1986 Vol. 4, No. 1
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Display Method:
1986, 4(1): 1-7.
Abstract:
Bauxite in China is mainly palaeoresiduum sedimentary bauxite deposits (98.83% in the total reserve), which is called the karst type abroad. And the lateritic type of bauxite deposits is only 1.17% in the total reserve. In China the genetic mechanism of palaeoresiduum sedimentary bauxite deposits is considered as the colloidal chemical sedimentation by the most mineralogists and it is considered as the sedimentation of meohanical elastics and suspended materials. Based on the research results as followings: 1) The Oxygen Isotope Analysis:the δ~(18)O‰. value(SMOW) of the diaspore, which is the main clay mineral in palaeoresiduum sedimentary bauxite deposits, is about +5-+ 10.9, average +9.2. This value verifies that the diaspore is formed by weathering and the crystalinity index of the clay minerals in the bauxite deposits shows the origin of terrigenous clastic materials as wells 2) No sedimentary traces which are often seen in water sediments, such as bedding, cross bedding, ripple mark and crack, are found in the deposits, and neither are animal fossils; 3) The ores of the palaeoresiduum sedimentary bauxite deposits are all earthy, semiearthy or dense in structure without exception and under microscope their textures are psammitic or gravel-clastic and the shape of the clastic is subround or sub-edge-anglar, indicating the sediments to be transported, and no mechanical differential sedimentation has been found, thus they are quite similar to the earthy or semiearthy clastic bauxite ores near palaeoshores or in the central of sea basins; 4) The striae on the surface of diaspores under scanning electron microscope and the cracks of oolitic grains under microscope indicate the transportation in atmosphere; 5) Pores are well developed in the bauxite ores under scanning electron microscope many miarolitic cavities, in which there are secondary diaspores with good crystalinity as well as boehmites and under microscope can be seen secondary kaolinites filled between psammitic grains and gravel-clastic grains, and the ores become poor in quality in a certain depth below ground water, which indicates that SiO2 has been leached away and alumina is enriched in the epidiagen-etic stage; the author thinks that the origin of the palaeoresiduum sedimentary deposits in China is "a terrestrial and hydatogenous deposit with superficial enrichment". The sedimentary process of the ores can be divided into three stages as followingS: 1) Alumina-bearing rocks in continent become drift-bed calcium lateritic beds or lateritic beds in bauxite-bearing residuum through weathering; 2) After sea water or lake water covers the eluvial beds, primary bauxite stratum in poor quality is formed during sedimentation; 3) The primary ore bed goes up with the rise of crust and, hence, enters into the superficial stage, upon the action of groundwater or surface water the SiO2 is leached but alumina enriched, and finally the bauxite deposit with industrial value is formed.
Bauxite in China is mainly palaeoresiduum sedimentary bauxite deposits (98.83% in the total reserve), which is called the karst type abroad. And the lateritic type of bauxite deposits is only 1.17% in the total reserve. In China the genetic mechanism of palaeoresiduum sedimentary bauxite deposits is considered as the colloidal chemical sedimentation by the most mineralogists and it is considered as the sedimentation of meohanical elastics and suspended materials. Based on the research results as followings: 1) The Oxygen Isotope Analysis:the δ~(18)O‰. value(SMOW) of the diaspore, which is the main clay mineral in palaeoresiduum sedimentary bauxite deposits, is about +5-+ 10.9, average +9.2. This value verifies that the diaspore is formed by weathering and the crystalinity index of the clay minerals in the bauxite deposits shows the origin of terrigenous clastic materials as wells 2) No sedimentary traces which are often seen in water sediments, such as bedding, cross bedding, ripple mark and crack, are found in the deposits, and neither are animal fossils; 3) The ores of the palaeoresiduum sedimentary bauxite deposits are all earthy, semiearthy or dense in structure without exception and under microscope their textures are psammitic or gravel-clastic and the shape of the clastic is subround or sub-edge-anglar, indicating the sediments to be transported, and no mechanical differential sedimentation has been found, thus they are quite similar to the earthy or semiearthy clastic bauxite ores near palaeoshores or in the central of sea basins; 4) The striae on the surface of diaspores under scanning electron microscope and the cracks of oolitic grains under microscope indicate the transportation in atmosphere; 5) Pores are well developed in the bauxite ores under scanning electron microscope many miarolitic cavities, in which there are secondary diaspores with good crystalinity as well as boehmites and under microscope can be seen secondary kaolinites filled between psammitic grains and gravel-clastic grains, and the ores become poor in quality in a certain depth below ground water, which indicates that SiO2 has been leached away and alumina is enriched in the epidiagen-etic stage; the author thinks that the origin of the palaeoresiduum sedimentary deposits in China is "a terrestrial and hydatogenous deposit with superficial enrichment". The sedimentary process of the ores can be divided into three stages as followingS: 1) Alumina-bearing rocks in continent become drift-bed calcium lateritic beds or lateritic beds in bauxite-bearing residuum through weathering; 2) After sea water or lake water covers the eluvial beds, primary bauxite stratum in poor quality is formed during sedimentation; 3) The primary ore bed goes up with the rise of crust and, hence, enters into the superficial stage, upon the action of groundwater or surface water the SiO2 is leached but alumina enriched, and finally the bauxite deposit with industrial value is formed.
1986, 4(1): 34-42.
Abstract:
The Fuping area in Shaanxi lies on the Weibei uplift along the southern margin of the Eerdousi Basin. The Zhaolaoyu Formation of the Middle-Upper Ordovician series in this area is characterized chiefly by hemipelagic thin-bedded lime mudstones interbedded with limestone breccias and calca-renites derived from gravity flow, In addition, there is a small amount of tuff, radiolarian chert and well-sorted thin-bedded calcarenite and calcisi-ltite which represent the equivalent of contourite. Body fossils are poor, mainly pelagic ostracod, radiolaria and graptolite. Benthonic organisms are rare, but deep-water trace fossils of the Nereites facies are abundant. Gravity flow deposits of the Zhaolaoyu Formation can be subdivided into five rock types: ( 1 ) homogeneous wackstone; ( 2 ) thin-bedded graded calcarenite; ( 3 ) graded rubble calcarenite; ( 4 ) limestone breccia with oriented fabric; and ( 5 ) chaotic limestone breccia. In general, the thin-bedded graded calcarenite and homogeneous wack-stones form turbidite with divisions BCE or CE of the Bouma sequence while the graded rubble calcarenite and homogeneous wackstones form turid-ite with divisions AE of the Bouma sequence.Limestone breccia with oriented fabric exhibits normal or inverse-to-normal grading. Tabular clasts are frequently sub-parallel to the bedding or imbricated. The features suggest that they were deposited from a gravally high-density turbidity current. Chaotic limestone breccias might have been debris flow sediments. The above lithofacies commonly form two specific associated sequences in the section. From bottom to top, the two sequences go as follows: ( 1 ) chaotic limestone breccia-→graded rubble calcarenite-→homogeneous wack- stone; ( 2 ) ungraded limestone breccia with oriented fabric-→inverse-to- normal grading limestone breccia-→graded rubble calcarenite-→calarenite with devisions BC of the Bauma sequence-→homogeneous wackstone. These sequences indicate that they are successive deposits derived from individual flow. However, the distinct lithofacies in the above sequences were probably deposited through several sedimention surges. Based on integrated sedimentological, paleontological and tectonic setting analyses, we suggest that the Weibei region, together with North China, be a united shallow-platform prior to the later period of the Middle Ordovician. Then it was subsided and developed into a continental margin of the back-arc basin owing to the subduction of the Qinling plate beneath the North China plate. The Fuping area might have been a N-E trending deep sea front trough that stretched from this back-arc basin into the North China carbonate platform.The gravity flow sediments were mainly transported in great sheet flows along the axis of the trough basin. These flows were probably resulted from the confluence of several minor gravity flows around the downslope margin of platform. The model presented here differs from either the submarine fan model or the carbonate slope model, but it is similar to the pattern of modern carbonate debris sheets of the Exuma Sound in the Bahamas.
The Fuping area in Shaanxi lies on the Weibei uplift along the southern margin of the Eerdousi Basin. The Zhaolaoyu Formation of the Middle-Upper Ordovician series in this area is characterized chiefly by hemipelagic thin-bedded lime mudstones interbedded with limestone breccias and calca-renites derived from gravity flow, In addition, there is a small amount of tuff, radiolarian chert and well-sorted thin-bedded calcarenite and calcisi-ltite which represent the equivalent of contourite. Body fossils are poor, mainly pelagic ostracod, radiolaria and graptolite. Benthonic organisms are rare, but deep-water trace fossils of the Nereites facies are abundant. Gravity flow deposits of the Zhaolaoyu Formation can be subdivided into five rock types: ( 1 ) homogeneous wackstone; ( 2 ) thin-bedded graded calcarenite; ( 3 ) graded rubble calcarenite; ( 4 ) limestone breccia with oriented fabric; and ( 5 ) chaotic limestone breccia. In general, the thin-bedded graded calcarenite and homogeneous wack-stones form turbidite with divisions BCE or CE of the Bouma sequence while the graded rubble calcarenite and homogeneous wackstones form turid-ite with divisions AE of the Bouma sequence.Limestone breccia with oriented fabric exhibits normal or inverse-to-normal grading. Tabular clasts are frequently sub-parallel to the bedding or imbricated. The features suggest that they were deposited from a gravally high-density turbidity current. Chaotic limestone breccias might have been debris flow sediments. The above lithofacies commonly form two specific associated sequences in the section. From bottom to top, the two sequences go as follows: ( 1 ) chaotic limestone breccia-→graded rubble calcarenite-→homogeneous wack- stone; ( 2 ) ungraded limestone breccia with oriented fabric-→inverse-to- normal grading limestone breccia-→graded rubble calcarenite-→calarenite with devisions BC of the Bauma sequence-→homogeneous wackstone. These sequences indicate that they are successive deposits derived from individual flow. However, the distinct lithofacies in the above sequences were probably deposited through several sedimention surges. Based on integrated sedimentological, paleontological and tectonic setting analyses, we suggest that the Weibei region, together with North China, be a united shallow-platform prior to the later period of the Middle Ordovician. Then it was subsided and developed into a continental margin of the back-arc basin owing to the subduction of the Qinling plate beneath the North China plate. The Fuping area might have been a N-E trending deep sea front trough that stretched from this back-arc basin into the North China carbonate platform.The gravity flow sediments were mainly transported in great sheet flows along the axis of the trough basin. These flows were probably resulted from the confluence of several minor gravity flows around the downslope margin of platform. The model presented here differs from either the submarine fan model or the carbonate slope model, but it is similar to the pattern of modern carbonate debris sheets of the Exuma Sound in the Bahamas.
1986, 4(1): 49-63.
Abstract:
Fiysch occurrs extensively in strata from Precambrian to Mesozoic in China. Since the 1950's, the research on flysch has been made, and a large number of data have been gathered. On the basis of these data and the author's observation,some problems concerning the study of flysch are discussed in this paper. The first part of this paper refers to some new views on the morphology of flysch. 1. Flysch is not completely composed of unitary rhythmic strata. It is usually composed of rhythmic strata separated by rock layers with a certain thickness and without rhythmic texture. The rhythmic and unrhythmic strata are interlaced with each other and form a higher grade combination called cyclothem, that is about scores or hundreds of meters in thickness. Every flysch formation can be divided into many cyclothems, Therefore, it is necessary to study both rhythmic and unrhythmic units in flysch at the same time. 2. The basic characteristics in a flysch rhythm do not lie in whether there exists a Bouma's sequence, which itself is merely an incomplete and idealized model. In fact, the rhythmic texture in flysch is more complex and diversified. One basic characteristic is the existence of graded bedding, which is shown not only in the A interval of Bouma's sequence, but also in all the other intervals. 3. The flysch rhythm is polygraded. Every interval in Boums's sequence may be heterogeneous. So it can be divided into many subordinate rhythms. For example, the subordinate rhythmic bedding in the A interval is mainly composed of sand ( or coarse silt ) layers separated by thin mud layers.But,in the E interval it is composed of mud layers seperated by thin sand layers. Some secondary parts in a subordinated rhythmic bedding appear to be lenticular or lens. Sometimes microrhythms, which may consist of graded bedding, exist within a secondary rhythum. 4. In the fine-detrital layers with only several centimeters in thickness, normal grading, reverse grading, and the transition between them may be discovered. In general, such a texture can be observed only by microscope. 5. There are large-scale cross beddings, foreset laminae and ripplemarks, including symmetric ones,microscale ones and interference ones. And there are also bidirectionnal crossbeddings,herringbone cross beddings,lens-like beddings, and abundant contemporaneous breccia in some flysch. Fragments of silt-stone may exist in the mudstone layer, and fragments of mudstone may exist in the siltstone layer. All this reflects that the sedimentary area has a shallow water environment with bottom currents, wave and tidal processes. The second part of this paper points out that the research on the nature of the formation order and formation series in which flysch occurs is of great significance in recognizing the plate tectonic setting in flysch accumulation.The formation order and series are the combination of some formations alternating vertically and horizontally during the development of the flysch basin. Three kinds of flysch formation order in China are classified as follows; 1 ) Eruptive rocks order; 2 ) Sedimentary rocks order; 3 ) E-ruptive sedimentary rocks order(table I). Their tectonic settings are respectively inter-plate, intra-plate, and continentalcrust rifting with micro-divergence processes. The origin of flysch is discussed in the third part. Reviewing the theorios on the origin of flysch, such as turbidity current, bottom current and oscillation, and taking the flasch of Later Ordovician in western Zhe-jiang Province as an example, the author interprets the genesis characteristics of shallow water with frequent bottom current process. On this basis, the author comes to the conclusion that the origin of flysch is diversitied, not simplex, like that of many other geological bodies. It is also considered that the turbidity current flysch and non-turbidity current flysch may exist simultaneously. The textures, such as rhythum, graded bedding, and the Bouma's sequence are not the bases to identify flysch origin, but the indicators to recognize it. In order To discriminate the origin of flysch,it is necessary to further reveal its concrete characteristics in many res-Pects。Some signs of distinguishing turbidity current flysch from nontur-bidity current flysch are listed in this paper.
Fiysch occurrs extensively in strata from Precambrian to Mesozoic in China. Since the 1950's, the research on flysch has been made, and a large number of data have been gathered. On the basis of these data and the author's observation,some problems concerning the study of flysch are discussed in this paper. The first part of this paper refers to some new views on the morphology of flysch. 1. Flysch is not completely composed of unitary rhythmic strata. It is usually composed of rhythmic strata separated by rock layers with a certain thickness and without rhythmic texture. The rhythmic and unrhythmic strata are interlaced with each other and form a higher grade combination called cyclothem, that is about scores or hundreds of meters in thickness. Every flysch formation can be divided into many cyclothems, Therefore, it is necessary to study both rhythmic and unrhythmic units in flysch at the same time. 2. The basic characteristics in a flysch rhythm do not lie in whether there exists a Bouma's sequence, which itself is merely an incomplete and idealized model. In fact, the rhythmic texture in flysch is more complex and diversified. One basic characteristic is the existence of graded bedding, which is shown not only in the A interval of Bouma's sequence, but also in all the other intervals. 3. The flysch rhythm is polygraded. Every interval in Boums's sequence may be heterogeneous. So it can be divided into many subordinate rhythms. For example, the subordinate rhythmic bedding in the A interval is mainly composed of sand ( or coarse silt ) layers separated by thin mud layers.But,in the E interval it is composed of mud layers seperated by thin sand layers. Some secondary parts in a subordinated rhythmic bedding appear to be lenticular or lens. Sometimes microrhythms, which may consist of graded bedding, exist within a secondary rhythum. 4. In the fine-detrital layers with only several centimeters in thickness, normal grading, reverse grading, and the transition between them may be discovered. In general, such a texture can be observed only by microscope. 5. There are large-scale cross beddings, foreset laminae and ripplemarks, including symmetric ones,microscale ones and interference ones. And there are also bidirectionnal crossbeddings,herringbone cross beddings,lens-like beddings, and abundant contemporaneous breccia in some flysch. Fragments of silt-stone may exist in the mudstone layer, and fragments of mudstone may exist in the siltstone layer. All this reflects that the sedimentary area has a shallow water environment with bottom currents, wave and tidal processes. The second part of this paper points out that the research on the nature of the formation order and formation series in which flysch occurs is of great significance in recognizing the plate tectonic setting in flysch accumulation.The formation order and series are the combination of some formations alternating vertically and horizontally during the development of the flysch basin. Three kinds of flysch formation order in China are classified as follows; 1 ) Eruptive rocks order; 2 ) Sedimentary rocks order; 3 ) E-ruptive sedimentary rocks order(table I). Their tectonic settings are respectively inter-plate, intra-plate, and continentalcrust rifting with micro-divergence processes. The origin of flysch is discussed in the third part. Reviewing the theorios on the origin of flysch, such as turbidity current, bottom current and oscillation, and taking the flasch of Later Ordovician in western Zhe-jiang Province as an example, the author interprets the genesis characteristics of shallow water with frequent bottom current process. On this basis, the author comes to the conclusion that the origin of flysch is diversitied, not simplex, like that of many other geological bodies. It is also considered that the turbidity current flysch and non-turbidity current flysch may exist simultaneously. The textures, such as rhythum, graded bedding, and the Bouma's sequence are not the bases to identify flysch origin, but the indicators to recognize it. In order To discriminate the origin of flysch,it is necessary to further reveal its concrete characteristics in many res-Pects。Some signs of distinguishing turbidity current flysch from nontur-bidity current flysch are listed in this paper.
1986, 4(1): 77-85.
Abstract:
In the famous Rigeze area of South Tibet,ophiolitic sedimentary rock series with thickness of hundreds metres, is extensively outcropped in the upper part of the Yaluzangbu ophiolite suite. It obviously deposits on the dark-purple or grey-green pillow-shaped lavas and sheeted dikes and belongs to the late Jurassic and early Cretaceous age. The ophiolitic sedimentary rocks can be divided into three sections from bottom to top: 1 .Ophiolitic slumping deposits; 2 .Ophiolitic clastic deposits with zeolite layer; 3 .Fine-clastic tuffaceous mudstones with carbonatite layer. The main rock types are ophiolitic slumping accumulation rocks, ophiolitic graywackes, zeolite, tuffite, tuffaceous silty mudstones, carbonatite, ect. As the rock series has a close relation to thp ophiolite suite, the source of deposits is mainly from the underlying basic lava, denudation materials of sheeted dikes and differentiated materials of contemporaneous volcanic-lava. However, a lot of terrigenous components have gradually been to the upper part of the rock series. These complex sediments underwent different chemical and physical actions on the unique geological background in the whole diagenetic process. As a result, distinct changes of the original sediments took place. They are mainly as follows: 1 .Formed by the different iation of volcanic materials and the disintegration of basic lavas,the clay minerals have changed into illite and chlorite, with the exception of a little remainig montmorillonite and kaolinite. This kind of stable clay-mineral compositions shows that they have been in the late stage of diagenetic deuterogenesis. 2 .In the whole rock series, though there is less carbonalite, it has commonly recrystallized. The strong resorption and replacement of other clasts in rocks can obviously be seen, and the boundary of grains is vague and bay-like. Some horse-stones of volcanic clastic rocks are almost replaced by carbonatite, In addition, most of the clasts have the shadew structure of original grain outline and every grain around the replacement remains forms into a "cross extinction lump." 3 .A large amount of volcanic glass in the lower sediment-tuff has changed inot microlitic quartz or chalcedonite quartz, but some still have irregular appearance specifically possessed by volcanic glass, while radiolarian siliceous rocks in tuffite bud are composed of siliceous ooze. Its opal and cristobalite,through dewatering, compressing and burying, changed into chalcedonite, and then became chalceonitic quartz and microlitic quartz. After being filled with siliceous materials, a large amount of radiolarian in radiolarian siliceous was crystallized into chalcedonite quartz. Microlitic quartzs are of good euhedral crystal under the scanning electron micriscope. 4 .In the lower part of the rock scries, besides scattering zeolite discoved in graywacke also a few layers of zeolite rocks, which are composed of lau-montite, authigenic prehnite, quartz, etc. According to the characteristics of mineral composition, the laumontite is composed of plagioclase and volcanic rocks which formed in the diagenentic process. In this special sedimentary strata,the change of diagenesis becomes greater and greater from top to bottom. The upper sedimentary bed is in the mudstone form. A great amount kaolinite is still reserved in clay minerals. With the depth increasing most clay minerals were transformed into illite and chlorite, and a lot of volcanic glass and authigenic quartz had been transformed into illite and chlorite,and a lot of velcanic glass and aulnigenic guartz had been transformed into chalcedonite quartz or microlitic quartz. At the same time, microlitic authigenic formed, too. Scattering zeolite minerals began to appear until some typical minerals of the late stage of diagenesis dueterogenesis appeared, such as laumontite and prehnite. These mtneralogical changes represent a complete diagenesis. Although this sedimentary rock series is not very thick, its diagensis changes are great. The factors influencing the diagenesis t
In the famous Rigeze area of South Tibet,ophiolitic sedimentary rock series with thickness of hundreds metres, is extensively outcropped in the upper part of the Yaluzangbu ophiolite suite. It obviously deposits on the dark-purple or grey-green pillow-shaped lavas and sheeted dikes and belongs to the late Jurassic and early Cretaceous age. The ophiolitic sedimentary rocks can be divided into three sections from bottom to top: 1 .Ophiolitic slumping deposits; 2 .Ophiolitic clastic deposits with zeolite layer; 3 .Fine-clastic tuffaceous mudstones with carbonatite layer. The main rock types are ophiolitic slumping accumulation rocks, ophiolitic graywackes, zeolite, tuffite, tuffaceous silty mudstones, carbonatite, ect. As the rock series has a close relation to thp ophiolite suite, the source of deposits is mainly from the underlying basic lava, denudation materials of sheeted dikes and differentiated materials of contemporaneous volcanic-lava. However, a lot of terrigenous components have gradually been to the upper part of the rock series. These complex sediments underwent different chemical and physical actions on the unique geological background in the whole diagenetic process. As a result, distinct changes of the original sediments took place. They are mainly as follows: 1 .Formed by the different iation of volcanic materials and the disintegration of basic lavas,the clay minerals have changed into illite and chlorite, with the exception of a little remainig montmorillonite and kaolinite. This kind of stable clay-mineral compositions shows that they have been in the late stage of diagenetic deuterogenesis. 2 .In the whole rock series, though there is less carbonalite, it has commonly recrystallized. The strong resorption and replacement of other clasts in rocks can obviously be seen, and the boundary of grains is vague and bay-like. Some horse-stones of volcanic clastic rocks are almost replaced by carbonatite, In addition, most of the clasts have the shadew structure of original grain outline and every grain around the replacement remains forms into a "cross extinction lump." 3 .A large amount of volcanic glass in the lower sediment-tuff has changed inot microlitic quartz or chalcedonite quartz, but some still have irregular appearance specifically possessed by volcanic glass, while radiolarian siliceous rocks in tuffite bud are composed of siliceous ooze. Its opal and cristobalite,through dewatering, compressing and burying, changed into chalcedonite, and then became chalceonitic quartz and microlitic quartz. After being filled with siliceous materials, a large amount of radiolarian in radiolarian siliceous was crystallized into chalcedonite quartz. Microlitic quartzs are of good euhedral crystal under the scanning electron micriscope. 4 .In the lower part of the rock scries, besides scattering zeolite discoved in graywacke also a few layers of zeolite rocks, which are composed of lau-montite, authigenic prehnite, quartz, etc. According to the characteristics of mineral composition, the laumontite is composed of plagioclase and volcanic rocks which formed in the diagenentic process. In this special sedimentary strata,the change of diagenesis becomes greater and greater from top to bottom. The upper sedimentary bed is in the mudstone form. A great amount kaolinite is still reserved in clay minerals. With the depth increasing most clay minerals were transformed into illite and chlorite, and a lot of volcanic glass and authigenic quartz had been transformed into illite and chlorite,and a lot of velcanic glass and aulnigenic guartz had been transformed into chalcedonite quartz or microlitic quartz. At the same time, microlitic authigenic formed, too. Scattering zeolite minerals began to appear until some typical minerals of the late stage of diagenesis dueterogenesis appeared, such as laumontite and prehnite. These mtneralogical changes represent a complete diagenesis. Although this sedimentary rock series is not very thick, its diagensis changes are great. The factors influencing the diagenesis t
1986, 4(1): 96-103.
Abstract:
The gas reservoir in the Lower Triassic Jialingjiang Group is the main gas layer in the Sichuan Basin. There are two different views on its gas source, non-indigenous gas and indigeneous gas. Those who hold the view that the gas is non-indigenous have the following opinions; ( 1 ) The organic carbon content in the Jialingjiang limestone is lower (about 0.1%), but the organic carbon content in the underlying Leping coal series (Upper Permian) is higher (over 0.5%);(2) The organic matter maturity of solid state in the Jialingjiang Group is in the stage between maturity to high-maturity (Ro 0.95 to 1.5%), In addition, the group also produces condensate and light crude oil(about 0.80 in speC1fic weight).Its δ13C value and the heavy hydrocarbon content show an unusual negative corre-lationship that is δ13C1＞δ13C2＞δ13C3.Therefore,the gas of high δsup>131value formed in the Leping coal series and then migrated to the Jialingjiang Group. The author holds the view that limestone-reservoired gas in the Jialingjiang Group is indigenous, and the main reasons are as follows: ( 1 ) The Jialingjiang Group is an interbedding between limestone, and gypsum. The limestone contains organic rocks with rich sapropel, which can be regarded as gas source rocks. This gas-producing layer is closed by the gypsum layer and has no apparent fault connecting with Permian; therefore, the Permian gas could not migrate into the Jialingjiang Group on a large scale and form area gas-producing layer. ( 2 ) The geochemical indices in the codensate and light crude oil of Jialingjiang Group are closely related to the source rocks of sapropel, but they are different from the source rocks of deviated humus in the Leping coal scries. ( 3 ) The maturity of the natural gas in the Jialingjiang Group, whi- ch is determined according to the different values of carbon isotope of gaseous hydrocarbon, is the same as the maturity of solid-state organic matter in the Jialingjiang Group. The maturity of the natural gas in the Indo-Chinese paleobuildup part in Luzhou belongs to high maturity at the early stage. Therefore, δ13C1＜δ13C2＜δ13C3 indicates nomal distribution in carbon isotope of gaseous hydrocarbon, but in the periphery of the Indo-Chinese Paleo-buildup part, the maturity of the natural gas belongs to high maturity at the late stage. And so,δ13C1＞δ13C2＜δ13C3 shows inverse distribution in carbon isotope of gaseous hydrocarbon. It is a reflection of maturity, but not the gas of highδ13C1 value from the Leping coal series, which is mixed into the peripery of the Indo-Chinese paleo-buildup part.
The gas reservoir in the Lower Triassic Jialingjiang Group is the main gas layer in the Sichuan Basin. There are two different views on its gas source, non-indigenous gas and indigeneous gas. Those who hold the view that the gas is non-indigenous have the following opinions; ( 1 ) The organic carbon content in the Jialingjiang limestone is lower (about 0.1%), but the organic carbon content in the underlying Leping coal series (Upper Permian) is higher (over 0.5%);(2) The organic matter maturity of solid state in the Jialingjiang Group is in the stage between maturity to high-maturity (Ro 0.95 to 1.5%), In addition, the group also produces condensate and light crude oil(about 0.80 in speC1fic weight).Its δ13C value and the heavy hydrocarbon content show an unusual negative corre-lationship that is δ13C1＞δ13C2＞δ13C3.Therefore,the gas of high δsup>131value formed in the Leping coal series and then migrated to the Jialingjiang Group. The author holds the view that limestone-reservoired gas in the Jialingjiang Group is indigenous, and the main reasons are as follows: ( 1 ) The Jialingjiang Group is an interbedding between limestone, and gypsum. The limestone contains organic rocks with rich sapropel, which can be regarded as gas source rocks. This gas-producing layer is closed by the gypsum layer and has no apparent fault connecting with Permian; therefore, the Permian gas could not migrate into the Jialingjiang Group on a large scale and form area gas-producing layer. ( 2 ) The geochemical indices in the codensate and light crude oil of Jialingjiang Group are closely related to the source rocks of sapropel, but they are different from the source rocks of deviated humus in the Leping coal scries. ( 3 ) The maturity of the natural gas in the Jialingjiang Group, whi- ch is determined according to the different values of carbon isotope of gaseous hydrocarbon, is the same as the maturity of solid-state organic matter in the Jialingjiang Group. The maturity of the natural gas in the Indo-Chinese paleobuildup part in Luzhou belongs to high maturity at the early stage. Therefore, δ13C1＜δ13C2＜δ13C3 indicates nomal distribution in carbon isotope of gaseous hydrocarbon, but in the periphery of the Indo-Chinese Paleo-buildup part, the maturity of the natural gas belongs to high maturity at the late stage. And so,δ13C1＞δ13C2＜δ13C3 shows inverse distribution in carbon isotope of gaseous hydrocarbon. It is a reflection of maturity, but not the gas of highδ13C1 value from the Leping coal series, which is mixed into the peripery of the Indo-Chinese paleo-buildup part.
1986, 4(1): 110-116.
Abstract:
The SO42-concentration in interstitial water and overlying water is analysed and examined with the gravity method and the volumetric method respectively. The results of both methods are consistent with each other. The gradient method is mainly used for measuring diffusion flux of SO42-.This method is based on Fick's first law, and proposed by referring to the use of SO42- gradient flux in the studies made by Goldhaber, et al.(1974),Berner(1976) and Goldhaber, etal.(1977).The equation is F =φDs (dc/dz) z=0, and may be simplified as F=-φDs△c/△z to measure.SO42-flux similarly. According to the data of SO42- gradient flux,some problems have been disccussed in the following aspects: 1.The SO42-concentration in the overlying water is lower than that in the surficial interstitial water significantly under the influence of the Changjiang River dilute water in the nearshore studying area in summer( June-August ).The seasonal negative SO42-flux diffusing up to the overlying water is produced thereby.In the fall, the SO42- concentration in the overlying water increases to or even beyond its concentration in the surficial interstitial water without the fresh water influence of the Changjiang River in the nearshore area mentioned above. In addition, the SO42-concentration in the surficial interstitial water is slightly lower tha that in summer with the Eh value decreasing and the density of SO42-reduction bacteria increasing in the autumn sediment. Therefore,the SO42-flux acrossing sediment-water interface is mostly transforming into positive flux which diffuses down to sediment in the fall in the nearshore studying area.2.The regional distribution characteristics of negative SO42-flux acrossing sediment-water interface is significant in the nearshore studying area in summer,the higher SO42- fluxes occur in the triangular region which is located in the southwest of the nearshore studying area(Fig.4),such as stations G8140, G8003,G8005,G8025,etc.and lower SO42- fluxes occur in the northeast of the nearshore studying area, such as stations G8009, G8001, G8011, etc.,These characteristics seem to be related to sediment types because the former are generally muddy stations, and the latter are generally sandy stations.So there is a negative correlation between SO42-flux and sandy content in sediments(Fig. 5 b).In addition,the negativeSO42- fluxes crossing sediment-water interface are significantly relative to disturbance of benthonic faunas because the higher density of benthonic faunas is in the sandy station in which the SO42-flux is lower.Therefore,the negative correlation between SO42-flux and the density of benthonic faunas is revealed (Fig. 5 a).The reason of this relationship is that the lower density of benthic faunas occurs in muddy stations and the higher density occur in sandy stations(Fig. 4 ),in which more benthonic species exist and benthonic disturbance is more powerful, surely resulting in more mixing between the overlying water with lower SO42-concentration and surficial interstitial water with higher SO42-concentration through benthonic irrigation.Thus the gradient of SO42-concentration and SO42-flux measured by the gradient method are reduced near the interface thereby. The results are as follows: 1.The SO42-fluxes crossing sediment-water interface are seasonal negative fluxes diffusing from sediments up to overlying water column in the nearshore area of the East China Sea continental shelf in summer. The main reason is that the Changjiang River fresh water seasonally dilutes SO42-in overlying sea water of the nearshore sea bottom. 2 .There is an obvious correlation among SO42-flux crossing sediment-water interface, region and sediment types.The main reason of this correlation is that the bentonic disturbance influenced by dilute fresh water restricts the SO42-concentration in overlying water and surficial interstitial water.
The SO42-concentration in interstitial water and overlying water is analysed and examined with the gravity method and the volumetric method respectively. The results of both methods are consistent with each other. The gradient method is mainly used for measuring diffusion flux of SO42-.This method is based on Fick's first law, and proposed by referring to the use of SO42- gradient flux in the studies made by Goldhaber, et al.(1974),Berner(1976) and Goldhaber, etal.(1977).The equation is F =φDs (dc/dz) z=0, and may be simplified as F=-φDs△c/△z to measure.SO42-flux similarly. According to the data of SO42- gradient flux,some problems have been disccussed in the following aspects: 1.The SO42-concentration in the overlying water is lower than that in the surficial interstitial water significantly under the influence of the Changjiang River dilute water in the nearshore studying area in summer( June-August ).The seasonal negative SO42-flux diffusing up to the overlying water is produced thereby.In the fall, the SO42- concentration in the overlying water increases to or even beyond its concentration in the surficial interstitial water without the fresh water influence of the Changjiang River in the nearshore area mentioned above. In addition, the SO42-concentration in the surficial interstitial water is slightly lower tha that in summer with the Eh value decreasing and the density of SO42-reduction bacteria increasing in the autumn sediment. Therefore,the SO42-flux acrossing sediment-water interface is mostly transforming into positive flux which diffuses down to sediment in the fall in the nearshore studying area.2.The regional distribution characteristics of negative SO42-flux acrossing sediment-water interface is significant in the nearshore studying area in summer,the higher SO42- fluxes occur in the triangular region which is located in the southwest of the nearshore studying area(Fig.4),such as stations G8140, G8003,G8005,G8025,etc.and lower SO42- fluxes occur in the northeast of the nearshore studying area, such as stations G8009, G8001, G8011, etc.,These characteristics seem to be related to sediment types because the former are generally muddy stations, and the latter are generally sandy stations.So there is a negative correlation between SO42-flux and sandy content in sediments(Fig. 5 b).In addition,the negativeSO42- fluxes crossing sediment-water interface are significantly relative to disturbance of benthonic faunas because the higher density of benthonic faunas is in the sandy station in which the SO42-flux is lower.Therefore,the negative correlation between SO42-flux and the density of benthonic faunas is revealed (Fig. 5 a).The reason of this relationship is that the lower density of benthic faunas occurs in muddy stations and the higher density occur in sandy stations(Fig. 4 ),in which more benthonic species exist and benthonic disturbance is more powerful, surely resulting in more mixing between the overlying water with lower SO42-concentration and surficial interstitial water with higher SO42-concentration through benthonic irrigation.Thus the gradient of SO42-concentration and SO42-flux measured by the gradient method are reduced near the interface thereby. The results are as follows: 1.The SO42-fluxes crossing sediment-water interface are seasonal negative fluxes diffusing from sediments up to overlying water column in the nearshore area of the East China Sea continental shelf in summer. The main reason is that the Changjiang River fresh water seasonally dilutes SO42-in overlying sea water of the nearshore sea bottom. 2 .There is an obvious correlation among SO42-flux crossing sediment-water interface, region and sediment types.The main reason of this correlation is that the bentonic disturbance influenced by dilute fresh water restricts the SO42-concentration in overlying water and surficial interstitial water.
1986, 4(1): 118-125.
Abstract:
Shanhuba in Chongqing is a channel bar in the upper reaches of the Changjiang River. In the different parts of the bar, there are a lot of different forms of stratification and bedding plane structure. The various ripple marks on the surface of the bar are comparable to those in the near-shore intertidal area. The typical"inverted V"sturcture on the cross-strati- fication of the channel bar is especially better than that on beach barrier and beach cusp. The sedimentary model established by studying the relationship between the bedding structure and grain-size cyclothems of the channel bar and its sedimentary history, can be used to look for fluvial sedimentary deposits. The Shanhuba channel bar in Chongqing will possibly be one of the best localities for making geological tours and researches on present channel bar.
Shanhuba in Chongqing is a channel bar in the upper reaches of the Changjiang River. In the different parts of the bar, there are a lot of different forms of stratification and bedding plane structure. The various ripple marks on the surface of the bar are comparable to those in the near-shore intertidal area. The typical"inverted V"sturcture on the cross-strati- fication of the channel bar is especially better than that on beach barrier and beach cusp. The sedimentary model established by studying the relationship between the bedding structure and grain-size cyclothems of the channel bar and its sedimentary history, can be used to look for fluvial sedimentary deposits. The Shanhuba channel bar in Chongqing will possibly be one of the best localities for making geological tours and researches on present channel bar.
1986, 4(1): 20-33.
Abstract:
Natural organic pigments can be found in sediments, crude oil, coal bitumen, oil shales, etc. A new organic pigment has been discovered in Tertiary-Sinian carbonates and other strata. Obviously, it originates mainly from organisms. It is of practical and theoretical significance in petroleum geology. This paper deals with my study on six Cambrian and Sinian specimens. First, the specimens were observed and identified by means of scanning electron microscop and microscope. Second, the specimens were characte-rized by palaeontology. It has been discovered that the main organisms in the specimens are the lowest bluegreen algae. No other organisms were found. Then, the pigment was extracted from geological samples by means of chloroform. Its solution was evaporated to nearly dry material. Later, the organic pigment extract was dissolved in n-hexane and evaporated to a volume of l-2ml, which was separated by column chromatography into three fractions -paraffin hydrocarbon, aromatic hydrocarbon and non-hydrocarbon. The non-hydrocarbon fraction was further separated by using thin layer chromatography of silicon G. The purified pigment compound was identified and studied by using the following instruments and methods: 1. Pigment element analysis: The elememt analysis was performed on a Italian 1106 element analyser, and the results are as follows: C = 71.3%, O=8.30%, H=7.63%, N=12.73%. Their ratio is: C:H:O:N: = 11.43:14. 67:1:1.69. The experimental formula of pigment is C22 H28 O2 N2. 2. SEM/EDAS analysis of metal ion in pigment: Metal ion in pigment was detected on a SEM/EDAX-501B. The analysis was made with the following method. Pigment was coated on the sample analyser and then determined by using energy spectroscopy scanning from sodium of atomic number 11 to uranium of atomic number 92, but no metal ion was found. 3. Ultraviolet-visible spectrophotometry: The sample was scanned from 200nm to 700nm. No absorption was seen in the ultraviolet range. But there were two absorption peaks in the visible range, 490nm and 520nm. Two same absorption peaks were found in the visible rang by continuous wavelength scanning on the CS-910 Dual-wavelength TLC scanner. 4. Fluorescent spectrophotometry: Since the red pigment has no ultraviolet absorption peaks because of the absence of its characteristic absorption in the ultraviolet range, there are also no characteristic fluorescence absorption peaks. 5. Gas chromatography: The pigment was analyzed by using 103 Gas Chromatography equipped with standard flame ionization detector (FID). The conditions are : glass capillary column, 47m length, 0.25 mm i.d. stationary phase MPPS. The temperature was programmed from 86℃ to 330℃ with 6℃/min. The peak didn't appear till 328℃. The analysis showed that the pigment was further purified after using TLC separation. 6. Mass spectrometric identification: The mass spectra were obtained on a D-300 mass spectrometer equipped with a solid sample probe. Samples were directly put in by a solid probe. The mass spectra showed that the main peaks were m/e 367 and 275. Based on these data, the author proposed a possible structure of the pigment. 7. ET-IR spectrophotometry identification: The result of ET-IR spectrum showed that the pigment had the following functional groups: the peak at 1708.9cm~(-1) representing carbonyl groups, the peaks at 2924.1cm~(-1), 1377.2 cm~(-1), and 2854.6cm~(-1), 1458.2cm~(-1) representing methyl and methylene respectively; and 3200cm~(-1) - 3600~(-1) absorption range indicating the occurrence ofNH group. 8. Nuclear magnetic resonance:Nuclear magnetic resonance spectra were recorded at 90 MHZ. CDCL3 was used as solvent with TMS internal reference. The nuclear magnetic resonance spectra showed the occurrence of RCH3, RCH2, NH, etc. The author believes that the pigment might originate from algae. Based on the above information and results, the author proposes the structure of the pigment for discussion. The paper covers in some details the reason of the pigment structure and its possible precursor, as well as theorigin of this pigment. Finally,the analyticity data of twelve core samples from a basin in China are listed showing the variation of the content of this pigment with depth,and its application to the petroleum exploration is discussed as follows:This pigment compound may be used as an index to identify the origin of organize matters,the type of source materials and the diagenetic environment of organic matters,and it can also be used to reflect the maturity and evolutional level of organic matters.
Natural organic pigments can be found in sediments, crude oil, coal bitumen, oil shales, etc. A new organic pigment has been discovered in Tertiary-Sinian carbonates and other strata. Obviously, it originates mainly from organisms. It is of practical and theoretical significance in petroleum geology. This paper deals with my study on six Cambrian and Sinian specimens. First, the specimens were observed and identified by means of scanning electron microscop and microscope. Second, the specimens were characte-rized by palaeontology. It has been discovered that the main organisms in the specimens are the lowest bluegreen algae. No other organisms were found. Then, the pigment was extracted from geological samples by means of chloroform. Its solution was evaporated to nearly dry material. Later, the organic pigment extract was dissolved in n-hexane and evaporated to a volume of l-2ml, which was separated by column chromatography into three fractions -paraffin hydrocarbon, aromatic hydrocarbon and non-hydrocarbon. The non-hydrocarbon fraction was further separated by using thin layer chromatography of silicon G. The purified pigment compound was identified and studied by using the following instruments and methods: 1. Pigment element analysis: The elememt analysis was performed on a Italian 1106 element analyser, and the results are as follows: C = 71.3%, O=8.30%, H=7.63%, N=12.73%. Their ratio is: C:H:O:N: = 11.43:14. 67:1:1.69. The experimental formula of pigment is C22 H28 O2 N2. 2. SEM/EDAS analysis of metal ion in pigment: Metal ion in pigment was detected on a SEM/EDAX-501B. The analysis was made with the following method. Pigment was coated on the sample analyser and then determined by using energy spectroscopy scanning from sodium of atomic number 11 to uranium of atomic number 92, but no metal ion was found. 3. Ultraviolet-visible spectrophotometry: The sample was scanned from 200nm to 700nm. No absorption was seen in the ultraviolet range. But there were two absorption peaks in the visible range, 490nm and 520nm. Two same absorption peaks were found in the visible rang by continuous wavelength scanning on the CS-910 Dual-wavelength TLC scanner. 4. Fluorescent spectrophotometry: Since the red pigment has no ultraviolet absorption peaks because of the absence of its characteristic absorption in the ultraviolet range, there are also no characteristic fluorescence absorption peaks. 5. Gas chromatography: The pigment was analyzed by using 103 Gas Chromatography equipped with standard flame ionization detector (FID). The conditions are : glass capillary column, 47m length, 0.25 mm i.d. stationary phase MPPS. The temperature was programmed from 86℃ to 330℃ with 6℃/min. The peak didn't appear till 328℃. The analysis showed that the pigment was further purified after using TLC separation. 6. Mass spectrometric identification: The mass spectra were obtained on a D-300 mass spectrometer equipped with a solid sample probe. Samples were directly put in by a solid probe. The mass spectra showed that the main peaks were m/e 367 and 275. Based on these data, the author proposed a possible structure of the pigment. 7. ET-IR spectrophotometry identification: The result of ET-IR spectrum showed that the pigment had the following functional groups: the peak at 1708.9cm~(-1) representing carbonyl groups, the peaks at 2924.1cm~(-1), 1377.2 cm~(-1), and 2854.6cm~(-1), 1458.2cm~(-1) representing methyl and methylene respectively; and 3200cm~(-1) - 3600~(-1) absorption range indicating the occurrence ofNH group. 8. Nuclear magnetic resonance:Nuclear magnetic resonance spectra were recorded at 90 MHZ. CDCL3 was used as solvent with TMS internal reference. The nuclear magnetic resonance spectra showed the occurrence of RCH3, RCH2, NH, etc. The author believes that the pigment might originate from algae. Based on the above information and results, the author proposes the structure of the pigment for discussion. The paper covers in some details the reason of the pigment structure and its possible precursor, as well as theorigin of this pigment. Finally,the analyticity data of twelve core samples from a basin in China are listed showing the variation of the content of this pigment with depth,and its application to the petroleum exploration is discussed as follows:This pigment compound may be used as an index to identify the origin of organize matters,the type of source materials and the diagenetic environment of organic matters,and it can also be used to reflect the maturity and evolutional level of organic matters.
1986, 4(1): 43-48.
Abstract:
The Lower Carboniferous Series is well developed in the Chanxian County area and can be divided into three formations: Jinling (C1j) , Ga-olishan ( C1g), and Hezhou ( C1h ) Formations. It is underlain by terrigenous clastic rocks of the Wutong Formation of Upper Devonian Series (D3w)and overlian by the carbonate rocks of the Huanglong Formation of the Middle Carboniferous series ( C2h ) . These formations are mostly composed of marine carbonates and commonly associated with sandstones and mudstones. It is 29 meters thick. Bioturbate structure appears mainly in the Gaolishan and Hezhou Formations. ( 1 ) Grey-white,medium-fine grained guartz arenite is a kind of very strong bioturbate rocks at the top of the Gaolishan Formation ( plate Ⅰ, 1、 2 ) . Two types of burrows can be seen on the weathered outcrop. The first type is large burrows with sand-filled laminae, which are 20cm long at the most, commonly 5-10cm long with diameters of 1-2cm. They mostly occur parallel to bedding planes. Some of them looks like heart-urchin burrows or possess echiurus burrows with spreites, and curved trails, redeposited tubes or conical pipes (H.E. Reineck, 1980, Fig. 554). The second type is shorter,single, bifurcated, or U-shaped borrws, perpendicular orinclined to bedding planes. The delicate forms can be preserved in single burrow systems. Most of them consist of dense, contorted, and interpenetrating burrows. These sandstones are the sediments of retransported organisms. They are formed from foreshore to upper shoreface in sandy beach. ( 2 ) A particular bioturbate structure-regular feeding trail can be found in grey-black micrite in the lower part of the Hezhou Formation ( pl-ateI, 3 ) . It is distributed along the bedding planes. It looks like the one in Fig. 4-23 in the "Sand and Sandstone" (Pettijohn, 1972), and Sei-lacher's (1964) "Zoophycus-facies", which are horizontal burrows in deep- water deposits, representing the rare trace fossils of offshore. ( 3 ) The upper slag limestone in the upper part of the Hezhou Formation is also a kind of strong bioturbate rocks. The slag or honeycomb-shaped structure appears at the top of the beds.Burrows may be bored holes of worms, molluscs and echinoderms, etc., which are generally smooth and either vertical or inclined at different angles to bedding planes. The filling of the bored holes is yellowgreen limemud ( plate 4, 5, Fig.2 ) . They were formed in the environments from upper shoreface to foreshore. Undoubtedly, the discovery of these marks would be helpful to the fa-cies-analysis of the Lower Carboniferous Series in the Chaoxian County area.
The Lower Carboniferous Series is well developed in the Chanxian County area and can be divided into three formations: Jinling (C1j) , Ga-olishan ( C1g), and Hezhou ( C1h ) Formations. It is underlain by terrigenous clastic rocks of the Wutong Formation of Upper Devonian Series (D3w)and overlian by the carbonate rocks of the Huanglong Formation of the Middle Carboniferous series ( C2h ) . These formations are mostly composed of marine carbonates and commonly associated with sandstones and mudstones. It is 29 meters thick. Bioturbate structure appears mainly in the Gaolishan and Hezhou Formations. ( 1 ) Grey-white,medium-fine grained guartz arenite is a kind of very strong bioturbate rocks at the top of the Gaolishan Formation ( plate Ⅰ, 1、 2 ) . Two types of burrows can be seen on the weathered outcrop. The first type is large burrows with sand-filled laminae, which are 20cm long at the most, commonly 5-10cm long with diameters of 1-2cm. They mostly occur parallel to bedding planes. Some of them looks like heart-urchin burrows or possess echiurus burrows with spreites, and curved trails, redeposited tubes or conical pipes (H.E. Reineck, 1980, Fig. 554). The second type is shorter,single, bifurcated, or U-shaped borrws, perpendicular orinclined to bedding planes. The delicate forms can be preserved in single burrow systems. Most of them consist of dense, contorted, and interpenetrating burrows. These sandstones are the sediments of retransported organisms. They are formed from foreshore to upper shoreface in sandy beach. ( 2 ) A particular bioturbate structure-regular feeding trail can be found in grey-black micrite in the lower part of the Hezhou Formation ( pl-ateI, 3 ) . It is distributed along the bedding planes. It looks like the one in Fig. 4-23 in the "Sand and Sandstone" (Pettijohn, 1972), and Sei-lacher's (1964) "Zoophycus-facies", which are horizontal burrows in deep- water deposits, representing the rare trace fossils of offshore. ( 3 ) The upper slag limestone in the upper part of the Hezhou Formation is also a kind of strong bioturbate rocks. The slag or honeycomb-shaped structure appears at the top of the beds.Burrows may be bored holes of worms, molluscs and echinoderms, etc., which are generally smooth and either vertical or inclined at different angles to bedding planes. The filling of the bored holes is yellowgreen limemud ( plate 4, 5, Fig.2 ) . They were formed in the environments from upper shoreface to foreshore. Undoubtedly, the discovery of these marks would be helpful to the fa-cies-analysis of the Lower Carboniferous Series in the Chaoxian County area.
1986, 4(1): 64-76.
Abstract:
Features of the mode and occurrence of ore bodies, the mineral assemblages and the texture and structure of ores in bed-bound Pb-Zn sulphide deposits are characterized by the syngenetic deposition diagenetic miner-algenesis and obvious remoulding of double thermal solution. In order to examine the possible migration forms and the concentration mechanism of lead and zinc during hydrothemal mineralization, we have made studies on the composition of mineral inclusion. of spholerite and calcite the sulful isotope of galena and sphalerite and the thermodynamic-condition analysis of mineralization. On this basis, the solubility of galena and sphalerite are determined in the NaCl-solution containing organic matters ( for example, α-Lam, H3Cit, etc.) or NH4OH, at 90℃. The phalerite solublity in NaCl-solution containing organic matters or NH4OH has come up to the minimum metal concentration of mineralization (about n×10-5M), and it increases with the rise of concentration and temperature of ligand in the solution. A maximun solubility ( about 25× 10-5M) is found in α-Lam H3C-it solution at 90℃. In addition, on the basis of the simultaneous equilibrium theory of hydrothermal system,the accumulative stable constants of diffrent zinc-lead in organic and organic complexes at different temperature ( 30°, 50°, 70°, 90°) and different ionic strength ( I= 0.1, 0.5), are determined within the ranges of 1 atm and the pH 4-8 by using the electrone potential method. This paper deals with the remobilization of leadzinc sulphide in source beds, its factors controlling its limit,the migration form, stability and distribution of lead and zinc in the low-temperature hyorothemal solution, the reproduction of sphalerite, the crystalline deposit of galena and the deposit mechanism of galena and sphalerite. Our study shows that the ability of remobilization and migration is linear with the Fronaenus function φ and the Ledan function ψ. Its limit is controlled by the kind and temperature of ligand ion in solution and the thermodynamic conditions of environment, such as T, Eh, and pH. In the Me-Cl-H2O thermal saline water of low-temperature, the migration form of zinc is mainly Zn2+ when Log Cl- is -2. With the increase of T and (Cl-), Zn2+ is replaced by ZnCln2-n. ZnCl32-. and ZnCl31- is preponderant in high salinewa- ter. Pb2+prevails only at T100℃ and Log(Cl-)-2 . 5 . PbCl24 is preferred in all other conditions. On the basis of our study and analysis, we have pointed out that the mineralization solution is mainly the Na-Ca-Cl type of thermal brine water bearing nich orgahic matters. This kind of thermal brine water extracts metallogenetic elements from the source bed, and transports them to the favorable structural locations. Thus, they turn into lead-zinc sulfide deposits under the control of geochemical impediments.
Features of the mode and occurrence of ore bodies, the mineral assemblages and the texture and structure of ores in bed-bound Pb-Zn sulphide deposits are characterized by the syngenetic deposition diagenetic miner-algenesis and obvious remoulding of double thermal solution. In order to examine the possible migration forms and the concentration mechanism of lead and zinc during hydrothemal mineralization, we have made studies on the composition of mineral inclusion. of spholerite and calcite the sulful isotope of galena and sphalerite and the thermodynamic-condition analysis of mineralization. On this basis, the solubility of galena and sphalerite are determined in the NaCl-solution containing organic matters ( for example, α-Lam, H3Cit, etc.) or NH4OH, at 90℃. The phalerite solublity in NaCl-solution containing organic matters or NH4OH has come up to the minimum metal concentration of mineralization (about n×10-5M), and it increases with the rise of concentration and temperature of ligand in the solution. A maximun solubility ( about 25× 10-5M) is found in α-Lam H3C-it solution at 90℃. In addition, on the basis of the simultaneous equilibrium theory of hydrothermal system,the accumulative stable constants of diffrent zinc-lead in organic and organic complexes at different temperature ( 30°, 50°, 70°, 90°) and different ionic strength ( I= 0.1, 0.5), are determined within the ranges of 1 atm and the pH 4-8 by using the electrone potential method. This paper deals with the remobilization of leadzinc sulphide in source beds, its factors controlling its limit,the migration form, stability and distribution of lead and zinc in the low-temperature hyorothemal solution, the reproduction of sphalerite, the crystalline deposit of galena and the deposit mechanism of galena and sphalerite. Our study shows that the ability of remobilization and migration is linear with the Fronaenus function φ and the Ledan function ψ. Its limit is controlled by the kind and temperature of ligand ion in solution and the thermodynamic conditions of environment, such as T, Eh, and pH. In the Me-Cl-H2O thermal saline water of low-temperature, the migration form of zinc is mainly Zn2+ when Log Cl- is -2. With the increase of T and (Cl-), Zn2+ is replaced by ZnCln2-n. ZnCl32-. and ZnCl31- is preponderant in high salinewa- ter. Pb2+prevails only at T100℃ and Log(Cl-)-2 . 5 . PbCl24 is preferred in all other conditions. On the basis of our study and analysis, we have pointed out that the mineralization solution is mainly the Na-Ca-Cl type of thermal brine water bearing nich orgahic matters. This kind of thermal brine water extracts metallogenetic elements from the source bed, and transports them to the favorable structural locations. Thus, they turn into lead-zinc sulfide deposits under the control of geochemical impediments.
1986, 4(1): 87-99.
Abstract:
Yanchang series of the Triassic in Shanxi-Gansu-Ningxia Basin is lacustrine facies consisting of developed source rocks, reservoirs and cap rocks. Its depositing center is in the south of the basin where multiple-stage deltas were formed. They are the target stratum inoil exploration of low permeability sandstones. Wuqi Delta is a typical one in these deltas. It has a perfect vertical sequence made up by the bottom, front and top of the delta. If the distribution of the delta is mapped with drilling data within 6000 km2, it looks just like a lobate. It is one of the construction-type deltas, which were formed under the condition of parity energy from two directions of lake and river.Through delineating the deltas of different priods and connecting well by well,it may be seen that it was formed by overlapping four deltas of different periods and extended toward the lake center. The drilling results are described in details, and sand bodies both in the distributary streams of the delta plain and in the delta front are regarded as predominant reservoir belts, thus providing the basis for estimating this delta. Having described Wuqi Delta, the author analysed and summarized the development characteristics of the Later Triassic deltas in Shanxi-Gansu -Ningxia Basin and found out the following preliminary rules: ( 1 ) The deltas existing in a basin are always in groups, not in individuals; ( 2 ) The developing scale of deltas is mainly controlled by the supply degree of deposits; ( 3 ) There is a direct propotion between the vertical sequence thickness of the delta and its plane distribution area. The thicker the vertical sequence, the thicker the main sandbody and the better the permeability and porosity as well as the prospecting result; ( 4 ) Along with the formation, development and disappearance of the basin, the deltaic area has undergone a developing process from small to large and then to small. The period of deposit peak was slightly later than the heyday of basin formation; (5) There were major constuction periods and certain development areas for a delta in the basin. After each construction period, regional pla-inazation or swampezation occurred, thus a favourable prospecting area matched with source rocks, reservoirs and cap rocks was formed; ( 6 ) There are two kinds of combination types of deltas in various periods, overlap type and spread type. The former is characterized by overlapping of multiple-stage deltas and distributed in the northeast of the basin, which is the most favourable area to exploration. The later trans-versally spreads in wide area and is distributed in the western margin of the basin, where there would be a large oil area once oil is found there; ( 7 ) Oil prospects of deltaic system throughout the northeast part of this basin, the match relationship of source rocks and reservoir rocks, trap conditions and exploration difficulties are also discussed and evaluated. Finally, the author makes some suggestions concerning further drilling work.
Yanchang series of the Triassic in Shanxi-Gansu-Ningxia Basin is lacustrine facies consisting of developed source rocks, reservoirs and cap rocks. Its depositing center is in the south of the basin where multiple-stage deltas were formed. They are the target stratum inoil exploration of low permeability sandstones. Wuqi Delta is a typical one in these deltas. It has a perfect vertical sequence made up by the bottom, front and top of the delta. If the distribution of the delta is mapped with drilling data within 6000 km2, it looks just like a lobate. It is one of the construction-type deltas, which were formed under the condition of parity energy from two directions of lake and river.Through delineating the deltas of different priods and connecting well by well,it may be seen that it was formed by overlapping four deltas of different periods and extended toward the lake center. The drilling results are described in details, and sand bodies both in the distributary streams of the delta plain and in the delta front are regarded as predominant reservoir belts, thus providing the basis for estimating this delta. Having described Wuqi Delta, the author analysed and summarized the development characteristics of the Later Triassic deltas in Shanxi-Gansu -Ningxia Basin and found out the following preliminary rules: ( 1 ) The deltas existing in a basin are always in groups, not in individuals; ( 2 ) The developing scale of deltas is mainly controlled by the supply degree of deposits; ( 3 ) There is a direct propotion between the vertical sequence thickness of the delta and its plane distribution area. The thicker the vertical sequence, the thicker the main sandbody and the better the permeability and porosity as well as the prospecting result; ( 4 ) Along with the formation, development and disappearance of the basin, the deltaic area has undergone a developing process from small to large and then to small. The period of deposit peak was slightly later than the heyday of basin formation; (5) There were major constuction periods and certain development areas for a delta in the basin. After each construction period, regional pla-inazation or swampezation occurred, thus a favourable prospecting area matched with source rocks, reservoirs and cap rocks was formed; ( 6 ) There are two kinds of combination types of deltas in various periods, overlap type and spread type. The former is characterized by overlapping of multiple-stage deltas and distributed in the northeast of the basin, which is the most favourable area to exploration. The later trans-versally spreads in wide area and is distributed in the western margin of the basin, where there would be a large oil area once oil is found there; ( 7 ) Oil prospects of deltaic system throughout the northeast part of this basin, the match relationship of source rocks and reservoir rocks, trap conditions and exploration difficulties are also discussed and evaluated. Finally, the author makes some suggestions concerning further drilling work.
1986, 4(1): 104-109.
Abstract:
Owing to specific geological environment the surface of quartz sand in Antarctica has a distinguishing microstructure, which has not been found in any low-latitude ocean areas and continental shelves. In this paper, by analyzing the microstructure of quartz sand surface of the Prydz Bay, we try to know the distinguishing characteristics of quartz sand surface, corresponding sedimentary environment, and the mechanical,physical and chemical factors. Our observation of several hundred electron micrographes of quartz sand indicates that on the surface of quartz sand, there are not only common collision pits and silica deposits, but also the forms which are peculiar in the Antarctic ocean area, such as widely-developed step fractures, big con-choidal fractures, glacial striae, etc. The distributions of these microstruc-t ure types are controlled strictly by the concrete and special environments. According to the regularity reflected by the mentioned-above surface mic-rostructure types, the rounded degree of the quartz sand, and features of detrital mineral associations and distributions, the collection area can be divided into two sedimentary environments, underwater area and beach area. The former can also be divided into the east sub-region and the west sub-region The factors affecting the quartz sand surface forms in the beach area are mainly the physical weathering and glacial compression action under the condition of severe cold and arid climate. So on the sand surface occur a large number of irregular fractures, conchoidal fractures and step fractures. The edges and corners of most grains are sharp, and the rounded grains are found unfrequently. The Prydz Bay is in an environment of deep sea basin. Great flow-ices occur on the ocean surface in winter, and most of them melt in summer. The sediments at the ocean bottom derive mainly from the weathered rocks of land, which are washed by ice-water, and the fragments carried by glacial. The area are affected by five water masses. They are the superficial water in the summer, the Antarctic water in the winter, the plutonic water round the Antarctica, the bottom water of Antarctica and ice shelf water. These water masses, circulations and waves provide dynamic factors for the carrying, striking and rubbing of sediments. As a result, the forms of quartz sand surface have not only the features found in the beach area, but also peculiar glacial striae in the high-latitude area. In addition, the V-shaped dissolution pits of directional arrangement can be found. Compared with the beach area, this area has more rounded grains. This paper also centres on the time sequence of the exogenic force actions which result in the overlapping of the imprints on quartz sand surface.
Owing to specific geological environment the surface of quartz sand in Antarctica has a distinguishing microstructure, which has not been found in any low-latitude ocean areas and continental shelves. In this paper, by analyzing the microstructure of quartz sand surface of the Prydz Bay, we try to know the distinguishing characteristics of quartz sand surface, corresponding sedimentary environment, and the mechanical,physical and chemical factors. Our observation of several hundred electron micrographes of quartz sand indicates that on the surface of quartz sand, there are not only common collision pits and silica deposits, but also the forms which are peculiar in the Antarctic ocean area, such as widely-developed step fractures, big con-choidal fractures, glacial striae, etc. The distributions of these microstruc-t ure types are controlled strictly by the concrete and special environments. According to the regularity reflected by the mentioned-above surface mic-rostructure types, the rounded degree of the quartz sand, and features of detrital mineral associations and distributions, the collection area can be divided into two sedimentary environments, underwater area and beach area. The former can also be divided into the east sub-region and the west sub-region The factors affecting the quartz sand surface forms in the beach area are mainly the physical weathering and glacial compression action under the condition of severe cold and arid climate. So on the sand surface occur a large number of irregular fractures, conchoidal fractures and step fractures. The edges and corners of most grains are sharp, and the rounded grains are found unfrequently. The Prydz Bay is in an environment of deep sea basin. Great flow-ices occur on the ocean surface in winter, and most of them melt in summer. The sediments at the ocean bottom derive mainly from the weathered rocks of land, which are washed by ice-water, and the fragments carried by glacial. The area are affected by five water masses. They are the superficial water in the summer, the Antarctic water in the winter, the plutonic water round the Antarctica, the bottom water of Antarctica and ice shelf water. These water masses, circulations and waves provide dynamic factors for the carrying, striking and rubbing of sediments. As a result, the forms of quartz sand surface have not only the features found in the beach area, but also peculiar glacial striae in the high-latitude area. In addition, the V-shaped dissolution pits of directional arrangement can be found. Compared with the beach area, this area has more rounded grains. This paper also centres on the time sequence of the exogenic force actions which result in the overlapping of the imprints on quartz sand surface.
1986, 4(1): 126-127.
Abstract:
The phosphatic red algae were discovered in the phosphorites of Sinian Doushantuo Formation in South China. The follwing are places where the red algae occur: Yichang and Jingmen-Xianyang region in Hubei province, Shimen in Hunan Province, Kaiyang and Wengan in Guizhou Province, Hanzhong and Mianxian in Shanxi Province, Shangrao in Jiangxi Province, and so on. The red algae belong to different families or genus, but most of them belong to Solenopora in Solenoporacae. The thallus of the red algal has the forms of nodule, column or complex coagulum. The thallus is composed of radial trichomes. The mineral component making up the cell wall is micri-tic apatite. The inside of the cell is frequently polluted by organic substances. The discovery of the phosphatic red algae is of great significance to paleontology, stratigraphy and phosphorite mineralogy.
The phosphatic red algae were discovered in the phosphorites of Sinian Doushantuo Formation in South China. The follwing are places where the red algae occur: Yichang and Jingmen-Xianyang region in Hubei province, Shimen in Hunan Province, Kaiyang and Wengan in Guizhou Province, Hanzhong and Mianxian in Shanxi Province, Shangrao in Jiangxi Province, and so on. The red algae belong to different families or genus, but most of them belong to Solenopora in Solenoporacae. The thallus of the red algal has the forms of nodule, column or complex coagulum. The thallus is composed of radial trichomes. The mineral component making up the cell wall is micri-tic apatite. The inside of the cell is frequently polluted by organic substances. The discovery of the phosphatic red algae is of great significance to paleontology, stratigraphy and phosphorite mineralogy.
