation researches on large rivers abroad, but the papers on delta sedimentation were published in the late seventies and the early-eighties in China. Recently delta studies are concentrating on fan-deltas and transgressive channel-filling sequence. The deltaic sedimentation studies contribute a favourable condition for comparison between deltaic sedim-etary systems in North and South China, which includes their general and distinct charactereristics. The pattern of main facies, the vertical sequence and the transgressive channel-filling sequence belong to the former, and the distribution model of deltaic sand bodies, the vertical superimposition, the facies criteria, the development and the reworking belong to the later (Table 1). This paper deals with the transgressive channel-filling sequence, the progradational rate and the reworking of Table 1 Correlation of the delta systems in Soth and North China deltaic systems. The transgressive channel-filling sequence overlain by deltaic sequence is a fining-upward one with an erasional base surface and gravelly sand or sand in its lower part. It usually contains foraminifera with an upward increase in marineness and also contains marine authigenic minerals such as glauconite in subtropic zone of South China. The transgressive channel-filling sequences in delta areas of the Yangtse, Luanhe, Nanliujiang Rivers can be put in order of marineness. The marineness of transgressive channel-filling sequence in the coastal area is higher than that in the apical area of the Yangtse delta. That in the coastal area of the Luanhe delta is similar to the later, but the transgressive channel-filling sequence in its apical area absents marine microfossil. According to simulating tests, field observations and our recent measurements in the Yangtse, Nanliujiang and Qiantangjiang Rivers, there are the intrusion of sea water, flood tidal current, the backwater caused by datum rising and the retrogressive aggradation in lower reaches of river. Data from modern tidal estuaries show that the distances of retrogressive aggradation, backwater, flood tidal current and intrusion of sea water decrease in proper order. The retrogressive aggradation caused by postglacial sea-level rising formed the transgressive channel-filling sequence, whose characteristics were controlled by flood tidal current and intrusion of sea water. During the maximum transgression, transgressive channel-filling sequence without marine criteria could develop where retrogressive aggradation occured but no flood tidal current, such as the Luanhe fandelta area. This would also develop in the subtropic Nanliujiang delta area, but it was rewoked into a single normal river sequence by the river.
The mid-seventies is the period of full bloom in delta sedimentation researches on large rivers abroad, but the papers on delta sedimentation were published in the late seventies and the early-eighties in China. Recently delta studies are concentrating on fan-deltas and transgressive channel-filling sequence. The deltaic sedimentation studies contribute a favourable condition for comparison between deltaic sedim-etary systems in North and South China, which includes their general and distinct charactereristics. The pattern of main facies, the vertical sequence and the transgressive channel-filling sequence belong to the former, and the distribution model of deltaic sand bodies, the vertical superimposition, the facies criteria, the development and the reworking belong to the later (Table 1). This paper deals with the transgressive channel-filling sequence, the progradational rate and the reworking of Table 1 Correlation of the delta systems in Soth and North China deltaic systems. The transgressive channel-filling sequence overlain by deltaic sequence is a fining-upward one with an erasional base surface and gravelly sand or sand in its lower part. It usually contains foraminifera with an upward increase in marineness and also contains marine authigenic minerals such as glauconite in subtropic zone of South China. The transgressive channel-filling sequences in delta areas of the Yangtse, Luanhe, Nanliujiang Rivers can be put in order of marineness. The marineness of transgressive channel-filling sequence in the coastal area is higher than that in the apical area of the Yangtse delta. That in the coastal area of the Luanhe delta is similar to the later, but the transgressive channel-filling sequence in its apical area absents marine microfossil. According to simulating tests, field observations and our recent measurements in the Yangtse, Nanliujiang and Qiantangjiang Rivers, there are the intrusion of sea water, flood tidal current, the backwater caused by datum rising and the retrogressive aggradation in lower reaches of river. Data from modern tidal estuaries show that the distances of retrogressive aggradation, backwater, flood tidal current and intrusion of sea water decrease in proper order. The retrogressive aggradation caused by postglacial sea-level rising formed the transgressive channel-filling sequence, whose characteristics were controlled by flood tidal current and intrusion of sea water. During the maximum transgression, transgressive channel-filling sequence without marine criteria could develop where retrogressive aggradation occured but no flood tidal current, such as the Luanhe fandelta area. This would also develop in the subtropic Nanliujiang delta area, but it was rewoked into a single normal river sequence by the river.
1988, 6(1): 80-87.
Abstract:
The basic structures of clay minerals are vary similar. The phase of clay minerals varies with the variation of physicochemical conditions during geological processes and it need not be disintegrated from one mineral A and then recrystallizes into another mineral B but A may be transformed towards B by a regulation of internal structure during a long time of geological process, so that there must be a transfor-mational stage of structure between mineral A and mineral B. The intermediate structures during transformation are just the problems which are discussed here.1 .The intermediate structure from 2:1 structure towards 1:1 structure (Fig.l.):it is formed by hydration of illite, the cations of K+ move out and the cations of H)+act on the oxygens on the conjunction points between tetrahdras and octahetras and change into(OH)一,so the 2:1 structure transforms into 1:1structure. During the transitional stage, the structure of the clay mineral is intermediate between the twokinds of domains under high resolution electron microscope and there are two kind of coexisting lattices, 10Åand 7Å(photo.l.).2.The intermediate structure from 2:1 form towards adjacent 2=1 form (Fig.4):in montmorillonite,because catioas of K+ infiltrafe into structure and interlayer water is moved out, the 15Åof d(001)is converted into 10 A,the product of the intermediate strucure is a disordered mined layered mineral (I/S). In the hypergenic zones it is just the reverse, the illite is hydrated and transformed towarrds moatmorillonite. and the product of intermediate structure is also the mixed-layered mineral (I/S). 3. The intermediate structure from layered chain structure towards layered structure (Fig.6),here is an example of sepiolite transformation into talc, under highresolution electron microscope the lattice image shows the coexistance (photo.2.3.4.)of rhombic lattice and layered lattice. The presence of such a kind of lattice imagemay indicate that with the loss of zeolitic water is sepiolite the (0H2 )- of sepiolite loses equilibrium, then acts with Si in the adjacent tetrahydra during diagenesis, andas a silicic asid sets free from sepiolite, that makes collapse of the layered chain of sepiolite and leads to the transformation into talc. At first, it shows a littledomains of talc insepiolite, subsequently the domains of talc increase with the decrease of sepiolite domains and finally the sepiolite is substituted by talc completely. 4. The intermediate structure of polymorphic convesion (Fig.B),the transform-ation from kaolinite into dickite map be a good example, this transformation happensat about 110℃-140`C due to the loos of equilibrium of interlayer stress, in order tokeep the equilibrium the A1十十十 cations begin to move and form the domains of 2Mtype, the 2M domains increase with the decrease of the Tc domains of kaolinite andthe kaolinite changes into dickite completely at last. The siglificance of resarch of intermediate structures is geology and industrialapplication has also been discussed. in the present paper.
The basic structures of clay minerals are vary similar. The phase of clay minerals varies with the variation of physicochemical conditions during geological processes and it need not be disintegrated from one mineral A and then recrystallizes into another mineral B but A may be transformed towards B by a regulation of internal structure during a long time of geological process, so that there must be a transfor-mational stage of structure between mineral A and mineral B. The intermediate structures during transformation are just the problems which are discussed here.1 .The intermediate structure from 2:1 structure towards 1:1 structure (Fig.l.):it is formed by hydration of illite, the cations of K+ move out and the cations of H)+act on the oxygens on the conjunction points between tetrahdras and octahetras and change into(OH)一,so the 2:1 structure transforms into 1:1structure. During the transitional stage, the structure of the clay mineral is intermediate between the twokinds of domains under high resolution electron microscope and there are two kind of coexisting lattices, 10Åand 7Å(photo.l.).2.The intermediate structure from 2:1 form towards adjacent 2=1 form (Fig.4):in montmorillonite,because catioas of K+ infiltrafe into structure and interlayer water is moved out, the 15Åof d(001)is converted into 10 A,the product of the intermediate strucure is a disordered mined layered mineral (I/S). In the hypergenic zones it is just the reverse, the illite is hydrated and transformed towarrds moatmorillonite. and the product of intermediate structure is also the mixed-layered mineral (I/S). 3. The intermediate structure from layered chain structure towards layered structure (Fig.6),here is an example of sepiolite transformation into talc, under highresolution electron microscope the lattice image shows the coexistance (photo.2.3.4.)of rhombic lattice and layered lattice. The presence of such a kind of lattice imagemay indicate that with the loss of zeolitic water is sepiolite the (0H2 )- of sepiolite loses equilibrium, then acts with Si in the adjacent tetrahydra during diagenesis, andas a silicic asid sets free from sepiolite, that makes collapse of the layered chain of sepiolite and leads to the transformation into talc. At first, it shows a littledomains of talc insepiolite, subsequently the domains of talc increase with the decrease of sepiolite domains and finally the sepiolite is substituted by talc completely. 4. The intermediate structure of polymorphic convesion (Fig.B),the transform-ation from kaolinite into dickite map be a good example, this transformation happensat about 110℃-140`C due to the loos of equilibrium of interlayer stress, in order tokeep the equilibrium the A1十十十 cations begin to move and form the domains of 2Mtype, the 2M domains increase with the decrease of the Tc domains of kaolinite andthe kaolinite changes into dickite completely at last. The siglificance of resarch of intermediate structures is geology and industrialapplication has also been discussed. in the present paper.
1988, 6(1): 97-101.
Abstract:
Phosphorite with abundant stromatolite in the Doushantuo Formation of Sinian System is well-developed and widespread in the Jingmen-Xiangyang region of Hubei. There are four phosphorite-beds, the first one consists of stromatolite, Baicalia minuta Komar, B. ampla Semikhatov, Conophyton yichengensis Cao (f. nov.), C. miloradovici Raaben, C. f., Paraconophyton hubeiensis Cao (f. nov.), Compactocol-lenia tuvensis Kor.; the second oncolite Osagia jianshanensis Cao (f.nov); the third oncolite Osagia minuta Z. Zhur. and the fourth oncolite, Osagia nersinica Yakschin and O. f.. P2O5 in the stromatolitic phosphorite accounts for 37.5% while the P2O5 in the oncolitic phosphorite 16-19% or less. Usually phosphorite appears in the offshore near platform, and is a kind of biochemigenic deposits.
Phosphorite with abundant stromatolite in the Doushantuo Formation of Sinian System is well-developed and widespread in the Jingmen-Xiangyang region of Hubei. There are four phosphorite-beds, the first one consists of stromatolite, Baicalia minuta Komar, B. ampla Semikhatov, Conophyton yichengensis Cao (f. nov.), C. miloradovici Raaben, C. f., Paraconophyton hubeiensis Cao (f. nov.), Compactocol-lenia tuvensis Kor.; the second oncolite Osagia jianshanensis Cao (f.nov); the third oncolite Osagia minuta Z. Zhur. and the fourth oncolite, Osagia nersinica Yakschin and O. f.. P2O5 in the stromatolitic phosphorite accounts for 37.5% while the P2O5 in the oncolitic phosphorite 16-19% or less. Usually phosphorite appears in the offshore near platform, and is a kind of biochemigenic deposits.
1988, 6(1): 109-117.
Abstract:
On the basis of the grain size analysis of thin sections from the drills and exposures, the sedimentary enviornments of C-P of the region on the south of the line of Tangshan, Beijing and Taiyuan are mainly studied. The sediments and grain size in the studied region vary thiner and corser from the north to west, thicker and finer the north to east. The sediment is mainly from the Yinshan Old-land. The sorting of grain-size is medium or better. The values of standard deviation and skewness of grain-size put on Friedman's scatter diagram show a fluvial environment from Lower Shiqianfeng Formation to Upper and Middle Taiyuan Formation and a littoral enviornment from Lower Taiyuan Formation to Benxi Formation. According to the distribution features and change patterns of curves of frequency and probability of gain size, C-M patterns and parameters of grain-size (mean grain-size, standard deviation, skewness and leptokurtosis), some sedimentary sub-environments are determined such as braided channel on alluvial fan, braided channel of upper and middle river, braided-meandeting channel, meandering channel, delta and shore, tide flat and lagoon. By the sedimental models, the conclusion can be given as follows; the sedimentary environment is marine in the early Middle Carboneferous, shore and tidal flat and lagoon in the middle Middle Carboneferous, littoral delta in the middle Later Carboneferous, distributary plain of delta in the early Early Permian, meand-ring river on the north of the line of Zhengzhou-Puyang-Jinan and distributary plain of delta on the south of that in the later Early Permian, braided-meandering river on the north of the line of Zhengzhou-Xuzhou and distributary plain of delta on the south of that in the early Later Permian.
On the basis of the grain size analysis of thin sections from the drills and exposures, the sedimentary enviornments of C-P of the region on the south of the line of Tangshan, Beijing and Taiyuan are mainly studied. The sediments and grain size in the studied region vary thiner and corser from the north to west, thicker and finer the north to east. The sediment is mainly from the Yinshan Old-land. The sorting of grain-size is medium or better. The values of standard deviation and skewness of grain-size put on Friedman's scatter diagram show a fluvial environment from Lower Shiqianfeng Formation to Upper and Middle Taiyuan Formation and a littoral enviornment from Lower Taiyuan Formation to Benxi Formation. According to the distribution features and change patterns of curves of frequency and probability of gain size, C-M patterns and parameters of grain-size (mean grain-size, standard deviation, skewness and leptokurtosis), some sedimentary sub-environments are determined such as braided channel on alluvial fan, braided channel of upper and middle river, braided-meandeting channel, meandering channel, delta and shore, tide flat and lagoon. By the sedimental models, the conclusion can be given as follows; the sedimentary environment is marine in the early Middle Carboneferous, shore and tidal flat and lagoon in the middle Middle Carboneferous, littoral delta in the middle Later Carboneferous, distributary plain of delta in the early Early Permian, meand-ring river on the north of the line of Zhengzhou-Puyang-Jinan and distributary plain of delta on the south of that in the later Early Permian, braided-meandering river on the north of the line of Zhengzhou-Xuzhou and distributary plain of delta on the south of that in the early Later Permian.
1988, 6(1): 13-20.
Abstract:
Step-like garnets, i.e. garnets with faceted surface, occur in heavy from the reservoir rocks of Lower Tertiary sandstones. Many people that it resulted from dissolution or chemical etching,but many evidences this is not true in the study area. The writer suggests that it is anmineral and can be used as an excellent mineral geothermo meter. Studies by means of SEM show that the surface microtexture of the surface microtexture of the step-like garnets consisted of euhedral crystal faces are very regular and well defined,no evidence of dissolution or chemical etching can be found. The chemical compositions are analyzed by energy dispesive analyser,which indicates that all of the authigenic garnets have certain chemical compositions similar to those of almandine. The authigenic garnet is an excellent mineral geothermometer, its distribution is closely related to its burial depth and the geothermal gradient. It is found in Oligocene sandstones at depth more than 2100m, the amount of the step-like garnets increases with the increase the shape tends tomore complex and more variable. The studied area was a downfauited basin with continuous subsidence during Cenozoic Period and favours to study the burial diagenetic minerals.In comparison of the calculated temperature correspoding to depths of various burial diagenetic minerals with the measured temperature of these minerals in studied area, it is suggested that the calculated temperature is approximate or equal to the temper-ature limit of these mineral formation.According to the calculation results of the data f rom 13 wells, it is demonstrated that the step-like garnets are formed at 92 1 5 C,which approximates to the threshold temperature (93`i})of the oil generation in Dongying Basin. It is important for the evolution of source rocks and reserviorrocks in a new exploration area. Detailed investigations of more deeply-buried sediments have shown that several kinds of burial diagenesis involving the almandine formation or precipitaion can contempraneously occur, such as the conversion of the smectite to illite in mudstone and the dissolution of the feldspar in sandstone.The coversion of smectite to illite involves the release of a considerable number of components including Fe, Mg,Si,all of which are required for the almandine formation.
Step-like garnets, i.e. garnets with faceted surface, occur in heavy from the reservoir rocks of Lower Tertiary sandstones. Many people that it resulted from dissolution or chemical etching,but many evidences this is not true in the study area. The writer suggests that it is anmineral and can be used as an excellent mineral geothermo meter. Studies by means of SEM show that the surface microtexture of the surface microtexture of the step-like garnets consisted of euhedral crystal faces are very regular and well defined,no evidence of dissolution or chemical etching can be found. The chemical compositions are analyzed by energy dispesive analyser,which indicates that all of the authigenic garnets have certain chemical compositions similar to those of almandine. The authigenic garnet is an excellent mineral geothermometer, its distribution is closely related to its burial depth and the geothermal gradient. It is found in Oligocene sandstones at depth more than 2100m, the amount of the step-like garnets increases with the increase the shape tends tomore complex and more variable. The studied area was a downfauited basin with continuous subsidence during Cenozoic Period and favours to study the burial diagenetic minerals.In comparison of the calculated temperature correspoding to depths of various burial diagenetic minerals with the measured temperature of these minerals in studied area, it is suggested that the calculated temperature is approximate or equal to the temper-ature limit of these mineral formation.According to the calculation results of the data f rom 13 wells, it is demonstrated that the step-like garnets are formed at 92 1 5 C,which approximates to the threshold temperature (93`i})of the oil generation in Dongying Basin. It is important for the evolution of source rocks and reserviorrocks in a new exploration area. Detailed investigations of more deeply-buried sediments have shown that several kinds of burial diagenesis involving the almandine formation or precipitaion can contempraneously occur, such as the conversion of the smectite to illite in mudstone and the dissolution of the feldspar in sandstone.The coversion of smectite to illite involves the release of a considerable number of components including Fe, Mg,Si,all of which are required for the almandine formation.
1988, 6(1): 29-38.
Abstract:
Recording to fades analysis, Taiyuan Formation of the upper Carboniferous in the region of Henan Province and Shandong Province, northern part of China, is deposited in sea inlet, tidal flat and shore marsh. The sandstones of Taiyuan Formation are mainly pure quartzose sandstones, deposited on the shoreface beach, tidal flat or other high energy environments. They are originally of high maturity, both in texture and in composition. During the long geologic processes, sandstones have undergone deep and complex diagenesis, with the formation of large amount of auth-higenetic quartz in the form of overgrowth and the gradual loss of primary pores. Analytical results of cathodoluminescence petrography, scanning electron microscopy and X-ray microanalysis reveal that quartz cementation is the dominating process responsible for the loss of primary pores. Quartz cement occurs mainly as overgrowths, which have the same optical orientation with the detrital grains. Outlines of original grains are poorly visible, or completely undistinguishable for most overgrowth grains. Under these cicurmst-ances, only the cathodoluminescnce technique can be effective in brimging the shape of grains to light. By luminescence microscopy, the detrital quartz grains display either brown or blue colour, depending on their source rocks. The authigenetic quartz, however, usually shows no colour of luminescence, or has dark brown colour. Two generations of quartz overgrowth in the Taiyuan quartzose sandstones are recognizable from the luminescence difference and the location of quartz cement. The dark brown authigenetic quartz, along grain boundaries, or filled in grain cracks, represents the early stage of quartz cementation. The great amount of non-lumiescence quartz, welded around the early overgrowth quartzs, marks the late stage of quartz cementation. According to pointcount calculation under cathodoluminescence, the authigenetic quartz accounts for 16 percent of the total quartz. The ratio of the amounts of authigenetic quartz between the early stage and late stage is about 1/3. This shows that the late quartz cementation is strong and progressive. It is generally accepted that the source of the silica cement in pure quartz sandstone includes: pressure solution in sandstones, alteration of clay minerals and dissolutin of small guartz grains in associated siltstones, dissolution of some detrital grains such as feldspar and rock fragments, the migretion of undergroundwater etc. Cathedoluminescence study has proved that intergranular pressare solution occurs only partially and locally. Concequently, it has little significant influence on quartz cementation,or in other words it cannot be the main source of authigenetic quartz. The quartz cement derived from pressure solution, according to the point-count data, accounts for only 10 percent. X-ray diffraction analysis of clay minerals in Taiyuan Formation and the upper strata leads us to the idea that the silica released during the alteration of smectite to illite in adjacent mudstones may play an important role in quartz cementation. A possible explination of the generations of overgrowth quartz may be like this: at early stage of diagenesis, the limitted intergranular pressure solution may derive dissolved silica, which, then is precipitated on adjacent quartz grains, or fills some cracks; with increase of burial depth, alteration of clay minerals in interbedded mudstones becomes strongly discharg, silica slowly migrates into sandstone with pore fluid and is precipitated. The formation temperature of the authigenetic quartz is also analysized by determining the homogeneous temperature, of fluid inclusions in quartz cement. During the process of this work, the temperature history of the area, on the basis of the vitrinite reflectance in shales; was taken into account. Through careful studies, a definite formation temperature ranging from 140°C to 150°C is finally established for authigenetic quartz. The strong quartz cementation in sandstones of Taiyuan Formation not only leads to the
Recording to fades analysis, Taiyuan Formation of the upper Carboniferous in the region of Henan Province and Shandong Province, northern part of China, is deposited in sea inlet, tidal flat and shore marsh. The sandstones of Taiyuan Formation are mainly pure quartzose sandstones, deposited on the shoreface beach, tidal flat or other high energy environments. They are originally of high maturity, both in texture and in composition. During the long geologic processes, sandstones have undergone deep and complex diagenesis, with the formation of large amount of auth-higenetic quartz in the form of overgrowth and the gradual loss of primary pores. Analytical results of cathodoluminescence petrography, scanning electron microscopy and X-ray microanalysis reveal that quartz cementation is the dominating process responsible for the loss of primary pores. Quartz cement occurs mainly as overgrowths, which have the same optical orientation with the detrital grains. Outlines of original grains are poorly visible, or completely undistinguishable for most overgrowth grains. Under these cicurmst-ances, only the cathodoluminescnce technique can be effective in brimging the shape of grains to light. By luminescence microscopy, the detrital quartz grains display either brown or blue colour, depending on their source rocks. The authigenetic quartz, however, usually shows no colour of luminescence, or has dark brown colour. Two generations of quartz overgrowth in the Taiyuan quartzose sandstones are recognizable from the luminescence difference and the location of quartz cement. The dark brown authigenetic quartz, along grain boundaries, or filled in grain cracks, represents the early stage of quartz cementation. The great amount of non-lumiescence quartz, welded around the early overgrowth quartzs, marks the late stage of quartz cementation. According to pointcount calculation under cathodoluminescence, the authigenetic quartz accounts for 16 percent of the total quartz. The ratio of the amounts of authigenetic quartz between the early stage and late stage is about 1/3. This shows that the late quartz cementation is strong and progressive. It is generally accepted that the source of the silica cement in pure quartz sandstone includes: pressure solution in sandstones, alteration of clay minerals and dissolutin of small guartz grains in associated siltstones, dissolution of some detrital grains such as feldspar and rock fragments, the migretion of undergroundwater etc. Cathedoluminescence study has proved that intergranular pressare solution occurs only partially and locally. Concequently, it has little significant influence on quartz cementation,or in other words it cannot be the main source of authigenetic quartz. The quartz cement derived from pressure solution, according to the point-count data, accounts for only 10 percent. X-ray diffraction analysis of clay minerals in Taiyuan Formation and the upper strata leads us to the idea that the silica released during the alteration of smectite to illite in adjacent mudstones may play an important role in quartz cementation. A possible explination of the generations of overgrowth quartz may be like this: at early stage of diagenesis, the limitted intergranular pressure solution may derive dissolved silica, which, then is precipitated on adjacent quartz grains, or fills some cracks; with increase of burial depth, alteration of clay minerals in interbedded mudstones becomes strongly discharg, silica slowly migrates into sandstone with pore fluid and is precipitated. The formation temperature of the authigenetic quartz is also analysized by determining the homogeneous temperature, of fluid inclusions in quartz cement. During the process of this work, the temperature history of the area, on the basis of the vitrinite reflectance in shales; was taken into account. Through careful studies, a definite formation temperature ranging from 140°C to 150°C is finally established for authigenetic quartz. The strong quartz cementation in sandstones of Taiyuan Formation not only leads to the
1988, 6(1): 50-57.
Abstract:
Storm deposits are well-developed in the Shasan Member of Oligocene in Dongpu Depression. The lacustrine tempestites have many sedimentary features. (1) Pene-contemporaneous deformation structures are well-developed including load structures, ball-and-pillow structures, flame structures, clastic dykes, concolute beddings, etc, The formation of these structures is related to sediment liquefaction and drai- nage, reflecting the characteristics of gravity flows. (2) Scour-and fill structures are conspicuous and they can be divided into two types, sand-filled scours and themud-filled ones cut into sands. The erossional structures, especially the mud-filled scours, seem to be uncommon in turbidite facies. They are the evidence of storm activity. (3) Sandstone tops of Bouma-like sequeces often disply oscillatory ripples. Parting lineations are often found in the parallel lamination sandstones. (4) Hummocky crosss-tratifications are characterized by gently curved, lowangle cross-lamination. Most researchers have specifically inferred their origin results from powerful oscillatory dominant or multidirectional flows. Despite uncertainty regarding the dynamics of formation, hummocky cross-stratification is now regarded as the best indicator of a storm influence in ancient sedimentary sequences. The absence of tidal currents in the lake greatly enhanced the potential for preservation of hummocfcy cross-stratification. (5) Biogenetic sedimentary structures are distinct. Storm activity may have mixed oxygen-rich surface water with stagnant basin water so as to provide more favorable conditions for development of benthic communities. After the storm is over, the sediment surface is then populated by burrowing infauna. The presence of escape burrows reflects a quick depositional event. The sedimentary sequences of the storm sand layers can be compared with Bouma Sequence, but they display more variable sand-stone tops. There are five principal types: (a) sandstone tops modified by subsequent organic reworking; (b) wave-rippled sand-stone tops; (c) sandstone tops displaying mud-filled scours; (d)sandstone tops displaying starved ripples; and (e) sharp sandstone tops. The storm layers vary between proximal and distal types: (a) channel-filled deposits, consisting of massive sandstones; (b) interchannel deposits with complete Sb-Se sequeccesf and (c) distal deposits, mainly consisting of thin silt beds with Sc-e, Sde. Based on single-well microfacies analysis and comparison of well-to-well correlations as well as their paleostructures, paleoclimaes, sources and nature of sand layers, a facies model is presented.
Storm deposits are well-developed in the Shasan Member of Oligocene in Dongpu Depression. The lacustrine tempestites have many sedimentary features. (1) Pene-contemporaneous deformation structures are well-developed including load structures, ball-and-pillow structures, flame structures, clastic dykes, concolute beddings, etc, The formation of these structures is related to sediment liquefaction and drai- nage, reflecting the characteristics of gravity flows. (2) Scour-and fill structures are conspicuous and they can be divided into two types, sand-filled scours and themud-filled ones cut into sands. The erossional structures, especially the mud-filled scours, seem to be uncommon in turbidite facies. They are the evidence of storm activity. (3) Sandstone tops of Bouma-like sequeces often disply oscillatory ripples. Parting lineations are often found in the parallel lamination sandstones. (4) Hummocky crosss-tratifications are characterized by gently curved, lowangle cross-lamination. Most researchers have specifically inferred their origin results from powerful oscillatory dominant or multidirectional flows. Despite uncertainty regarding the dynamics of formation, hummocky cross-stratification is now regarded as the best indicator of a storm influence in ancient sedimentary sequences. The absence of tidal currents in the lake greatly enhanced the potential for preservation of hummocfcy cross-stratification. (5) Biogenetic sedimentary structures are distinct. Storm activity may have mixed oxygen-rich surface water with stagnant basin water so as to provide more favorable conditions for development of benthic communities. After the storm is over, the sediment surface is then populated by burrowing infauna. The presence of escape burrows reflects a quick depositional event. The sedimentary sequences of the storm sand layers can be compared with Bouma Sequence, but they display more variable sand-stone tops. There are five principal types: (a) sandstone tops modified by subsequent organic reworking; (b) wave-rippled sand-stone tops; (c) sandstone tops displaying mud-filled scours; (d)sandstone tops displaying starved ripples; and (e) sharp sandstone tops. The storm layers vary between proximal and distal types: (a) channel-filled deposits, consisting of massive sandstones; (b) interchannel deposits with complete Sb-Se sequeccesf and (c) distal deposits, mainly consisting of thin silt beds with Sc-e, Sde. Based on single-well microfacies analysis and comparison of well-to-well correlations as well as their paleostructures, paleoclimaes, sources and nature of sand layers, a facies model is presented.
1988, 6(1): 70-79.
Abstract:
The Qinlan port, including its adjacent sea,is a complex depositional system,which consists of the southern and northern bays connected by tidal path,and theshallow beaches on both sides of the tidal path.The analysis of their surfacesediments showes that the depositional features of the sediments are controlled by theenergy conditions and material sources. According to the sedimentological analysis, the authors recognize two kinds ofdepositional features from the environments mentioned above,(1),the NorthernBamen Bay and northern part of the tidal path represent one kind,in which the riverprocess plays the main role but the tidal process takes some influences, too.Mostof the sediments in this kind of environments are terrigenous debris with smallamount of intrabasin organic fragments. The sorting is poor or very poor and thesize ranges from coarse to fine; (2),The southern part of the tidal path and Gaol-ong Bay connecting with off-sea represent another kind of environments in whichthe tidal process plays the main role but the river process takes some influences.Its main sediments are intrabasin fine一size organic fragments,sorting well,withquantities of terrigenous debris. Various sedimentological data of quantitativeanalysis indicate that the depositional conditions in the shallow beaches on bothsides of tidal path and the beaches with obvious erosion are in the medium statebetween the two kinds mentioned above. Waxing and waning of the river process and tidal process in the two sedimentaryenvironments which have different depositional conditions cause the debris to mix indifferent proportion and form the dynamic equilibrium of deposit supply and energyconditions,namely the dynamic equilibrium among transporting depositing andreforming of sediments. And this may be one of the important reasons that the adjacentsea of the Qinlan port and the tidal path may not accumulate in large amount ofterrigenous debris.
The Qinlan port, including its adjacent sea,is a complex depositional system,which consists of the southern and northern bays connected by tidal path,and theshallow beaches on both sides of the tidal path.The analysis of their surfacesediments showes that the depositional features of the sediments are controlled by theenergy conditions and material sources. According to the sedimentological analysis, the authors recognize two kinds ofdepositional features from the environments mentioned above,(1),the NorthernBamen Bay and northern part of the tidal path represent one kind,in which the riverprocess plays the main role but the tidal process takes some influences, too.Mostof the sediments in this kind of environments are terrigenous debris with smallamount of intrabasin organic fragments. The sorting is poor or very poor and thesize ranges from coarse to fine; (2),The southern part of the tidal path and Gaol-ong Bay connecting with off-sea represent another kind of environments in whichthe tidal process plays the main role but the river process takes some influences.Its main sediments are intrabasin fine一size organic fragments,sorting well,withquantities of terrigenous debris. Various sedimentological data of quantitativeanalysis indicate that the depositional conditions in the shallow beaches on bothsides of tidal path and the beaches with obvious erosion are in the medium statebetween the two kinds mentioned above. Waxing and waning of the river process and tidal process in the two sedimentaryenvironments which have different depositional conditions cause the debris to mix indifferent proportion and form the dynamic equilibrium of deposit supply and energyconditions,namely the dynamic equilibrium among transporting depositing andreforming of sediments. And this may be one of the important reasons that the adjacentsea of the Qinlan port and the tidal path may not accumulate in large amount ofterrigenous debris.
1988, 6(1): 88-96.
Abstract:
A rare type of marine sepiolite in China was first reported from Leping County, Jiangxi Province in 1947 (R. Zhang, 1947). In 1963, Peng Qirui founed the existence of talc and quartz associated with the sepiolite by means of DTA and XRD. In recent years, Professor R. Zhang considered the talc may be the result of the transformation of crystal structure of sepiolite underdeep buried condition (R.Zhan, 1981) R. Zhang and Z. Yang, 1985), In this paper the authors briefly summarized the achievement of sepiolite phasetransformation both in laboratory experiments and in field observations, which has been reported in publications. It is noticed that sepiolite is stable under hydrothermal condition at temperature below 310°. At higher temperature sepiolite undergoes the following transformation: sepiolite→ (stevensite)→hydrotalc→talc (+quartz). Since the associated minerals-talc, stevensite and quartz are major factors to influence the ore quality and evaluation in industry, it is important to deal with the sepiolite phase-transformation during the diagenesis processing. The phase-transformation of sepiolite in the early Permian in south China is an only example in the world, and also a nature example to study sedimentary diagenesis. The major factors of the transformation are palaeothermals, pressure and geological time. The most important factor for sepiolite to be transformed into talc is palaeo- temperature. It should be pointed out that the transformation can be taken place at lower palaeotemperature rather than 310°C which obtained from the artifical experiments. A sensible way to determine the palaeotemperature under buried condition is the degree of coalification of the Permian coal seams (Table 1,2). The reflectance of vitrinite is particularly useful since measurements need not be confined to coal, but can be undertaken on other sediments which contain plant fragments preserved as vitrinite. So, vitrinite reflectance in the Permian sedimentary rocks can be used as an indication of burial temperature reached by sepiolite. According to the vitrinite reflectance (Table 3), the authors suggest that the favourable diagenetic temperature for the transformation is below 120°C. Based on the regional distribution of the Permian coal rank, the authors consider that the sepiolite phase- transformation shows a synchronous relationship with coal metamorphism. It can be shown that the distibution areas of the lower rank of coal (subbituminous coal) conform evidently to those of sepiolite on the map of the trend surface analysis (Fig. 4 , ) by means of the computer VICTOR-9000. Therefore, the geological, prospective significance of the phase-transformation for sepiolite lies in the possibility for predicting the existing regions of sepiolite based on the lower rank of coal.
A rare type of marine sepiolite in China was first reported from Leping County, Jiangxi Province in 1947 (R. Zhang, 1947). In 1963, Peng Qirui founed the existence of talc and quartz associated with the sepiolite by means of DTA and XRD. In recent years, Professor R. Zhang considered the talc may be the result of the transformation of crystal structure of sepiolite underdeep buried condition (R.Zhan, 1981) R. Zhang and Z. Yang, 1985), In this paper the authors briefly summarized the achievement of sepiolite phasetransformation both in laboratory experiments and in field observations, which has been reported in publications. It is noticed that sepiolite is stable under hydrothermal condition at temperature below 310°. At higher temperature sepiolite undergoes the following transformation: sepiolite→ (stevensite)→hydrotalc→talc (+quartz). Since the associated minerals-talc, stevensite and quartz are major factors to influence the ore quality and evaluation in industry, it is important to deal with the sepiolite phase-transformation during the diagenesis processing. The phase-transformation of sepiolite in the early Permian in south China is an only example in the world, and also a nature example to study sedimentary diagenesis. The major factors of the transformation are palaeothermals, pressure and geological time. The most important factor for sepiolite to be transformed into talc is palaeo- temperature. It should be pointed out that the transformation can be taken place at lower palaeotemperature rather than 310°C which obtained from the artifical experiments. A sensible way to determine the palaeotemperature under buried condition is the degree of coalification of the Permian coal seams (Table 1,2). The reflectance of vitrinite is particularly useful since measurements need not be confined to coal, but can be undertaken on other sediments which contain plant fragments preserved as vitrinite. So, vitrinite reflectance in the Permian sedimentary rocks can be used as an indication of burial temperature reached by sepiolite. According to the vitrinite reflectance (Table 3), the authors suggest that the favourable diagenetic temperature for the transformation is below 120°C. Based on the regional distribution of the Permian coal rank, the authors consider that the sepiolite phase- transformation shows a synchronous relationship with coal metamorphism. It can be shown that the distibution areas of the lower rank of coal (subbituminous coal) conform evidently to those of sepiolite on the map of the trend surface analysis (Fig. 4 , ) by means of the computer VICTOR-9000. Therefore, the geological, prospective significance of the phase-transformation for sepiolite lies in the possibility for predicting the existing regions of sepiolite based on the lower rank of coal.
1988, 6(1): 102-108.
Abstract:
Shandan County is situated in the passageway of Hexi, Gansu Province, at the foot of the Qilian Mountains. In this region outcrops of Permian System are very common with a distinct appearance and their geological structure is uncomplicated. Volcanic-lastic rock is discovered in the lower series of Permian System, namely the Dahuang-gou Group, in Chaihuoguo of Shandan and it is described as follows: It is brick red, rough and interlayered in the continental sedimentary rocks of the lower series of Permian System with a thickness of 6-10 meters and its horizontal bedding is indistinct. Beneath the layer is a volcanic breccia which has 1.2 meters in thickness and consists of lava breccia and crystal fragments. It has a volcanic breccis texture. Tuff is mainly composed of vitric fragments accounting for more than 50 percent. Diameter of the fragment is 0.25-0.50 mm and shapes are mainly bow-curved, angulat, archedand triangular porous. The rock can be named as vitric tuff according to the clasificatory principles of volcaniclastic rock summed up by F. J. Pettijohn. and determined to be the attribute of limealkali series on the basis of analytical data. The discovery of volcaniclastic rock in Chaihuoguo of Shandan is of significance in three aspects. (1) The volcaniclastic rock is characterized: by. K2O/Na2O 1 , Fe2O3FeO, (FeO + Fe2O3)MgO a little higher and characteristic of grain-size and discoverd in continental clastic rocks of lower series of Permian System. All of these have shown with the surroundings of shallow water environment. It is a sediment of fall ash. (2) The layer of pyroclastic rock which has a certain thickness and a special colour can be distinctly regarded as a marker bed and used in the respect of areal stratigraphical contrast. (3) The first discovery of volcaniclastic rock has been confirmed the fact that there was a volcanic activity present in the area of Shandan and its neighbourhood in the Early Permian, and this will provide a series of the most useful geological information for the researches of areal geology.
Shandan County is situated in the passageway of Hexi, Gansu Province, at the foot of the Qilian Mountains. In this region outcrops of Permian System are very common with a distinct appearance and their geological structure is uncomplicated. Volcanic-lastic rock is discovered in the lower series of Permian System, namely the Dahuang-gou Group, in Chaihuoguo of Shandan and it is described as follows: It is brick red, rough and interlayered in the continental sedimentary rocks of the lower series of Permian System with a thickness of 6-10 meters and its horizontal bedding is indistinct. Beneath the layer is a volcanic breccia which has 1.2 meters in thickness and consists of lava breccia and crystal fragments. It has a volcanic breccis texture. Tuff is mainly composed of vitric fragments accounting for more than 50 percent. Diameter of the fragment is 0.25-0.50 mm and shapes are mainly bow-curved, angulat, archedand triangular porous. The rock can be named as vitric tuff according to the clasificatory principles of volcaniclastic rock summed up by F. J. Pettijohn. and determined to be the attribute of limealkali series on the basis of analytical data. The discovery of volcaniclastic rock in Chaihuoguo of Shandan is of significance in three aspects. (1) The volcaniclastic rock is characterized: by. K2O/Na2O 1 , Fe2O3FeO, (FeO + Fe2O3)MgO a little higher and characteristic of grain-size and discoverd in continental clastic rocks of lower series of Permian System. All of these have shown with the surroundings of shallow water environment. It is a sediment of fall ash. (2) The layer of pyroclastic rock which has a certain thickness and a special colour can be distinctly regarded as a marker bed and used in the respect of areal stratigraphical contrast. (3) The first discovery of volcaniclastic rock has been confirmed the fact that there was a volcanic activity present in the area of Shandan and its neighbourhood in the Early Permian, and this will provide a series of the most useful geological information for the researches of areal geology.
1988, 6(1): 118-127.
Abstract:
This paper deals with the study on asphaltenes extractd by benzen-methyl alcohol from 11 source rocks from Huashen No 1 well of the Lower Xingmin Group (Cretaceous) in the Jinxi-Huahai basin, Northwest China. The relation between the porperties of the asphatenes and petroleum evolution is studied by elements analysis, infrared spectrum, electron spin resonance and nuclear magnetis resonamce. experiments 1. Method for preparing asphaltenes Source rocks are extracted by benzene-methyl alcohol (9:1) Asphaltenes are prepared in the standard way by two times of precipitation from the benzen-methyl alcohol extract with 10 parts of hexane. 2. Element analysis; Element analysis is performed on a ZWF-1-type element analyser and the percentages of are obtained. Then H/C atom rate and O/C atom rate are calclated. 3. Infrared spectrum: The analysis is made with the following method: Powder asphaltenes are prepared 0.25% bromine potassium piece Subsequent was scanned by the infrared spectrometer of IR-440 type. The result of infrared spectrum shows that the asphaltenes have the following fuctional group: the peaks at 2900 cm-1, 1380 cm-1, 2850 cm-1, 1450 cm-1 representing methyl and methylene respectively; and the peaks at 750cm-1, 810 cm-1, 860 cm-1, 1280 cm-1. 1620 cm-1. 3050 cm-1, reflecting aromatic hydrocarbon characteristic absorption peaks and the peaks at 1030 cm-1, 1650 cm-1, 1700 cm-1, 3400 cm-1, representing ether groups, quinone groups, carbonyl groups and NH group respectvel.y 4. Electron spin resonance: Powder asphaltenes are put in a glass tube with DPPH reference, then detected by the ESR-3 spectrometer at room temperature. Conclusion Based on the above data, the following ideas are conceived: 1) During oil formation the asphaltenes are the material of "interim type". Asphal-tene molecule consists of condensed nucleus benzen rings with alkylated side chain; 2) Properties of asphaltenes in structure are relatived to the types of the source materials. Organic parent materials in Huashen No 1 well belong to a mixture type which mainly contains humic substance. 3) The asphaltenes are heavy components of the soluble extract. The stages are observed from soure rocks in Hnashen No 1 well. The depth of 1357m-1768m is the lower mature stage while 1800m-2700m is the higher mature stage. The maximal threshold of the formation of crude oil is 1800m in Huashen No 1 well of the Huahai Basin.
This paper deals with the study on asphaltenes extractd by benzen-methyl alcohol from 11 source rocks from Huashen No 1 well of the Lower Xingmin Group (Cretaceous) in the Jinxi-Huahai basin, Northwest China. The relation between the porperties of the asphatenes and petroleum evolution is studied by elements analysis, infrared spectrum, electron spin resonance and nuclear magnetis resonamce. experiments 1. Method for preparing asphaltenes Source rocks are extracted by benzene-methyl alcohol (9:1) Asphaltenes are prepared in the standard way by two times of precipitation from the benzen-methyl alcohol extract with 10 parts of hexane. 2. Element analysis; Element analysis is performed on a ZWF-1-type element analyser and the percentages of are obtained. Then H/C atom rate and O/C atom rate are calclated. 3. Infrared spectrum: The analysis is made with the following method: Powder asphaltenes are prepared 0.25% bromine potassium piece Subsequent was scanned by the infrared spectrometer of IR-440 type. The result of infrared spectrum shows that the asphaltenes have the following fuctional group: the peaks at 2900 cm-1, 1380 cm-1, 2850 cm-1, 1450 cm-1 representing methyl and methylene respectively; and the peaks at 750cm-1, 810 cm-1, 860 cm-1, 1280 cm-1. 1620 cm-1. 3050 cm-1, reflecting aromatic hydrocarbon characteristic absorption peaks and the peaks at 1030 cm-1, 1650 cm-1, 1700 cm-1, 3400 cm-1, representing ether groups, quinone groups, carbonyl groups and NH group respectvel.y 4. Electron spin resonance: Powder asphaltenes are put in a glass tube with DPPH reference, then detected by the ESR-3 spectrometer at room temperature. Conclusion Based on the above data, the following ideas are conceived: 1) During oil formation the asphaltenes are the material of "interim type". Asphal-tene molecule consists of condensed nucleus benzen rings with alkylated side chain; 2) Properties of asphaltenes in structure are relatived to the types of the source materials. Organic parent materials in Huashen No 1 well belong to a mixture type which mainly contains humic substance. 3) The asphaltenes are heavy components of the soluble extract. The stages are observed from soure rocks in Hnashen No 1 well. The depth of 1357m-1768m is the lower mature stage while 1800m-2700m is the higher mature stage. The maximal threshold of the formation of crude oil is 1800m in Huashen No 1 well of the Huahai Basin.
