1993 Vol. 11, No. 3
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Display Method:
1993, 11(3): 1-6.
Abstract:
Taking the Jurassic coal seams of the sourthern margin of Junggar Basin as an example, the present paper studied the fluvial sedmentary types that developed in the grand ground surface of meta - plainized and low - steep swamp, identfied five kinds of river courses and established their lateral evolution models, they are: braided flow meandering, high meandering, braided meandering and anastomosing river. The author concluded that the Jurassic coal -forming period have the feature of balanced supplement, that is,the basin's subsiding rate is equal to the sedimentary filling rate. Sediments that loaded by the rivers steadily differentiated according to the energy law and wide spreaded evenly. No sedimentary axis could be formed under such environment, but there are various kind of rivers devloping charicterized by siginificant laterl evolution. Braided meandering river and anastomosing river that identified by the author are different from each other in the aspects of rock assemblage, the ratio of thickness of the course to its overlying fine sediments, composition of micro - facies and so on, it can be deduced that the former carried multiple loads and has the feature of lateral accretion, while the later was developed in the low land of the swamp plain and its course is narrow, its sediments are fine and dominanted by suspended loads, its sedimentation is mainly vertical accretion. These two kinds of river are the typical stream forms that developing on the background of swamp. The sedimentary cycle of Jurassic coal-bearing strata in the southern marginof Jung gar basin is similar with that of non - marine Appalachian - type in North America, both of the cycles were started by water enchrochment that resulted from the accerleration of crust's subsidance and ended with the water dereliction that caused by the retarding of crust subsiding and the startingof uplifting. In the period of Badaowan to Toutunhe, a perfect enchroachment-dereliction cycle was formed, and swamp coal were mainly formed at the beginning of enchroachment (i.e., Badaowan period) and the end of dereliction (Xishanyao period). The most widely enchroachment and dereliction were occurred in San'gonghe and Toutunhe period respectively. This regularly sedimentary cycle are dominantly controlled by the activity of the overthr ust nappe which situated in the sourthem margin of the basin,whilst the sedimentary process and lateral evolution of swamp rivers may be mainly depended on the variation of palaeomorphlogic features, topographic slope, water dinamics and the condition of plant cover. The sedimentary sub-rythms (with the thickness of 1 - 100m) that caused by the differences of course types were considered to be the basic units of the cycles of coal -bearing strata, moreover, the basic units were controlled by tectonics and climate.
Taking the Jurassic coal seams of the sourthern margin of Junggar Basin as an example, the present paper studied the fluvial sedmentary types that developed in the grand ground surface of meta - plainized and low - steep swamp, identfied five kinds of river courses and established their lateral evolution models, they are: braided flow meandering, high meandering, braided meandering and anastomosing river. The author concluded that the Jurassic coal -forming period have the feature of balanced supplement, that is,the basin's subsiding rate is equal to the sedimentary filling rate. Sediments that loaded by the rivers steadily differentiated according to the energy law and wide spreaded evenly. No sedimentary axis could be formed under such environment, but there are various kind of rivers devloping charicterized by siginificant laterl evolution. Braided meandering river and anastomosing river that identified by the author are different from each other in the aspects of rock assemblage, the ratio of thickness of the course to its overlying fine sediments, composition of micro - facies and so on, it can be deduced that the former carried multiple loads and has the feature of lateral accretion, while the later was developed in the low land of the swamp plain and its course is narrow, its sediments are fine and dominanted by suspended loads, its sedimentation is mainly vertical accretion. These two kinds of river are the typical stream forms that developing on the background of swamp. The sedimentary cycle of Jurassic coal-bearing strata in the southern marginof Jung gar basin is similar with that of non - marine Appalachian - type in North America, both of the cycles were started by water enchrochment that resulted from the accerleration of crust's subsidance and ended with the water dereliction that caused by the retarding of crust subsiding and the startingof uplifting. In the period of Badaowan to Toutunhe, a perfect enchroachment-dereliction cycle was formed, and swamp coal were mainly formed at the beginning of enchroachment (i.e., Badaowan period) and the end of dereliction (Xishanyao period). The most widely enchroachment and dereliction were occurred in San'gonghe and Toutunhe period respectively. This regularly sedimentary cycle are dominantly controlled by the activity of the overthr ust nappe which situated in the sourthem margin of the basin,whilst the sedimentary process and lateral evolution of swamp rivers may be mainly depended on the variation of palaeomorphlogic features, topographic slope, water dinamics and the condition of plant cover. The sedimentary sub-rythms (with the thickness of 1 - 100m) that caused by the differences of course types were considered to be the basic units of the cycles of coal -bearing strata, moreover, the basic units were controlled by tectonics and climate.
1993, 11(3): 25-30.
Abstract:
In southern China there distributes widespreadly a thick suite of early Paleozoic flysch deposites extending from northern Guangdong.western Fujian.western Zhejiang.southern Jiangxi to south eastern Hunan, which make up an important geological component of southern China. The flysch, however, has been seldom studied with regard to sedimentology and there is few knowledge about the tectonic settings untill now. Paleozoic sandstones in southwestern Jiangxi are discussed petrologically and geochemically in the paper in order to identify their provenance and tectonic settings. The early Paleozoic deposits include the Cambrian and Ordovician and lack of the Silurian. The stratigraphic sequences are clear in the areas of Yongxin -Taihe and Congyi - Dayu. The Cambian is divided into three groups, i. e. Niujiaohe Group (L. Cam. ),Gaotan Group (M. Cam. )and Shuishi Group (U. Cam. ) and the Ordovician divided into five formations, Jueshangou (L. Ord. ). Qixiling (L. Ord. ). Longxi (M.Ord. ). Hanjiang (M.Ord. )and Shikou Formation (U. Ord. ). The sandstones are chiefly graywackes and the major detrital composition of it are quartz, feldspar and lith clact. The quartz content is very high (65 - 80%) and most of them are monocrystalline ones. Cathodolu-minescenece analysis of the quartz grain shows that most of the quartz are brown and less violet. Higher SiO2 content (79.9%). Lower Al2O3/SiO2 ratio (0. 13), higher Al2O3/(CaO + Na2O) (9. 94) ratio (9. 94) and higher K2O/Na2O ratio (1. 9) are the major elemental features of the sandstones. REE analysis of the sandstone manifests higher total REE content (167ppm), enreched LREE, higher (La/Yb). value (12. 51) and negative Eu abnormally. Compare the chemical composition of sandstones with those in the known tectonic settings.it shows that the former were formed in a passive continental margin and their provenance was sedimentary rocks and crystalline rocks including gneiss, schist and granitoids etc. There are some different ideas on the tectonics of southeastern China. Flysch in southwestern Jiangxi locates between Yangtze Plate and Cathaysian Plate tectonically. To the west of flysch belt is the littoral and neritic deposit facies area in the Yangtze Plate margin and to the east of it is Longquan - Jianou melange zone in northwestern margin of Cathaysian Plate. According to the plate tectonic pattern of southeast China.it can be inferred that the study area belongs to the passive margin of Yangtze Plate and the provenance are the basement and the cover of the plate.
In southern China there distributes widespreadly a thick suite of early Paleozoic flysch deposites extending from northern Guangdong.western Fujian.western Zhejiang.southern Jiangxi to south eastern Hunan, which make up an important geological component of southern China. The flysch, however, has been seldom studied with regard to sedimentology and there is few knowledge about the tectonic settings untill now. Paleozoic sandstones in southwestern Jiangxi are discussed petrologically and geochemically in the paper in order to identify their provenance and tectonic settings. The early Paleozoic deposits include the Cambrian and Ordovician and lack of the Silurian. The stratigraphic sequences are clear in the areas of Yongxin -Taihe and Congyi - Dayu. The Cambian is divided into three groups, i. e. Niujiaohe Group (L. Cam. ),Gaotan Group (M. Cam. )and Shuishi Group (U. Cam. ) and the Ordovician divided into five formations, Jueshangou (L. Ord. ). Qixiling (L. Ord. ). Longxi (M.Ord. ). Hanjiang (M.Ord. )and Shikou Formation (U. Ord. ). The sandstones are chiefly graywackes and the major detrital composition of it are quartz, feldspar and lith clact. The quartz content is very high (65 - 80%) and most of them are monocrystalline ones. Cathodolu-minescenece analysis of the quartz grain shows that most of the quartz are brown and less violet. Higher SiO2 content (79.9%). Lower Al2O3/SiO2 ratio (0. 13), higher Al2O3/(CaO + Na2O) (9. 94) ratio (9. 94) and higher K2O/Na2O ratio (1. 9) are the major elemental features of the sandstones. REE analysis of the sandstone manifests higher total REE content (167ppm), enreched LREE, higher (La/Yb). value (12. 51) and negative Eu abnormally. Compare the chemical composition of sandstones with those in the known tectonic settings.it shows that the former were formed in a passive continental margin and their provenance was sedimentary rocks and crystalline rocks including gneiss, schist and granitoids etc. There are some different ideas on the tectonics of southeastern China. Flysch in southwestern Jiangxi locates between Yangtze Plate and Cathaysian Plate tectonically. To the west of flysch belt is the littoral and neritic deposit facies area in the Yangtze Plate margin and to the east of it is Longquan - Jianou melange zone in northwestern margin of Cathaysian Plate. According to the plate tectonic pattern of southeast China.it can be inferred that the study area belongs to the passive margin of Yangtze Plate and the provenance are the basement and the cover of the plate.
1993, 11(3): 44-51.
Abstract:
The mixing of gases is ubiquitous in nature because of their special physical property. The mixed gas is formed by mixing of different genetic types of natural gases,and reflected obviously the gas geochemical features. If define one origin type of natural gas as one end member, the mixed gases would be divided into two. three and multiple end members. The common and significant type of mixed gas is of two end members which consists of three large groups: (a)mixing of gas with inorganic and organic origins ;(b)mixing of organic origin gases with different source type; (c)mixing of gases with different evloution stags; Gas migration, especially second migration that caused by diffusion and infiltration, is the main way which make the mixing of different types of gases. The first condition for mixing of natural gases is the existence of gas sources of different types and evolution stages. The chemical composition,stable isotopic composition of carbon and hydrogen and the noble gas isotopic composition are the main markers to differentiate mixed gases. Isotopic composition of the noble gas is an important tool to differentiate the mixed natural gases with crust and mantle sources,while the stable isotopes are to differentiate the mixed natural gases with different genetic types and evlution stages. It should be pointed out that it could effectively differentiate mixed gases by comobining geologic backgrounds and various geo-chemical parameters. By study the mechannism and conditions of mixed gases formation and analyse some examples,the mixing model of two -member gases was established.
The mixing of gases is ubiquitous in nature because of their special physical property. The mixed gas is formed by mixing of different genetic types of natural gases,and reflected obviously the gas geochemical features. If define one origin type of natural gas as one end member, the mixed gases would be divided into two. three and multiple end members. The common and significant type of mixed gas is of two end members which consists of three large groups: (a)mixing of gas with inorganic and organic origins ;(b)mixing of organic origin gases with different source type; (c)mixing of gases with different evloution stags; Gas migration, especially second migration that caused by diffusion and infiltration, is the main way which make the mixing of different types of gases. The first condition for mixing of natural gases is the existence of gas sources of different types and evolution stages. The chemical composition,stable isotopic composition of carbon and hydrogen and the noble gas isotopic composition are the main markers to differentiate mixed gases. Isotopic composition of the noble gas is an important tool to differentiate the mixed natural gases with crust and mantle sources,while the stable isotopes are to differentiate the mixed natural gases with different genetic types and evlution stages. It should be pointed out that it could effectively differentiate mixed gases by comobining geologic backgrounds and various geo-chemical parameters. By study the mechannism and conditions of mixed gases formation and analyse some examples,the mixing model of two -member gases was established.
1993, 11(3): 57-63.
Abstract:
Some freshwater Molluscs shells are collected from modern freshwater lake and Quternary stratum in China,in which climate and environment have been known in detail. The oxygen istopic composition of freshwater Molluscs shells are analysed for discussing relationship between the oxygen isotopic composition of shell and terrestrial climate and enviroment,and it used to reconstruct the past climatic chang. In this paper, the whole shell sample are analysed for discussing relationship between shell δ18OPDB and annual mean temperature and δ18OSMOW of lake water. The results show that: Molluscs shell in freshwater Lake are rich in O.δ18 OPDB5‰, in comparision with marine Molluscs. The δ18OPDB value of Molluscs shells which lived in same area are similar; but that which lived in different area are different. During moisture climate, δ18OPDB value of shells range from -5. 1～-10. 2‰. The shell is richer in O, with of gtadually increasing. δ18OPDB of shell is related to δ18OP(SMOW) of annual mean precipitation. The linear equation is δ18Op(SMOW) = 1. 07δ18OS -0. 58. During dry climate. the oxygen isotopic composition of shell is rich in O. All these indicate that the oxygen isotopic composition of whole shell is inherited from that of Lake water. The freshwater Molluscs shell fossils from Quternary stratum is also rich in δ18O, is similar ro modern Molluscs shell, The δ18OPDB of shell range from - 6. 2- 14. 6‰. For example, in Kunming area.the δ18OPDB value of shell fossil from different age is different. The δ18O offset value is up to 7‰. During moisture and warm climate, the Molluses shell fossils is rich in O. in comparision with modern shell in some area. Showing that the global temperature is high,and the precipitation and melt of the snow is on the increase, this water is rich in O6 and flowed to Lake, where the Molluscs Lived in, thus the molluscs is also rich in O1 During dry and cool climate, the Molluscs shell fossils is show that, the global temperature is low, ind the pricipita-tion is decrease, but the evaporation is strong, so that the light isotopic composition are esccped thus, water body is rich in O, and concentrated in lake, where the Molluscs lived in, thus the Molluscs is also rich in O. In all above,the δ18O of fossil shell from lake. Sensetively recorded past wet and terrestrial climate chang.
Some freshwater Molluscs shells are collected from modern freshwater lake and Quternary stratum in China,in which climate and environment have been known in detail. The oxygen istopic composition of freshwater Molluscs shells are analysed for discussing relationship between the oxygen isotopic composition of shell and terrestrial climate and enviroment,and it used to reconstruct the past climatic chang. In this paper, the whole shell sample are analysed for discussing relationship between shell δ18OPDB and annual mean temperature and δ18OSMOW of lake water. The results show that: Molluscs shell in freshwater Lake are rich in O.δ18 OPDB5‰, in comparision with marine Molluscs. The δ18OPDB value of Molluscs shells which lived in same area are similar; but that which lived in different area are different. During moisture climate, δ18OPDB value of shells range from -5. 1～-10. 2‰. The shell is richer in O, with of gtadually increasing. δ18OPDB of shell is related to δ18OP(SMOW) of annual mean precipitation. The linear equation is δ18Op(SMOW) = 1. 07δ18OS -0. 58. During dry climate. the oxygen isotopic composition of shell is rich in O. All these indicate that the oxygen isotopic composition of whole shell is inherited from that of Lake water. The freshwater Molluscs shell fossils from Quternary stratum is also rich in δ18O, is similar ro modern Molluscs shell, The δ18OPDB of shell range from - 6. 2- 14. 6‰. For example, in Kunming area.the δ18OPDB value of shell fossil from different age is different. The δ18O offset value is up to 7‰. During moisture and warm climate, the Molluses shell fossils is rich in O. in comparision with modern shell in some area. Showing that the global temperature is high,and the precipitation and melt of the snow is on the increase, this water is rich in O6 and flowed to Lake, where the Molluscs Lived in, thus the molluscs is also rich in O1 During dry and cool climate, the Molluscs shell fossils is show that, the global temperature is low, ind the pricipita-tion is decrease, but the evaporation is strong, so that the light isotopic composition are esccped thus, water body is rich in O, and concentrated in lake, where the Molluscs lived in, thus the Molluscs is also rich in O. In all above,the δ18O of fossil shell from lake. Sensetively recorded past wet and terrestrial climate chang.
1993, 11(3): 82-87.
Abstract:
Compositional characteristics of pentacyclic tritepanoids in modern marsh sediments of southern Gansu is discussed by means of GC -MS. Five novel compounds of de -A-lupenes in 1 - 4 samples were found. By means of mass spectra, they are determined as: de - A - lup -18(19) - ene(two isomers), de -A -lup -12(13) -ene, de -A -lup -5 (10), 18(19) -diene and de -A-lup -5(10), 11(12)-diene. It is assumed that 3 - ketolupane and 3 -ke-tolupane acid are the precursor of the lupenes. De - A - lupenes are formed by ways of complete loss of ring A, resulting from a 3,4 cleavage and the last of carboxyl,de - A - lupanes acid are degraded products of lu-panoids during early diagenisis stage and also biomarkers indicating higher plant input. Hopanoids are composed of C27,C30,C31,hopenes and C27,C29-C32 hopanes. There is a higher propotion of Cu hopane in the 1 - 4 samples. C31 and CM hopanes are only present at small concentration. Therefore it is prorposed that C29 hopanes may mainly originated form higher plants, while high carbon number hopanoids from bacteria and aquatic organism. Isomerides of hopanes are composed of ββ-βα and αβ hopanes. ββ hopanes are predominant ; hopenes have reladtively higher concentration. These points reflect the characteristics of organic material during diagenesis stage. The discovery of C29,C30 ring D momoaromatic 8,14-secohopanes in the 1 - 4 samples is significant,which is presence may be related to acidic medium (pH=5) and weak oxidation-weak reduction enviromnent as well as activity of microbes in the modern marsh sediments of southern Gansu.
Compositional characteristics of pentacyclic tritepanoids in modern marsh sediments of southern Gansu is discussed by means of GC -MS. Five novel compounds of de -A-lupenes in 1 - 4 samples were found. By means of mass spectra, they are determined as: de - A - lup -18(19) - ene(two isomers), de -A -lup -12(13) -ene, de -A -lup -5 (10), 18(19) -diene and de -A-lup -5(10), 11(12)-diene. It is assumed that 3 - ketolupane and 3 -ke-tolupane acid are the precursor of the lupenes. De - A - lupenes are formed by ways of complete loss of ring A, resulting from a 3,4 cleavage and the last of carboxyl,de - A - lupanes acid are degraded products of lu-panoids during early diagenisis stage and also biomarkers indicating higher plant input. Hopanoids are composed of C27,C30,C31,hopenes and C27,C29-C32 hopanes. There is a higher propotion of Cu hopane in the 1 - 4 samples. C31 and CM hopanes are only present at small concentration. Therefore it is prorposed that C29 hopanes may mainly originated form higher plants, while high carbon number hopanoids from bacteria and aquatic organism. Isomerides of hopanes are composed of ββ-βα and αβ hopanes. ββ hopanes are predominant ; hopenes have reladtively higher concentration. These points reflect the characteristics of organic material during diagenesis stage. The discovery of C29,C30 ring D momoaromatic 8,14-secohopanes in the 1 - 4 samples is significant,which is presence may be related to acidic medium (pH=5) and weak oxidation-weak reduction enviromnent as well as activity of microbes in the modern marsh sediments of southern Gansu.
1993, 11(3): 93-104.
Abstract:
The study area situtates in western Shandong including Xinwen, Feicheng, Yanzhou, Tengxian, Zibuo coal fields ect. This paper mainly deals with Carboniferous strata for the study of volcanic deposits. According to petrlolgical and mineralogical determination by means of polarizing microscope. X - ray diffraction, infrared absorption, spectrum and chemerical analysis ect., composition, texture, sedimentary structures and distribution of pyroclastic rocks of the Carboniferous coal measure in the area are reached. The pyroclastics belong to itermediate - acidic basicity and consist principally the crystalline materials of quartz, plagiocase, sanidine and biotite etc., intermediate and glassy rock fragments and a little of shards. The content matrix is high. The diagenetic mineralogical alteration of pyroclastics is intense, they may be chloritiza-tion, clayization, calcitization or devitritilation of volcarnic glass etc. The results of chemical analysis about the primary composition are consistent with that of petrologic analysis. Ti, P. Cr, Ga, V, Sr, Zr in pyroclastic rocks are higher ban that in normal sedimentation. Compared with the means of trace elemets in the Crust, Na, V, Mn, Cr, Ni, Co and Fe is very low and Zr, K. La and Ce is very high in pyroclastic rocks. Additionally, the ratio between TiO2 and Al2O3 is low, it is found that pyroclastic meterials are intermediate -acidic basicity and tend to be alkaline and come from the crust. Pyroclastic rock is rich in the LREE, poor in the HREE and have a distinct negative anomalty of Eu, shows the original protolith types of pyroclastic materials are neutral extrusive -rock related to continental-crust - deriver alkaline femic rock, indicaing that the volcanic eruption originated from the rift valley with the continental plates. According to the mentioned data the serwater encroachment of the Middle Carboniferous Benxi stage in the Linyi area is earlier than in other areas of southrn North China. There are differences in sedimentary assemblage of the Upper Carboniferous between south and north divided by Xinwen and Feicheng, and the Upper Permian coal - bearing series on the south of Fengxian and Peixian is south type and northern facies. All of that are directly controlled by tectonic movements at that time and the resuited volcanic action. Therefore, the sedimentary type of the Carboniferous is a coal -bearing sediment of volanic - sedimentary facies association. The finds of similar pyroclastics in other areas of North China also show that the crustal movemet of the Carboniferous in North China is not stable and there are large tectonic movements and freguent volcanic actions. There are a few layers of volcanogenic tonsteins in the coal measure which are steadly and widely occrued over the area. For example, The coal seam No. 11 in Xinwen, No. 15 and No. 16 in Laiwu, No. 7 in Feicheng and No. 15 in Linyi, Jining and Tengxian correspond to each other.
The study area situtates in western Shandong including Xinwen, Feicheng, Yanzhou, Tengxian, Zibuo coal fields ect. This paper mainly deals with Carboniferous strata for the study of volcanic deposits. According to petrlolgical and mineralogical determination by means of polarizing microscope. X - ray diffraction, infrared absorption, spectrum and chemerical analysis ect., composition, texture, sedimentary structures and distribution of pyroclastic rocks of the Carboniferous coal measure in the area are reached. The pyroclastics belong to itermediate - acidic basicity and consist principally the crystalline materials of quartz, plagiocase, sanidine and biotite etc., intermediate and glassy rock fragments and a little of shards. The content matrix is high. The diagenetic mineralogical alteration of pyroclastics is intense, they may be chloritiza-tion, clayization, calcitization or devitritilation of volcarnic glass etc. The results of chemical analysis about the primary composition are consistent with that of petrologic analysis. Ti, P. Cr, Ga, V, Sr, Zr in pyroclastic rocks are higher ban that in normal sedimentation. Compared with the means of trace elemets in the Crust, Na, V, Mn, Cr, Ni, Co and Fe is very low and Zr, K. La and Ce is very high in pyroclastic rocks. Additionally, the ratio between TiO2 and Al2O3 is low, it is found that pyroclastic meterials are intermediate -acidic basicity and tend to be alkaline and come from the crust. Pyroclastic rock is rich in the LREE, poor in the HREE and have a distinct negative anomalty of Eu, shows the original protolith types of pyroclastic materials are neutral extrusive -rock related to continental-crust - deriver alkaline femic rock, indicaing that the volcanic eruption originated from the rift valley with the continental plates. According to the mentioned data the serwater encroachment of the Middle Carboniferous Benxi stage in the Linyi area is earlier than in other areas of southrn North China. There are differences in sedimentary assemblage of the Upper Carboniferous between south and north divided by Xinwen and Feicheng, and the Upper Permian coal - bearing series on the south of Fengxian and Peixian is south type and northern facies. All of that are directly controlled by tectonic movements at that time and the resuited volcanic action. Therefore, the sedimentary type of the Carboniferous is a coal -bearing sediment of volanic - sedimentary facies association. The finds of similar pyroclastics in other areas of North China also show that the crustal movemet of the Carboniferous in North China is not stable and there are large tectonic movements and freguent volcanic actions. There are a few layers of volcanogenic tonsteins in the coal measure which are steadly and widely occrued over the area. For example, The coal seam No. 11 in Xinwen, No. 15 and No. 16 in Laiwu, No. 7 in Feicheng and No. 15 in Linyi, Jining and Tengxian correspond to each other.
1993, 11(3): 114-118.
Abstract:
The study area of the lower reach of Bailongjiang river is located in Longnan area and belongs to southern Qinling folded belt of western Qinling complex structural zone. Bikou group of lower Silurain (Slbk) developed very well, which is a set of greenschist series metamorphosed by clastic rock, volcanic rock and carbonate rock of marine facies, and is the source rock of the placer gold. A lot of evidences on neotectonism indicate that Bailongjiang valley had been risen, and the strata were weathered and denuded since Quaternary Period, provided a favourable tectonic condition for migration and enrichment of the placer gold. The negative locations such as fault depression and tectonic valley become the storing site of the placer gold. Moreover, the warm, moist climate and powerful hydrodynamic power also provide a favourable condition for enrichment of the placer gold. According to the analytical results of heavy concentrate samples which collected from alluvial flat at Fengpingzi, grade of the placer gold increaes with the depth at vertical section, 3. 5 - 5m and 7. 5m -11m are enrichment section of the placer gold; the outside point bar, near midchannel is the distributive zone of high grade at transverse section. So the deep mining is suitable for the placer gold deposit of alluvial flat in lower reach of Bailongjiang.
The study area of the lower reach of Bailongjiang river is located in Longnan area and belongs to southern Qinling folded belt of western Qinling complex structural zone. Bikou group of lower Silurain (Slbk) developed very well, which is a set of greenschist series metamorphosed by clastic rock, volcanic rock and carbonate rock of marine facies, and is the source rock of the placer gold. A lot of evidences on neotectonism indicate that Bailongjiang valley had been risen, and the strata were weathered and denuded since Quaternary Period, provided a favourable tectonic condition for migration and enrichment of the placer gold. The negative locations such as fault depression and tectonic valley become the storing site of the placer gold. Moreover, the warm, moist climate and powerful hydrodynamic power also provide a favourable condition for enrichment of the placer gold. According to the analytical results of heavy concentrate samples which collected from alluvial flat at Fengpingzi, grade of the placer gold increaes with the depth at vertical section, 3. 5 - 5m and 7. 5m -11m are enrichment section of the placer gold; the outside point bar, near midchannel is the distributive zone of high grade at transverse section. So the deep mining is suitable for the placer gold deposit of alluvial flat in lower reach of Bailongjiang.
1993, 11(3): 7-12.
Abstract:
Strata of Wufeng age are widely distributed in Yangtze Plate,and our sedimental types can be recognized from east to west, i.e., Yushan, Yuqia.Yichang and Hanyuan type. Yichang type is characterized by graptolite black shales Wufeng Formation Two different opinions about the sedimental environment of Wufeng Formation have been arguing in recent years: i.e., shallow sea deposits or deep sea deposits. Based on the paleontology, petrogrphic characteristics,especialy the analyses of the rare earth elements, the authors concluded that the graptolite black shales of Wufeng Formation were deposited in a epicontinemal shallow restricted basin. Yushan type consists mainly of micritic limestone, bird-eye limestone and shales bearing abundant algae, corals, brachiopods, trilobites. This type constructs some isolated carbonate reef platformes staning on the southeast margin of the restricted basin. Between the restricted basin and carbonate reef platformes, there is a depression trough filled by shallow water flysch deposits called Yuqian Formation or Changwu Formation. Hanyuan type developed in the west part of Yangtze Plate and consists of carbonate rocks and black shales, representing another type of reef carbonate platform and ramp.
Strata of Wufeng age are widely distributed in Yangtze Plate,and our sedimental types can be recognized from east to west, i.e., Yushan, Yuqia.Yichang and Hanyuan type. Yichang type is characterized by graptolite black shales Wufeng Formation Two different opinions about the sedimental environment of Wufeng Formation have been arguing in recent years: i.e., shallow sea deposits or deep sea deposits. Based on the paleontology, petrogrphic characteristics,especialy the analyses of the rare earth elements, the authors concluded that the graptolite black shales of Wufeng Formation were deposited in a epicontinemal shallow restricted basin. Yushan type consists mainly of micritic limestone, bird-eye limestone and shales bearing abundant algae, corals, brachiopods, trilobites. This type constructs some isolated carbonate reef platformes staning on the southeast margin of the restricted basin. Between the restricted basin and carbonate reef platformes, there is a depression trough filled by shallow water flysch deposits called Yuqian Formation or Changwu Formation. Hanyuan type developed in the west part of Yangtze Plate and consists of carbonate rocks and black shales, representing another type of reef carbonate platform and ramp.
1993, 11(3): 37-43.
Abstract:
Ordos Basin is one of the largest coal-bearing basin in China. In this paper. 103 species of spores and pollen grains referred to 60 genera, form the Yan'an Formation, the Middle Jurassic coal series of ZK1534 dril Ihole in Yuling region of this basin, have been studied. In the sporo - pollen assemblage of the formation, the percentage of pteridophyta spores amounts to 60. 4%, the pollen grains of gymnospermae to 39. 5%. Among the spores, Cyathididtes and Delloidospora are predominant (33. 1%). Osmundacidites (3. 0%), Duplexisporites (3.2%), Converrucosisporites (2.7%), Neoraistrickia (2.2%), Cibotiumspora (1. 6%), and Lycopdiumsporites (0. 6%) are comparatively abundant. Among the pollen grains, Cycadopitts (26. 7%) is the most important, the rest pollen grains only have small amount. By studing sporo -pollen assemblage, in terms of actuopaleontology and the ecoenvironment of the affiliated plants, the main spores and pollen (over 1 % on average) could be divided into three ecotypes: (a) Hu-midophytes, representative dispersed sporo -pollen are Lycopodiumsportes, Neoraistridia, Calamospora. Osmundacidites, Duplexisporites and Steresporites. (b) Humidomesophytes, are Delloidospora, Cyathidites, Ci- botiumspora and Converrucosisporites. (c) Arid - mesophytes, are Cyca dopites and Disaccites. Besides this, the percentage of each ecotype and diversity (by) D=N(N -1)/∑《sub》（-0s Ni (ni -1) of sporo -pollen are calculated. The ecotype and diversity can be used as main ecoelements to reflecte the palaeoclimate. The former might be the main result of humidity changes and the later might reflect the variation of humidity and temperature. When the humidity and temperature are more suitable to the plant comunity developing and its species flourishing, the diversity might be maximum, and if the circumstance is contrary to above, the diversity might decrease. Morever, the sedimentary environment is considered. All these studing results show that the palaeoclimate of the Middle Jurassic period (Yanan stage) could be divided into three comparative dry periods, they are, the first member, the lower third member and the upper fouth membert and three comparative hot periods: the first to the lower second member, the lower third member and the upper fouth member; During middle -upper third member sediment period, the palaeoclimate is appropriate, palynoflora is fluorishing and delta plain facies is extensively distributed, those make the No. 3 coalbed (in the top of the third member) have a great thickness, wide distribution and a good industry value.
Ordos Basin is one of the largest coal-bearing basin in China. In this paper. 103 species of spores and pollen grains referred to 60 genera, form the Yan'an Formation, the Middle Jurassic coal series of ZK1534 dril Ihole in Yuling region of this basin, have been studied. In the sporo - pollen assemblage of the formation, the percentage of pteridophyta spores amounts to 60. 4%, the pollen grains of gymnospermae to 39. 5%. Among the spores, Cyathididtes and Delloidospora are predominant (33. 1%). Osmundacidites (3. 0%), Duplexisporites (3.2%), Converrucosisporites (2.7%), Neoraistrickia (2.2%), Cibotiumspora (1. 6%), and Lycopdiumsporites (0. 6%) are comparatively abundant. Among the pollen grains, Cycadopitts (26. 7%) is the most important, the rest pollen grains only have small amount. By studing sporo -pollen assemblage, in terms of actuopaleontology and the ecoenvironment of the affiliated plants, the main spores and pollen (over 1 % on average) could be divided into three ecotypes: (a) Hu-midophytes, representative dispersed sporo -pollen are Lycopodiumsportes, Neoraistridia, Calamospora. Osmundacidites, Duplexisporites and Steresporites. (b) Humidomesophytes, are Delloidospora, Cyathidites, Ci- botiumspora and Converrucosisporites. (c) Arid - mesophytes, are Cyca dopites and Disaccites. Besides this, the percentage of each ecotype and diversity (by) D=N(N -1)/∑《sub》（-0s Ni (ni -1) of sporo -pollen are calculated. The ecotype and diversity can be used as main ecoelements to reflecte the palaeoclimate. The former might be the main result of humidity changes and the later might reflect the variation of humidity and temperature. When the humidity and temperature are more suitable to the plant comunity developing and its species flourishing, the diversity might be maximum, and if the circumstance is contrary to above, the diversity might decrease. Morever, the sedimentary environment is considered. All these studing results show that the palaeoclimate of the Middle Jurassic period (Yanan stage) could be divided into three comparative dry periods, they are, the first member, the lower third member and the upper fouth membert and three comparative hot periods: the first to the lower second member, the lower third member and the upper fouth member; During middle -upper third member sediment period, the palaeoclimate is appropriate, palynoflora is fluorishing and delta plain facies is extensively distributed, those make the No. 3 coalbed (in the top of the third member) have a great thickness, wide distribution and a good industry value.
1993, 11(3): 52-56.
Abstract:
There are three kinds of helium in the earth,i. e. atmospheric,crust derived and mantle derived ones, which's He/4He ratio are 1. 4 × 10-4,2 × 10-10,1. 1 × 10-5 respectively. Mainly resourced from natural gas reservoirs,helium concentration if mainly related to the α decay of urinium and thorium, thus,its enrichment generally is accompaning by the decrease of He/4He ratio, ordimarily in the grade of 10-8. Based on the recent years of the both side of Tancheng - Lushan Fault in eastern China,the author found the helium abundance reached or higher than 0. 1% in some industrial gas droll holes,i.e.,up to the standard of industrial helieum reservoir,but the intresting point is that the He/4He ratio measured is as high as 3.7-6.36×10-6. As atmospheric He can be neglected in industrial wells, and the calculation shows that the mantle derived He can up to 33.7-57. 3% of these He gases,then the industrial He reservoirs in the sedimentary crust that derived from the mantle were first found internationally. It is a discover of a new helium source, moreover, it not only provided information of the analysis, migration, reservoir of mantle volatile components, but also a geological body to study on the hot point of geoseience.i. e, the relationship between the crust and the mantle. And the discovery of industrial helium reservoir is also significant of the research of non - biogenic methane and so on.
There are three kinds of helium in the earth,i. e. atmospheric,crust derived and mantle derived ones, which's He/4He ratio are 1. 4 × 10-4,2 × 10-10,1. 1 × 10-5 respectively. Mainly resourced from natural gas reservoirs,helium concentration if mainly related to the α decay of urinium and thorium, thus,its enrichment generally is accompaning by the decrease of He/4He ratio, ordimarily in the grade of 10-8. Based on the recent years of the both side of Tancheng - Lushan Fault in eastern China,the author found the helium abundance reached or higher than 0. 1% in some industrial gas droll holes,i.e.,up to the standard of industrial helieum reservoir,but the intresting point is that the He/4He ratio measured is as high as 3.7-6.36×10-6. As atmospheric He can be neglected in industrial wells, and the calculation shows that the mantle derived He can up to 33.7-57. 3% of these He gases,then the industrial He reservoirs in the sedimentary crust that derived from the mantle were first found internationally. It is a discover of a new helium source, moreover, it not only provided information of the analysis, migration, reservoir of mantle volatile components, but also a geological body to study on the hot point of geoseience.i. e, the relationship between the crust and the mantle. And the discovery of industrial helium reservoir is also significant of the research of non - biogenic methane and so on.
1993, 11(3): 64-71.
Abstract:
Organic matter of metasediments from Shixia,Longshui of South China and New Caledonia. has been studied by laser Raman microprobe. In all cases the Raman spectrum of two main bands at 1600cm-1 and 1350cm-1 having a bandwidth at half peak intersity respectively in the range 30 - 80 and 30 - 250cm-1 depending on thermal maturity. The spectra are similar to anthracite coals and heat treated industrial carbons. Three distinct types of organic matter originating in sapropelic kerogen can be recognized in the carbonaceous slates of Longshui; (a) indigenous. (b) hydrothermal metamorphis, (c) migration bitumen. There are differences on the intensities,positions and widthes of the Raman bands characteristic of these types of organic matter. Indigenous organic matter of a suite of metasediments from New Caledonia was examined to mdetermine changes in the Raman spectra with thermal maturity. As the reflectance of the canbon increases from R°max (%) = 2. 10 to 14. 9, the width of the 1350cm-1 Raman band decreases from 200 to 30 cm2 At the same time, the and separation deceases form 255 to 230cm-1, with increasing reflectance.while the ratio of band areas increases from 0. 38 to 1. 0.
Organic matter of metasediments from Shixia,Longshui of South China and New Caledonia. has been studied by laser Raman microprobe. In all cases the Raman spectrum of two main bands at 1600cm-1 and 1350cm-1 having a bandwidth at half peak intersity respectively in the range 30 - 80 and 30 - 250cm-1 depending on thermal maturity. The spectra are similar to anthracite coals and heat treated industrial carbons. Three distinct types of organic matter originating in sapropelic kerogen can be recognized in the carbonaceous slates of Longshui; (a) indigenous. (b) hydrothermal metamorphis, (c) migration bitumen. There are differences on the intensities,positions and widthes of the Raman bands characteristic of these types of organic matter. Indigenous organic matter of a suite of metasediments from New Caledonia was examined to mdetermine changes in the Raman spectra with thermal maturity. As the reflectance of the canbon increases from R°max (%) = 2. 10 to 14. 9, the width of the 1350cm-1 Raman band decreases from 200 to 30 cm2 At the same time, the and separation deceases form 255 to 230cm-1, with increasing reflectance.while the ratio of band areas increases from 0. 38 to 1. 0.
1993, 11(3): 88-92.
Abstract:
Based on results from 41 oriented cores collected from northwestern and southwestern margins of the Tarim Basin, this paper presents a brief introduction of our recent study on the Devonian System therein. Paleomagnetic data suggest that paleolatitude of the southwestern margin was much lower than that of the norhwestern margin (about 12°). The former was amalgamated to the later during rapid northward drifting of the Tarim Block happening within Carbono-Devonian period. This kind of differential motions among sub -units of the block should be a significant element on tectonic evolution and evaluation of oil and gas within the western part of the Tarim Basin.
Based on results from 41 oriented cores collected from northwestern and southwestern margins of the Tarim Basin, this paper presents a brief introduction of our recent study on the Devonian System therein. Paleomagnetic data suggest that paleolatitude of the southwestern margin was much lower than that of the norhwestern margin (about 12°). The former was amalgamated to the later during rapid northward drifting of the Tarim Block happening within Carbono-Devonian period. This kind of differential motions among sub -units of the block should be a significant element on tectonic evolution and evaluation of oil and gas within the western part of the Tarim Basin.
1993, 11(3): 105-113.
Abstract:
Several clay rock beds ware found near the Permian-Triassic interface of Southern China, and there is a large mass of extinction. There are two opinions on the cause of the extinction, i. e., outer-space crash event and volcanism of the earth. The author, after analyzed the non - clay components the mentioned clay beds in Zhongliangshan of Chongqing, found some microspherulitic and clastic minerals that featured by the following characters. 1. Microspherulitic material, with the diameters of 30-150μm and composed by (1) ferruginous, (2) siliceous and (3) lithical components. Division 1 is very round (nearly standard globular) with smooth surface or decorated by modular bulges. The most outstanding feature is their graphic texture on the surface, which made of dendritic, small bulges, holes of eruption and fusion crust. EDX analysis shows that the elemental components are Fe (avrage in 85. 0%), Si (12. 3% in average), some Al, Ni, Cr, Mg and Mn, distribute inhomogenously. The highest concentration of Fe is found in the eruption holes and on the crust around the holes, Al and Si concentrated on the surface of the spherulitic balls, especially on the noduler bulges. concentrated on the noduler bulges, while Ni, Cr and Mn only found inside the eruption holes and Mg only on the surface of the spherule. No obvious diffence between the dendritic bulges and the depressed parts in the distribution of Fe and Si. Division 2 and 3. siliceous and lithical microspherulitic matters, are global or pear - like, mostly with a simple smooth surface. and a few have eruption holes. EDX analysis revealed that the component of silicer-ous one is Si (75. 2%). Al (15. 0%), some Ti and Fe, and for lithical ones, are mainly lithophile elements, i.e., Si, Al, K, Fe, Zn, Ti and Mg. 2. Clastic Minerals Include zircon, magnetite, hexagonxl dipyramid quartz and mtile. Most of them are excellent euhedral crystals with few trace of abrasion, and in the size of 30-300μm. The crystal form of quartz is frequently hexagonal dipyramid. Some of zircon, so called "double prisms and double pyramids", belongs to S22 type of Pupin (1980), representing the forming temperature appproxi-mately 850℃. The crystal form of magnetite mainly is rhombic dodecahedron. The types and crystal forms of clastic minerals have the characters reflecting that the origin of clay rock near the Permian -Triassic boundary could be related to volcanic activities. The siliceous and lithical micro-spherules also could be pyroclast because of their high content of Ti Their surface with melting structure of high temperature, such as eruption holes,also resulted from volcaic eruption. The forruginous microspherule with graphic textrue also have fusion crust formed at high temperature process like that seen in siliceous and lithical microspherulitic matter but no Ti has been found in them. In the core part of ferruginous microspherulitic matter there is relatively high content of Ni but no Si has been found. In contrast, Si and Al are mainly distrbuted in the part near surface of the ferruginous microspherulitic matter it is our proposal that this dind of microspherulitic matter could be of extraterrestrial origin, i.e., cosmic dust. It follows form our study that both extraterrestrial dashevent and terrestrial volcanicity probably be happened at teh end of the permian in southern chinaand both could be related to the mass extinction.
Several clay rock beds ware found near the Permian-Triassic interface of Southern China, and there is a large mass of extinction. There are two opinions on the cause of the extinction, i. e., outer-space crash event and volcanism of the earth. The author, after analyzed the non - clay components the mentioned clay beds in Zhongliangshan of Chongqing, found some microspherulitic and clastic minerals that featured by the following characters. 1. Microspherulitic material, with the diameters of 30-150μm and composed by (1) ferruginous, (2) siliceous and (3) lithical components. Division 1 is very round (nearly standard globular) with smooth surface or decorated by modular bulges. The most outstanding feature is their graphic texture on the surface, which made of dendritic, small bulges, holes of eruption and fusion crust. EDX analysis shows that the elemental components are Fe (avrage in 85. 0%), Si (12. 3% in average), some Al, Ni, Cr, Mg and Mn, distribute inhomogenously. The highest concentration of Fe is found in the eruption holes and on the crust around the holes, Al and Si concentrated on the surface of the spherulitic balls, especially on the noduler bulges. concentrated on the noduler bulges, while Ni, Cr and Mn only found inside the eruption holes and Mg only on the surface of the spherule. No obvious diffence between the dendritic bulges and the depressed parts in the distribution of Fe and Si. Division 2 and 3. siliceous and lithical microspherulitic matters, are global or pear - like, mostly with a simple smooth surface. and a few have eruption holes. EDX analysis revealed that the component of silicer-ous one is Si (75. 2%). Al (15. 0%), some Ti and Fe, and for lithical ones, are mainly lithophile elements, i.e., Si, Al, K, Fe, Zn, Ti and Mg. 2. Clastic Minerals Include zircon, magnetite, hexagonxl dipyramid quartz and mtile. Most of them are excellent euhedral crystals with few trace of abrasion, and in the size of 30-300μm. The crystal form of quartz is frequently hexagonal dipyramid. Some of zircon, so called "double prisms and double pyramids", belongs to S22 type of Pupin (1980), representing the forming temperature appproxi-mately 850℃. The crystal form of magnetite mainly is rhombic dodecahedron. The types and crystal forms of clastic minerals have the characters reflecting that the origin of clay rock near the Permian -Triassic boundary could be related to volcanic activities. The siliceous and lithical micro-spherules also could be pyroclast because of their high content of Ti Their surface with melting structure of high temperature, such as eruption holes,also resulted from volcaic eruption. The forruginous microspherule with graphic textrue also have fusion crust formed at high temperature process like that seen in siliceous and lithical microspherulitic matter but no Ti has been found in them. In the core part of ferruginous microspherulitic matter there is relatively high content of Ni but no Si has been found. In contrast, Si and Al are mainly distrbuted in the part near surface of the ferruginous microspherulitic matter it is our proposal that this dind of microspherulitic matter could be of extraterrestrial origin, i.e., cosmic dust. It follows form our study that both extraterrestrial dashevent and terrestrial volcanicity probably be happened at teh end of the permian in southern chinaand both could be related to the mass extinction.
