1988 Vol. 6, No. 3
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Display Method:
1988, 6(3): 1-10.
Abstract:
China is one of the most important Carboniferous bauxitebearing countries in the world.One hundred and more large and mediumsized Carboniferous bauxite deposits with the reserve of one billion tones have been found. About 75% of the total deposits occured mainly on the Middle Carboniferous karst basement of North China plateform, subordinately on the lower Carboniferous karst surface in G-uizhou. Only a few of them belong to geosynclinal karst bauxite (merely found in small-sized deposits in Mount Wushibei of Xingjiang ) . Nearly all of the bauxite are diasporite karst ones,with a few small sized bauxite deposits accompanied by boehmite. As a rule, diasporite, as well as dickite accompanied sometimes therein, are not formed under normal temperature and pressure, but derived from other minerals or substances in deuter-diagenesis period. The formation of the deposits is believed to take place near the ancient equator (deduced from theory of plate movement), resulted from severe chemical weathering under moist and hot climate, and from "consecutive formation" suah as short-distance transportation, deposition, diagenesis,deuterogene, hypergene and post-weathering. Very few deposits have undergone contact metamorphism. Differences manifest themselves in various parts and deposits. The material comes mainly from alumi-nasilicate rock and the weathering resideum of limestone. Colloform and debris are, in varying degrees, both the modes of transportation. Abundant good-quality b-auxites are formed mainly in lakes, lagoons and gulf, ore is closely related to t-he desilication desulphate and deferrization during the post-weathering and leaching. But those formed in marshes and rivers are inferior and small in scale. Due to the slight motions of shaking or frequent seismic activities ( including sub-kastification in pay bed after sedimentation in the crust of pene-plateform after deposition of bauxite, the above-mentioned main factors accompanied with the effect of flood and windstorm made the bauxite bed of deposition again or m-ore times eroded by the waves of waterflow and migrated faintly or subsided, even broken down. During this time, "interior fragment" was produced. And then the turbidity current deposit and windstorm deposit of bauxite was formed, (note: Tie author is the first man who put forward the newtheory "the bauxite of windstorm deposit" , but it is only an initial idea and needs a further study ) The bauxite of turbidity current deposit mainly occurs in the deep lake district. There the sorting and the thickness of bed is uneven ( several centermeters to meters ) . The sequence of grain is thick on bottom and fine upper, showwing a decrease in energy. The bauxite of windstorm deposit occurs mainly in the shallow lake district. There the bauxite is stored well. The thickness of flag bed is uniform ( from several centimeters to tens of centimeters ), with a sequence of fine grain on bottom and thick upper, howing a increase in energy. The author believes that both diosporite and dickite which sometimes contains constitutional water in Carboniferous bauxite in China is frequently formed by solidus reaction and solid transportation during diagenesis and deuterogene. The composition of O isotope in it is unchanged basically. It means a "preservation"; conversely, that formed by solution, the primary compositions of O isotope are exchanged ( see Fig.1) . Detailly, the diosporite is formed by alumina-gel in aocient crust of weathering( suspended transportation ) and colloidal solution at the initial stage of diagenesis of reductive environment ( including transformed by gibbsite). The phenomena of constitutional water ( means colloidal water from ancient crust of weathering), vegetating recrystallizing and sequence belong to the solid reaction.The exchange in diagenesis and deutero-water of 0 isotope is uot caused, so the O isotope possess preservation of "weathering crust" 5 and"laterite property" 7. It is derived from kaolinite deposited from ancient weathering crust and gel since the deuterogene present solid
China is one of the most important Carboniferous bauxitebearing countries in the world.One hundred and more large and mediumsized Carboniferous bauxite deposits with the reserve of one billion tones have been found. About 75% of the total deposits occured mainly on the Middle Carboniferous karst basement of North China plateform, subordinately on the lower Carboniferous karst surface in G-uizhou. Only a few of them belong to geosynclinal karst bauxite (merely found in small-sized deposits in Mount Wushibei of Xingjiang ) . Nearly all of the bauxite are diasporite karst ones,with a few small sized bauxite deposits accompanied by boehmite. As a rule, diasporite, as well as dickite accompanied sometimes therein, are not formed under normal temperature and pressure, but derived from other minerals or substances in deuter-diagenesis period. The formation of the deposits is believed to take place near the ancient equator (deduced from theory of plate movement), resulted from severe chemical weathering under moist and hot climate, and from "consecutive formation" suah as short-distance transportation, deposition, diagenesis,deuterogene, hypergene and post-weathering. Very few deposits have undergone contact metamorphism. Differences manifest themselves in various parts and deposits. The material comes mainly from alumi-nasilicate rock and the weathering resideum of limestone. Colloform and debris are, in varying degrees, both the modes of transportation. Abundant good-quality b-auxites are formed mainly in lakes, lagoons and gulf, ore is closely related to t-he desilication desulphate and deferrization during the post-weathering and leaching. But those formed in marshes and rivers are inferior and small in scale. Due to the slight motions of shaking or frequent seismic activities ( including sub-kastification in pay bed after sedimentation in the crust of pene-plateform after deposition of bauxite, the above-mentioned main factors accompanied with the effect of flood and windstorm made the bauxite bed of deposition again or m-ore times eroded by the waves of waterflow and migrated faintly or subsided, even broken down. During this time, "interior fragment" was produced. And then the turbidity current deposit and windstorm deposit of bauxite was formed, (note: Tie author is the first man who put forward the newtheory "the bauxite of windstorm deposit" , but it is only an initial idea and needs a further study ) The bauxite of turbidity current deposit mainly occurs in the deep lake district. There the sorting and the thickness of bed is uneven ( several centermeters to meters ) . The sequence of grain is thick on bottom and fine upper, showwing a decrease in energy. The bauxite of windstorm deposit occurs mainly in the shallow lake district. There the bauxite is stored well. The thickness of flag bed is uniform ( from several centimeters to tens of centimeters ), with a sequence of fine grain on bottom and thick upper, howing a increase in energy. The author believes that both diosporite and dickite which sometimes contains constitutional water in Carboniferous bauxite in China is frequently formed by solidus reaction and solid transportation during diagenesis and deuterogene. The composition of O isotope in it is unchanged basically. It means a "preservation"; conversely, that formed by solution, the primary compositions of O isotope are exchanged ( see Fig.1) . Detailly, the diosporite is formed by alumina-gel in aocient crust of weathering( suspended transportation ) and colloidal solution at the initial stage of diagenesis of reductive environment ( including transformed by gibbsite). The phenomena of constitutional water ( means colloidal water from ancient crust of weathering), vegetating recrystallizing and sequence belong to the solid reaction.The exchange in diagenesis and deutero-water of 0 isotope is uot caused, so the O isotope possess preservation of "weathering crust" 5 and"laterite property" 7. It is derived from kaolinite deposited from ancient weathering crust and gel since the deuterogene present solid
1988, 6(3): 19-28.
Abstract:
In the earlier stage of 1980's,almost a handred of scientists from several institutes organized by the Earth Sciences Division of Academia Sinica synthetically studied the enviroments and sediments of Dianchi, Erhai and Fuxian Lakes, what dealt with in this paper is one of these research achievements. Stress was put on the basic conditions of coal and oil formation,through the study of the quantity and quan-ylity of aquatic organisms of the three lakes, the relationship between sedimentary environments and organic materials, evolution tendency of organic materials during early-burial and early diagenesis. Relating to the formation conditions of Cenozoic coal and oil in China,the paper puts forward six viewpoints as follows: 1. Both depression and fault subsidence are necessary tectonic background conditions for oil and coal formation. 2. If the climate zone in which the lakes stand can ensure the water salinity neceessary for the multiplication of aquatic organisms and continental organic materials, the favorable conditions for the preservation of organic materials can be got. particularly,when the climatic zone is relatively dry and water salinity is not higher than that in which gypsum can deposit, the essential water mediu conditions for aquatic plants multiplication could be satisfied. Furthermore,if the rainfall of the lake is less than evapration the permanent layered water with high salinity is much more profitable to form in deep lake so that the organic materials can better preserved 3. The nutrient type of lakes is also an important factor for the multiplication of aguatic organisms. Both Dianchi lake of rich nutient type and Erhai Lake of middle nutrient type are favourable for the multiplication of auatic organisms. So aquatic plants communities are wealthy and the producive ability of aeuatic organisms is high.On the contrary,in the poorly nutrient Fuxian Lake, there is less community and the yield is much lower. 4. As to the depth of lake water, coal formation reguires less than 10 meters, which can provide sufficient sunshine for aquatic plant growing.But for the oil for mation, the depth of lake water must be at least deeper than the wavebases,so that organic materials cannot be easily oxidated after their deposition.From the investi- gation of three lakes in Yunnan, the depth of wavebases is less than 10 meters.If the lake water is deeper than the thermal layer, that is in the sedimentary regions with the water depth of 20-30 meters,the deposited organic materials will be affected less easily by the vertical convection of lake water,so to be perserved better. 5. Research data on the lake-water physics collected from all the world have suggested that lakes with permanent layered water,as the specific gravity of the bottom water is larger and the salinity higher and the content of dissolved oxygen lower, are suitable for the preservation of deposited organic materials. Therefore,it s one of the profitbale conditions for oil formation in deep lakes. Although Fuxia Lake is a deep lake, it has only seasonal layered water, so the dissolved oxygen in 100m water depth can reach to about 4mg/L, and there are aquatic earthworms in the bottom of the lake at 150m.It shows that the reducing condition has not been formed yet at the bottom of Fuxian Lake.That is another reason why Fuxian Lake is not suitable for oil formation. 6. As to the conditions of coal formation,besides the sufficient mass and preservation of organic materials, small input of continental clastic materials is also the ssential factor.
In the earlier stage of 1980's,almost a handred of scientists from several institutes organized by the Earth Sciences Division of Academia Sinica synthetically studied the enviroments and sediments of Dianchi, Erhai and Fuxian Lakes, what dealt with in this paper is one of these research achievements. Stress was put on the basic conditions of coal and oil formation,through the study of the quantity and quan-ylity of aquatic organisms of the three lakes, the relationship between sedimentary environments and organic materials, evolution tendency of organic materials during early-burial and early diagenesis. Relating to the formation conditions of Cenozoic coal and oil in China,the paper puts forward six viewpoints as follows: 1. Both depression and fault subsidence are necessary tectonic background conditions for oil and coal formation. 2. If the climate zone in which the lakes stand can ensure the water salinity neceessary for the multiplication of aquatic organisms and continental organic materials, the favorable conditions for the preservation of organic materials can be got. particularly,when the climatic zone is relatively dry and water salinity is not higher than that in which gypsum can deposit, the essential water mediu conditions for aquatic plants multiplication could be satisfied. Furthermore,if the rainfall of the lake is less than evapration the permanent layered water with high salinity is much more profitable to form in deep lake so that the organic materials can better preserved 3. The nutrient type of lakes is also an important factor for the multiplication of aguatic organisms. Both Dianchi lake of rich nutient type and Erhai Lake of middle nutrient type are favourable for the multiplication of auatic organisms. So aquatic plants communities are wealthy and the producive ability of aeuatic organisms is high.On the contrary,in the poorly nutrient Fuxian Lake, there is less community and the yield is much lower. 4. As to the depth of lake water, coal formation reguires less than 10 meters, which can provide sufficient sunshine for aquatic plant growing.But for the oil for mation, the depth of lake water must be at least deeper than the wavebases,so that organic materials cannot be easily oxidated after their deposition.From the investi- gation of three lakes in Yunnan, the depth of wavebases is less than 10 meters.If the lake water is deeper than the thermal layer, that is in the sedimentary regions with the water depth of 20-30 meters,the deposited organic materials will be affected less easily by the vertical convection of lake water,so to be perserved better. 5. Research data on the lake-water physics collected from all the world have suggested that lakes with permanent layered water,as the specific gravity of the bottom water is larger and the salinity higher and the content of dissolved oxygen lower, are suitable for the preservation of deposited organic materials. Therefore,it s one of the profitbale conditions for oil formation in deep lakes. Although Fuxia Lake is a deep lake, it has only seasonal layered water, so the dissolved oxygen in 100m water depth can reach to about 4mg/L, and there are aquatic earthworms in the bottom of the lake at 150m.It shows that the reducing condition has not been formed yet at the bottom of Fuxian Lake.That is another reason why Fuxian Lake is not suitable for oil formation. 6. As to the conditions of coal formation,besides the sufficient mass and preservation of organic materials, small input of continental clastic materials is also the ssential factor.
1988, 6(3): 41-49.
Abstract:
Ring D aromatized 8,14-secohopanes ( C29-C30 ) and benzohopanes ( C32-C35 ) have been detected in particular abundance in the aromatic fractions of cru de oils a-nd source rocks from the western depression of Liao-He Basin.The variations of a-mount of both families with depth have been studied and showed that there are more benzohopanes in source rocks shallower than 2800m depth and more ring D aromatized 8,14-secohopanes deeper than 2800m. Both families are thought to be the products formed from bacterial hopanoid p-recursors. Benzohopanes are particularly abundant in immature source rocks. They might be formed directly from the C35 bacterial hopanol by chemical reaction atten-ed by microorganism in the early stage of sedimentation. With increasing tempreu-re, they can be easily destroyed, probably by cleavage of ring C which is unstable, to some of bicyclic terpanes or tricycloditerpanes and alfcylated indanes whitch occurring in crude oils and source rocks. Ring D aromatized 8,14-secohopanes do not appear until threshold. They may be formed from hopanoid precursors by aromatization cleavage of the fragile 8 (14) b-ond on ring C under thermol stress. Until 2800 M their amount is increasing. Fuct-her thermol stress would destroy this family, in particular by cleavage of 11(12) bond and side chain,both are fragile benzylic position,and yield some of bicyclic terpanes and alkylated indanes. The rate of destruction is lower than that of benzohopanes, probably due to the stable molecular structure of ring D aromatized 8,14-secohopanes which has one less 6-membered carbon ring than that of benzohopanes. In short, there are differances in the time and the rate of their formation and destruction. It is difficult to assum from their molecular structure that ring D aromatized 8, 14-secohpanes and benzohopanes can be transformed each other under thermol stress. But the ratio of (C29-C33)ring D aromatized 8, 14-secohopanes/(C29-C33 ring D aromatized 8, 14-secohopanes + C32-C35benzohopanes ) , MAH parameter briefly, can act as a powerful maturation parameter. MAH parameter increases steadily with increasing maturation. because of the differance in the time and the rate of formation and destruction of these two families. In our studied basin, the value of MAH parameter is 0.3-0.5 for upper oil-generating zone and 0.5-1.0 for lower oil-generating zone
Ring D aromatized 8,14-secohopanes ( C29-C30 ) and benzohopanes ( C32-C35 ) have been detected in particular abundance in the aromatic fractions of cru de oils a-nd source rocks from the western depression of Liao-He Basin.The variations of a-mount of both families with depth have been studied and showed that there are more benzohopanes in source rocks shallower than 2800m depth and more ring D aromatized 8,14-secohopanes deeper than 2800m. Both families are thought to be the products formed from bacterial hopanoid p-recursors. Benzohopanes are particularly abundant in immature source rocks. They might be formed directly from the C35 bacterial hopanol by chemical reaction atten-ed by microorganism in the early stage of sedimentation. With increasing tempreu-re, they can be easily destroyed, probably by cleavage of ring C which is unstable, to some of bicyclic terpanes or tricycloditerpanes and alfcylated indanes whitch occurring in crude oils and source rocks. Ring D aromatized 8,14-secohopanes do not appear until threshold. They may be formed from hopanoid precursors by aromatization cleavage of the fragile 8 (14) b-ond on ring C under thermol stress. Until 2800 M their amount is increasing. Fuct-her thermol stress would destroy this family, in particular by cleavage of 11(12) bond and side chain,both are fragile benzylic position,and yield some of bicyclic terpanes and alkylated indanes. The rate of destruction is lower than that of benzohopanes, probably due to the stable molecular structure of ring D aromatized 8,14-secohopanes which has one less 6-membered carbon ring than that of benzohopanes. In short, there are differances in the time and the rate of their formation and destruction. It is difficult to assum from their molecular structure that ring D aromatized 8, 14-secohpanes and benzohopanes can be transformed each other under thermol stress. But the ratio of (C29-C33)ring D aromatized 8, 14-secohopanes/(C29-C33 ring D aromatized 8, 14-secohopanes + C32-C35benzohopanes ) , MAH parameter briefly, can act as a powerful maturation parameter. MAH parameter increases steadily with increasing maturation. because of the differance in the time and the rate of formation and destruction of these two families. In our studied basin, the value of MAH parameter is 0.3-0.5 for upper oil-generating zone and 0.5-1.0 for lower oil-generating zone
1988, 6(3): 70-77.
Abstract:
The Upper permian Series in Langdai district of Liuzhi County, western Gui-zhou, is composed of cyclical sequences of basaltic lithic sandstones, siltssones, mudstones and coalbeds. An examination of sedimantary features reveals that all these layers were deposited in didal-swamp and subtidal enviroments. The description of diagenetic sequence for the basaltic lithic sandstone is given in the present paper, and the genesis of the authigenic minerals, i.e., Ti-Fe montmorillonite, Chlorite, ferrodolomite and ferrocalcite, in this sort of rock are discussed in detail on the basis of the authors study mean of various laboratory procedures such as thin section petrography, scanning electron microscopic analysis, electron prooe analysis, X-ray diffraction analysis,and carbon and oxygen isotope analysis for the carbonate, etc. . It is pointed out that: 1. The diagenetic sequence of basaltic lithic sandstones is Ti-Fe montmorillonite →c→ompaction→chloritization→dissolution→silicif ication, pyritization→ ferrodolomitization→ferrocalcitization→ferritzation, hemetitization. 2. The diagenetic stage and enviroment of basaltic lithic sandstones may be divided into. 1 )Shallow burial, early diagenetic stage, acid water enviroment; 2 ) Deepburial-mesodiagentic stage, weak base acid alkalinity water enviroment; 3 ) Nearsurface, late diagenetic, meteoric freshwater enviroment. 3. Geneses of these authingenic minerals are essentially controlled by the variety of combination patterns of the following factors: 1 ) composition and textur-e of the sandstones) 2 ) characteristics of assemblages of the sedimentary layers; 3 ) the reduction level of organic matter and its thermal maturation; 4 ) trasfor-mation and dehydration of clay minerals in the mudstones; 5 ) compection and 6 ) temperature and acidity or alkalinity of pore water
The Upper permian Series in Langdai district of Liuzhi County, western Gui-zhou, is composed of cyclical sequences of basaltic lithic sandstones, siltssones, mudstones and coalbeds. An examination of sedimantary features reveals that all these layers were deposited in didal-swamp and subtidal enviroments. The description of diagenetic sequence for the basaltic lithic sandstone is given in the present paper, and the genesis of the authigenic minerals, i.e., Ti-Fe montmorillonite, Chlorite, ferrodolomite and ferrocalcite, in this sort of rock are discussed in detail on the basis of the authors study mean of various laboratory procedures such as thin section petrography, scanning electron microscopic analysis, electron prooe analysis, X-ray diffraction analysis,and carbon and oxygen isotope analysis for the carbonate, etc. . It is pointed out that: 1. The diagenetic sequence of basaltic lithic sandstones is Ti-Fe montmorillonite →c→ompaction→chloritization→dissolution→silicif ication, pyritization→ ferrodolomitization→ferrocalcitization→ferritzation, hemetitization. 2. The diagenetic stage and enviroment of basaltic lithic sandstones may be divided into. 1 )Shallow burial, early diagenetic stage, acid water enviroment; 2 ) Deepburial-mesodiagentic stage, weak base acid alkalinity water enviroment; 3 ) Nearsurface, late diagenetic, meteoric freshwater enviroment. 3. Geneses of these authingenic minerals are essentially controlled by the variety of combination patterns of the following factors: 1 ) composition and textur-e of the sandstones) 2 ) characteristics of assemblages of the sedimentary layers; 3 ) the reduction level of organic matter and its thermal maturation; 4 ) trasfor-mation and dehydration of clay minerals in the mudstones; 5 ) compection and 6 ) temperature and acidity or alkalinity of pore water
1988, 6(3): 96-103.
Abstract:
Through studying foraminifera and associated bionomics in the upper Carboniferous-Lower Permian sedimentary section of YaoLin, ZheJiang province, China, the paper divided the benthonic foraminiferas from carbonate platform into three types of assemblages. Type 1 ( R ) is the assemblages of the foraminifera from the restricted sea platform, which are characteristic of minor bodies and walls with fibrous and micritzed texture, such as Nodosaria, Glomospira, Geinitzina, Ammodiscus, and Eolasiodiscus. Type 2 ( O ) is the assemblage of the foraminifera from the open sea platform, which are characteristic of large bodies and shells with two-layer texture, Such as Cribrogenerina, Climacammina, Pachyphloin, Padangin, and Endothyra. TypeS ( B ) is the assemblage of the foraminifera from the basin, which are characteristic of minor bodies and shells with the fine sparry texture, associated with minor and thin-shell Ostrcada, and mixed with a lot of afloat Rodiolarians. The genus and species of the foraminiferas are similar to the type 1. According to the differences of rock textures, mineral compositions, foram-iniferal features and sedimentary strcutures, these have been divided into R1 R2 Ra O1O2 O3 and B, existing in sixteen carbonate microfacies respectively. The sedimentary emvironments which are represented by the foraminifera assemblages corresponding to the first, second, third seventh and eighth face belts of the ideal model of stardard face belts which was established by J. L. wilson, 1975. The microfacies represented by type B and subassemblages O1 and O2 have best potentials of oil-gas generation. The microfacies represented by subassem-blage O3 and R3 have good reseryoir space of oil-gas.
Through studying foraminifera and associated bionomics in the upper Carboniferous-Lower Permian sedimentary section of YaoLin, ZheJiang province, China, the paper divided the benthonic foraminiferas from carbonate platform into three types of assemblages. Type 1 ( R ) is the assemblages of the foraminifera from the restricted sea platform, which are characteristic of minor bodies and walls with fibrous and micritzed texture, such as Nodosaria, Glomospira, Geinitzina, Ammodiscus, and Eolasiodiscus. Type 2 ( O ) is the assemblage of the foraminifera from the open sea platform, which are characteristic of large bodies and shells with two-layer texture, Such as Cribrogenerina, Climacammina, Pachyphloin, Padangin, and Endothyra. TypeS ( B ) is the assemblage of the foraminifera from the basin, which are characteristic of minor bodies and shells with the fine sparry texture, associated with minor and thin-shell Ostrcada, and mixed with a lot of afloat Rodiolarians. The genus and species of the foraminiferas are similar to the type 1. According to the differences of rock textures, mineral compositions, foram-iniferal features and sedimentary strcutures, these have been divided into R1 R2 Ra O1O2 O3 and B, existing in sixteen carbonate microfacies respectively. The sedimentary emvironments which are represented by the foraminifera assemblages corresponding to the first, second, third seventh and eighth face belts of the ideal model of stardard face belts which was established by J. L. wilson, 1975. The microfacies represented by type B and subassemblages O1 and O2 have best potentials of oil-gas generation. The microfacies represented by subassem-blage O3 and R3 have good reseryoir space of oil-gas.
1988, 6(3): 112-117.
Abstract:
Geological setting: Dongpu Depression, located on the banks of the Yellow River at the boundary of Henan Prov. and Hebei Prov., belongs to the mid-southern part of Huabei Basin in the view of reginal tectonics. This depression, with the area of 5300 km2, is a Mesozoicr-Cenozoic grabenlike salt-lake sedimentary basin, dominantly including Paleozoic basement and Cenozoic sediments. Luxi Uplift and Neihuang Uplift respectively-lie each side of the depression. During the Mesozoic-Cenozoic tectonic movement violent faults and depression happened in this area and sediments more than 7000 meters thick deposited in the basin. Among which the Lower-Tertiary sediments are nearly 6000 meters thick and they could be divided upward into two big cycles. These cycles include four rock-salt cyclothems whose total thick-ness is about 1400 meters. The cyclothems change horizontally a lot in facies and are superposedly distributed over 600 km2 in the northern part of the depression, forming ideally regional overlying strataiof oil-gas reservoirs and constituting a good combination of reservoirs and coving strata with lower sandstone strata. In addition, the Upper-Tertiary sediments are a suite of massive sandstone and sandmudstone interbeddings. The thickness is about 1000-1500 meters and geoth-ermal gradient 3.360°C/100m. All of these characteristics indicated that this area is a favourable oil-gas basin. Beneath the Cenozoic sediments, Carboniferous-Permian coal series with the thickness of 800-1100m are widely distributed. Their role, played in secondary gas formation after the burial of Cenozoic sediments and the transportation, is accumulation of industrial gas reservoirs, i.e. the coal-formed gasm has already drawn much attention. Geochemical features of Ar isotopes in natural gases: Based on more than fifty data of Ar isotopes obtained by autnors in this area, the natural gasos in the study area can be divided into three groups according to the variation of Ar40/Ar36 ratios. The ratio of Group I ranges from 331 to 626, averagely 477, Group Ⅱ633-889, aver ragely 757; Group Ⅲ 959-1175, averagely 1087. Comparison of gas resources. Ar in natural gases mainly comesfrom atmospheric air. First, it goesointo sedimentary rocks or underground water during sedimentation and diagen esis. Then it joins in natural gases in the degasing process and becomes one of the micro-components of natural gases. Since Ar is a very stable noble gas, there was no geochemical reaction happened during the process mentioned above. Ar, therefore, keeps no change in quantity and isotopic abound ance, i.e. Ar40/Ar36 = 295.5. In fact, the measured value is often higher than that, sometimes even widely different. The main reason for that is caused by the increase of Ar40 decayed from K40 in potassium minerals contained in adjoin-ing rocks and underground water. Therefore, the older the geological age of adjoining rocks is, the more the rad-ioac tive Ar40is produced and correspondingly the higher the Ar40/Ar86 ratio in natural gases is. Hence it is of certain significance to employ the Ar40/Ar38 ratio as a geochemical index to trace gas strata and gas resources, to estimate gas age, and to identify coal-formed gases. The natural gases incZhongyuan Gasfield has been divided into three types based on the Ar40/Ar36 ratio aboundance. Each type represents a different genesis and is associated with different oil-gas source rocks. The Type I gas has the lowest radioactive Ar40 accumulation compared with the other two types, its average Ar40/Ar36 ratio is about 477. Its source rocks, therefore, might be related to the youngest oil-gas source rocks, i.e.Tertiary Shahejie Group in the depression. The Type Ⅲ gas has the highest radioacsiveAr40accumulation among the three types, its average Ar40/Ar36 ratio is about 1087. So its source rocks might have somthing to do with the Carboniferous-permian coal series which are beneath the Oligocene strata in the depression, namely belonging to a kind of coal-formed gases. The Type Ⅱ gas has an average Ar40/Ar36 ratio which is 75
Geological setting: Dongpu Depression, located on the banks of the Yellow River at the boundary of Henan Prov. and Hebei Prov., belongs to the mid-southern part of Huabei Basin in the view of reginal tectonics. This depression, with the area of 5300 km2, is a Mesozoicr-Cenozoic grabenlike salt-lake sedimentary basin, dominantly including Paleozoic basement and Cenozoic sediments. Luxi Uplift and Neihuang Uplift respectively-lie each side of the depression. During the Mesozoic-Cenozoic tectonic movement violent faults and depression happened in this area and sediments more than 7000 meters thick deposited in the basin. Among which the Lower-Tertiary sediments are nearly 6000 meters thick and they could be divided upward into two big cycles. These cycles include four rock-salt cyclothems whose total thick-ness is about 1400 meters. The cyclothems change horizontally a lot in facies and are superposedly distributed over 600 km2 in the northern part of the depression, forming ideally regional overlying strataiof oil-gas reservoirs and constituting a good combination of reservoirs and coving strata with lower sandstone strata. In addition, the Upper-Tertiary sediments are a suite of massive sandstone and sandmudstone interbeddings. The thickness is about 1000-1500 meters and geoth-ermal gradient 3.360°C/100m. All of these characteristics indicated that this area is a favourable oil-gas basin. Beneath the Cenozoic sediments, Carboniferous-Permian coal series with the thickness of 800-1100m are widely distributed. Their role, played in secondary gas formation after the burial of Cenozoic sediments and the transportation, is accumulation of industrial gas reservoirs, i.e. the coal-formed gasm has already drawn much attention. Geochemical features of Ar isotopes in natural gases: Based on more than fifty data of Ar isotopes obtained by autnors in this area, the natural gasos in the study area can be divided into three groups according to the variation of Ar40/Ar36 ratios. The ratio of Group I ranges from 331 to 626, averagely 477, Group Ⅱ633-889, aver ragely 757; Group Ⅲ 959-1175, averagely 1087. Comparison of gas resources. Ar in natural gases mainly comesfrom atmospheric air. First, it goesointo sedimentary rocks or underground water during sedimentation and diagen esis. Then it joins in natural gases in the degasing process and becomes one of the micro-components of natural gases. Since Ar is a very stable noble gas, there was no geochemical reaction happened during the process mentioned above. Ar, therefore, keeps no change in quantity and isotopic abound ance, i.e. Ar40/Ar36 = 295.5. In fact, the measured value is often higher than that, sometimes even widely different. The main reason for that is caused by the increase of Ar40 decayed from K40 in potassium minerals contained in adjoin-ing rocks and underground water. Therefore, the older the geological age of adjoining rocks is, the more the rad-ioac tive Ar40is produced and correspondingly the higher the Ar40/Ar86 ratio in natural gases is. Hence it is of certain significance to employ the Ar40/Ar38 ratio as a geochemical index to trace gas strata and gas resources, to estimate gas age, and to identify coal-formed gases. The natural gases incZhongyuan Gasfield has been divided into three types based on the Ar40/Ar36 ratio aboundance. Each type represents a different genesis and is associated with different oil-gas source rocks. The Type I gas has the lowest radioactive Ar40 accumulation compared with the other two types, its average Ar40/Ar36 ratio is about 477. Its source rocks, therefore, might be related to the youngest oil-gas source rocks, i.e.Tertiary Shahejie Group in the depression. The Type Ⅲ gas has the highest radioacsiveAr40accumulation among the three types, its average Ar40/Ar36 ratio is about 1087. So its source rocks might have somthing to do with the Carboniferous-permian coal series which are beneath the Oligocene strata in the depression, namely belonging to a kind of coal-formed gases. The Type Ⅱ gas has an average Ar40/Ar36 ratio which is 75
1988, 6(3): 11-18.
Abstract:
The celestites ( SrSO4) , found in Yonghe, Liuyang County, Hunan Province, wich occur in carbonates of the Chihsia formation of the Lower Permian, are associated with sepiolite deposites. Since the celestite is an important industrial mineral, the discovery of it in this area is of some economic value. The single crystals of the celestite in Yonghe are long-column. Commonly surrounds the siliceous detritus and shows druses texture as chrysanthemum shape.Therefore,it is called "chrysanthemum-stone" too. By the observation of microscope, the refractive index and the other optical properties of the celestite are as follows: Ng = 1.630, Np = 1.622, positive biaxial crystal and middle ( 2V ) angle. Its X-ray diffraction pattern is characterised by peaks, d = 2.731 A , d = 3.972 A , d = 3.295A.There is another characteristic peak of the calcite,d = 3.03 A .In the infrared absorption spectrum pattern there is spectrum of the standard celestite such as 1295.16cm-1, 1195.56cm-1, 1136.81cm-1, 1090.76cm-1, 991.81cm-1, 640.74cm-1, and 610.64cm-1.The differential thermal analysis ( DTA ) curve shows two endothermic peaks. One is relateed to 740°C, perhaps this results from a small amount of the carbonate mineral in the sample. Another appears at 1146°C and its shape is sharp and wide.This is the characteristic peak of celestite created by the isodimorphism.From the analysis results mentioned above, the authors consider that the mineral composition of the celestite deposited in Yonghe is mainly celestites and a few calcites. The chemical composition of the celestite from Yonghe is as follows: SrO 54.21%,CaO 1.65%,MgO 0.25%,BaO 0.01%,A12O3 0.04%, Fe 2O3 0.02% and SO343.32% According to the calculation of oxygenatom, its crystal-chemcal formula is (Sr 0.97600, Ba0.0012)0.97612SO4. The origin of the celestite in Yonghe is very interesting.The analysis of Sr-iso-tope indicated that the strontium of the celestite was derived from sea water.It can be suggested that the chrysanthemum-shape celestite formed the during diagenetic period, after carbonates precipitated, according to the characteristics; ( 1 ) The chrysanthemum-shape celestites grew around fossil debris of brachiopoda and gastropoda. ( 2 ) The celestites are centred in the nodular limestones which formed during diagenetic period. ( 3 ) The celestites replaced the early calcites. ( 4 ) The carbonate suffered strong diagenesis based on the analysis results of carbon and oxygen isotope of calcite, δ13C = 3.720,δ18O=-4.269.
The celestites ( SrSO4) , found in Yonghe, Liuyang County, Hunan Province, wich occur in carbonates of the Chihsia formation of the Lower Permian, are associated with sepiolite deposites. Since the celestite is an important industrial mineral, the discovery of it in this area is of some economic value. The single crystals of the celestite in Yonghe are long-column. Commonly surrounds the siliceous detritus and shows druses texture as chrysanthemum shape.Therefore,it is called "chrysanthemum-stone" too. By the observation of microscope, the refractive index and the other optical properties of the celestite are as follows: Ng = 1.630, Np = 1.622, positive biaxial crystal and middle ( 2V ) angle. Its X-ray diffraction pattern is characterised by peaks, d = 2.731 A , d = 3.972 A , d = 3.295A.There is another characteristic peak of the calcite,d = 3.03 A .In the infrared absorption spectrum pattern there is spectrum of the standard celestite such as 1295.16cm-1, 1195.56cm-1, 1136.81cm-1, 1090.76cm-1, 991.81cm-1, 640.74cm-1, and 610.64cm-1.The differential thermal analysis ( DTA ) curve shows two endothermic peaks. One is relateed to 740°C, perhaps this results from a small amount of the carbonate mineral in the sample. Another appears at 1146°C and its shape is sharp and wide.This is the characteristic peak of celestite created by the isodimorphism.From the analysis results mentioned above, the authors consider that the mineral composition of the celestite deposited in Yonghe is mainly celestites and a few calcites. The chemical composition of the celestite from Yonghe is as follows: SrO 54.21%,CaO 1.65%,MgO 0.25%,BaO 0.01%,A12O3 0.04%, Fe 2O3 0.02% and SO343.32% According to the calculation of oxygenatom, its crystal-chemcal formula is (Sr 0.97600, Ba0.0012)0.97612SO4. The origin of the celestite in Yonghe is very interesting.The analysis of Sr-iso-tope indicated that the strontium of the celestite was derived from sea water.It can be suggested that the chrysanthemum-shape celestite formed the during diagenetic period, after carbonates precipitated, according to the characteristics; ( 1 ) The chrysanthemum-shape celestites grew around fossil debris of brachiopoda and gastropoda. ( 2 ) The celestites are centred in the nodular limestones which formed during diagenetic period. ( 3 ) The celestites replaced the early calcites. ( 4 ) The carbonate suffered strong diagenesis based on the analysis results of carbon and oxygen isotope of calcite, δ13C = 3.720,δ18O=-4.269.
1988, 6(3): 29-40.
Abstract:
Bangmai Basin is situated on Linchang granitic body of Sanjiang-Dianzhong longitudinal tectonic system in South-West China. This basin is an asymmetrical inte-rmontane synclinal basin with a Hercynian-Yanshan granitic body (r43-r52) as its basement. Its overlying Strata are made up of the coal-bearing clastic rocks of Ne-ogene. Coal seams consist of lower and upper coal-bearing rocks of N1. the lower rocks ( N11-N15 ) are: clastic rocks, sandstone intercalated with coal, conglomerate layer,fine sand intercalated with clay and lenticular coal and diatomite; the upper rocks (N16-N18)are: interstralified grit and find sand, clayey siltstone and claystone, conglomeratic grit. Germanium ore mostly occurres within the N12 stratiform, stra-toid layers or lenses coal seam. Germanium ore is chiefly of germanium-lignite type. Germanium-bearing coals are mainly lignites with lower graded incoalation. The microcomponents of coals mostly are collinite-semicollinite intercalated with stable components (cuticle,resinite and spore etc. ) and mineral elastics. The coal's type belongs to semidurain, semiclarain duro-clarain and claro-durain. In order to probe into the existent form of germanim in coal, we have adopted five kinds of analytical methods. They are electronic probe analysis ( linear scanning ), separation of heavy liquid (six samples were separated in the solution of v-arious specific gravities, namely 1 . 20, 1 . 28, 1 . 35, 1 . 45, 1 . 55, 1 . 80, 1 . 80 ), electric osmosis, chemical extraction-humic acid, bitumen and grade-extraction ( suitable chemical reagent and condition are chosen for the determination of metallic existent state in samples ) . We carried out simulated test of humic complex germanium in the laboratory, beside analysis.According to infrared spectral analysis, changes of spectral zone w-ere found, that was 1700cm-1 wavecrest almost disappeared, 1250cm-1 peak weaken-es and 1600cm-1 peak strengthened, 1400cm-1peak slightly strengthened. No doubt, these illustrate the formation of humic germanium complex. Afterward, through d-ifferential thermal analysis and measurement of pH variation of media,these further prove the presence of humic germanium complex. In summary, The author considers that the existent forms of germanium in uranium-bearing coals mainly are: 1 . keep chemical combination with organic matter closely, usually take the form of humic germanium complex and germanium organic compound. 2 . In the state of absorption, germanium is absorbed by some organic matter, clay minerals and limonite etc. 3 . A few part take isomorphous form. Geological concentration conditions for mineralization are favorable structure and paleogeographic enviroment of lithofacies, rich germanium source and advantageous geohydrologic state etc. Simultaneously the incoalation of coal-bearing strata controlled the whole process of germanium mineralization.
Bangmai Basin is situated on Linchang granitic body of Sanjiang-Dianzhong longitudinal tectonic system in South-West China. This basin is an asymmetrical inte-rmontane synclinal basin with a Hercynian-Yanshan granitic body (r43-r52) as its basement. Its overlying Strata are made up of the coal-bearing clastic rocks of Ne-ogene. Coal seams consist of lower and upper coal-bearing rocks of N1. the lower rocks ( N11-N15 ) are: clastic rocks, sandstone intercalated with coal, conglomerate layer,fine sand intercalated with clay and lenticular coal and diatomite; the upper rocks (N16-N18)are: interstralified grit and find sand, clayey siltstone and claystone, conglomeratic grit. Germanium ore mostly occurres within the N12 stratiform, stra-toid layers or lenses coal seam. Germanium ore is chiefly of germanium-lignite type. Germanium-bearing coals are mainly lignites with lower graded incoalation. The microcomponents of coals mostly are collinite-semicollinite intercalated with stable components (cuticle,resinite and spore etc. ) and mineral elastics. The coal's type belongs to semidurain, semiclarain duro-clarain and claro-durain. In order to probe into the existent form of germanim in coal, we have adopted five kinds of analytical methods. They are electronic probe analysis ( linear scanning ), separation of heavy liquid (six samples were separated in the solution of v-arious specific gravities, namely 1 . 20, 1 . 28, 1 . 35, 1 . 45, 1 . 55, 1 . 80, 1 . 80 ), electric osmosis, chemical extraction-humic acid, bitumen and grade-extraction ( suitable chemical reagent and condition are chosen for the determination of metallic existent state in samples ) . We carried out simulated test of humic complex germanium in the laboratory, beside analysis.According to infrared spectral analysis, changes of spectral zone w-ere found, that was 1700cm-1 wavecrest almost disappeared, 1250cm-1 peak weaken-es and 1600cm-1 peak strengthened, 1400cm-1peak slightly strengthened. No doubt, these illustrate the formation of humic germanium complex. Afterward, through d-ifferential thermal analysis and measurement of pH variation of media,these further prove the presence of humic germanium complex. In summary, The author considers that the existent forms of germanium in uranium-bearing coals mainly are: 1 . keep chemical combination with organic matter closely, usually take the form of humic germanium complex and germanium organic compound. 2 . In the state of absorption, germanium is absorbed by some organic matter, clay minerals and limonite etc. 3 . A few part take isomorphous form. Geological concentration conditions for mineralization are favorable structure and paleogeographic enviroment of lithofacies, rich germanium source and advantageous geohydrologic state etc. Simultaneously the incoalation of coal-bearing strata controlled the whole process of germanium mineralization.
1988, 6(3): 60-69.
Abstract:
Concerning the origin of dolomitite of Huanglong group of Mid-Carboniferous in Western Pingle trough, according to feild geological research, determination under pol-arizing microscope, analysis of common elements and O, isotopes and so on, this article consider that dolomitite was not the result of primary sedimentation but of metasomatism. However, the diffeerences among textures, structures and the various gentic types of dolomitite represented different mechanisms of origin. According to the size of crystal and the difference of textures and structures of dolomite, dolomitite can be sorted into two main genetic types. 1 . Parasyngenetic dolomitite Micritic dolomitite, powder crystal dolomitite, algal micritic dolomitite, algal laminated bedding dolomitite are the mainly rock types in which always can be seen such sedimentary characteristics as bird-eyes, contraction fissures, burrows and salt karst structures, the sedimentary environment showed to be a hot, dry and a high evaporation rate tidal flat. Micro-silt crystalline, xenomorphic granular textures can be seen under electr-on-scanning-and polarizing microscops. This kinds of dolomite stands for the feature of parasyngenetic dolomitite under fast diagenesis in the hypersaline sea water environment. 2. Diagentic dolomitite The main rock types is fine-coase crystalline dolomitite intercalated by irregular thin bedings of micritic dolomitite and algal micritic, yet can be seen huge-crystalline dolomitie above the section. The sedimentary characteistics mainly horizontal burrows and beddings, bird-eyes and contraction fissures can be seen in micritic and algal laminated bedding dolomitite. organisms are comparatively rarely. The sedimentary enviroment is tidal flat lagoon. The fine coares crystalline texture. idiomorphic extent slab-rhombic crystalline, and the fogcentre ring-basnd, not only revealed a salty changing environment but alsobe important signs of diegenetic dolomitite. This kind of dolomite wa of the feature of diagenetic dolomitite of sluggish crystallization. Through the analysis and study, the author discovered that trace element-Sr and δ18O and δ13C isotpes values of micro silt crystalline and fine coarse crystalline dolomitite have evident discrepancy, sepecially δ18O and δ18C isotops values in this region. This reflected that dolomitites were formed in different sedimentary ( diagenetic ) environments and diaentic stages, it is a supplementary sign to analysis the origin of dolomitite. In this the paper the author proposed two models of dolomitite origin which may be apipled in this region. 1. The dolomitite model of hypersaline sea water The Hypersatine sea water sink into sediment because of it's solution weight. So the Ca cationes was replaced by Mg cationes and dolomitization have taken place in the carbonate sediments, followed that formed dolomitite of micro-silt crystalline. 2 . The dolomitite model of the mixture water The mixing of fresh water ( underground water and precipitate water ) and the sea water of hypersaline ( or normal sea water ) , taken place in the flow zone of underground fresh water. These conditions favoured the replacement of dolomitite because the salinity droped drastically and the Mg/C ratio changed less in the pore-water, formed dolomitite of coarse crystalline.
Concerning the origin of dolomitite of Huanglong group of Mid-Carboniferous in Western Pingle trough, according to feild geological research, determination under pol-arizing microscope, analysis of common elements and O, isotopes and so on, this article consider that dolomitite was not the result of primary sedimentation but of metasomatism. However, the diffeerences among textures, structures and the various gentic types of dolomitite represented different mechanisms of origin. According to the size of crystal and the difference of textures and structures of dolomite, dolomitite can be sorted into two main genetic types. 1 . Parasyngenetic dolomitite Micritic dolomitite, powder crystal dolomitite, algal micritic dolomitite, algal laminated bedding dolomitite are the mainly rock types in which always can be seen such sedimentary characteristics as bird-eyes, contraction fissures, burrows and salt karst structures, the sedimentary environment showed to be a hot, dry and a high evaporation rate tidal flat. Micro-silt crystalline, xenomorphic granular textures can be seen under electr-on-scanning-and polarizing microscops. This kinds of dolomite stands for the feature of parasyngenetic dolomitite under fast diagenesis in the hypersaline sea water environment. 2. Diagentic dolomitite The main rock types is fine-coase crystalline dolomitite intercalated by irregular thin bedings of micritic dolomitite and algal micritic, yet can be seen huge-crystalline dolomitie above the section. The sedimentary characteistics mainly horizontal burrows and beddings, bird-eyes and contraction fissures can be seen in micritic and algal laminated bedding dolomitite. organisms are comparatively rarely. The sedimentary enviroment is tidal flat lagoon. The fine coares crystalline texture. idiomorphic extent slab-rhombic crystalline, and the fogcentre ring-basnd, not only revealed a salty changing environment but alsobe important signs of diegenetic dolomitite. This kind of dolomite wa of the feature of diagenetic dolomitite of sluggish crystallization. Through the analysis and study, the author discovered that trace element-Sr and δ18O and δ13C isotpes values of micro silt crystalline and fine coarse crystalline dolomitite have evident discrepancy, sepecially δ18O and δ18C isotops values in this region. This reflected that dolomitites were formed in different sedimentary ( diagenetic ) environments and diaentic stages, it is a supplementary sign to analysis the origin of dolomitite. In this the paper the author proposed two models of dolomitite origin which may be apipled in this region. 1. The dolomitite model of hypersaline sea water The Hypersatine sea water sink into sediment because of it's solution weight. So the Ca cationes was replaced by Mg cationes and dolomitization have taken place in the carbonate sediments, followed that formed dolomitite of micro-silt crystalline. 2 . The dolomitite model of the mixture water The mixing of fresh water ( underground water and precipitate water ) and the sea water of hypersaline ( or normal sea water ) , taken place in the flow zone of underground fresh water. These conditions favoured the replacement of dolomitite because the salinity droped drastically and the Mg/C ratio changed less in the pore-water, formed dolomitite of coarse crystalline.
1988, 6(3): 78-88.
Abstract:
The area of the Shelf Basin of East China Sea is about 0.77 million km2 and there are many minor structures in it. The deposits in this Shelf Basin are huge (up to 15000m thick). There would be plenty of oil and gas resource in this area Based on drilling records, two exploring wells have produced, oil and gas Fourty minerals have been identified from 559 samples of five exploring wells. Besides, there are three minerale( Moissanite, Native Lead and minute magntitzed iron ball -the dust in the space ) the sources of which are unknown. The percentages of grain size of heavy minerals have been calculated with statistic method of grain size and the light minerals have been counted with eyes, Several assemblages of heavy minerals have been determined in this paper and the corelation of these assemblages has been made already (fig2-5). The assemblages of heavy minerals of four wells ( fig 1 ) are described as follows: 1. The five assemblages of Lingfeng Well No. 1 from the top to the bottom are Amphibole-Epidote-Pyrite Assemblage(extending 428m and belonging to the Dong-ghai Group ) , Pyrite-Siderite Assemblage ( extending 576m and belonging to the Sa-ntan to the Yuquan Formation), Siderite-Tourmaline-Granet Assemblage (extanding 281m and belon ging to the upper of Oujiang Formation),Sdierite-Pyrite Assemblage ( extending 569m and belonging to the lower of oujiang Formation) , Pyrite-siderite Assemblage(extending 446m and belonging to the Lingfeng Formation ) . 2. The five assemblages of Pinghu Well No. 1 from the top to the bottom are Tourmaline-Zircon-Amphibole Assemblage ( extending 445m aed belonging to the Oonghai Group) , Zircon-Amphibole-Epidote-Siderite Assemblage ( extending 544.5m and belonging to the santan Formation), Tourmaline- Granet-Sidrite Assemblage ( extending 887.5m and belonging to the lower of yuquan Formation to the upper of Hailongjing Formation), Tourmaline-Siderte-Assemblage ( extending 2114.5 and belonging to the lower of Hailongjing Formation to the Pinghu Formation ) . 3. The five assemblage of Yuquan Well No. 1 from the top to the bottom are Pyrite-Epidote-Amphibole Assemblage ( extending 375m and belonging to the Donghai Group) , Epidote-Amphibole-Siderite Assemblage ( extending 666m and belonging to the Santan Formation), Siderite Assemblage ( extending 460m and belonging to the upper of Yupuan Formation), Zircon-Tourmaline-Granet Assemblage( extending 1065m and belonging to the lower of Yuyuan Formation to the upper of Hai-longjing Formation), Siderite Assemblage ( extending 221.5m and belonging to the lower of Hailongjing Formation to the Huagang Formation ) . 4. The five assemblage of Longjing Well No. 2 from the top to bottom are Pyrite-Amphibole-Epidote Assemblage ( extending 413m and belonging to the Dong-hai Group), Epidoteamphibole-Siderite Assemblage ( extending 497m and belonging to the Santan Formation), Siderite Assemblage ( extending 1316.5m and belonging to the Yuquan Formation), Siderite Assemblage ( extending 1316.5m and belonging to the yuquan Formation), Tourmaline-Granet-Siderite Assemblage (exending 869.5m and belonging to the Hailongjing Formation), Zircon-Tourmaline-Siderite-Gra-net Assemblage ( extending 1021.26m and belonging to the Huagang Formation to the upper of pinghu Formation ) . The assemblages of heavy minerals of Pinghu Well No. 1 and Yuquan Well No 1 can be corelated more easyly. The Longjing Well No. 2 located at the north of the Pinghu Well No. 1 and the Yuquan well No. 1 only can be corelated with two wells above from the Donghai Group to the Santan Formation. The assemblage of heavy minerals of Lingfeng Well No. 1 are different from the other wells except the assemblage belonging to the Donghai Group.
The area of the Shelf Basin of East China Sea is about 0.77 million km2 and there are many minor structures in it. The deposits in this Shelf Basin are huge (up to 15000m thick). There would be plenty of oil and gas resource in this area Based on drilling records, two exploring wells have produced, oil and gas Fourty minerals have been identified from 559 samples of five exploring wells. Besides, there are three minerale( Moissanite, Native Lead and minute magntitzed iron ball -the dust in the space ) the sources of which are unknown. The percentages of grain size of heavy minerals have been calculated with statistic method of grain size and the light minerals have been counted with eyes, Several assemblages of heavy minerals have been determined in this paper and the corelation of these assemblages has been made already (fig2-5). The assemblages of heavy minerals of four wells ( fig 1 ) are described as follows: 1. The five assemblages of Lingfeng Well No. 1 from the top to the bottom are Amphibole-Epidote-Pyrite Assemblage(extending 428m and belonging to the Dong-ghai Group ) , Pyrite-Siderite Assemblage ( extending 576m and belonging to the Sa-ntan to the Yuquan Formation), Siderite-Tourmaline-Granet Assemblage (extanding 281m and belon ging to the upper of Oujiang Formation),Sdierite-Pyrite Assemblage ( extending 569m and belonging to the lower of oujiang Formation) , Pyrite-siderite Assemblage(extending 446m and belonging to the Lingfeng Formation ) . 2. The five assemblages of Pinghu Well No. 1 from the top to the bottom are Tourmaline-Zircon-Amphibole Assemblage ( extending 445m aed belonging to the Oonghai Group) , Zircon-Amphibole-Epidote-Siderite Assemblage ( extending 544.5m and belonging to the santan Formation), Tourmaline- Granet-Sidrite Assemblage ( extending 887.5m and belonging to the lower of yuquan Formation to the upper of Hailongjing Formation), Tourmaline-Siderte-Assemblage ( extending 2114.5 and belonging to the lower of Hailongjing Formation to the Pinghu Formation ) . 3. The five assemblage of Yuquan Well No. 1 from the top to the bottom are Pyrite-Epidote-Amphibole Assemblage ( extending 375m and belonging to the Donghai Group) , Epidote-Amphibole-Siderite Assemblage ( extending 666m and belonging to the Santan Formation), Siderite Assemblage ( extending 460m and belonging to the upper of Yupuan Formation), Zircon-Tourmaline-Granet Assemblage( extending 1065m and belonging to the lower of Yuyuan Formation to the upper of Hai-longjing Formation), Siderite Assemblage ( extending 221.5m and belonging to the lower of Hailongjing Formation to the Huagang Formation ) . 4. The five assemblage of Longjing Well No. 2 from the top to bottom are Pyrite-Amphibole-Epidote Assemblage ( extending 413m and belonging to the Dong-hai Group), Epidoteamphibole-Siderite Assemblage ( extending 497m and belonging to the Santan Formation), Siderite Assemblage ( extending 1316.5m and belonging to the Yuquan Formation), Siderite Assemblage ( extending 1316.5m and belonging to the yuquan Formation), Tourmaline-Granet-Siderite Assemblage (exending 869.5m and belonging to the Hailongjing Formation), Zircon-Tourmaline-Siderite-Gra-net Assemblage ( extending 1021.26m and belonging to the Huagang Formation to the upper of pinghu Formation ) . The assemblages of heavy minerals of Pinghu Well No. 1 and Yuquan Well No 1 can be corelated more easyly. The Longjing Well No. 2 located at the north of the Pinghu Well No. 1 and the Yuquan well No. 1 only can be corelated with two wells above from the Donghai Group to the Santan Formation. The assemblage of heavy minerals of Lingfeng Well No. 1 are different from the other wells except the assemblage belonging to the Donghai Group.
1988, 6(3): 105-111.
Abstract:
By observing the rock slice of the old mud-rock flow sediments at Bao Lue line with a polaring microscope, the author discovered some of their special textures and structures l.Microtextures 1) Supporting matrix texture This texture is composel of microcl astics which are some non-chemical deposits and less than 0.05mm in diameter these microclastics are cramcd among the fragme: nts. This is one kind of texture which belongs to high viscid and turbid sediments, ts. 2) Supporting clastic parlicles texture The big or relatively big fragments are in contact with each other at points, The microclastics are cramed only among this fragments, and their amount is small. This is a texture which is the result of a steady flow environment. 3) Sieve-like texture Its cheracteristics is that there are no or a few microclasties among fragment in the sediments. These fragments are not in contact with each other. This results from that the microclastics deposited earlier were carried away by following water flow. 2.Microstructures 1) Massive structure Its characsteristics are that the fragments have a disordered arrangement.This results from that the mass flow deposited quickly. 2) Local directional structure A few fragments are roughly directive in debris flow sediments. The fragments AB plane intersects the bedding plane with angle 50 to 30°. A few fragments were floated off by high viscosity mud fluid. Then they depo sited slowly when stoped. So this structure is formed in sediment. 3 ) Vertical directional structure A few strip of fragment insert in the sediment with angle 90° or more than 45°. This structure is deemed to be characstaristic structure of mass-flow deposit. 4 ) Ring and hemi-ring structure A few fine sands and silts encircle the relative big fragment with their a-axices and their a-axises parallel the configuration of fragmet.Eneircling when the fragment is encircled in full is called ring structure. When the fragment is encircled partly, it is called hemiring structure. Chief mechanism forming this structure is that a-axises of microclastic Parallel the configuration of fragment for reduction of resistance when they move around the fragment. 5 ) Flow linear structure The a-axises of a lot of fine sands and silts are parallel to the strik line of void detween two fragments. And the changes of their azimutbes follow the strik line of void. These fine fragments in fluid are floated and thea-axises are parallel the flow direction. When they deposit in the void spece, they keep this state in sediment. 6 ) Volution structure When a lot of fine sands and silts set around a centre and their a-axises link up each other this structure is formed. The mechanism is related to the high viscosity turbidity current. 7 ) Directional structure The AB planes of most fragments in general order.intersect the bedding plane with angle 5° to 30°. The cause of formation is relate to lower turbidity corrent or braided strea stream. 8) Bedding structure Bedding structure is formed by some laminaes, whose colour, granularity, ingredient are different from that of country rock. It is formed by action of water flow and low viscosity turbidity current. There are some composition of textures and structures of themselves in each sed imentary facis.This compositions are important characteristics of sedimentary facis in the old debris flow sediment.
By observing the rock slice of the old mud-rock flow sediments at Bao Lue line with a polaring microscope, the author discovered some of their special textures and structures l.Microtextures 1) Supporting matrix texture This texture is composel of microcl astics which are some non-chemical deposits and less than 0.05mm in diameter these microclastics are cramcd among the fragme: nts. This is one kind of texture which belongs to high viscid and turbid sediments, ts. 2) Supporting clastic parlicles texture The big or relatively big fragments are in contact with each other at points, The microclastics are cramed only among this fragments, and their amount is small. This is a texture which is the result of a steady flow environment. 3) Sieve-like texture Its cheracteristics is that there are no or a few microclasties among fragment in the sediments. These fragments are not in contact with each other. This results from that the microclastics deposited earlier were carried away by following water flow. 2.Microstructures 1) Massive structure Its characsteristics are that the fragments have a disordered arrangement.This results from that the mass flow deposited quickly. 2) Local directional structure A few fragments are roughly directive in debris flow sediments. The fragments AB plane intersects the bedding plane with angle 50 to 30°. A few fragments were floated off by high viscosity mud fluid. Then they depo sited slowly when stoped. So this structure is formed in sediment. 3 ) Vertical directional structure A few strip of fragment insert in the sediment with angle 90° or more than 45°. This structure is deemed to be characstaristic structure of mass-flow deposit. 4 ) Ring and hemi-ring structure A few fine sands and silts encircle the relative big fragment with their a-axices and their a-axises parallel the configuration of fragmet.Eneircling when the fragment is encircled in full is called ring structure. When the fragment is encircled partly, it is called hemiring structure. Chief mechanism forming this structure is that a-axises of microclastic Parallel the configuration of fragment for reduction of resistance when they move around the fragment. 5 ) Flow linear structure The a-axises of a lot of fine sands and silts are parallel to the strik line of void detween two fragments. And the changes of their azimutbes follow the strik line of void. These fine fragments in fluid are floated and thea-axises are parallel the flow direction. When they deposit in the void spece, they keep this state in sediment. 6 ) Volution structure When a lot of fine sands and silts set around a centre and their a-axises link up each other this structure is formed. The mechanism is related to the high viscosity turbidity current. 7 ) Directional structure The AB planes of most fragments in general order.intersect the bedding plane with angle 5° to 30°. The cause of formation is relate to lower turbidity corrent or braided strea stream. 8) Bedding structure Bedding structure is formed by some laminaes, whose colour, granularity, ingredient are different from that of country rock. It is formed by action of water flow and low viscosity turbidity current. There are some composition of textures and structures of themselves in each sed imentary facis.This compositions are important characteristics of sedimentary facis in the old debris flow sediment.
1988, 6(3): 118-129.
Abstract:
The finding of Jiantianba reef in Lichuan of Hubei province at the end of the 1970's the gas firld in Jiannan reef with high output, and the sponge reef's (emergent and buried ) continuously discovered at the beginning ofr the 1980's in the east Sichuan and northeast Sichuan areas, provide models fol search of new types of gas field. Since more than ten years, over thirty organic reefs(mainly made of sponge and hydra ) have been found successi-vely in the Permian strata of south Guizhou, Yuannan, Guanxi, east Sichuan and west Hubei. Sixteen of them(including Honghua ua reef in Kaixian ) distribute in group and in row along the east Sichuan and west-Hubei areas, A number of reef gas fields was confirmed primarily by drilling in the east Sichuan and west Hubei areas which promoted the authors to study the ree f forming mechanism regionally of some typical organic reefs ( Kaixian Honghua Lichuan Jiantianba, Ziyun Shitouzhai, etc. ) .In recent years, after research of reef-forming sequence and the distribution, it was concluded that the basement made of platform basin sediments ( rich in silica) and arenitic banks is the necessary environment for organic reef form-ation. Based on the geochemical and thermodynamic property of silica, anomalous supplement and particular sedimentary environment (restricted shallow sea ) were discussed it was proposed that the silica-rich platform basin in restricted shallow sea from the late Permian Wujiaping to Changxing bank in platform open shallow sea, is mostly reef-forming environment of basin-bank in heritance and of bank-reef association.
The finding of Jiantianba reef in Lichuan of Hubei province at the end of the 1970's the gas firld in Jiannan reef with high output, and the sponge reef's (emergent and buried ) continuously discovered at the beginning ofr the 1980's in the east Sichuan and northeast Sichuan areas, provide models fol search of new types of gas field. Since more than ten years, over thirty organic reefs(mainly made of sponge and hydra ) have been found successi-vely in the Permian strata of south Guizhou, Yuannan, Guanxi, east Sichuan and west Hubei. Sixteen of them(including Honghua ua reef in Kaixian ) distribute in group and in row along the east Sichuan and west-Hubei areas, A number of reef gas fields was confirmed primarily by drilling in the east Sichuan and west Hubei areas which promoted the authors to study the ree f forming mechanism regionally of some typical organic reefs ( Kaixian Honghua Lichuan Jiantianba, Ziyun Shitouzhai, etc. ) .In recent years, after research of reef-forming sequence and the distribution, it was concluded that the basement made of platform basin sediments ( rich in silica) and arenitic banks is the necessary environment for organic reef form-ation. Based on the geochemical and thermodynamic property of silica, anomalous supplement and particular sedimentary environment (restricted shallow sea ) were discussed it was proposed that the silica-rich platform basin in restricted shallow sea from the late Permian Wujiaping to Changxing bank in platform open shallow sea, is mostly reef-forming environment of basin-bank in heritance and of bank-reef association.
