1984 Vol. 2, No. 4
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Display Method:
1984, 2(4): 1-7.
Abstract:
In China, there has been a rapid development of research on turbidity and other gravity flow sediments since middle 1970's. The First National Symposium on Tur-bidite was held in Nanning, Guangxi, China from 14th to 21st October,1983.Twenty seven papers about turbidite and other gravity flow sediments were read out at the meeting. This symposium will undoubtedly bring about a great advance in the study of turbidity and other gravity flow sedimentations. In this paper, the development in researches on turbidity and other gravity flow sedimentations has been summarized. In the last ten years,the researches showed that gravity flow deposits were widespread both in geologic time and space. It was reported that turbidites were spreaded in Late Archean,Proterozoic, Cambrian, Ordovician, Silurian, Devonian, Carboiferous,Permian,Triassic,Jurassic, Cretaceous,Tertiary and Quaternary. The locations at which turbidite occurred were dispersed almost in every province of China. The Paleogeographic environments in which turbidite was formed were of great variety, including modern and ancient fault lake basin, continental rift, aulacogen, foreand back-arc basin, slope of sea mount, ocean basin and passive continental margin, etc. It has been found that some pyroclastic turbidites with great thickness are spread extensively such as those in middle-late Permian and early Triassic in Yunnan-Guizhou-Guangxi basin. Some new types of turbidites have been reported, e. g. the ophiolite-fragment turbidite from Cretaceous in Tibet and tuff-bearing siliceous turbidite within Proterozoic Yanbian ophiolite suite, Sichuan Province. There have been some results in the study on carbonate gravity flow sediments. For example, Mei Zhichao et al. ( 1982 ) reported the carbonate debris flow sediments from Middle Ordovician in Shaanxi Province and Gao Zhenzhong and Liu Huai-po(1983) studied the Triassic carbonate gravity flow deposit in Shiwandashan Mountain Range. Based on these results, several models of gravity flow sedimentations have been established and some inferences have been made about the tectonic sitting in which these sediments deposited. The potential resources in turbidites and other gravity flow deposits have been explored. Turbidite hydrocarbon reservoirs are found in many oil fields. Li Jiliang et al. ( 1978 ) reported the sedimentary characteristics of oil-bearing turbidite. According to the depositional trend, they predicated the existence of deltaic sand body which is confirmed now. It is noticed that there are metallogenetic conditions of multi-metal, gold and uranium in some turbidites. Some new methods have been used to study gravity flow sedimentation by Chinese sedimentologists, such as deep water sampling,seismic stratigraphic technique, x-ray photography and study of trace fossils. In this paper,some proposals for further research on gravity flow sedimentation have been put forward.
In China, there has been a rapid development of research on turbidity and other gravity flow sediments since middle 1970's. The First National Symposium on Tur-bidite was held in Nanning, Guangxi, China from 14th to 21st October,1983.Twenty seven papers about turbidite and other gravity flow sediments were read out at the meeting. This symposium will undoubtedly bring about a great advance in the study of turbidity and other gravity flow sedimentations. In this paper, the development in researches on turbidity and other gravity flow sedimentations has been summarized. In the last ten years,the researches showed that gravity flow deposits were widespread both in geologic time and space. It was reported that turbidites were spreaded in Late Archean,Proterozoic, Cambrian, Ordovician, Silurian, Devonian, Carboiferous,Permian,Triassic,Jurassic, Cretaceous,Tertiary and Quaternary. The locations at which turbidite occurred were dispersed almost in every province of China. The Paleogeographic environments in which turbidite was formed were of great variety, including modern and ancient fault lake basin, continental rift, aulacogen, foreand back-arc basin, slope of sea mount, ocean basin and passive continental margin, etc. It has been found that some pyroclastic turbidites with great thickness are spread extensively such as those in middle-late Permian and early Triassic in Yunnan-Guizhou-Guangxi basin. Some new types of turbidites have been reported, e. g. the ophiolite-fragment turbidite from Cretaceous in Tibet and tuff-bearing siliceous turbidite within Proterozoic Yanbian ophiolite suite, Sichuan Province. There have been some results in the study on carbonate gravity flow sediments. For example, Mei Zhichao et al. ( 1982 ) reported the carbonate debris flow sediments from Middle Ordovician in Shaanxi Province and Gao Zhenzhong and Liu Huai-po(1983) studied the Triassic carbonate gravity flow deposit in Shiwandashan Mountain Range. Based on these results, several models of gravity flow sedimentations have been established and some inferences have been made about the tectonic sitting in which these sediments deposited. The potential resources in turbidites and other gravity flow deposits have been explored. Turbidite hydrocarbon reservoirs are found in many oil fields. Li Jiliang et al. ( 1978 ) reported the sedimentary characteristics of oil-bearing turbidite. According to the depositional trend, they predicated the existence of deltaic sand body which is confirmed now. It is noticed that there are metallogenetic conditions of multi-metal, gold and uranium in some turbidites. Some new methods have been used to study gravity flow sedimentation by Chinese sedimentologists, such as deep water sampling,seismic stratigraphic technique, x-ray photography and study of trace fossils. In this paper,some proposals for further research on gravity flow sedimentation have been put forward.
1984, 2(4): 8-18.
Abstract:
Since the past decade increasing interest has been taken in the use of trace fos-sits as paleoecological indicators, the influence of bioturbation upon sedimentaryprocesses and the nature interaction within the soft-bottom community. This paperbegins with a presentationof the behavioral characteristics and classification of tracefossils，and then a discussion of their use in paleoenviron m ental reconstruction.Trace fossils map be used to distingush marine from non-marine and transitionaldeposits. The most successful application of ichnologp to sedimentology is in theaspect of facies analyses and paleobathymetric zonation of marine deposits. Tracefossils can furnish valuable information concerning the general depositional proces-ses，the relative rate of deposition and erosion and the characteristics of current,bottom matter. The trace fossils assemblage of a deposit can be compared with bodyfossils and lithologicaI evidence so as to reconstruct a m odel of the ancient environ-ments.
Since the past decade increasing interest has been taken in the use of trace fos-sits as paleoecological indicators, the influence of bioturbation upon sedimentaryprocesses and the nature interaction within the soft-bottom community. This paperbegins with a presentationof the behavioral characteristics and classification of tracefossils，and then a discussion of their use in paleoenviron m ental reconstruction.Trace fossils map be used to distingush marine from non-marine and transitionaldeposits. The most successful application of ichnologp to sedimentology is in theaspect of facies analyses and paleobathymetric zonation of marine deposits. Tracefossils can furnish valuable information concerning the general depositional proces-ses，the relative rate of deposition and erosion and the characteristics of current,bottom matter. The trace fossils assemblage of a deposit can be compared with bodyfossils and lithologicaI evidence so as to reconstruct a m odel of the ancient environ-ments.
1984, 2(4): 33-46.
Abstract:
Turbidites are common in tectnically active lake basins. There are two kinds of turbidites, i. e. episodical and steady turbidites. Several examples are discussed in this paper based on the data from western Sichuan, China and Switzerland. Facts demonstrate that the recognition of the two is possible according to their sedimentary sequence, grain size distribution and their relations with the surrounding facies. The episodical turbidite might be triggered by catastrophic events, e. g. earthquake, volcanism and gravitational slumping. Owing to the small size of the basin in mountainous region,argillaceous breccia or brecciated mudstone occurs at the bottom of the sequence, indicating a slumping on great scale. The thickness of the breccia is rather variable. The content of the breccia is obviously related to the source rock nearby. The occurrence of the breccia is, therefore, a significant feature of the episodical turbidite of a lake basin. The breccia is found in the late Triassic Jiangzhou basin and in the lake Zurich where a catastrophic slumping took place 100 years ago and resulted in a turbidite sequence with argillaceous breccia at the bottom. The episodical lacustrine turbidites occur within the deep-water lacustrine muddy deposits as a result of catastrophic slumping and interrupt the normal facies sequence. The grain size distribution shows very typical characteristics on the log-probability plot coincident with the conclusion reached by Walker ( 1979 ) from the hydrodynamic analysis of the Bouma sequence. All the samples from the beds A and B of the Bouma sequence own a grain size distribution of suspended load, but the bed C is distinct with a traction component which is of log-normal distribution and appears as an independent population. The steady turbidites owe their origin to flood river. Although they have simi- lar profile structure except the lack of slumping-induced breccia, the position of the steady turbidite in the facies sequence is definite, usually they occur at the top part of a regradational sequence, indicating a largest flood stage, so that the existence of steady turbidite might indicate a climatic event prevailing in a wide area. The pattern of grain size distribution of the steady turbidite is basically the same as that of the episodical turbidite. But there are some deposited components in the bed A, which constitute an independent population with better sorting and reversed graded sequence. Lacustrine turbidites are typical members of the sequence of the incipient rift, and are of importance to understanding ancient rifts.
Turbidites are common in tectnically active lake basins. There are two kinds of turbidites, i. e. episodical and steady turbidites. Several examples are discussed in this paper based on the data from western Sichuan, China and Switzerland. Facts demonstrate that the recognition of the two is possible according to their sedimentary sequence, grain size distribution and their relations with the surrounding facies. The episodical turbidite might be triggered by catastrophic events, e. g. earthquake, volcanism and gravitational slumping. Owing to the small size of the basin in mountainous region,argillaceous breccia or brecciated mudstone occurs at the bottom of the sequence, indicating a slumping on great scale. The thickness of the breccia is rather variable. The content of the breccia is obviously related to the source rock nearby. The occurrence of the breccia is, therefore, a significant feature of the episodical turbidite of a lake basin. The breccia is found in the late Triassic Jiangzhou basin and in the lake Zurich where a catastrophic slumping took place 100 years ago and resulted in a turbidite sequence with argillaceous breccia at the bottom. The episodical lacustrine turbidites occur within the deep-water lacustrine muddy deposits as a result of catastrophic slumping and interrupt the normal facies sequence. The grain size distribution shows very typical characteristics on the log-probability plot coincident with the conclusion reached by Walker ( 1979 ) from the hydrodynamic analysis of the Bouma sequence. All the samples from the beds A and B of the Bouma sequence own a grain size distribution of suspended load, but the bed C is distinct with a traction component which is of log-normal distribution and appears as an independent population. The steady turbidites owe their origin to flood river. Although they have simi- lar profile structure except the lack of slumping-induced breccia, the position of the steady turbidite in the facies sequence is definite, usually they occur at the top part of a regradational sequence, indicating a largest flood stage, so that the existence of steady turbidite might indicate a climatic event prevailing in a wide area. The pattern of grain size distribution of the steady turbidite is basically the same as that of the episodical turbidite. But there are some deposited components in the bed A, which constitute an independent population with better sorting and reversed graded sequence. Lacustrine turbidites are typical members of the sequence of the incipient rift, and are of importance to understanding ancient rifts.
1984, 2(4): 58-65.
Abstract:
There is a series of Ceno-Mesozoic basins located to the north of Nan-Ling, to the south of Yinshan and to the east of western He-Nan in eastern China. Recently, marine fossils have been found one after another in the Paleogene of these basins, the fact reflects that the sediments in the Paleogene are not exclusively non-marine ones. The marine fossils and their embedded layers show the definite distributive ragula-rity as follows: (l)Laterally, they appear in the basins or depressions near present- major river systems, which were possibly connected with the sea in ancient times. ( 2 ) vertically, the marine fossils are only found in a few horizons of small thickness within the Paleogene and can be related to the period when the water bodies of these basins extended with increased salinity. It is inferred that these marine fossils resulted from the ingression of sea water. ( 3 ) The marine fossils are discontinuous each other among basins but their horizons are stable. The above mentioned characteristics imply that the Paleogene of Eastern China was deposited in many down-faulted or down-warped lacustrine and swampy basins which were drained through major river systems connected with the sea, and thus might be invaded by sea water. In this paper this kind of special sedimentary environment is called "Paralic island-lake system", characterized by the ingression of sea water due to the relative rise of sea level. The deposition in the basins or depressions of paralic island-lake system was probably controlled or affected by the global cycles relative changes of sea level. The development of Paleogene paralic island-lake environment in Eastern China and the invasion of sea water can be attributed to the diktyogenesis of the Chinese continental margin from late Yenshanian to early HIMALAYA. This diktyogenesis brought about the development of the paralic island-lake system occupying a vast area of relative low attitude and sharp relief.In addition, the opening of the Japan Sea Basil provided the necessary condition for the ingression of sea water which was responsible for the deposition of the Paleogene marine fossils bearing horizons in Eastern China. Paralic island-lake system is a kind of sedimento-tectonic environment favoura ble to the generation and accumulation of oil and gas. The sedimento-tectonic circumstance including the conversion of faultdown to warpdown, the sharp relief, and the transgression/regession of waterbody involving sea water invasion determined the sedimentary strata of paralic island-lake system, which were composed of multiple source beds, mainly with mixed type organic matter, multiple reservoirs of various types, multiple forms of trap and multiple kinds of oil/gas pool. In a word, the environment of paralic island-lake system possesses a favoured condition in respect of petroleum geology
There is a series of Ceno-Mesozoic basins located to the north of Nan-Ling, to the south of Yinshan and to the east of western He-Nan in eastern China. Recently, marine fossils have been found one after another in the Paleogene of these basins, the fact reflects that the sediments in the Paleogene are not exclusively non-marine ones. The marine fossils and their embedded layers show the definite distributive ragula-rity as follows: (l)Laterally, they appear in the basins or depressions near present- major river systems, which were possibly connected with the sea in ancient times. ( 2 ) vertically, the marine fossils are only found in a few horizons of small thickness within the Paleogene and can be related to the period when the water bodies of these basins extended with increased salinity. It is inferred that these marine fossils resulted from the ingression of sea water. ( 3 ) The marine fossils are discontinuous each other among basins but their horizons are stable. The above mentioned characteristics imply that the Paleogene of Eastern China was deposited in many down-faulted or down-warped lacustrine and swampy basins which were drained through major river systems connected with the sea, and thus might be invaded by sea water. In this paper this kind of special sedimentary environment is called "Paralic island-lake system", characterized by the ingression of sea water due to the relative rise of sea level. The deposition in the basins or depressions of paralic island-lake system was probably controlled or affected by the global cycles relative changes of sea level. The development of Paleogene paralic island-lake environment in Eastern China and the invasion of sea water can be attributed to the diktyogenesis of the Chinese continental margin from late Yenshanian to early HIMALAYA. This diktyogenesis brought about the development of the paralic island-lake system occupying a vast area of relative low attitude and sharp relief.In addition, the opening of the Japan Sea Basil provided the necessary condition for the ingression of sea water which was responsible for the deposition of the Paleogene marine fossils bearing horizons in Eastern China. Paralic island-lake system is a kind of sedimento-tectonic environment favoura ble to the generation and accumulation of oil and gas. The sedimento-tectonic circumstance including the conversion of faultdown to warpdown, the sharp relief, and the transgression/regession of waterbody involving sea water invasion determined the sedimentary strata of paralic island-lake system, which were composed of multiple source beds, mainly with mixed type organic matter, multiple reservoirs of various types, multiple forms of trap and multiple kinds of oil/gas pool. In a word, the environment of paralic island-lake system possesses a favoured condition in respect of petroleum geology
1984, 2(4): 77-87.
Abstract:
Uranium-bearing coal deposits in China occur in some Meso-Cenozoic continental sedimentary basins which mainly spread over intermontane down-faulted basins of geosynclinal folded and upwarped regions. The uranium-bearing basin basement consists of granite or acidic volcanic rocks;uranium abundance is more than 8 ppm. Underground water in uranium ore areas is characterizied by bicarbonate K-Xa, sulfates and bicarbonate Ca(K)-Na types;PH = 6-7.5;uranium abundance is n. 10-7-n.10-8g/l and n.10-8-n.10-5g/l in arid regions. This deposit, by its occurrence, can be classified into three categories: (1) ore bodies occurring above the unconformable plane of the basin basement, (2) below unconformable plane in sedimentary formation,(3)in the coal-bearing detrital formation. This paper describes some geochemical characteristics of uranium-bearing coals as follows: 1. Uranium-bearing coals are mainly lignites of low-rank metamorphism. The components of coals mostly are collinite (or telinite), interbeded with fusain fragments and mixed with stable components ( cuticle, resinite, spore, etc. ) . The coal's type bel ngs to semidurain-semiclarain, durain with clarain, claro-durain and duro-clarain. On the basis of analytical data, we may come to the conclusion that uranium content is negatively correlative with CY, HYcontents, H/C atomic ratio and Vf, and positively correlative with S. 2. In uranium-bearing coals the forms of uranium existence are complex. U-ranium is in the form of absorption monominerals and organic complexes. Monomi-nerals are pitchblende,coffinite and uranophane, sklodowskite, tyuyamunite, sch-rockingerite, autunite and torbernite. Absorbents consist of vitrain compound, clay minerals and colloidal pyrites. Organic complexes are humic uranyl complex and uraniferous bitumen. 3. Enrichment of organic materials to uranium is realized by special functions of self-decomposition and synthetic products in the diagenetic process. These functions consist of adsorption, reduction, ion exchange, complexation or chelation, etc. Adsorption and reduction are specially chief functions of enrichments to uranium in diagenetic and supergene stages. 4. Genesis of uranium-bearing coal deposits consist of the diagenetic and the epigenetic. According to the occurrence of ore bodies uranium deposits formed in the process of coal bed formation are typically diagenetic;uranium deposits occurring above or below the unconformable plane are mainly epigenetic.
Uranium-bearing coal deposits in China occur in some Meso-Cenozoic continental sedimentary basins which mainly spread over intermontane down-faulted basins of geosynclinal folded and upwarped regions. The uranium-bearing basin basement consists of granite or acidic volcanic rocks;uranium abundance is more than 8 ppm. Underground water in uranium ore areas is characterizied by bicarbonate K-Xa, sulfates and bicarbonate Ca(K)-Na types;PH = 6-7.5;uranium abundance is n. 10-7-n.10-8g/l and n.10-8-n.10-5g/l in arid regions. This deposit, by its occurrence, can be classified into three categories: (1) ore bodies occurring above the unconformable plane of the basin basement, (2) below unconformable plane in sedimentary formation,(3)in the coal-bearing detrital formation. This paper describes some geochemical characteristics of uranium-bearing coals as follows: 1. Uranium-bearing coals are mainly lignites of low-rank metamorphism. The components of coals mostly are collinite (or telinite), interbeded with fusain fragments and mixed with stable components ( cuticle, resinite, spore, etc. ) . The coal's type bel ngs to semidurain-semiclarain, durain with clarain, claro-durain and duro-clarain. On the basis of analytical data, we may come to the conclusion that uranium content is negatively correlative with CY, HYcontents, H/C atomic ratio and Vf, and positively correlative with S. 2. In uranium-bearing coals the forms of uranium existence are complex. U-ranium is in the form of absorption monominerals and organic complexes. Monomi-nerals are pitchblende,coffinite and uranophane, sklodowskite, tyuyamunite, sch-rockingerite, autunite and torbernite. Absorbents consist of vitrain compound, clay minerals and colloidal pyrites. Organic complexes are humic uranyl complex and uraniferous bitumen. 3. Enrichment of organic materials to uranium is realized by special functions of self-decomposition and synthetic products in the diagenetic process. These functions consist of adsorption, reduction, ion exchange, complexation or chelation, etc. Adsorption and reduction are specially chief functions of enrichments to uranium in diagenetic and supergene stages. 4. Genesis of uranium-bearing coal deposits consist of the diagenetic and the epigenetic. According to the occurrence of ore bodies uranium deposits formed in the process of coal bed formation are typically diagenetic;uranium deposits occurring above or below the unconformable plane are mainly epigenetic.
1984, 2(4): 97-110.
Abstract:
The Pleistocene dolomites occurred in the abrasion flat and coast of the inter-tidal zone of the fringing rear reef in Paipu area，Zuan County,Hainan Island，Chi-na. The abrasion flat is made of sediments of the littoral-river sandy-conglome-ratic facies, including abundant mould of marine mollusca. On the flat the sea cliff consists of littoral lagoonal mudy siltfine sand facies. Dolomites(dolostone)consist of dolomite and clastic grains. It is confirmed by the identifications of thin section, staining techniques, thermocouple analysis，X-ray- diffraction techniques，scanning electron microscopy. electron probe microanaly-sis, chemical quantitative analysis etc. There are two kinds of dolomites: 1) dolomite of euhedral rhombic crystal witii tonal tenure; 2) clear, limpid dolomite formed by fissure filling and shell moalding. The origin of dolomites is of replacement in the early diagenesis stage, Thereare three patterns of occureaces of dolomites: 1) Dolomitic sandy conglomerateformed by- coarse clas'tic deposits and dolomite has a bedding structure, 40-50cm inthickness, and consists of gravels, several cm to 30cm in major diameter and do-lomite, having the forms of matrix and cement, It has been known now as the coar-sest elastic materials associated with dolomite, 2) Sandy dolomite of lenticular orbedding structure 8-30cm, in thickness，interlayers with elastic depositss it consi-sts of 75% dolomite and about 20-25% elastic materiels and authigenic minerals, 3)Dolomite crystals and dolomitized infiltration tubules distribute in muddy sand-siltbed. The latter has circle and oval cross section and concentric stratoid structure.The loose and rough central area and outer stratum consist of 10-40% dolomite.The fine inner stratum dolomitized intensely consists of 900u dolomite and only 5%elastic materials and 5% pore space. The silts- elastic particles have relict structure,caused by replacement (Plat. I, 3，II，5-7，Table 4) Thcre arc three kinds of dolomitiza tion, which may be sure in this region: 1. Dolomitization of the miring of fresh ground water and sea water in inter-tidal zone of coast and in the mouth of small river. These conditions favour thereplacement of dolomite because of the drastical dropping of salinity and the Mg/Caratio remaining less variance. 2. Dolomitization of schizahaline pore- water in the intertidal zone .It forms clear, limpid dolomite, replacing shell of mollusca and filling the tension crack with a lamellar arrangement. 3, Dolomitization of plants forms dolomitized in(il'tralion tubule, It is di-rectly- controlled by the physiological action of plants around their roots. In the in-tertidal zone of the coast, because the transpiration and respiration of plants elec-tip-ely suck up moisture and cationes and drain off the C02 and organic acid, thesalinity and Mg Ca ratio become higher and higher,and the microenvironment nearthe root becomes favourable of the replacement, Thus，the dissolution，precipitationand metasomatism of carbonate take place and dolomitized infiltration tubules areformed around the root system, This local intense dolomitization forces the peo-ple to realize the possibility of forming dolomite(dolostone) by replacing elastic rocks on gig en conditions
The Pleistocene dolomites occurred in the abrasion flat and coast of the inter-tidal zone of the fringing rear reef in Paipu area，Zuan County,Hainan Island，Chi-na. The abrasion flat is made of sediments of the littoral-river sandy-conglome-ratic facies, including abundant mould of marine mollusca. On the flat the sea cliff consists of littoral lagoonal mudy siltfine sand facies. Dolomites(dolostone)consist of dolomite and clastic grains. It is confirmed by the identifications of thin section, staining techniques, thermocouple analysis，X-ray- diffraction techniques，scanning electron microscopy. electron probe microanaly-sis, chemical quantitative analysis etc. There are two kinds of dolomites: 1) dolomite of euhedral rhombic crystal witii tonal tenure; 2) clear, limpid dolomite formed by fissure filling and shell moalding. The origin of dolomites is of replacement in the early diagenesis stage, Thereare three patterns of occureaces of dolomites: 1) Dolomitic sandy conglomerateformed by- coarse clas'tic deposits and dolomite has a bedding structure, 40-50cm inthickness, and consists of gravels, several cm to 30cm in major diameter and do-lomite, having the forms of matrix and cement, It has been known now as the coar-sest elastic materials associated with dolomite, 2) Sandy dolomite of lenticular orbedding structure 8-30cm, in thickness，interlayers with elastic depositss it consi-sts of 75% dolomite and about 20-25% elastic materiels and authigenic minerals, 3)Dolomite crystals and dolomitized infiltration tubules distribute in muddy sand-siltbed. The latter has circle and oval cross section and concentric stratoid structure.The loose and rough central area and outer stratum consist of 10-40% dolomite.The fine inner stratum dolomitized intensely consists of 900u dolomite and only 5%elastic materials and 5% pore space. The silts- elastic particles have relict structure,caused by replacement (Plat. I, 3，II，5-7，Table 4) Thcre arc three kinds of dolomitiza tion, which may be sure in this region: 1. Dolomitization of the miring of fresh ground water and sea water in inter-tidal zone of coast and in the mouth of small river. These conditions favour thereplacement of dolomite because of the drastical dropping of salinity and the Mg/Caratio remaining less variance. 2. Dolomitization of schizahaline pore- water in the intertidal zone .It forms clear, limpid dolomite, replacing shell of mollusca and filling the tension crack with a lamellar arrangement. 3, Dolomitization of plants forms dolomitized in(il'tralion tubule, It is di-rectly- controlled by the physiological action of plants around their roots. In the in-tertidal zone of the coast, because the transpiration and respiration of plants elec-tip-ely suck up moisture and cationes and drain off the C02 and organic acid, thesalinity and Mg Ca ratio become higher and higher,and the microenvironment nearthe root becomes favourable of the replacement, Thus，the dissolution，precipitationand metasomatism of carbonate take place and dolomitized infiltration tubules areformed around the root system, This local intense dolomitization forces the peo-ple to realize the possibility of forming dolomite(dolostone) by replacing elastic rocks on gig en conditions
1984, 2(4): 19-32.
Abstract:
Nanpan River seg is located in the junction of Yunnan, Guizhou and Guangxi Provinces and its area is about 100, 000 km2. Besides isolated carbonate platforms which are different in size and roughly distribute in the WE direction, a set of volcaniclastic turbidite and chemigenic or biochemigenic silicilith associated with it were extensively deposited in this area from late Maokou Stage to Early Triassic epoch. Its maximum thickness is up to 1, 400. There is still a dispute about the lithologic character, naming, distributive regularity, eruptive mechanism and depositional mechanism of the volcaniclastic turbidite and silicilith. On the basis of the results of the field and laboratory work over four years, the author has pointed out that it is a set of andesitic volcaniclastic turbidite that erupted along the rift belt on sea floor and belongs to an ash flow type. According to the regional distributive regularity of the section types of different lithologic fabrics it can be divided into three types. ( 1 ) Volcanic lasfic avalanche-turbidite type ( 2 ) Dust cloud-suspension depositional type ( 3 ) The super type of volcaniclastic turbidity current and calciclastic turbidity fan. Nanpan River seg was located in Yunkai-Wuyi back-arc expending belt in late Paleozoic epoch. On the folede basement of early Paleozoic epoch, the activity of the seg became so strong that the crust thinned and back arc was expending. Thus paleogeomorphologic prototype which showed the form of alternation of trenches with platforms revealed itself. Under the great influence of Dongwu movement, the basement rift movmeent in NW, NE and NS directions happened in this area and this paleostructure was formed from the graben type of trenches alternating with the carbonate platforms that belong to horst type. Soon after eruption and intrusion of basic magma, in the trenche,there frequently happened intermediate ash flow tuffs eruption and after the middle Triassic the whole area began to subside. Then the seg mainly received calciclastic gravity flow sediments that came from adjacent carbonate platforms and terrigenous clastic turbidity sediments from the east part of Yunkai Mountain. In addition, there was a bit of the turbidity sediments resulting from acidic magma eruption during early Ladinic stage. The regional strong folding of the second episode of Indo-China movements made the sedimentary depositional history come to end. Two types of turbidite without submarine fan were summarized by Walker (1978). The first is the exogeosynclinal situation, the second is in the predeltaic areas on the craton. Nanpan River seg was located in back-arc expending belt from late Maokou stage to Early Triassic epoch. Actually, the graben type trench in this area is an exogeosyncline. The difference between them consists in material source, turbidity sediments in this seg from ash flow type tuffaceous materials erupted in the trench. So it is a unique turbidite mode without submarine fan.
Nanpan River seg is located in the junction of Yunnan, Guizhou and Guangxi Provinces and its area is about 100, 000 km2. Besides isolated carbonate platforms which are different in size and roughly distribute in the WE direction, a set of volcaniclastic turbidite and chemigenic or biochemigenic silicilith associated with it were extensively deposited in this area from late Maokou Stage to Early Triassic epoch. Its maximum thickness is up to 1, 400. There is still a dispute about the lithologic character, naming, distributive regularity, eruptive mechanism and depositional mechanism of the volcaniclastic turbidite and silicilith. On the basis of the results of the field and laboratory work over four years, the author has pointed out that it is a set of andesitic volcaniclastic turbidite that erupted along the rift belt on sea floor and belongs to an ash flow type. According to the regional distributive regularity of the section types of different lithologic fabrics it can be divided into three types. ( 1 ) Volcanic lasfic avalanche-turbidite type ( 2 ) Dust cloud-suspension depositional type ( 3 ) The super type of volcaniclastic turbidity current and calciclastic turbidity fan. Nanpan River seg was located in Yunkai-Wuyi back-arc expending belt in late Paleozoic epoch. On the folede basement of early Paleozoic epoch, the activity of the seg became so strong that the crust thinned and back arc was expending. Thus paleogeomorphologic prototype which showed the form of alternation of trenches with platforms revealed itself. Under the great influence of Dongwu movement, the basement rift movmeent in NW, NE and NS directions happened in this area and this paleostructure was formed from the graben type of trenches alternating with the carbonate platforms that belong to horst type. Soon after eruption and intrusion of basic magma, in the trenche,there frequently happened intermediate ash flow tuffs eruption and after the middle Triassic the whole area began to subside. Then the seg mainly received calciclastic gravity flow sediments that came from adjacent carbonate platforms and terrigenous clastic turbidity sediments from the east part of Yunkai Mountain. In addition, there was a bit of the turbidity sediments resulting from acidic magma eruption during early Ladinic stage. The regional strong folding of the second episode of Indo-China movements made the sedimentary depositional history come to end. Two types of turbidite without submarine fan were summarized by Walker (1978). The first is the exogeosynclinal situation, the second is in the predeltaic areas on the craton. Nanpan River seg was located in back-arc expending belt from late Maokou stage to Early Triassic epoch. Actually, the graben type trench in this area is an exogeosyncline. The difference between them consists in material source, turbidity sediments in this seg from ash flow type tuffaceous materials erupted in the trench. So it is a unique turbidite mode without submarine fan.
1984, 2(4): 47-57.
Abstract:
Since the end of Mesozoic, Bohai Bay region has been influenced by the diving of Pacific Plate from east to west and acted by the stretching forces so as to form many fault-depressions, in which more turbidity fans are developed. The developing stage of turbidity fans is concordant with that of the strong -sinking of lake basin. In the study region the turbidity fans distribute mainly in the third member of Shahejie Formation. The chief depositional features of the turbidity fans are as follows. 1. The turbidity fans mainly consist of conglomerate, sandy-conglomerate, sandstone, siltstone and interbedded frequently with the dark mudstone. They are predominately unsorted admixtures of sand and pebbles in a muddy matrix, namely greywacke, feldspathic litharenite or litharenite. They are characterized by higher rock fragment contents, ranging from 30% to 50%. 2. The cumulative probability curves of deposits in turbidity fans show a population ( a gentle curve ) without obvious breaker, illustrating that the turbidity is dominantly graded suspension, C-M pattern of the sediments is a rectangle paralle 1 to the basic line(M=C), value C(l%)being 100μ to 800μ, value M(50%)40-800μ. 3.The primary sedimentary structures and their vertical assemblages illustrate that there are two kinds of vertical sequences, that is,classical turbidite sequence (with Bouma sequence ) and unclassical turbidite sequence ( without Bouma sepu-ence). 4. Flute cast, groove cast and load cast are common in the turbidite bottom-side in this area, and sometimes the flame structure can be seen. This paper also deals with the difference between the two kinds of tuibidity fans-flood turbidity fan and slump turbidity fan. Finally this paper discusses the oil-bearing ability in the turbidity fan.
Since the end of Mesozoic, Bohai Bay region has been influenced by the diving of Pacific Plate from east to west and acted by the stretching forces so as to form many fault-depressions, in which more turbidity fans are developed. The developing stage of turbidity fans is concordant with that of the strong -sinking of lake basin. In the study region the turbidity fans distribute mainly in the third member of Shahejie Formation. The chief depositional features of the turbidity fans are as follows. 1. The turbidity fans mainly consist of conglomerate, sandy-conglomerate, sandstone, siltstone and interbedded frequently with the dark mudstone. They are predominately unsorted admixtures of sand and pebbles in a muddy matrix, namely greywacke, feldspathic litharenite or litharenite. They are characterized by higher rock fragment contents, ranging from 30% to 50%. 2. The cumulative probability curves of deposits in turbidity fans show a population ( a gentle curve ) without obvious breaker, illustrating that the turbidity is dominantly graded suspension, C-M pattern of the sediments is a rectangle paralle 1 to the basic line(M=C), value C(l%)being 100μ to 800μ, value M(50%)40-800μ. 3.The primary sedimentary structures and their vertical assemblages illustrate that there are two kinds of vertical sequences, that is,classical turbidite sequence (with Bouma sequence ) and unclassical turbidite sequence ( without Bouma sepu-ence). 4. Flute cast, groove cast and load cast are common in the turbidite bottom-side in this area, and sometimes the flame structure can be seen. This paper also deals with the difference between the two kinds of tuibidity fans-flood turbidity fan and slump turbidity fan. Finally this paper discusses the oil-bearing ability in the turbidity fan.
1984, 2(4): 66-76.
Abstract:
This paper centers on the quantitative study of the correlation between germanium and the petrographic constituents of coal experimentally. Through the flotation separation of the lignite of this basin by heavy liquid, sixty-six separation specimens in the various specific gravity ranks ( s. g. r ) , namely<1.35, 1.35-1.45, 1.45-1.55, 1.55-1.59, >1.59, are obtained, the detection of their content of germanium and the determination of their polished sections of petrographic coal indicate that the distribution of germanium in the lignite is not only various according to the petrographic types of coal, but also is controlled by the different s. g. r. and the various petrographic constituents of coal, in this aspect there is a regular successive variance. On the basis of the distributive characteristics and the variances of the content of the inorganic and organic components as vell as the microlithotypes of these specimens, and according to their corresponding tenor of germanium, they can be divided into three groups. 1. <1.36 s.g. r. : The organic components amount to 95.2%, the vitrintes make up 93.5% of the former, the stable components include microsporinite, cuiticle and retinite etc.. Fusain hasn't been seen. The average content of germanium is 48.4 ppm. 2.>1.59 s. g. r. : The inorganic components amount to 89.3%, most of them are argillaceous, with a few pyrites, quartz and quartzose detritus, the organic components are all vitrinites. Stable component and fusinite can be found. The average content of germanium is only 7.5ppm. 3. 1.35-1.59 s.g.r. : Along with the raise of s.g r.,the inorganic components increase progressively, but the organic components, the vitrinites and the stable components as well as germanium decrease successivelly, nevertheless a trace of the fusite exists. Except the very few abnormities caused by the influence of the stable components, the content of germanium and various components lie between the above-mentioned two groups. Therefrom it suggests that the content of germanium is surely relative to the organic components closely and has a little to do with the inorganic components. Germanium exists mainly in the vitrinites of the lignite, namely in the gelatinous components, and is very rare in the stable components and the fusites group.Therefore that the vitrain and clarain turn into the enriched bodies of germanium should be attributed to their abundant gelatinous fabric. Finally, through the study of the germanium-bearing conditions of modern higher plants and lower plants in peat bog, and the analysis of the geological characteristics concerned, the machanism of the enrichment of germanium in coal is pursued tentatively.
This paper centers on the quantitative study of the correlation between germanium and the petrographic constituents of coal experimentally. Through the flotation separation of the lignite of this basin by heavy liquid, sixty-six separation specimens in the various specific gravity ranks ( s. g. r ) , namely<1.35, 1.35-1.45, 1.45-1.55, 1.55-1.59, >1.59, are obtained, the detection of their content of germanium and the determination of their polished sections of petrographic coal indicate that the distribution of germanium in the lignite is not only various according to the petrographic types of coal, but also is controlled by the different s. g. r. and the various petrographic constituents of coal, in this aspect there is a regular successive variance. On the basis of the distributive characteristics and the variances of the content of the inorganic and organic components as vell as the microlithotypes of these specimens, and according to their corresponding tenor of germanium, they can be divided into three groups. 1. <1.36 s.g. r. : The organic components amount to 95.2%, the vitrintes make up 93.5% of the former, the stable components include microsporinite, cuiticle and retinite etc.. Fusain hasn't been seen. The average content of germanium is 48.4 ppm. 2.>1.59 s. g. r. : The inorganic components amount to 89.3%, most of them are argillaceous, with a few pyrites, quartz and quartzose detritus, the organic components are all vitrinites. Stable component and fusinite can be found. The average content of germanium is only 7.5ppm. 3. 1.35-1.59 s.g.r. : Along with the raise of s.g r.,the inorganic components increase progressively, but the organic components, the vitrinites and the stable components as well as germanium decrease successivelly, nevertheless a trace of the fusite exists. Except the very few abnormities caused by the influence of the stable components, the content of germanium and various components lie between the above-mentioned two groups. Therefrom it suggests that the content of germanium is surely relative to the organic components closely and has a little to do with the inorganic components. Germanium exists mainly in the vitrinites of the lignite, namely in the gelatinous components, and is very rare in the stable components and the fusites group.Therefore that the vitrain and clarain turn into the enriched bodies of germanium should be attributed to their abundant gelatinous fabric. Finally, through the study of the germanium-bearing conditions of modern higher plants and lower plants in peat bog, and the analysis of the geological characteristics concerned, the machanism of the enrichment of germanium in coal is pursued tentatively.
1984, 2(4): 88-96.
Abstract:
Gammacerane in crude oil and source rocks belongs to a pantacyclic triterpane series and occurs at the eluted peak between 17β(H), 21a(H)-30-homohopane 20R and 17α(H), 2lβ(H)-30-homomortane on m/e 191 mass chromatogram. It has not been found in marine crude oil and source rocks. This compound is one of the terrestrial markers of sedimentary facies. The study of crude oil and source rocks from terrestrial sediment in our country shows that gammacerane is distributed in the terrestrial crude oil and source rocks with different abundance, depending on the corresponding sedimentary environment, the type and maturity of organic matters, etc. Usually, a great abundance of gammacerane presents in the samples of a sapropelic kerogen or humic-sapropelic kerogen, existing in semideep or deep water sediments, especially in shales deposited in the salt lakes, and the less presents in the shallow water sediments of lake facies and swamp facies in sapropelic-humic kerogen. In the case of the same type of kerogen, the abundance of gammacerane decreases with the increase of the function of thermodynamics and the maturation of organic matters as well as the buried depth of crude oil and sedimentary rocks. According to the distribution of gammacerane in the sediments and the recent tetrahymanol as a precursor of gammacerane in the recent plants and animals, the author infers that the genesis of gammacerane is as follows: 1 ) It originates from the protozoan living in the terrestrial lake. 2) It originates from higher plants such as fern. The tetrahymanol in these plants is brought into the lakes by the surface water and groundwater, and deposited with other matters, The tetrahymanol would be more abundant with the increase of concentration of salt in the lake water, because aquatic algal, from which hopanoid mainly derived, decreased and the preservation of'the organic matters in the water or sediments improved. This is the reason for the highest concentration of gammacerane in the salt lake sediments. 3 ) It originates from the composition of some terpenoid in the continental plants. The author considers that gammacerane is a better indicator in petroleum geochemistry. It can be used to indicate sedimentary environment, type of kerogen, maturation of organic matters, and can be applied to indicating correlation between source rocks and crude oil with specific geological and geochemical conditions.
Gammacerane in crude oil and source rocks belongs to a pantacyclic triterpane series and occurs at the eluted peak between 17β(H), 21a(H)-30-homohopane 20R and 17α(H), 2lβ(H)-30-homomortane on m/e 191 mass chromatogram. It has not been found in marine crude oil and source rocks. This compound is one of the terrestrial markers of sedimentary facies. The study of crude oil and source rocks from terrestrial sediment in our country shows that gammacerane is distributed in the terrestrial crude oil and source rocks with different abundance, depending on the corresponding sedimentary environment, the type and maturity of organic matters, etc. Usually, a great abundance of gammacerane presents in the samples of a sapropelic kerogen or humic-sapropelic kerogen, existing in semideep or deep water sediments, especially in shales deposited in the salt lakes, and the less presents in the shallow water sediments of lake facies and swamp facies in sapropelic-humic kerogen. In the case of the same type of kerogen, the abundance of gammacerane decreases with the increase of the function of thermodynamics and the maturation of organic matters as well as the buried depth of crude oil and sedimentary rocks. According to the distribution of gammacerane in the sediments and the recent tetrahymanol as a precursor of gammacerane in the recent plants and animals, the author infers that the genesis of gammacerane is as follows: 1 ) It originates from the protozoan living in the terrestrial lake. 2) It originates from higher plants such as fern. The tetrahymanol in these plants is brought into the lakes by the surface water and groundwater, and deposited with other matters, The tetrahymanol would be more abundant with the increase of concentration of salt in the lake water, because aquatic algal, from which hopanoid mainly derived, decreased and the preservation of'the organic matters in the water or sediments improved. This is the reason for the highest concentration of gammacerane in the salt lake sediments. 3 ) It originates from the composition of some terpenoid in the continental plants. The author considers that gammacerane is a better indicator in petroleum geochemistry. It can be used to indicate sedimentary environment, type of kerogen, maturation of organic matters, and can be applied to indicating correlation between source rocks and crude oil with specific geological and geochemical conditions.
1984, 2(4): 111-126.
Abstract:
This paper delt with the origins of borates in the saline lakes of Qinghai-Xizang plateau mainly on the basis of the characteristics of the borate distribution, the paragenesis mineral group and some results of our experiments. 1. The distribution and paragenesis mineral group of borates in the saline lakes of Qinghai-Xizang Plateau Borates are mainly distributed in a lot of saline lakes from the southern side of the Qilian mountain to the north side of the Gangdisi-Tanggula mountains. As to the age, most of them exist in the Holocene sediments ( up to now, borates have been precipitating in some salt lakes yet) ,but only a few of them in the Late Pleistocene. However, they are mostly concentrated at the side of lake-basin supplied with hotspring water. In the salt lakes of this area,the discovered borates are as follows: tincalconite, ulexite, pinnoite, kurnakovite, inderite, hungchaoite, hydroboracite, trigonomagne-borite and carboborite etc. Among them borax and tincalconite ( secondary ) are mainly found in the salt lakes of carbonate-type, and the pinnoite, kurnakovite and other Mg-borates in those of sulphate type. Borates are always in paragenesis with clay and various saltminerals. Borax and tincalconite ( secondary ) are always associated with mirabilite, thenardite, hy-dromagnesite, calcite, northupite, thermonatrite,and soda. Ulexite with carbonate-clay and mirabilite. Pinnoite is always associated with ulexite and may also be associated with carbonate, mirabilite, or bloedite-epsomite. Kurnakovite is always associated with inderite and the both letters can form a single ore-layer respectively. Borates can be formed in the different concentrating-stages of saline lakes. 2. The origins of borates in the saline lakes of Qinghai-Xizang Plateau In the Qinghai-Xizang Plateau, the geothermal activity is very strong, and the geothermal water ( hot spring water ) contains a lot of boron ( B2O3 being 84mg/l on the average, the maximum 1561mg/l ) . The acid rocks ( neutral rocks and basic rocks) are well developed there. Their B-content is higher ( the maximum coateat of B2O3 up to 2000 p. p. m. ) , so that it can provide abundant substance resources for the boron concentration and borate formation in the saline lakes of this area. Besides, since the Late Pleistocene the Qinghai-Xizang Plateau has been rapidly rising up, the climate gradually turning to cold and dry. It is helpful to provide advantageous conditions for the formation of saline lakes and their borates. In order to find out the forming conditions of borates, we have simulated the natural condition to carry out the experiments of diluting, freezing evaporation, freezing and unmoved- setting using the brines, spring water and hot spring water taken from Dachaidan Salt Lake ( Mg2S04-subtype ) , Zhacang-Caka Salt Lake ( Na2SO4-subtype ) and Jilin Lake ( carbonate type) and the distilled water. Borates have been obtained from over 4o samples. Inderite is predominant and there are also kurnakovite, as well as other Mg-borates. They appeared at the different stages of the brine concentration. ( 1 ) Mixing action: The borates associated with clay carbonate, gypsum and mirabilite would be formed when they were distributed in the belt supplied with external water and the lake water was at the diluting stage. ( 2 ) The condition of low-temperature: It may impel and speed up the formation of borates iundern the low-temperature condition. Generally, the borates in paragenesis with low-temperature minerals of mirabilite etc. should be formed under this condition. ( 3 ) Stable condition: Generally, the fomation of all the borates requires a rather stable environment (i. e. stable equilibrium condition) except the extreme high-content of boron in brines. For example: after having bu riedthe salt sediments the borates were separated from intercrystal brine, pore water and interstitial water in the salt sediments. ( 4 ) The type and composition of B-bearing brine and the correlation between boron and other components in the B-bearing brine decide to a certain extent thespecies and paragenesis mineral group of forming borates， Especially. the Mg-bo-ates might be formed in the sulphate-type water-bodies of the different concentrat-ing stages and compositions. The difference between the borate species obtained from the experiments andthe nature mainly results from the difference of brine composition and the latteralteration of brine composition，as well as the latter secondary change of minerals.
This paper delt with the origins of borates in the saline lakes of Qinghai-Xizang plateau mainly on the basis of the characteristics of the borate distribution, the paragenesis mineral group and some results of our experiments. 1. The distribution and paragenesis mineral group of borates in the saline lakes of Qinghai-Xizang Plateau Borates are mainly distributed in a lot of saline lakes from the southern side of the Qilian mountain to the north side of the Gangdisi-Tanggula mountains. As to the age, most of them exist in the Holocene sediments ( up to now, borates have been precipitating in some salt lakes yet) ,but only a few of them in the Late Pleistocene. However, they are mostly concentrated at the side of lake-basin supplied with hotspring water. In the salt lakes of this area,the discovered borates are as follows: tincalconite, ulexite, pinnoite, kurnakovite, inderite, hungchaoite, hydroboracite, trigonomagne-borite and carboborite etc. Among them borax and tincalconite ( secondary ) are mainly found in the salt lakes of carbonate-type, and the pinnoite, kurnakovite and other Mg-borates in those of sulphate type. Borates are always in paragenesis with clay and various saltminerals. Borax and tincalconite ( secondary ) are always associated with mirabilite, thenardite, hy-dromagnesite, calcite, northupite, thermonatrite,and soda. Ulexite with carbonate-clay and mirabilite. Pinnoite is always associated with ulexite and may also be associated with carbonate, mirabilite, or bloedite-epsomite. Kurnakovite is always associated with inderite and the both letters can form a single ore-layer respectively. Borates can be formed in the different concentrating-stages of saline lakes. 2. The origins of borates in the saline lakes of Qinghai-Xizang Plateau In the Qinghai-Xizang Plateau, the geothermal activity is very strong, and the geothermal water ( hot spring water ) contains a lot of boron ( B2O3 being 84mg/l on the average, the maximum 1561mg/l ) . The acid rocks ( neutral rocks and basic rocks) are well developed there. Their B-content is higher ( the maximum coateat of B2O3 up to 2000 p. p. m. ) , so that it can provide abundant substance resources for the boron concentration and borate formation in the saline lakes of this area. Besides, since the Late Pleistocene the Qinghai-Xizang Plateau has been rapidly rising up, the climate gradually turning to cold and dry. It is helpful to provide advantageous conditions for the formation of saline lakes and their borates. In order to find out the forming conditions of borates, we have simulated the natural condition to carry out the experiments of diluting, freezing evaporation, freezing and unmoved- setting using the brines, spring water and hot spring water taken from Dachaidan Salt Lake ( Mg2S04-subtype ) , Zhacang-Caka Salt Lake ( Na2SO4-subtype ) and Jilin Lake ( carbonate type) and the distilled water. Borates have been obtained from over 4o samples. Inderite is predominant and there are also kurnakovite, as well as other Mg-borates. They appeared at the different stages of the brine concentration. ( 1 ) Mixing action: The borates associated with clay carbonate, gypsum and mirabilite would be formed when they were distributed in the belt supplied with external water and the lake water was at the diluting stage. ( 2 ) The condition of low-temperature: It may impel and speed up the formation of borates iundern the low-temperature condition. Generally, the borates in paragenesis with low-temperature minerals of mirabilite etc. should be formed under this condition. ( 3 ) Stable condition: Generally, the fomation of all the borates requires a rather stable environment (i. e. stable equilibrium condition) except the extreme high-content of boron in brines. For example: after having bu riedthe salt sediments the borates were separated from intercrystal brine, pore water and interstitial water in the salt sediments. ( 4 ) The type and composition of B-bearing brine and the correlation between boron and other components in the B-bearing brine decide to a certain extent thespecies and paragenesis mineral group of forming borates， Especially. the Mg-bo-ates might be formed in the sulphate-type water-bodies of the different concentrat-ing stages and compositions. The difference between the borate species obtained from the experiments andthe nature mainly results from the difference of brine composition and the latteralteration of brine composition，as well as the latter secondary change of minerals.
