1992 Vol. 10, No. 3
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Display Method:
1992, 10(3): 1-9.
Abstract:
Since 1980's, mankind has entered the era of developing the high-new science and technology. The comprchensive use of computers has brought about the changes to the working and living sturctures of (he people. Rapid development of traffic, communication and space navigation has promoted the way of the contaet between the people all over the world, resulting in close links of each aspect. People can have new and deep understanding of the nature from unceasing obtain of scientific and technological results and abundant information. Morever, the changes of concepts and way of thought, in turn, advance the research of science and technology. Being in this epoch-making stage. We, sedmentologists are inevitable impelled to take the study field of our own into account to keep abreast of the time, enabling the research of sedimentology to develop together with other subjects. On the basis of the brief overview of key advances on some subjects of geology in the last ten years and a brlef hindsight of a number of important events in the development in sedimentology, several following sig- ant views are prsented by the author on the research of sedimentology in the era of high-new science.tnd technology of today. 1. Changing concepts and way of thought needs to extricate ourselves from the method traditionally dominated by intuitional experience remarks and from lacking strict logical reasoning, which should be replaced by the methology of strict scientific logical reasoning, by which scientific experimental examination can be carried out. Mean while, theory substitutes for the fixed theory and the traditional sedimentalogical theory may be collated and stipulated with the viewpoint of plate moment. The new catastrophism subtitules for the old uniformitarianism as well. 2 Apply as much as possible the high-new thchniques and method to sedmentology in order to probe it macorscopically and microscopically to a greater extent and to bring about steady improvement in techniques and method of sedimentology as such. 3 Pay more attention to the exchange with other subjects to the overlapping and infiltration of different branches of learning so as to enrich the theories of sedimentology, to open up the new domain of sedimenlological research and to establish the new branches. 4. Place the importance on the research of the global changes, and participate in the international cooperation of GSGP in a wider range and at higher levels. 5. Take an active part in the research of International Lithosphere Program (ILP) so as to help sedimentology to be one of the chief support in this research and to improve, in turn, the theory of sedimentology. 6. Pay more attention to the research of basin analysis, give full play to the supriority of sedimentology in geophysics, geotectonics, organic geochemistry- stratigraphy and structural geology for the purpose of promoting the combination and development of varying subjects. 7. Sedimentology is supposed to take effect in solving the major problems of human being, i.e. population, resources and environment, finding the foothold and combination point of its own in society, economic consturciton and markets. 8. Break the "modelling-type" with renewal and creation of research methods and engage in scientific research in the light of specific practice.
Since 1980's, mankind has entered the era of developing the high-new science and technology. The comprchensive use of computers has brought about the changes to the working and living sturctures of (he people. Rapid development of traffic, communication and space navigation has promoted the way of the contaet between the people all over the world, resulting in close links of each aspect. People can have new and deep understanding of the nature from unceasing obtain of scientific and technological results and abundant information. Morever, the changes of concepts and way of thought, in turn, advance the research of science and technology. Being in this epoch-making stage. We, sedmentologists are inevitable impelled to take the study field of our own into account to keep abreast of the time, enabling the research of sedimentology to develop together with other subjects. On the basis of the brief overview of key advances on some subjects of geology in the last ten years and a brlef hindsight of a number of important events in the development in sedimentology, several following sig- ant views are prsented by the author on the research of sedimentology in the era of high-new science.tnd technology of today. 1. Changing concepts and way of thought needs to extricate ourselves from the method traditionally dominated by intuitional experience remarks and from lacking strict logical reasoning, which should be replaced by the methology of strict scientific logical reasoning, by which scientific experimental examination can be carried out. Mean while, theory substitutes for the fixed theory and the traditional sedimentalogical theory may be collated and stipulated with the viewpoint of plate moment. The new catastrophism subtitules for the old uniformitarianism as well. 2 Apply as much as possible the high-new thchniques and method to sedmentology in order to probe it macorscopically and microscopically to a greater extent and to bring about steady improvement in techniques and method of sedimentology as such. 3 Pay more attention to the exchange with other subjects to the overlapping and infiltration of different branches of learning so as to enrich the theories of sedimentology, to open up the new domain of sedimenlological research and to establish the new branches. 4. Place the importance on the research of the global changes, and participate in the international cooperation of GSGP in a wider range and at higher levels. 5. Take an active part in the research of International Lithosphere Program (ILP) so as to help sedimentology to be one of the chief support in this research and to improve, in turn, the theory of sedimentology. 6. Pay more attention to the research of basin analysis, give full play to the supriority of sedimentology in geophysics, geotectonics, organic geochemistry- stratigraphy and structural geology for the purpose of promoting the combination and development of varying subjects. 7. Sedimentology is supposed to take effect in solving the major problems of human being, i.e. population, resources and environment, finding the foothold and combination point of its own in society, economic consturciton and markets. 8. Break the "modelling-type" with renewal and creation of research methods and engage in scientific research in the light of specific practice.
1992, 10(3): 16-24.
Abstract:
Clastic rocks as hydrocarbon reservoir are prevailed overwhelmingly in the continental lake basins. The smaller scales in basin area and water body of lake lead to more serious heterogeneities of interlayer, areal, inlayer and micropore scales in the continental clastic reservoirs than in the marine analogues. Eight clastic filling models can be distinguished in the lake basins depended on the tectonic setting, the evolutional stage when they deposited and the fluctuation of lake level. Under the background of long distance between the sediment source area and the depocenter and the gently gradient slope, the loniitudianl alluvial fan-braided river-meandering river-delta filling model is developed along the long axis, parallel to the strike of tectonic framework, of a lake basin, while the transversal alluvial fan -fan delta-sublacustrine fan filling model is developed in the steep, deeply faulted side along the short axis due to the short distance between the sediment source area and the depocenter and the steeply gradient slope. These two filling models can be regarded as the end-members in the lake basins, among them there are a series of transitional filling patterns developed. Some particular models can also be observed: the fluvial sandbodies all most cover the overall basin during the dying stage, and the sandflat prevails in the littoral environment during the evaporated stage in a saline lake. The clastic reservoirs deposited in different environments are distinctively characterized by their own heterogeneities. Alluviat fan conglomerates and conglomeratic rocks are characterized by the complicated pore-texiure in terms of its bimodal grain texture, also the occurrence of seive and debris flow deposits can much worsen the reservoir heterogeneity. The fining upwards in grain size and narrow width of the fluvial sandbody reser-voir、 bring about a low recovery efficient in waterflooding, however, often a high productivity can be found. A deltaic sandbody just has an opposite reservoir heterogeneity to the fluvial one, and always a high recovery efficient in waterflooding can be got. The beach and bar sandbodies are no significant volumetrically in a lake basin, however, its high productibity and homogeneous reservoir properties have been noticed interestingly In sublacustrine fan environment, the sandbodies, which could be served as hydrocarbon reservoir are mainly of channelized deposit in the middly fan and fault-bounded trough subenvironments and of lenticular deposit in front area. Through outcrop work to enrich a quantified geological konwledge base for building the geological models of continental reservoirs will be a main target facing to the reservoir sedimentologists
Clastic rocks as hydrocarbon reservoir are prevailed overwhelmingly in the continental lake basins. The smaller scales in basin area and water body of lake lead to more serious heterogeneities of interlayer, areal, inlayer and micropore scales in the continental clastic reservoirs than in the marine analogues. Eight clastic filling models can be distinguished in the lake basins depended on the tectonic setting, the evolutional stage when they deposited and the fluctuation of lake level. Under the background of long distance between the sediment source area and the depocenter and the gently gradient slope, the loniitudianl alluvial fan-braided river-meandering river-delta filling model is developed along the long axis, parallel to the strike of tectonic framework, of a lake basin, while the transversal alluvial fan -fan delta-sublacustrine fan filling model is developed in the steep, deeply faulted side along the short axis due to the short distance between the sediment source area and the depocenter and the steeply gradient slope. These two filling models can be regarded as the end-members in the lake basins, among them there are a series of transitional filling patterns developed. Some particular models can also be observed: the fluvial sandbodies all most cover the overall basin during the dying stage, and the sandflat prevails in the littoral environment during the evaporated stage in a saline lake. The clastic reservoirs deposited in different environments are distinctively characterized by their own heterogeneities. Alluviat fan conglomerates and conglomeratic rocks are characterized by the complicated pore-texiure in terms of its bimodal grain texture, also the occurrence of seive and debris flow deposits can much worsen the reservoir heterogeneity. The fining upwards in grain size and narrow width of the fluvial sandbody reser-voir、 bring about a low recovery efficient in waterflooding, however, often a high productivity can be found. A deltaic sandbody just has an opposite reservoir heterogeneity to the fluvial one, and always a high recovery efficient in waterflooding can be got. The beach and bar sandbodies are no significant volumetrically in a lake basin, however, its high productibity and homogeneous reservoir properties have been noticed interestingly In sublacustrine fan environment, the sandbodies, which could be served as hydrocarbon reservoir are mainly of channelized deposit in the middly fan and fault-bounded trough subenvironments and of lenticular deposit in front area. Through outcrop work to enrich a quantified geological konwledge base for building the geological models of continental reservoirs will be a main target facing to the reservoir sedimentologists
1992, 10(3): 47-56.
Abstract:
Advancing and deepening in coal-forming theory of marine fades undoubtedly bring the new reform and progress in many fields of the coal-bearing sedimentology. It takes the further steps to enrich and deepen the theory. The foundation for reunderstanding the huge basins of coal accumulation on Late Paleozoic, exploring the new coal accumulation law and enlarging the new coal resources is established. These progresses and achievements are discussed from the following seven research fields. 1. Coal-forming environments of marine facies - coal-forming models of peat flats. Mangroves or tidal plants having a similar bioecology with mangroves could grow abundantly in the intertidal and supertidal flats of tropical and subtropical zones and could form the peat deposits over a large area under the suitable condition. Such the direct coal-forming environments in the tidal flats are called "peat flats". Peat flats and peat swamps are two kinds of environment types,with completely different natures, the first of which is the marine tidal flat environments. According to the different characteristics of peat fiats on coal-bearing formations of Late Paleozoic in China, peat fiats can be classified into five models such as: lagoon peat flats, back barrier peat flats, tidal delta peat flats, carbonate platform peat fiats and back reef peat fiats types. 2. The research of comparative sedimentology on modern tropical mangrove tidal flats. This paper deals with the characteristics of mangrove plant communities, the deposits of the mangrove tidal flats and the coal petrographic compositions of the mangrove peats, and points out that the sulphur in mangrove peats is characterized by high pyrite contents, the sulphate in water medium of the tidal flats is the final resource of sulphur and the accession of sulphur mainly takes place in penecontemporaneous stage. "The present is the key to the past". It is an important apporach to establish the coal-forming environment of marine facies in ancient peat fiats from the research of the modern mangrove tidal flats and mangrove peats, and utilizing the method of the comparative sedimentology. 3. The character of the epeiric sea, the tidal deposits and their ldading role on coal-bearing formation of Late Paleozoic in China are demonstrated and recognized. Authors put forward that the coal-bearing formations of Late Paleozoic were formed respectively in epeiric environments of Huabei and Yangzi plates which are both huge basins of coal accumulation in North and South China, and are made up with distinctive clean, muddy or mixed coal-bearing sedimentary systems in epeiric sea. 4. Platform barrier island nad complex sedimentary systems in coal-bearing formation. If the marine coal-forming environments of peat flats are similarly present a lot except the continental coal-forming environments of swamps, and the restricted zone in coal- forming environments of marine facies is broken through. The new sedimentary systems of coal-bearing formations will be discovered. The barrier island, carbonate platform, the complex with barrier island and platform and the complex with barrier island and delta sedimentary systems in coal-beraing formation have been put forward. 5. Geological events and their depositional records in coal accumulation bsins, of which storm and volcanic event deposits are more important. Tempestites are classified as the back flow tempestites -distal, proximal and proximal shallow water carbonate tempestites, the stirring carbonate tempestites and the proximal sandstone tempestites. 6. The methodology on the study of lithofacies-paleogeography of coal field. This can be briefly summarized as the method of "quantitative environment analysis of sections and drawing up maps by means of sedimentary facies ratio". First, the quantitative environmental analysis of the single field section is as the basis; second, the procedure from point to line, from line to face and from face to three-dimensional geometry is used to combine field observation with indoor analysis; third, on the basis
Advancing and deepening in coal-forming theory of marine fades undoubtedly bring the new reform and progress in many fields of the coal-bearing sedimentology. It takes the further steps to enrich and deepen the theory. The foundation for reunderstanding the huge basins of coal accumulation on Late Paleozoic, exploring the new coal accumulation law and enlarging the new coal resources is established. These progresses and achievements are discussed from the following seven research fields. 1. Coal-forming environments of marine facies - coal-forming models of peat flats. Mangroves or tidal plants having a similar bioecology with mangroves could grow abundantly in the intertidal and supertidal flats of tropical and subtropical zones and could form the peat deposits over a large area under the suitable condition. Such the direct coal-forming environments in the tidal flats are called "peat flats". Peat flats and peat swamps are two kinds of environment types,with completely different natures, the first of which is the marine tidal flat environments. According to the different characteristics of peat fiats on coal-bearing formations of Late Paleozoic in China, peat fiats can be classified into five models such as: lagoon peat flats, back barrier peat flats, tidal delta peat flats, carbonate platform peat fiats and back reef peat fiats types. 2. The research of comparative sedimentology on modern tropical mangrove tidal flats. This paper deals with the characteristics of mangrove plant communities, the deposits of the mangrove tidal flats and the coal petrographic compositions of the mangrove peats, and points out that the sulphur in mangrove peats is characterized by high pyrite contents, the sulphate in water medium of the tidal flats is the final resource of sulphur and the accession of sulphur mainly takes place in penecontemporaneous stage. "The present is the key to the past". It is an important apporach to establish the coal-forming environment of marine facies in ancient peat fiats from the research of the modern mangrove tidal flats and mangrove peats, and utilizing the method of the comparative sedimentology. 3. The character of the epeiric sea, the tidal deposits and their ldading role on coal-bearing formation of Late Paleozoic in China are demonstrated and recognized. Authors put forward that the coal-bearing formations of Late Paleozoic were formed respectively in epeiric environments of Huabei and Yangzi plates which are both huge basins of coal accumulation in North and South China, and are made up with distinctive clean, muddy or mixed coal-bearing sedimentary systems in epeiric sea. 4. Platform barrier island nad complex sedimentary systems in coal-bearing formation. If the marine coal-forming environments of peat flats are similarly present a lot except the continental coal-forming environments of swamps, and the restricted zone in coal- forming environments of marine facies is broken through. The new sedimentary systems of coal-bearing formations will be discovered. The barrier island, carbonate platform, the complex with barrier island and platform and the complex with barrier island and delta sedimentary systems in coal-beraing formation have been put forward. 5. Geological events and their depositional records in coal accumulation bsins, of which storm and volcanic event deposits are more important. Tempestites are classified as the back flow tempestites -distal, proximal and proximal shallow water carbonate tempestites, the stirring carbonate tempestites and the proximal sandstone tempestites. 6. The methodology on the study of lithofacies-paleogeography of coal field. This can be briefly summarized as the method of "quantitative environment analysis of sections and drawing up maps by means of sedimentary facies ratio". First, the quantitative environmental analysis of the single field section is as the basis; second, the procedure from point to line, from line to face and from face to three-dimensional geometry is used to combine field observation with indoor analysis; third, on the basis
1992, 10(3): 78-84.
Abstract:
Evaporite is an important rock type because of its economic value. In the earth's surficial water body, the easy-dissolved salts can deposit and form evaporite by evaporation, condensation and crystallization The research of evaporite theory has become to a special branch of science with the countinously discovery of evaporite deposits and the development of geophsics and geochemistry. In the past two to three decades, the theoritical research of evaporite reached its peak, accompany with the study of modern sedimentation, more and more new models of salt forming have been put forward and the classical ones had been surmounted, accompliented and modified, China is an evaporites devoloping country, the study of modern diagenesis of evaporite is the key to reveal the mechanics of palaeo-evaporite. The present paper, based on the stastics of modern saline lakes in Qinghai-Tibet Plateau, emphasized that the deep water body is one of the important material source of salt forming; suggested that the theoritical fundation of evaporite forming is the cyclation of natural water in salt-bearing basin, and the cy cle of saline water disslution is the key factor both in the study of diagenesis and catagenesis; disscused the evolution of hypersalin water, and especially emphasised the significance of dating and fluid enclusion of salt minerals. The world-wide spreaded models of salt forming in the past three decades and the generally domesticlly adopted models in the recent years are introduced brifly in this paper too. And the author believes that the theory of evaporite forming will certainly go to a new stage on basis of the evolutional study on evaporite.
Evaporite is an important rock type because of its economic value. In the earth's surficial water body, the easy-dissolved salts can deposit and form evaporite by evaporation, condensation and crystallization The research of evaporite theory has become to a special branch of science with the countinously discovery of evaporite deposits and the development of geophsics and geochemistry. In the past two to three decades, the theoritical research of evaporite reached its peak, accompany with the study of modern sedimentation, more and more new models of salt forming have been put forward and the classical ones had been surmounted, accompliented and modified, China is an evaporites devoloping country, the study of modern diagenesis of evaporite is the key to reveal the mechanics of palaeo-evaporite. The present paper, based on the stastics of modern saline lakes in Qinghai-Tibet Plateau, emphasized that the deep water body is one of the important material source of salt forming; suggested that the theoritical fundation of evaporite forming is the cyclation of natural water in salt-bearing basin, and the cy cle of saline water disslution is the key factor both in the study of diagenesis and catagenesis; disscused the evolution of hypersalin water, and especially emphasised the significance of dating and fluid enclusion of salt minerals. The world-wide spreaded models of salt forming in the past three decades and the generally domesticlly adopted models in the recent years are introduced brifly in this paper too. And the author believes that the theory of evaporite forming will certainly go to a new stage on basis of the evolutional study on evaporite.
1992, 10(3): 96-103.
Abstract:
The research of sedimentary minerals produced in China has achievablely progressed for the recent dec-a.le or the basis of the sedimentary development, especially the phosphorite research has got abrrakthrough progress. The phoshhorite research has made two steps in a decade: the first is from the chem-tcalsedimentary theory to the physical enrichmentary nne and the second is the development of the biomineralization theory. Upper Sinian Epoch to the early period of Lower Cumhri}n Epoch is an unprecedented prosperous per:-od of the phosphorus microorganism and it is also the most important phosphorus mineralization one inChina, and tens of billion tons of phosphorus ore were formed. Many phosphorus microorganisms, suchas agla.and small shell fossils (the latter one is only produced in ore of Lower Cambrian) with variuusshapes have been found in phosphorites of every industrial mineral deposit and they are the main componentsof phosphorite. Among them the phosphorus microorganism is mainly f}ronu bacteria of procarytes to fungusof euearyotes. Up till now, three communities have been found, i.e., bacteria, actinomyces and mould.The author adopted microbiology, biochemistry and medicine to the piiosphorite research and discussed thephosphorite biomineralization, biological enrichment phospl;orus mechanism about tW oxidizingphosphoric acidification and biological calicification as will as expound the phosphorite biological cause onthe basris of the phosphorite petro-biological characteristics. The biological characteristics of the chemicalcomponents and the infrared absorptive spectrum, and the rare-earth element compositions and so on areanalysed, Phosphorite is actually a special biological rock and the phosphate composition ranges fromultramicros 0.05 }m-0.5}m to macroscopic particles front silt to medu}n sand. The phosphorite is consisted of single species bacteria and bacteria groupe, which consists of the same species microorganism and themicroorganism commuwties, which consist of the different species microorganism (including alga) as well as the small fossil shells. The phosphorite petro-types can be subdivided as micro-phosphorite. cumtila,rspharolith. coated granule. algal bacterium granule, strumutolithic, agglumerative. oncolitrsand small shell phosphorite.Organic chemical compound of life organizauon, such as remaining amino acid and nucleic acid etc., are commonly discovered by the analysis of organic chemical cumposition. On the ba sis of analysis of infrared spectrum there are organic pigments，-CH3，-CH2,-C=H2OH and the vibration frequency of phosphorite is similar to one of the bone apatite of dinosauria, tortoiseand so on. The rare-earth elemetn standardization match model of the every phosphorite closesmodel of apatite with the typical biological cause from Palaeozoic Era to modern times.and hyolithto the match Mficroorganism is culsely related to circumstance tii multiplying circumstance condition ofmicroorganism relates internally to tile sedimentary circumstance of phosphorite. There are a lot of physicaland chemical conditions that influence the growing of microorganism, the important faotors aretemperature, Eh, pH and light. These most suitable conditions of.he microorganism breeding and grow-ing are closely related to the conditions of phosphorite forming. T'he 0biological breeding field" of the most suitable phosphorus biological growing and multiplying inocean shows no different from the palaeogeograpitical unit of the phusphorite mineralization. We call the bio-logical breeding field as“the epicontinental subqueous galley wall" which is the most favourableminerogenetic belt of phosphorite. Our research has discovered the two main industrial mineral layea ofDoushantuo period along the epicontinental subqueous galley wall which distribute from the western Hubeito the; middle Gui::hou offer as the regular overlap migration sediment according to the ingression and seacurrent directions. This law may be an universal one, otherwise, the two industrial mineral layers in theeastern Yunnan during Lower Cambrian Epoch offer also as the regular migration seiiiment according to theingression and sea current directions. This law can be used to survey and research for minerals.
The research of sedimentary minerals produced in China has achievablely progressed for the recent dec-a.le or the basis of the sedimentary development, especially the phosphorite research has got abrrakthrough progress. The phoshhorite research has made two steps in a decade: the first is from the chem-tcalsedimentary theory to the physical enrichmentary nne and the second is the development of the biomineralization theory. Upper Sinian Epoch to the early period of Lower Cumhri}n Epoch is an unprecedented prosperous per:-od of the phosphorus microorganism and it is also the most important phosphorus mineralization one inChina, and tens of billion tons of phosphorus ore were formed. Many phosphorus microorganisms, suchas agla.and small shell fossils (the latter one is only produced in ore of Lower Cambrian) with variuusshapes have been found in phosphorites of every industrial mineral deposit and they are the main componentsof phosphorite. Among them the phosphorus microorganism is mainly f}ronu bacteria of procarytes to fungusof euearyotes. Up till now, three communities have been found, i.e., bacteria, actinomyces and mould.The author adopted microbiology, biochemistry and medicine to the piiosphorite research and discussed thephosphorite biomineralization, biological enrichment phospl;orus mechanism about tW oxidizingphosphoric acidification and biological calicification as will as expound the phosphorite biological cause onthe basris of the phosphorite petro-biological characteristics. The biological characteristics of the chemicalcomponents and the infrared absorptive spectrum, and the rare-earth element compositions and so on areanalysed, Phosphorite is actually a special biological rock and the phosphate composition ranges fromultramicros 0.05 }m-0.5}m to macroscopic particles front silt to medu}n sand. The phosphorite is consisted of single species bacteria and bacteria groupe, which consists of the same species microorganism and themicroorganism commuwties, which consist of the different species microorganism (including alga) as well as the small fossil shells. The phosphorite petro-types can be subdivided as micro-phosphorite. cumtila,rspharolith. coated granule. algal bacterium granule, strumutolithic, agglumerative. oncolitrsand small shell phosphorite.Organic chemical compound of life organizauon, such as remaining amino acid and nucleic acid etc., are commonly discovered by the analysis of organic chemical cumposition. On the ba sis of analysis of infrared spectrum there are organic pigments，-CH3，-CH2,-C=H2OH and the vibration frequency of phosphorite is similar to one of the bone apatite of dinosauria, tortoiseand so on. The rare-earth elemetn standardization match model of the every phosphorite closesmodel of apatite with the typical biological cause from Palaeozoic Era to modern times.and hyolithto the match Mficroorganism is culsely related to circumstance tii multiplying circumstance condition ofmicroorganism relates internally to tile sedimentary circumstance of phosphorite. There are a lot of physicaland chemical conditions that influence the growing of microorganism, the important faotors aretemperature, Eh, pH and light. These most suitable conditions of.he microorganism breeding and grow-ing are closely related to the conditions of phosphorite forming. T'he 0biological breeding field" of the most suitable phosphorus biological growing and multiplying inocean shows no different from the palaeogeograpitical unit of the phusphorite mineralization. We call the bio-logical breeding field as“the epicontinental subqueous galley wall" which is the most favourableminerogenetic belt of phosphorite. Our research has discovered the two main industrial mineral layea ofDoushantuo period along the epicontinental subqueous galley wall which distribute from the western Hubeito the; middle Gui::hou offer as the regular overlap migration sediment according to the ingression and seacurrent directions. This law may be an universal one, otherwise, the two industrial mineral layers in theeastern Yunnan during Lower Cambrian Epoch offer also as the regular migration seiiiment according to theingression and sea current directions. This law can be used to survey and research for minerals.
1992, 10(3): 114-123.
Abstract:
With the development of oil and gas exploration, a number of high quality clastic rock reservoirs at great depth have been discovered both domestically and abroad. Concerning the porosity, some of them have dominant secondary porosity and others are dominated by preserved primary porosity. Specially the discovery of the later ones changes one's idea of porosity deadline, which attracts petroleum geologists' great attention. Combining new progress and new theory of diagenesis both domestically and abroad with some case history about diagenesis and porosity evolution in some major oil and gas area in our country, this paper describes the new progress of porosity origin, evolution and prediction of clastic reservoir rocks. 1. The dissolution of aluminosilicate is often stronger than carbonate in the reservoirs of some major oil and gas area in our country, wihch is shown that the dissolution of the organic acids in the diagenesis is very clear. The dissolution of organic acids is closely related to the type of kerogen evolved by organic matter in continental sandstone-shale. Type Ⅱ and Ⅲ have higher convertibility from kerogen to organic acids in comparison with type Ⅰ. 2. The origin of high quality reservoirs at great depth with dominant preserved primary intergranular porosity is closely related with burial history of the reservoir rocks. These kinds of reservoirs, Mesozoic and Paleozoic, are widely distributed in Tabei area, Tarim Basin. Lower geothermal grediant, lower thermal maturity, short time of strong chemical diagenesis (80-120℃) and deep burial only since Pliocene, all these are the reasons that resulted in the wide distribution of these reservoirs in the area. 3. Hypogene flow, supergene flow and convection were the main forms of water migration in sedimentary system. It was one of the domination that the secondary porosity development was controlled by the amount of migration of dissolved matter together with fluid migration. Many secondary porosities were often developed and closely related with unconformity and interruption of deposition in geological history because the surfaces of unconformity and interruption of deposition were considered that the sedimentary prism had a period of exposure and leaching. 4. The new progress of clastic rocks diagenesis and porosity evolution has a great significance of the prediction of reseervoir properties. But it is not well perfect yet and still in the investigation stage. It is an urgent need to investigate the various types of models of reservoir porosity origin, evolution and preservation at different geological settings, only in this way, the prediction of reservoir properties could be improved.
With the development of oil and gas exploration, a number of high quality clastic rock reservoirs at great depth have been discovered both domestically and abroad. Concerning the porosity, some of them have dominant secondary porosity and others are dominated by preserved primary porosity. Specially the discovery of the later ones changes one's idea of porosity deadline, which attracts petroleum geologists' great attention. Combining new progress and new theory of diagenesis both domestically and abroad with some case history about diagenesis and porosity evolution in some major oil and gas area in our country, this paper describes the new progress of porosity origin, evolution and prediction of clastic reservoir rocks. 1. The dissolution of aluminosilicate is often stronger than carbonate in the reservoirs of some major oil and gas area in our country, wihch is shown that the dissolution of the organic acids in the diagenesis is very clear. The dissolution of organic acids is closely related to the type of kerogen evolved by organic matter in continental sandstone-shale. Type Ⅱ and Ⅲ have higher convertibility from kerogen to organic acids in comparison with type Ⅰ. 2. The origin of high quality reservoirs at great depth with dominant preserved primary intergranular porosity is closely related with burial history of the reservoir rocks. These kinds of reservoirs, Mesozoic and Paleozoic, are widely distributed in Tabei area, Tarim Basin. Lower geothermal grediant, lower thermal maturity, short time of strong chemical diagenesis (80-120℃) and deep burial only since Pliocene, all these are the reasons that resulted in the wide distribution of these reservoirs in the area. 3. Hypogene flow, supergene flow and convection were the main forms of water migration in sedimentary system. It was one of the domination that the secondary porosity development was controlled by the amount of migration of dissolved matter together with fluid migration. Many secondary porosities were often developed and closely related with unconformity and interruption of deposition in geological history because the surfaces of unconformity and interruption of deposition were considered that the sedimentary prism had a period of exposure and leaching. 4. The new progress of clastic rocks diagenesis and porosity evolution has a great significance of the prediction of reseervoir properties. But it is not well perfect yet and still in the investigation stage. It is an urgent need to investigate the various types of models of reservoir porosity origin, evolution and preservation at different geological settings, only in this way, the prediction of reservoir properties could be improved.
1992, 10(3): 133-144.
Abstract:
The deep water carbonate study in China began at the end of 70s. The Late Paleozoic and Early Triassic deep water carbonates in Nanpan River area is far better Known, as a whole, than are the those else-where in China, which were initially described and studied in some detail by Carbonate Research Section of SWPI. Since 1980, Subsequent work has been done more detaily by many people and units. Deep Water Carbonates which bear several kinds of mineral resources, distribute in East Yunnan, South Guizhou, Guangxi, North Guangdong and South Hunan from Late Paleozoic to Early Triassic, and with very thick sequences. Detailed research on deep water carbonate in this area has obviously theoretical and economic significance. During the Late Paleozoic, the research area located at the passive continental margin of S-SW part of South China Plate. The main tectonism that developed in this area was rift. There were a series of NW and NE rifts occured, but the main orientation was NE. The grabens surrounded the isolated horsts and had long active history. There were also a series of NE and NW rifts developed on the in-continente in North Guangxi, North Guangdong and South Hunan and created grabens which surrounded the isolated horsts. These isolated horsts, with near-shore platforms, developed into isolated carbonate platforms and the inherited shallow water carbonate depositional areas while the narrow grabens in which the deep water carbonate turbidites and some volcanic clastic turbidites, as well as silicatites deposited. On the slopes of isolated platforms, the by-pass margin depositional beds developed. The generation, development and extinction of rifts and splitting fault troughs were not simultaneously and formed discordant interplatform trough, platform margin slope environments. Except Qingzhou inherited surviving trough, the rift troughs developed at the continental margin area in South east Yunnan, South west Guangxi at the first time. From the continental margin to in-continental area, the development of rift troughs was tardy gradually with NE trend. The rift troughs in South Hunan has not start to develop until Late Devonian. The paleo-geographic framework of trough-platform extincted in Late Carboniferous in Northeast Guangxi. After the Dongwu Orogery, the trough- platform framework survived only in Nanpan River depression area and continued to Middle Triassic. The strong tectogenesis and deep rift troughs developed all over the Late Paleozoic, the obviously volcanic activity distributed along the rifts. The isolated platforms, which were limited by deep rift troughs, were relatively small in area and with great on numbers. Meanwhile, very weak tectogenesis and shallow rifts developed in the in-continental area. No volcano acted along the shallow troughs. The by-pass margin-depositional margin or depositional margin sediments occured on the slopes. Usually tie continental platform margins show the characteristics of ramp with very thick depositional margin sediments sequences. The extinction of platform-trough framework was as a result of weak tectogenesis and super-input of sediments. During the Late Carboniferous (Weining stage) , the small rift troughs with some deep water carbonates developed in Longyan, West Fujian, Guangzhou and Zhaoqing, South Guangdong. Including isolated platforms, inter-platform troughs and the margin slope of tie continental platform, the deep water environment is determined as under storm wave base. According to petrologic, paleotonlogic, paleoecologic characteristics, intergrated with the information of trough development and platform margin topographic condition, the research area can be divided into several sub-environments in the Late Paleozoic. According to geochemical analyses, the very prospective hydrocarbon source rocks distribute in the middle to low margin slopes of isolated platform, deep ramps of tie continental platform margin and inter-platform troughs. Although the content of organic carbon is higher and the silicalite and siliceous mud are the good hydrocarbon
The deep water carbonate study in China began at the end of 70s. The Late Paleozoic and Early Triassic deep water carbonates in Nanpan River area is far better Known, as a whole, than are the those else-where in China, which were initially described and studied in some detail by Carbonate Research Section of SWPI. Since 1980, Subsequent work has been done more detaily by many people and units. Deep Water Carbonates which bear several kinds of mineral resources, distribute in East Yunnan, South Guizhou, Guangxi, North Guangdong and South Hunan from Late Paleozoic to Early Triassic, and with very thick sequences. Detailed research on deep water carbonate in this area has obviously theoretical and economic significance. During the Late Paleozoic, the research area located at the passive continental margin of S-SW part of South China Plate. The main tectonism that developed in this area was rift. There were a series of NW and NE rifts occured, but the main orientation was NE. The grabens surrounded the isolated horsts and had long active history. There were also a series of NE and NW rifts developed on the in-continente in North Guangxi, North Guangdong and South Hunan and created grabens which surrounded the isolated horsts. These isolated horsts, with near-shore platforms, developed into isolated carbonate platforms and the inherited shallow water carbonate depositional areas while the narrow grabens in which the deep water carbonate turbidites and some volcanic clastic turbidites, as well as silicatites deposited. On the slopes of isolated platforms, the by-pass margin depositional beds developed. The generation, development and extinction of rifts and splitting fault troughs were not simultaneously and formed discordant interplatform trough, platform margin slope environments. Except Qingzhou inherited surviving trough, the rift troughs developed at the continental margin area in South east Yunnan, South west Guangxi at the first time. From the continental margin to in-continental area, the development of rift troughs was tardy gradually with NE trend. The rift troughs in South Hunan has not start to develop until Late Devonian. The paleo-geographic framework of trough-platform extincted in Late Carboniferous in Northeast Guangxi. After the Dongwu Orogery, the trough- platform framework survived only in Nanpan River depression area and continued to Middle Triassic. The strong tectogenesis and deep rift troughs developed all over the Late Paleozoic, the obviously volcanic activity distributed along the rifts. The isolated platforms, which were limited by deep rift troughs, were relatively small in area and with great on numbers. Meanwhile, very weak tectogenesis and shallow rifts developed in the in-continental area. No volcano acted along the shallow troughs. The by-pass margin-depositional margin or depositional margin sediments occured on the slopes. Usually tie continental platform margins show the characteristics of ramp with very thick depositional margin sediments sequences. The extinction of platform-trough framework was as a result of weak tectogenesis and super-input of sediments. During the Late Carboniferous (Weining stage) , the small rift troughs with some deep water carbonates developed in Longyan, West Fujian, Guangzhou and Zhaoqing, South Guangdong. Including isolated platforms, inter-platform troughs and the margin slope of tie continental platform, the deep water environment is determined as under storm wave base. According to petrologic, paleotonlogic, paleoecologic characteristics, intergrated with the information of trough development and platform margin topographic condition, the research area can be divided into several sub-environments in the Late Paleozoic. According to geochemical analyses, the very prospective hydrocarbon source rocks distribute in the middle to low margin slopes of isolated platform, deep ramps of tie continental platform margin and inter-platform troughs. Although the content of organic carbon is higher and the silicalite and siliceous mud are the good hydrocarbon
1992, 10(3): 10-15.
Abstract:
Sequence stratigraphy, an important and significant development in sedimentology and stratigraphy, has made the sedimentary basin filling analysis both theoretical and methodological. Setting up the chronstratigraphic framework and determinging the building blocks have: now become the major'tasks in basin analysis. This paper describes the rapid development in sequence stratigraphy and its relationship with other subjects such as depositional system analysis, tectono-stratigraphy and event stratigraphy. The inter-relationship among these subjects will become the basis for a new genetic stratigraphy system that centents the sequence stratigraphy. This system will strongly support the research in sedimentay basin anaiysis. Studies in sandbody architectural units, the basis for sedimentology of oil reservoir is also part of the research in building blocks of basin filling. This paper discussed the construction of sequence stratigraphic models for various basins, especially the intraplate paralic basins and the inland basius, both being the major types in China. The paper also discusses problems in theoretical research in China related to sequence stratigraphy, suggestions are as follows: 1. Based upon the sedimentology, micropaleontology and magnetostratigraphy research of the South China sea basis and East China sea basin, the Cenozoic sea level changes scheme could be constructed firstly, also the generalized schemes of sea level changes of the other periods in mainland could be put forward. 2.There are optimum conditions for the studies of Paleozoic seqquence stratigraphy from intracontinent to continent margin of the Yangtze and Sino-Korean cratons. 3. Mesozoic and Cenozoic inland basins cover vast area of China continent. To strudy sequence stratigraphy in the lacustrine basins is of great significance, and the indirect efficacy of sea level changes to lacustrine basin may be a key problem. Tectonism has great influence on the extensional and flexural basins in the continental area so tectono-stratigraphy analysis has more importance in the basin research.
Sequence stratigraphy, an important and significant development in sedimentology and stratigraphy, has made the sedimentary basin filling analysis both theoretical and methodological. Setting up the chronstratigraphic framework and determinging the building blocks have: now become the major'tasks in basin analysis. This paper describes the rapid development in sequence stratigraphy and its relationship with other subjects such as depositional system analysis, tectono-stratigraphy and event stratigraphy. The inter-relationship among these subjects will become the basis for a new genetic stratigraphy system that centents the sequence stratigraphy. This system will strongly support the research in sedimentay basin anaiysis. Studies in sandbody architectural units, the basis for sedimentology of oil reservoir is also part of the research in building blocks of basin filling. This paper discussed the construction of sequence stratigraphic models for various basins, especially the intraplate paralic basins and the inland basius, both being the major types in China. The paper also discusses problems in theoretical research in China related to sequence stratigraphy, suggestions are as follows: 1. Based upon the sedimentology, micropaleontology and magnetostratigraphy research of the South China sea basis and East China sea basin, the Cenozoic sea level changes scheme could be constructed firstly, also the generalized schemes of sea level changes of the other periods in mainland could be put forward. 2.There are optimum conditions for the studies of Paleozoic seqquence stratigraphy from intracontinent to continent margin of the Yangtze and Sino-Korean cratons. 3. Mesozoic and Cenozoic inland basins cover vast area of China continent. To strudy sequence stratigraphy in the lacustrine basins is of great significance, and the indirect efficacy of sea level changes to lacustrine basin may be a key problem. Tectonism has great influence on the extensional and flexural basins in the continental area so tectono-stratigraphy analysis has more importance in the basin research.
1992, 10(3): 40-46.
Abstract:
Based on the systematic analysis and study made recently of several sedimentarv core, and high resulu-tion geophysical records from the Yclluw Sea Shelf the writer believes that the global-change view must be fakm to carry、oul comprehensive unaly-,is m;d }innpari、uns in the study of sedimentary characteristics ofChiua Shelf. In the later stage of Late Pleistovene, the palaeoenvironmeat of China Shelf was different fromboth North America in which Laureatide Ive Sheet developed and Europe pith Scandinavia Ice Sheet oc-cured. Instead of ice sheet, large range of desert and loess distribution area (including most area of China's shelf) occurred in the Asian Continent. At the end of the last glavial period, the ice sheets in NorthAmerica and Europe Continent began to meit providing the North.American shelf and Europe shelf withsufticienl. wWer sources. Local crust oscillations further enhanced the washing dower of rivers. When the con-trnenla lce sheets melted over, the tivers passing or cntering the continental attelf lost ther runoff After the transgression of the Holocene, ntaw trace, of buried palaeorhanncls have nattarally bean left over on thecontinental sheaf ar.das As the sediment :ry environment of ('tuna C ontinental Shelf wts characterized by dryand cold, the chill` was not only bare,l and without the protection of ice sheet but also eroded by stormy inthe most prevailing of the ice age. Therefore, eolation ivas the basic effect on the China Shelf area in the iat-er stage of late Yleistoccne. As known up to now, major sedimentary types of the shelf desertization are(1) long. seale," tolation surfacc. (2) mixing accumulation of large area,(3) sedimentary structure- ofreposvanglc type and (4) typical sediments of buried sand-duets.
Based on the systematic analysis and study made recently of several sedimentarv core, and high resulu-tion geophysical records from the Yclluw Sea Shelf the writer believes that the global-change view must be fakm to carry、oul comprehensive unaly-,is m;d }innpari、uns in the study of sedimentary characteristics ofChiua Shelf. In the later stage of Late Pleistovene, the palaeoenvironmeat of China Shelf was different fromboth North America in which Laureatide Ive Sheet developed and Europe pith Scandinavia Ice Sheet oc-cured. Instead of ice sheet, large range of desert and loess distribution area (including most area of China's shelf) occurred in the Asian Continent. At the end of the last glavial period, the ice sheets in NorthAmerica and Europe Continent began to meit providing the North.American shelf and Europe shelf withsufticienl. wWer sources. Local crust oscillations further enhanced the washing dower of rivers. When the con-trnenla lce sheets melted over, the tivers passing or cntering the continental attelf lost ther runoff After the transgression of the Holocene, ntaw trace, of buried palaeorhanncls have nattarally bean left over on thecontinental sheaf ar.das As the sediment :ry environment of ('tuna C ontinental Shelf wts characterized by dryand cold, the chill` was not only bare,l and without the protection of ice sheet but also eroded by stormy inthe most prevailing of the ice age. Therefore, eolation ivas the basic effect on the China Shelf area in the iat-er stage of late Yleistoccne. As known up to now, major sedimentary types of the shelf desertization are(1) long. seale," tolation surfacc. (2) mixing accumulation of large area,(3) sedimentary structure- ofreposvanglc type and (4) typical sediments of buried sand-duets.
1992, 10(3): 70-77.
Abstract:
There are many methods of studying and mapping of lithofacies paleogeography. This paper will describe the methodology of lithofacies paleogeography that was advocated by the present author, "Single factor analysis and comprehensive mapping method", with the example from the lithofacies paleogeographic study and mapping of Majiagou Group of Middle Ordovician of Ordos Region. By " single factor" , meant is the factors which can independently reflect certain aspects of the sedimentary environments. Single Factor Analysis and Comprehensive Mapping Method includes three steps. First, earnest petrological and petrographical study of each section should be made in order to obtain various firsthand complete and reliable quantitative and qualitative data, especially quantitative data, and to understand the characteristics of sedimentary environments of each stratigraphical interval in the section. Second, select those factors which can independently reflect some aspects of sedimentary environments ( i. e, single factors) from these quantitative data. And then the percentage content of each single factor in each section of the whole area, followed the requisite mapping unit, should be calculated to draw out various corresponding fundamental single factor maps. They are mainly various isoline maps. These fundamental single factor maps can quantitatively reflect different characteristics of sedimentary environments of the slratigraphical interval of the area. This is Single Factor Analysis. Third, Having synthesized these fundamental single facotr maps and combined with other quantitative and qualitative data and other regional geology data, through all-sided analysis and comprehensive judgement, with the dross discarded and the essential selected, the false eliminated and the true retained, the lithofacies paleogeographical maps of the mapping unit of the area can be compiled finally. This is Comprehensive Mapping. The core of this method is quantification. That is, on the basis of quantitative data, starting with analysis of quantitative fundamental single factor maps, then through comprehensive analysis and judgement, finally the quantitative lithofacies paleogeographical maps can be compiled. In these lithofacies pqleogeographicai maps, the determination of each plaeogeographical unit is based on definite quantitavtive data. This type of lithofacies paleogeographical maps is therefore no loger sketchy. This makes lithofacies pqleogeographicai maps developed into a quantitative stage. The following single factors are used in this paper: thickness, terrigenous materials, shallow-water grains, penecontemporaneous dolostones, gypsum, colors and so on. On the basis of various fundamental single factor maps of each formation of Majiagou Group of Ordos Region, combined with other quantitative and qualitative data, through all- sided analysis and judgement, the lithofacies paleogeographical maps of Majiagou Age I to VI of Middle Ordovician of Ordos Region wrer drawn out. The lithofacies paleogeography of Majiagou Age I may be generalized by following: Outside the lands wre flats (dolomite flats, etc); Inside the flats were lakes (gypsum salty lakes and gypsum lakes); Outside the flats were banks (embryonkc banks); Outside the banks were seas (open seas) and outside the seas were troughs (deep-water troughs). In Majiagou Age Ⅱ, the transgression was enlarged so that the whole area was open sea except three small lands. In the open sea there were some embryonic banks and penebanks scatterred. The lithofacies plaeogeography of Majiagou Age Ⅲ and Ⅴ were similar to that of Majiagou Age I. The lithofacies paleogeography of Majiagou Age n and IV were similar to that of Majiagou AgeⅡ. Generally speaking, form Majiagou Age Ⅰ to Ⅵ, three transgressions and three regressions appearred alternatively. They constructed a series of complete cycle of transgression and regression of triple assemblage and three similar, opposite and complementary, antithetical assemblages of lithofacies paleogeography in Majiagou Age of Middle Ordovic
There are many methods of studying and mapping of lithofacies paleogeography. This paper will describe the methodology of lithofacies paleogeography that was advocated by the present author, "Single factor analysis and comprehensive mapping method", with the example from the lithofacies paleogeographic study and mapping of Majiagou Group of Middle Ordovician of Ordos Region. By " single factor" , meant is the factors which can independently reflect certain aspects of the sedimentary environments. Single Factor Analysis and Comprehensive Mapping Method includes three steps. First, earnest petrological and petrographical study of each section should be made in order to obtain various firsthand complete and reliable quantitative and qualitative data, especially quantitative data, and to understand the characteristics of sedimentary environments of each stratigraphical interval in the section. Second, select those factors which can independently reflect some aspects of sedimentary environments ( i. e, single factors) from these quantitative data. And then the percentage content of each single factor in each section of the whole area, followed the requisite mapping unit, should be calculated to draw out various corresponding fundamental single factor maps. They are mainly various isoline maps. These fundamental single factor maps can quantitatively reflect different characteristics of sedimentary environments of the slratigraphical interval of the area. This is Single Factor Analysis. Third, Having synthesized these fundamental single facotr maps and combined with other quantitative and qualitative data and other regional geology data, through all-sided analysis and comprehensive judgement, with the dross discarded and the essential selected, the false eliminated and the true retained, the lithofacies paleogeographical maps of the mapping unit of the area can be compiled finally. This is Comprehensive Mapping. The core of this method is quantification. That is, on the basis of quantitative data, starting with analysis of quantitative fundamental single factor maps, then through comprehensive analysis and judgement, finally the quantitative lithofacies paleogeographical maps can be compiled. In these lithofacies pqleogeographicai maps, the determination of each plaeogeographical unit is based on definite quantitavtive data. This type of lithofacies paleogeographical maps is therefore no loger sketchy. This makes lithofacies pqleogeographicai maps developed into a quantitative stage. The following single factors are used in this paper: thickness, terrigenous materials, shallow-water grains, penecontemporaneous dolostones, gypsum, colors and so on. On the basis of various fundamental single factor maps of each formation of Majiagou Group of Ordos Region, combined with other quantitative and qualitative data, through all- sided analysis and judgement, the lithofacies paleogeographical maps of Majiagou Age I to VI of Middle Ordovician of Ordos Region wrer drawn out. The lithofacies paleogeography of Majiagou Age I may be generalized by following: Outside the lands wre flats (dolomite flats, etc); Inside the flats were lakes (gypsum salty lakes and gypsum lakes); Outside the flats were banks (embryonkc banks); Outside the banks were seas (open seas) and outside the seas were troughs (deep-water troughs). In Majiagou Age Ⅱ, the transgression was enlarged so that the whole area was open sea except three small lands. In the open sea there were some embryonic banks and penebanks scatterred. The lithofacies plaeogeography of Majiagou Age Ⅲ and Ⅴ were similar to that of Majiagou Age I. The lithofacies paleogeography of Majiagou Age n and IV were similar to that of Majiagou AgeⅡ. Generally speaking, form Majiagou Age Ⅰ to Ⅵ, three transgressions and three regressions appearred alternatively. They constructed a series of complete cycle of transgression and regression of triple assemblage and three similar, opposite and complementary, antithetical assemblages of lithofacies paleogeography in Majiagou Age of Middle Ordovic
1992, 10(3): 85-95.
Abstract:
Carbonate deposition of China is characterized by multiages, multi- environments and multi-rock types. Under the influence of multi-orogenies, diagenetic environments are variable, superimposition of diagenesis is evident, diagenetic assemblage is complicated, and meteoric fresh water and burial diagenesis that closely related with the concentration of oil arid gas are extremely common. Detailed studies of diagenetic terrains' features, diagenetic assemblage, and diagenetic models of different times will be benifit to the prediction of oil-generating, storage and cover. Of all the diagenesis, fresh water dissolution, burial dissolution, dolomitization, first-generation cementation, degypsification, dedolomitization are diagenesis that protect or form various porosities. With the constraints of these diagenesis, secondary solution opening and cave, intergranular pore, intercrystal pore or intercrystal solution opening, solution fissure, etc, could be evolved in the rocks. The compaction, cementation, recrystalization and bruial infilling in the rocks are unfavourable to the conservation of primary porosities and the formation of secondary porosities. According to low content of trace element, such Sr and Mn, low negative δ~(13)C, poor cathodoluminescence and fabric of rocks, meteoric fresh water diagenetic environments can be defined, and hence, the marine, mixed-water and burial diagenetic environments can be differentiated. Different diagenetic environments are characterized by different diagenetic sequence and diagenetic assemblage. Types of porosities and reservoiring performance of rocks are also controlled evidently by diagenetic environments. Based on characteristics of rocks, minerals, geochemistry of trace elementes and marks of isotopic geochemistries stable carbon and oxygen, as well as cathodoluminescence of textural component, etc. of the diagenetic terrain, different diagenesis and their evolution extent can be differentiated. This paper take beach facies as an example, suggest a diagenetic model of beach facies on the basis of synthesized diagenesis of diferent kinds of shoat deposition and porosity evolution history. This model summarized rock fabrics, diagenesis, porosity types and identifying remarks, elc. and reflect the processes of diagenetic evolution of shoat depo,ition andreservoiring space formation. Diagenetic model can be used to eiaborate diagenetic evolution stages and patterns of any sedimentary body, demoristrate the diagenetic assemblage, porosity types, reservoiring performance of rocks, and to analyse diagenetic environment and deep study the diageneiic facles. At the same time, it can also be used to etrlarge the felld of oil and gas exploration, and to prediet. diagenetic trap and to evaluate potential reservoir.
Carbonate deposition of China is characterized by multiages, multi- environments and multi-rock types. Under the influence of multi-orogenies, diagenetic environments are variable, superimposition of diagenesis is evident, diagenetic assemblage is complicated, and meteoric fresh water and burial diagenesis that closely related with the concentration of oil arid gas are extremely common. Detailed studies of diagenetic terrains' features, diagenetic assemblage, and diagenetic models of different times will be benifit to the prediction of oil-generating, storage and cover. Of all the diagenesis, fresh water dissolution, burial dissolution, dolomitization, first-generation cementation, degypsification, dedolomitization are diagenesis that protect or form various porosities. With the constraints of these diagenesis, secondary solution opening and cave, intergranular pore, intercrystal pore or intercrystal solution opening, solution fissure, etc, could be evolved in the rocks. The compaction, cementation, recrystalization and bruial infilling in the rocks are unfavourable to the conservation of primary porosities and the formation of secondary porosities. According to low content of trace element, such Sr and Mn, low negative δ~(13)C, poor cathodoluminescence and fabric of rocks, meteoric fresh water diagenetic environments can be defined, and hence, the marine, mixed-water and burial diagenetic environments can be differentiated. Different diagenetic environments are characterized by different diagenetic sequence and diagenetic assemblage. Types of porosities and reservoiring performance of rocks are also controlled evidently by diagenetic environments. Based on characteristics of rocks, minerals, geochemistry of trace elementes and marks of isotopic geochemistries stable carbon and oxygen, as well as cathodoluminescence of textural component, etc. of the diagenetic terrain, different diagenesis and their evolution extent can be differentiated. This paper take beach facies as an example, suggest a diagenetic model of beach facies on the basis of synthesized diagenesis of diferent kinds of shoat deposition and porosity evolution history. This model summarized rock fabrics, diagenesis, porosity types and identifying remarks, elc. and reflect the processes of diagenetic evolution of shoat depo,ition andreservoiring space formation. Diagenetic model can be used to eiaborate diagenetic evolution stages and patterns of any sedimentary body, demoristrate the diagenetic assemblage, porosity types, reservoiring performance of rocks, and to analyse diagenetic environment and deep study the diageneiic facles. At the same time, it can also be used to etrlarge the felld of oil and gas exploration, and to prediet. diagenetic trap and to evaluate potential reservoir.
1992, 10(3): 104-113.
Abstract:
The passive continental margina are formed in southern, western and northern margins of Huaxia Plate during Devonian because of the opening of Old Tethys. According to the crust character, tectonic activity, sedimentation and vocanism etc., the sedimentary basins in South China can be divided into eight types: intracontinental strike-slipping basins, intracontinental depression basin, intracontinental marginal fault basin, continental marginal strike-slipping basin and intercontinental depression basin, intracontinental marginal fault basin, contintinental marginal strike-slipping basin and intercontinental basin. The formation and evolution of the basin are controlled by the basement fault activity, change of transgression- regression and sedimentation, including four stages: beginning, enlarging and differentiation of the basin, strong rifting-depression and shallowing-filling. In the beginning stage, tectonic active is not obvious, developed terrigenous clastic sediments. However, during the enlarging and differentiating periods, tectonic activity is strong and followed by submarine vocanism and sensitive transgression, deep-water basin initiated and occurred shelf-elastics and carbonate ramp sedimentation. During strong rifting-depressing stage, tectonic activity is strongest, vocanism is obvious, transgression is great and developed deep-water basin sedimentation, lithofacies differentiation was very obvious. Youjiang area and Nanling area are all passive margin of yangtze paleocontinent, but lithofacies-tectonic framework is obviously differentiated: the former is mainly NW direction intensive rifit-ing-depression, while the latter is typical of NE direction basement faulting-slipping. The author think these are the result of spreading of Jinshajiang River-Ailaoshan Mountain of Old Tethys, resulting in contamporneously intensive rifting in Youjiang area. During pre-Devonian, developed serveral NE direction basement faulting zones in Nanling area. Under the influence of transform fault resulted from ocean basin spreading, these basement fault zones developed right-lateral strike slipping, and finally formed Nanling strike-slipping basin.
The passive continental margina are formed in southern, western and northern margins of Huaxia Plate during Devonian because of the opening of Old Tethys. According to the crust character, tectonic activity, sedimentation and vocanism etc., the sedimentary basins in South China can be divided into eight types: intracontinental strike-slipping basins, intracontinental depression basin, intracontinental marginal fault basin, continental marginal strike-slipping basin and intercontinental depression basin, intracontinental marginal fault basin, contintinental marginal strike-slipping basin and intercontinental basin. The formation and evolution of the basin are controlled by the basement fault activity, change of transgression- regression and sedimentation, including four stages: beginning, enlarging and differentiation of the basin, strong rifting-depression and shallowing-filling. In the beginning stage, tectonic active is not obvious, developed terrigenous clastic sediments. However, during the enlarging and differentiating periods, tectonic activity is strong and followed by submarine vocanism and sensitive transgression, deep-water basin initiated and occurred shelf-elastics and carbonate ramp sedimentation. During strong rifting-depressing stage, tectonic activity is strongest, vocanism is obvious, transgression is great and developed deep-water basin sedimentation, lithofacies differentiation was very obvious. Youjiang area and Nanling area are all passive margin of yangtze paleocontinent, but lithofacies-tectonic framework is obviously differentiated: the former is mainly NW direction intensive rifit-ing-depression, while the latter is typical of NE direction basement faulting-slipping. The author think these are the result of spreading of Jinshajiang River-Ailaoshan Mountain of Old Tethys, resulting in contamporneously intensive rifting in Youjiang area. During pre-Devonian, developed serveral NE direction basement faulting zones in Nanling area. Under the influence of transform fault resulted from ocean basin spreading, these basement fault zones developed right-lateral strike slipping, and finally formed Nanling strike-slipping basin.
1992, 10(3): 124-132.
Abstract:
Hydrothermal sedimentation is referred to the sedimentation that occurring in the water bodies under the rock-water interface resulting from the hot water upmigration and extrusion under the sedimentary interface, including the contemporaneous (pene-contemporaneous) replacement and infilling happening near the interface. Several petroloical criteria to identify the hydrothermal dimentation are as follows: 1.Contemporaneous (pene-contemporaneous) replacement and infilling with sediments mainly occur in the surrounding rock near the sedimentary interface before the hot water extrusion, usually appearing in the form of veins and altered mass, distributing under the hydrothermal sediments. 2. Erupted bandings and laminae are the results of the hot water extrution from weak to strong and to weak again. In the profile, the block is in the center and bandings and laminae distribute symmetrilly in both sides. The bandings and laminae are usually formed by the hydrothermal sediments themselves or their alternation with the backgroud sediments. 3. Reef-siliceous rock suite is composed of basin-typed reef-beach-phased carbonate and its overlying siliceous rock (including silicified rocks) accompanied by unstable volcanic (and / or subvolcanic) rocks. Important ore- bearing geologic bodies are often found in the transitional position of the reeflimestone-siliceous rock. The shape of ore-body and quility and fabric of ores are related to its occurrence position in reef-siliceous rock suite. More than 10 ore-bearing eef-siliceous rock suites have been found in China and abroad.
Hydrothermal sedimentation is referred to the sedimentation that occurring in the water bodies under the rock-water interface resulting from the hot water upmigration and extrusion under the sedimentary interface, including the contemporaneous (pene-contemporaneous) replacement and infilling happening near the interface. Several petroloical criteria to identify the hydrothermal dimentation are as follows: 1.Contemporaneous (pene-contemporaneous) replacement and infilling with sediments mainly occur in the surrounding rock near the sedimentary interface before the hot water extrusion, usually appearing in the form of veins and altered mass, distributing under the hydrothermal sediments. 2. Erupted bandings and laminae are the results of the hot water extrution from weak to strong and to weak again. In the profile, the block is in the center and bandings and laminae distribute symmetrilly in both sides. The bandings and laminae are usually formed by the hydrothermal sediments themselves or their alternation with the backgroud sediments. 3. Reef-siliceous rock suite is composed of basin-typed reef-beach-phased carbonate and its overlying siliceous rock (including silicified rocks) accompanied by unstable volcanic (and / or subvolcanic) rocks. Important ore- bearing geologic bodies are often found in the transitional position of the reeflimestone-siliceous rock. The shape of ore-body and quility and fabric of ores are related to its occurrence position in reef-siliceous rock suite. More than 10 ore-bearing eef-siliceous rock suites have been found in China and abroad.
1992, 10(3): 145-153.
Abstract:
The Upper Sinian Dengying Formation of Yangtze region is subdivided into the Lower and Upper members, between both the parallel unconformity occurs commonly. Recently, the paleokarst cave phosphorites are found in the upper part of the Lower member dolostones of the Dengying Formation at the southern and northern margins of Western Hubei Platform which is a subordinate unit of the Great Yangtze Platform (Text-fig. 1 and 2). At Wangjiabao area, Nanzhang County, located in the northern margin of Western Hubei Platform, the paleokarst cave phosphorites range from the eroded surface between the both members of the Dengying Formation downwards to 70 m and consist of phosphorite and dolostonedetritus, terrigenous sands and clay minerals, disorderly or laminatedly. A bed of phosphorites, about 2 m in thickness, composed of intraclastic phosphorite (PI. Ⅱ , 14) , oncoid and laminated algal phosphorite, and phosphorous conglomerate, sandstone and mudstone or shale, extends on the eroded surface. This horizon of the paleokarst caves was formed because of exposure of the platform margin into land at the end of Early Dengying age, whereas the filling process took place in the beginning time of later Dengying trans gression. At Zhangjiaxi of Dayong County situated in the southern margin of the platform, the lower member of the Dengying Formation is overlaid with the Niuditang Formation black shale of the lower Cambrian for lack of the upper member. Usually, a thin bed of phosphorites occurred at the base part of the Niudrtang Formation black shale, several to tens of centimeters in thickness, commonly bearing collophanite lumps, concretions and intraclasts, in which Protospongia spicules and endolithic algal or fungous borings (5 to 10 μm in diameter) are very abundant locally. A sink hole is found. It spreads from the eroded surface downwards into the lower member dolostones of the Dengying Formation and is filled with the Niuditang Formation shale and phosphorites (PI. Ⅰ , 1). The paleokarst caves distribute in the upper part of the Lower member dolostones of the Denying Formation in horizon, and are filled with phosphorite and dolostone clasts, sometimes with laminated algal phosphorite and barite layer in some of large caves (PI. Ⅰ 2). Poorly preserved filaments and coccoids of blue-green algae (PI. Ⅰ , 3 and 4) are occasionally seen in the algal phosphorite, while endolithic algal borings (15 to 50 μm in diameter) filled with dolomite can be frequently found (PI. Ⅰ , 5 and 6). The skeleton-like fragment also occurs in the collophanite layer deopsited within paleokarst cave (PI. Ⅱ, 13).Obviously, this horizon of paleokarst cave phosphorites was formed in the early stage of Early Cambrian. The formative stages of the paleokarst cave phosphorites at Zhangjiaxi seem as follows: (1) the margin of the coarbonate platform elevated and exposed subaerially to form paleokarst caves under warm and moist condition; (2) the algal carbonate sediments developed on the sea bottom and in some of large karstcaves when the platform subsided and was covered with shallow seawater; (3) phosophorous solution carried by upwelling current rapidly replaced the algal carbonate sediments or precipitated in phosphanite on the sea bottom; (4) endolithic algal borings and burrows occurred in the phosphate sediments; (5) phosphate and dolomitic debris, came from the phosphate deposits on the sea bottom and from the lower member dolostones of the Dengying Formation which are the country rock of the paleokarst caves and the fundamental of Late Dengying and Early Cambrian intergressions, filled within the paleokarst caves; (6) dolosparite cements precipitated in the birdseye-like pores, the burrows (PI. Ⅱ, 11) and the remainder intergrain pores; (7) barite precipitated in the cave spaces remaining open after dolomite cementation, or sedimented in layer in the caves which had been not full filled. The above evidences show that two crustal movements arose respectively at the ends of Early Dengying age and of Sinian to cause the formations of pale
The Upper Sinian Dengying Formation of Yangtze region is subdivided into the Lower and Upper members, between both the parallel unconformity occurs commonly. Recently, the paleokarst cave phosphorites are found in the upper part of the Lower member dolostones of the Dengying Formation at the southern and northern margins of Western Hubei Platform which is a subordinate unit of the Great Yangtze Platform (Text-fig. 1 and 2). At Wangjiabao area, Nanzhang County, located in the northern margin of Western Hubei Platform, the paleokarst cave phosphorites range from the eroded surface between the both members of the Dengying Formation downwards to 70 m and consist of phosphorite and dolostonedetritus, terrigenous sands and clay minerals, disorderly or laminatedly. A bed of phosphorites, about 2 m in thickness, composed of intraclastic phosphorite (PI. Ⅱ , 14) , oncoid and laminated algal phosphorite, and phosphorous conglomerate, sandstone and mudstone or shale, extends on the eroded surface. This horizon of the paleokarst caves was formed because of exposure of the platform margin into land at the end of Early Dengying age, whereas the filling process took place in the beginning time of later Dengying trans gression. At Zhangjiaxi of Dayong County situated in the southern margin of the platform, the lower member of the Dengying Formation is overlaid with the Niuditang Formation black shale of the lower Cambrian for lack of the upper member. Usually, a thin bed of phosphorites occurred at the base part of the Niudrtang Formation black shale, several to tens of centimeters in thickness, commonly bearing collophanite lumps, concretions and intraclasts, in which Protospongia spicules and endolithic algal or fungous borings (5 to 10 μm in diameter) are very abundant locally. A sink hole is found. It spreads from the eroded surface downwards into the lower member dolostones of the Dengying Formation and is filled with the Niuditang Formation shale and phosphorites (PI. Ⅰ , 1). The paleokarst caves distribute in the upper part of the Lower member dolostones of the Denying Formation in horizon, and are filled with phosphorite and dolostone clasts, sometimes with laminated algal phosphorite and barite layer in some of large caves (PI. Ⅰ 2). Poorly preserved filaments and coccoids of blue-green algae (PI. Ⅰ , 3 and 4) are occasionally seen in the algal phosphorite, while endolithic algal borings (15 to 50 μm in diameter) filled with dolomite can be frequently found (PI. Ⅰ , 5 and 6). The skeleton-like fragment also occurs in the collophanite layer deopsited within paleokarst cave (PI. Ⅱ, 13).Obviously, this horizon of paleokarst cave phosphorites was formed in the early stage of Early Cambrian. The formative stages of the paleokarst cave phosphorites at Zhangjiaxi seem as follows: (1) the margin of the coarbonate platform elevated and exposed subaerially to form paleokarst caves under warm and moist condition; (2) the algal carbonate sediments developed on the sea bottom and in some of large karstcaves when the platform subsided and was covered with shallow seawater; (3) phosophorous solution carried by upwelling current rapidly replaced the algal carbonate sediments or precipitated in phosphanite on the sea bottom; (4) endolithic algal borings and burrows occurred in the phosphate sediments; (5) phosphate and dolomitic debris, came from the phosphate deposits on the sea bottom and from the lower member dolostones of the Dengying Formation which are the country rock of the paleokarst caves and the fundamental of Late Dengying and Early Cambrian intergressions, filled within the paleokarst caves; (6) dolosparite cements precipitated in the birdseye-like pores, the burrows (PI. Ⅱ, 11) and the remainder intergrain pores; (7) barite precipitated in the cave spaces remaining open after dolomite cementation, or sedimented in layer in the caves which had been not full filled. The above evidences show that two crustal movements arose respectively at the ends of Early Dengying age and of Sinian to cause the formations of pale
