1987 Vol. 5, No. 1
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Display Method:
1987, 5(1): 1-9.
Abstract:
Phosphorite ore deposits are widely distributed in South China. They have been found in almost every system through the geological ages. But about 70% of the industrial phosphate deposits are accumulated in the Sinian and Cambrian strata in Yunnan, Guizhou, Sichuan, Hunan, Hubei and other provinces in South China. Sinian is one of the most important mineralization periods of phosphorite in China. More than half of the industrial phosphate deposits were formed in the epicontinental sea of South China Platform during this time. The Sinian phosphorite is mainly distributed around archipelagos or islands and the submarine highlands, forming a mineral zone or group of phosphorite beds controlled by the palaeotectonics and palaeogeomorphy of the platform. Several phosphorite horizones have been found in Cambrian strata of China, but the most important one in South China is lying in the bottom of Cambrian. During Early-Cambrian, thick marine phosphate deposite, consisting of mudy or siliceous phosphorites, were formed in the epicontinental sea of the South China Platform, distributed chiefly along the eastside of the "Hubei-Sichuan-Yunnan Island Arc" , in the west, and along the westside of the "South Yangzi Archipelago" in the east, The former is much important than the latter, and the industrial ore deposits are chiefly confined in the former. Going further to the southeast, the phosphorite ore deposite are hardly found in the bottom of the Cambrian flysch-like deposite in the South China Trough. During Late Sinian and Early Cambrian, the cold deep water rich in phosphorus might be flowing into the South China marine basin from the Arctic Region in the southeast, and then many large and small phosphorite ore deposits were generated around the basin in favourable terrains such as: archipelagos, islands and submarine highlands, by the processes of mechanical, chemical and organic concentration and deposition. The depositional environments of phosphorite are briefly discussed in this paper as follows: 1) the character of rock assemblage of phosphate-bearing series;2)the relationship between the phosphorite ore deposits and the transgression and regression due to the tectonic movement;3) the latitudinal distribution of phosphorite and palaeoclimate conditions;4) the palaeogeomorphic features of phosphrite deposition) 5) the geochemical conditions of phosphorite deposition;6) the organic effects on phosphorite deposition;7) the hydrodynamic conditions of phosphorite deposition;and 8) the phosphorus sources.
Phosphorite ore deposits are widely distributed in South China. They have been found in almost every system through the geological ages. But about 70% of the industrial phosphate deposits are accumulated in the Sinian and Cambrian strata in Yunnan, Guizhou, Sichuan, Hunan, Hubei and other provinces in South China. Sinian is one of the most important mineralization periods of phosphorite in China. More than half of the industrial phosphate deposits were formed in the epicontinental sea of South China Platform during this time. The Sinian phosphorite is mainly distributed around archipelagos or islands and the submarine highlands, forming a mineral zone or group of phosphorite beds controlled by the palaeotectonics and palaeogeomorphy of the platform. Several phosphorite horizones have been found in Cambrian strata of China, but the most important one in South China is lying in the bottom of Cambrian. During Early-Cambrian, thick marine phosphate deposite, consisting of mudy or siliceous phosphorites, were formed in the epicontinental sea of the South China Platform, distributed chiefly along the eastside of the "Hubei-Sichuan-Yunnan Island Arc" , in the west, and along the westside of the "South Yangzi Archipelago" in the east, The former is much important than the latter, and the industrial ore deposits are chiefly confined in the former. Going further to the southeast, the phosphorite ore deposite are hardly found in the bottom of the Cambrian flysch-like deposite in the South China Trough. During Late Sinian and Early Cambrian, the cold deep water rich in phosphorus might be flowing into the South China marine basin from the Arctic Region in the southeast, and then many large and small phosphorite ore deposits were generated around the basin in favourable terrains such as: archipelagos, islands and submarine highlands, by the processes of mechanical, chemical and organic concentration and deposition. The depositional environments of phosphorite are briefly discussed in this paper as follows: 1) the character of rock assemblage of phosphate-bearing series;2)the relationship between the phosphorite ore deposits and the transgression and regression due to the tectonic movement;3) the latitudinal distribution of phosphorite and palaeoclimate conditions;4) the palaeogeomorphic features of phosphrite deposition) 5) the geochemical conditions of phosphorite deposition;6) the organic effects on phosphorite deposition;7) the hydrodynamic conditions of phosphorite deposition;and 8) the phosphorus sources.
1987, 5(1): 26-36.
Abstract:
Kerogen structures of oil shales (Type Ⅰ, Ⅱ) sampling from Fushun, Maoming, Huangxian and lignite (Type Ⅲ) from Huanxian, and their artificial-thermal-degradation samples (the final thermal temperature is 375-510℃) have been investigated by using the X-ray diffaction technique (XRD). The XRD experimental curves were adjusted for polarization;normalized to electron units by fitting the adjusted curve to the independent scattering curve of carbon at the angle sin θ/A = 0.50;expressed in "reduced intensity" by substracting the incoherent scattering intensity of carbon and dividing by the independent coherent scattering intensity of carbon. The information extracted from the XRD structural parameters, such as intensity fractions (f), stacking height (Lc), peak position (sin9/A) of 002 and gamma band, indicates that the immature oil shale kerogen is constructed mainly by aliphatics, taking shape of a three dimentional netted and cage structure crosslinked by ring clusters and alkyl chains randomly, with bitumen trapped in the pores. The carbon aromaticity of an immature kerogen assessed by the XRD parameter f002 often gives a negative deviation with that measured by n. m. r. spectroscopy, it implies that part of aromatic rings may not be presented in the stacking structure of the aromatic clusters. The deviation is eliminated gradually as the maturity of the kerogen increases due to the progress of graphitization. Two XRD parameters, f001 and Lc, have shown their close relations both to the kerogen type and to maturity. Owing to the higher content of aromatic carbon and heteroatoms, the type Ⅲ kerogen gives higher f002 and lower Lc values than those of the type Ⅰ and Ⅱ with analogous maturity. A XRD diagram with f002 versus Lc of kerogens of different types and maturities can indicate the different evolution paths for different types of kerogen (Fig. 7), so it may be available to characterize kerogen as well as the H/C-O/C diagram which is commonly used.
Kerogen structures of oil shales (Type Ⅰ, Ⅱ) sampling from Fushun, Maoming, Huangxian and lignite (Type Ⅲ) from Huanxian, and their artificial-thermal-degradation samples (the final thermal temperature is 375-510℃) have been investigated by using the X-ray diffaction technique (XRD). The XRD experimental curves were adjusted for polarization;normalized to electron units by fitting the adjusted curve to the independent scattering curve of carbon at the angle sin θ/A = 0.50;expressed in "reduced intensity" by substracting the incoherent scattering intensity of carbon and dividing by the independent coherent scattering intensity of carbon. The information extracted from the XRD structural parameters, such as intensity fractions (f), stacking height (Lc), peak position (sin9/A) of 002 and gamma band, indicates that the immature oil shale kerogen is constructed mainly by aliphatics, taking shape of a three dimentional netted and cage structure crosslinked by ring clusters and alkyl chains randomly, with bitumen trapped in the pores. The carbon aromaticity of an immature kerogen assessed by the XRD parameter f002 often gives a negative deviation with that measured by n. m. r. spectroscopy, it implies that part of aromatic rings may not be presented in the stacking structure of the aromatic clusters. The deviation is eliminated gradually as the maturity of the kerogen increases due to the progress of graphitization. Two XRD parameters, f001 and Lc, have shown their close relations both to the kerogen type and to maturity. Owing to the higher content of aromatic carbon and heteroatoms, the type Ⅲ kerogen gives higher f002 and lower Lc values than those of the type Ⅰ and Ⅱ with analogous maturity. A XRD diagram with f002 versus Lc of kerogens of different types and maturities can indicate the different evolution paths for different types of kerogen (Fig. 7), so it may be available to characterize kerogen as well as the H/C-O/C diagram which is commonly used.
1987, 5(1): 58-68.
Abstract:
This paper deals with the samples from four profiles in Keshi Depression and Xi-nan Depression in the southwestern part of Talimu Basin.All the samples are obtained from marine mudstones and sandy-mudstones with the exception of a few ones from the Late Cretaceous and Early Tertiary limestone. Owing to the great thickness of covering strata in this region, it is difficult to get samples by drilling. So it seems impossible to observe the metamorphic degree of organic matter by studying various clay minerals in deep drilling cores. In this case, the author is trying to explain the paleogeographical environment and the problems about petroleum and gas geology of the Late Cretaceous and Early Tertiary in the southwestern part of Talimu Basin by measuring the diffraction maximum of illite (001). The author usually measures the crystallinity of illite by recognizing the shapes of the diffraction maximum of the mineral. The method of the acute index, which Dunoyer de Segonzac G. (1969) used to calculate illite crystallinity, needs special experiment equipment and conditions. Ren Leifu (1984) suggested that the "opening index" (Ns) be used to indicate the opening degree of diffraction maximum of illite. This method is easier to use in measurement, sample preparation and calculation. In fact, the index is not effected by the experiment equipment and condition, because it is only a scale. The formation of opening illite is related to the separation of K+ from the inter-layers. Based on the variation of opening index of illite from the four profiles, it is clear that its formation is related to some factors, such as the paleoclimate and paleogeographic environments. They are as follows: 1) the variation shows that the climate in the Late Cretaceous and Early Tertiary became dry by degrees;2)The samples in the same horizon from different locations in the basin have different opening indexes. So it is possible to infer the boundary of the sea basin;3) The variation indicates the ingression situation, and the maximum opening index is identical with the ingression. This is coincident with the data of field geology. Regular shape variation of diffraction maximum of illite in samples from weathering zones can still reflect the original gaological situation in their local site. This conclusion means that the rocks in this region do not undergo strong weathering and diagenesis. If the clay minerals in the cropped rocks have a very low grade of degeneration in weathering zones, samples from the cropping can be used to study the association and transformation of clay minerals and to determine the metamorphic degree of organic matter and the favourable area for oil or gas exploration. In three of the four profiles, the composition of clay minerals is dominated by illite and chlorite with the exception that the association of clay minerals in Simu-hana Profile is a little different from those three ones. Such a kind of clay minerals is not favourable for the formation of oil.
This paper deals with the samples from four profiles in Keshi Depression and Xi-nan Depression in the southwestern part of Talimu Basin.All the samples are obtained from marine mudstones and sandy-mudstones with the exception of a few ones from the Late Cretaceous and Early Tertiary limestone. Owing to the great thickness of covering strata in this region, it is difficult to get samples by drilling. So it seems impossible to observe the metamorphic degree of organic matter by studying various clay minerals in deep drilling cores. In this case, the author is trying to explain the paleogeographical environment and the problems about petroleum and gas geology of the Late Cretaceous and Early Tertiary in the southwestern part of Talimu Basin by measuring the diffraction maximum of illite (001). The author usually measures the crystallinity of illite by recognizing the shapes of the diffraction maximum of the mineral. The method of the acute index, which Dunoyer de Segonzac G. (1969) used to calculate illite crystallinity, needs special experiment equipment and conditions. Ren Leifu (1984) suggested that the "opening index" (Ns) be used to indicate the opening degree of diffraction maximum of illite. This method is easier to use in measurement, sample preparation and calculation. In fact, the index is not effected by the experiment equipment and condition, because it is only a scale. The formation of opening illite is related to the separation of K+ from the inter-layers. Based on the variation of opening index of illite from the four profiles, it is clear that its formation is related to some factors, such as the paleoclimate and paleogeographic environments. They are as follows: 1) the variation shows that the climate in the Late Cretaceous and Early Tertiary became dry by degrees;2)The samples in the same horizon from different locations in the basin have different opening indexes. So it is possible to infer the boundary of the sea basin;3) The variation indicates the ingression situation, and the maximum opening index is identical with the ingression. This is coincident with the data of field geology. Regular shape variation of diffraction maximum of illite in samples from weathering zones can still reflect the original gaological situation in their local site. This conclusion means that the rocks in this region do not undergo strong weathering and diagenesis. If the clay minerals in the cropped rocks have a very low grade of degeneration in weathering zones, samples from the cropping can be used to study the association and transformation of clay minerals and to determine the metamorphic degree of organic matter and the favourable area for oil or gas exploration. In three of the four profiles, the composition of clay minerals is dominated by illite and chlorite with the exception that the association of clay minerals in Simu-hana Profile is a little different from those three ones. Such a kind of clay minerals is not favourable for the formation of oil.
1987, 5(1): 77-85.
Abstract:
Dickite found in the shaft of Yungang Coal Field occurs in downcast pillar close to coal seams at the top of Datong Formation of Middle Jurassic. It fills in pores and cracks of rocks, being in spotted block and network of vein. The main characteristics of this mineral are as follows : it is white-powdery aggregate with well lubricating,in most cases, its crystal takes the shape of hexa- gonal tabular;refractive index : Ng = l.567-1.568, Nm =1.563-1.564, Np = 1.561-1.562 Ng-Np=0.006 Ng//b, ApΛ(010)CΛNp=11°αΛNm=15°, (+) 2V=65°, parallel extinction, length slow. Under the scanning electromicroscope, its shapes are hexagonal prism or pagoda-like. Its chemical compositions are : SiO2 = 46.54%, Al2O3 = 38.99%, H2O+ 13.93%, SiO3: Al2O3 = 202 : 100. Its thermography curve has a intense endothermic peak at 670°, the curve is gently slope in the side of lower temperature and steeply in the side of higher temperature. In the figure of X-ray diffraction curves, peaks at d (021) =4.2442, d (012) = 3.9549,d (022) =3.7855 appear in the range of 2θ = 20°-24°;and between 2θ = 34°and 40°,four continnuous diffraction peaks appear.In the infrared spectrogram absorption, peaks at 3708,3640,3614cm(-1) occur in high frequency range, the frequency is from higher to lower, while the intensity of absorption peaks is from weak to strong. All of these data fully prove that the dickite from this district is similar to that from other districts. Owing to the fact that this mineral is found at the depth of about 400m under the earth's surface and intergrows with pyrite, the dickite may be formed in the condition of the reducing environment with less than 15℃ temperature.
Dickite found in the shaft of Yungang Coal Field occurs in downcast pillar close to coal seams at the top of Datong Formation of Middle Jurassic. It fills in pores and cracks of rocks, being in spotted block and network of vein. The main characteristics of this mineral are as follows : it is white-powdery aggregate with well lubricating,in most cases, its crystal takes the shape of hexa- gonal tabular;refractive index : Ng = l.567-1.568, Nm =1.563-1.564, Np = 1.561-1.562 Ng-Np=0.006 Ng//b, ApΛ(010)CΛNp=11°αΛNm=15°, (+) 2V=65°, parallel extinction, length slow. Under the scanning electromicroscope, its shapes are hexagonal prism or pagoda-like. Its chemical compositions are : SiO2 = 46.54%, Al2O3 = 38.99%, H2O+ 13.93%, SiO3: Al2O3 = 202 : 100. Its thermography curve has a intense endothermic peak at 670°, the curve is gently slope in the side of lower temperature and steeply in the side of higher temperature. In the figure of X-ray diffraction curves, peaks at d (021) =4.2442, d (012) = 3.9549,d (022) =3.7855 appear in the range of 2θ = 20°-24°;and between 2θ = 34°and 40°,four continnuous diffraction peaks appear.In the infrared spectrogram absorption, peaks at 3708,3640,3614cm(-1) occur in high frequency range, the frequency is from higher to lower, while the intensity of absorption peaks is from weak to strong. All of these data fully prove that the dickite from this district is similar to that from other districts. Owing to the fact that this mineral is found at the depth of about 400m under the earth's surface and intergrows with pyrite, the dickite may be formed in the condition of the reducing environment with less than 15℃ temperature.
1987, 5(1): 94-103.
Abstract:
The fossil diatom in the Yellow Sea since the Late Pleistocene can be divided into five diatom zones in ascendant order. 1. Cyclotella striata-Coscinodiscus-H yalodiscus subtilis diatom zones 2. Coscinodiscus radiatus-H yalodiscus subtilis-Cyclotella stytorum diatom zone;3. Coscinocdiscus radiatus-Coscinodiscus perforatus-Coscinodiscus argus diatom zones 4. Corcinodiscus-Cyclotella-Coscinodiscus argus diatom zone;5. Coscinodiscus diatom zone or Cyclotella stylorum-Hyalodiscus subtilis diatom zone. Most kinds of the fossil diatom from the above zones are marine species, indicating the marine environment. The two beds above and beneath Zone Ⅰ contain two fresh water algal zones, reflecting that, because sea level lowered owing to the cold climate during the Late Pleistocene Dali glaciation (Subglaciation Ⅰ, Ⅱ), the continental shelf of the Yellow Sea exposed twice and became a plain dotted with many lakes and swamps in which various species of fresh water algae lived. When the climate became warm and the sea level rose during the subinterglaciation;the continental shelf of the Yellow Sea was submerged by sea water. There lived various diatoms contained in Zone Ⅰ. Transgression happened because the climate became warm globally during the Ho-locene Epoch. In the Yellow Sea there lived many diatoms mentioned in Zones Ⅱ, Ⅰ, Ⅳ and Ⅴ. Zone Ⅰ contains the most abundant pelagic species and more subtropical species, reflecting the maxium temperature and expanded sea area. It should be considered the Atlantic period. Zones Ⅳ and Ⅴ are considered the Subbreal and Subatla-ntic period, and Zone Ⅱ the Boreal-Preboreal period. All this can be proved by 14C data.
The fossil diatom in the Yellow Sea since the Late Pleistocene can be divided into five diatom zones in ascendant order. 1. Cyclotella striata-Coscinodiscus-H yalodiscus subtilis diatom zones 2. Coscinodiscus radiatus-H yalodiscus subtilis-Cyclotella stytorum diatom zone;3. Coscinocdiscus radiatus-Coscinodiscus perforatus-Coscinodiscus argus diatom zones 4. Corcinodiscus-Cyclotella-Coscinodiscus argus diatom zone;5. Coscinodiscus diatom zone or Cyclotella stylorum-Hyalodiscus subtilis diatom zone. Most kinds of the fossil diatom from the above zones are marine species, indicating the marine environment. The two beds above and beneath Zone Ⅰ contain two fresh water algal zones, reflecting that, because sea level lowered owing to the cold climate during the Late Pleistocene Dali glaciation (Subglaciation Ⅰ, Ⅱ), the continental shelf of the Yellow Sea exposed twice and became a plain dotted with many lakes and swamps in which various species of fresh water algae lived. When the climate became warm and the sea level rose during the subinterglaciation;the continental shelf of the Yellow Sea was submerged by sea water. There lived various diatoms contained in Zone Ⅰ. Transgression happened because the climate became warm globally during the Ho-locene Epoch. In the Yellow Sea there lived many diatoms mentioned in Zones Ⅱ, Ⅰ, Ⅳ and Ⅴ. Zone Ⅰ contains the most abundant pelagic species and more subtropical species, reflecting the maxium temperature and expanded sea area. It should be considered the Atlantic period. Zones Ⅳ and Ⅴ are considered the Subbreal and Subatla-ntic period, and Zone Ⅱ the Boreal-Preboreal period. All this can be proved by 14C data.
1987, 5(1): 114-124.
Abstract:
This paper deals with the distribution, controlling factors and geochemical characteristics of the organic material, nitrogen and phosphorus in the Pacific western region (2°-8°N, 170°-173° 20′E)by analysing the amount of the organic material, nitrogen and phosphorus of seven core samples and comparing the grain-size, miner-alogical and biological data of the sediments. The result shows that the average contents of organic material and nitrogen in the surface sediments are similar to those in the surface sediments in the Atlantic western part and the south of the Indian Ocean, but the content of phosphorus is double that in the south of the Indian Ocean. The plane distribution of organic material and nitrogen is just the same. The contents in the southeast are both higher than those in the northwest and increase with the amount of silicon increasing in the sediments. The contents of organic material and nitrogen have positive correlation with the depth of the water and negative correlation with the number of foraminifera in the sediments. The contents of organic material and nitrogen in the sediments are lower than those in the shallow area on the continental shelf. It is because the region is far from land and the sedimentation rate is very low. The sediments come mainly from the synthese of the chemical and biological reactions in sea water. It is suggested that the apatites [Ca5(P02)3OH] added to the sediments during volcanic eruption serve as a reason why the content of phosphorus in the region is higher than that in the shallow water on the continental shelf and in the south of the Indian Ocean. The distribution of the contents of organic material and nitrogen is controlled mainly by the biological type and the amount of clay in the sediments. The amount of phosphorus is controlled mainly by minerals and subsequently by the biological type and the amount of clay in the sediments. The average value of C(org)/N in the surface sediments in the Pacific western region is 14. 98 with a range from 11. 21 to 30. 43. The C(org)/N ratio of the sediments in the region is higher than that in the Atlantic and the shallow area on the continental shelf. It is apparently caused by the following main factors : 1) the poor source of mineral;2)the lower sedimentation rate;and 3)the mineralization of some nitrogenous compounds in the surface sediments. However, the ratio of C(org)/N in the sediments from 0-100cm shows a slight change or no change in the some stations owing to the fact that the affect of bacterium in the deep-sea sediments has weakened or disappeared. There is a positive correlation between the organic material and nitrogen in the sediments. It can be expressed by the equation (Yn = 0.0592C-0.016, r = 0.966). It indicates that the nitrogen in the sediments exists mainly in forms of proteins, amino acids, etc. The correlation between nitrogen and phosphorus can be expressed by the equation: (Yn = 0.1036p + 0.0204, r = 0.500). It shows that the phosphorus exists in forms of inorganic compounds (for example, apatites [Ca5(PO2) 3OH]) besides bio-organic compounds. The relationship between organic material, nitrogen and phosphorus and dioxide silicon and calcium carbonate in the sediments is influenced by the contents of dioxide silicon and calcium carbonate in the sedi ments. When the contents of dioxide silicon and calcium carbonate are about 45% and 5 % respectively and when the contents of dioxide silicon, calcium carbonate change slightly, the contents of organic material, nitrogen and phosphorus change apparently. When the contents of dioxide silicon and calcium carbonate lie between 15%-44%and 10%-60% respectively, the contents of organic material, nitrogen and phosphorus almost have no change. When the contents of dioxide silicon and calcium carbonate are in the ranges of 0-15% and 65%-85% respectively, C. N. P : CaCO3 and C. X. P :SiO2 are about 1 (- 1).
This paper deals with the distribution, controlling factors and geochemical characteristics of the organic material, nitrogen and phosphorus in the Pacific western region (2°-8°N, 170°-173° 20′E)by analysing the amount of the organic material, nitrogen and phosphorus of seven core samples and comparing the grain-size, miner-alogical and biological data of the sediments. The result shows that the average contents of organic material and nitrogen in the surface sediments are similar to those in the surface sediments in the Atlantic western part and the south of the Indian Ocean, but the content of phosphorus is double that in the south of the Indian Ocean. The plane distribution of organic material and nitrogen is just the same. The contents in the southeast are both higher than those in the northwest and increase with the amount of silicon increasing in the sediments. The contents of organic material and nitrogen have positive correlation with the depth of the water and negative correlation with the number of foraminifera in the sediments. The contents of organic material and nitrogen in the sediments are lower than those in the shallow area on the continental shelf. It is because the region is far from land and the sedimentation rate is very low. The sediments come mainly from the synthese of the chemical and biological reactions in sea water. It is suggested that the apatites [Ca5(P02)3OH] added to the sediments during volcanic eruption serve as a reason why the content of phosphorus in the region is higher than that in the shallow water on the continental shelf and in the south of the Indian Ocean. The distribution of the contents of organic material and nitrogen is controlled mainly by the biological type and the amount of clay in the sediments. The amount of phosphorus is controlled mainly by minerals and subsequently by the biological type and the amount of clay in the sediments. The average value of C(org)/N in the surface sediments in the Pacific western region is 14. 98 with a range from 11. 21 to 30. 43. The C(org)/N ratio of the sediments in the region is higher than that in the Atlantic and the shallow area on the continental shelf. It is apparently caused by the following main factors : 1) the poor source of mineral;2)the lower sedimentation rate;and 3)the mineralization of some nitrogenous compounds in the surface sediments. However, the ratio of C(org)/N in the sediments from 0-100cm shows a slight change or no change in the some stations owing to the fact that the affect of bacterium in the deep-sea sediments has weakened or disappeared. There is a positive correlation between the organic material and nitrogen in the sediments. It can be expressed by the equation (Yn = 0.0592C-0.016, r = 0.966). It indicates that the nitrogen in the sediments exists mainly in forms of proteins, amino acids, etc. The correlation between nitrogen and phosphorus can be expressed by the equation: (Yn = 0.1036p + 0.0204, r = 0.500). It shows that the phosphorus exists in forms of inorganic compounds (for example, apatites [Ca5(PO2) 3OH]) besides bio-organic compounds. The relationship between organic material, nitrogen and phosphorus and dioxide silicon and calcium carbonate in the sediments is influenced by the contents of dioxide silicon and calcium carbonate in the sedi ments. When the contents of dioxide silicon and calcium carbonate are about 45% and 5 % respectively and when the contents of dioxide silicon, calcium carbonate change slightly, the contents of organic material, nitrogen and phosphorus change apparently. When the contents of dioxide silicon and calcium carbonate lie between 15%-44%and 10%-60% respectively, the contents of organic material, nitrogen and phosphorus almost have no change. When the contents of dioxide silicon and calcium carbonate are in the ranges of 0-15% and 65%-85% respectively, C. N. P : CaCO3 and C. X. P :SiO2 are about 1 (- 1).
1987, 5(1): 132-136.
Abstract:
There are Muli, Jiancang, Wailihada and Roshui Coalmines in the Muli coal-bearing field, Qinghai. Coal-bearing sequences corresponding to "Qing-Gan Depression" were deposited in an uneven subsidence basin, being formed under the strengthening of geo-crust activity after the Triassic period. The grain size of coal-bearing sediments in the river environment of Middle-Lower Jurassic gradually becomes coarse to fine from bottom to top, but the Upper Jurassic shows fine grain size in the lower part and coarse in the upper part, reflecting a lacustrine environment. The subsidence basin is relatively closed down and the thickness of sediments alters a lot. The petrological changes and characteristics of grain-size distribution are as follows : 1. Sediments of river facies and lacustrine-coastal facies are medium or coarse sandstones with Type A distribution, containing pebbled sandstone and 5 % matrix. 2. Sediments of shallow-lacustrine facies and river-point-bar facies are fine sandstones with Type B, C, D distribution, and most of them are matrix-bearing sandstones (5-20%matrix). 3. Sediments of transitional facies (from the river point bar to the muddy swamp of back bar) are coarse silty sandstones with Type E distribution and most of them are matrix sandstones (20-50% matrix). 4. Sediments of deep lacustrine facies and peat- swamp facies mostly consist of materials 0.03mm ≈ 5 φ in diameter. The river-facies sediments of the lower part of Middle Lower Jurassic are the main portion of the coal-bearing sepuence. So the various coal mines in the Qilian coalfield can be contrasted with each other and the way of looking for coal in future is to find out subsidence basins of NWW-SEE extension along syncline in this area.
There are Muli, Jiancang, Wailihada and Roshui Coalmines in the Muli coal-bearing field, Qinghai. Coal-bearing sequences corresponding to "Qing-Gan Depression" were deposited in an uneven subsidence basin, being formed under the strengthening of geo-crust activity after the Triassic period. The grain size of coal-bearing sediments in the river environment of Middle-Lower Jurassic gradually becomes coarse to fine from bottom to top, but the Upper Jurassic shows fine grain size in the lower part and coarse in the upper part, reflecting a lacustrine environment. The subsidence basin is relatively closed down and the thickness of sediments alters a lot. The petrological changes and characteristics of grain-size distribution are as follows : 1. Sediments of river facies and lacustrine-coastal facies are medium or coarse sandstones with Type A distribution, containing pebbled sandstone and 5 % matrix. 2. Sediments of shallow-lacustrine facies and river-point-bar facies are fine sandstones with Type B, C, D distribution, and most of them are matrix-bearing sandstones (5-20%matrix). 3. Sediments of transitional facies (from the river point bar to the muddy swamp of back bar) are coarse silty sandstones with Type E distribution and most of them are matrix sandstones (20-50% matrix). 4. Sediments of deep lacustrine facies and peat- swamp facies mostly consist of materials 0.03mm ≈ 5 φ in diameter. The river-facies sediments of the lower part of Middle Lower Jurassic are the main portion of the coal-bearing sepuence. So the various coal mines in the Qilian coalfield can be contrasted with each other and the way of looking for coal in future is to find out subsidence basins of NWW-SEE extension along syncline in this area.
1987, 5(1): 10-25.
Abstract:
The majority of oil and gas in China and Australia formed in terrestrial sedimentary basins. Eleven oil samples collected from Eromanga Basin were provided generously by Australia Delhi petroleum Company in 1984. They were sampled from the Middle Jurassic-Early Cretaceous strata. On the basis of mass-spetrometer and capillary chromatogarphy analyses, they are characterised by paraffin-base crude oil with high ratio of pristane/phytane and heavy δ13C value. The compositions of samples are more or less alike, and carbon atom numbers of the principle peak distribute widely from C10 to C21 with a little isoprenoid and the ratios of Pr/nC17 and Ph/nC18 are 0.22-0.49, 0.04-0.09 respectively, only Brikhead oil samples of Charro have a high ratio of Pr/nC17 (0.74) . In accordance with the ratios of Pr/Ph, Pr/nC17 and Ph/nC18 the samples can be divided into three sub-groups approximately. The ratios of Pr/Ph in the three sub-groups A,B,C are 4.0-6.0, 6.0-6.5, 8.0-9.63 respectively, coinciding with the distribution pattern of hydrocarbon chromatogram. Theδ13C values of eleven oil samples range f rom-23 .53‰ to-26.24‰. A lot of scholars useδ13C (-2.6‰)as a boundary value to tell oils formed in marine environment from that in terrestrial. But geological data indicate that the samples are generated in terrestrial environment. According to the ratios of Pr/Ph, Pr/nC17 and Ph/nC18, the Chinese terrestrial petroleum can be classified into four types. TypeⅠ: The ratio of Pr/Ph is near 1.0 (0.87-1.39) with medium pristane and phytane content. The ratios of Pr/nC17 and Ph/nC18 are 0.18-0.61 and 0.15-0.77 respectively. It is generated in fresh-brackish lacustrine sediments. The majority of marine oils distribute in this range. Type Ⅱ: the ratio of Pr/Ph is less than 0.80(0.33-0.70), the phytane content is specially high, usually with predominant odd carbon numbers in lower carbon numbers, meanwhile the predominance of even carbon numbers in higher ones when phytane is regarded as a boundary. Type Ⅱ forms in saline lacustrine enviroment and some of marine crude oils formed in saline enviroment probably have this kind of characteristics. The ratio of Pr/Ph in Type Ⅲ is more than 2.50 (2.75-4.28) with very low content of isoprenoid and the ratios of Pr/nC17, Ph/nC18 are less than 0.85, 0.21 respectively. It is generated in river-lacustrine or swamp deposits. The environment of forming type Ⅳ is peaty-swamp or bog. The ratio of Pr/Ph is 7.23, while those of Pr/nC17, Ph/nC18 are 1.27, 0.18 respectively. Type Ⅲ and Type Ⅳ are similar in characteristics, however, there is a high content of isoprenoid in the latter. The value of C in the Chinese terrestrial petroleum distributes from -20‰to -32‰widely. Owing to the δ13C value of oils formed in salt lacustrine deposits and some of swamps is heavier than -26‰ as well, to authors opinion, it could not use the δ13C value (-26‰) to separate marine oils from terrestrial ones. However, on the basis of statistical probability, we can distinguish between fresh-brackish lacustrine and marine oils by using δ13C (-26‰) as a boundary value. This paper introduces a new graph which expresses the relationship between the ratio of Pr/Ph and the value of δ13C in determining the environments of oil formation. The different regions of the graphrespcct different geochemical environments in which variant types of crude oils are generated, such as Region Ⅰ: the fresh-brackish lacustrine, Ⅱ: the salt water lacustrine, Ⅲ: the river -lacustrine, Ⅳ: the peat-bog, Ⅴ: the marine.
The majority of oil and gas in China and Australia formed in terrestrial sedimentary basins. Eleven oil samples collected from Eromanga Basin were provided generously by Australia Delhi petroleum Company in 1984. They were sampled from the Middle Jurassic-Early Cretaceous strata. On the basis of mass-spetrometer and capillary chromatogarphy analyses, they are characterised by paraffin-base crude oil with high ratio of pristane/phytane and heavy δ13C value. The compositions of samples are more or less alike, and carbon atom numbers of the principle peak distribute widely from C10 to C21 with a little isoprenoid and the ratios of Pr/nC17 and Ph/nC18 are 0.22-0.49, 0.04-0.09 respectively, only Brikhead oil samples of Charro have a high ratio of Pr/nC17 (0.74) . In accordance with the ratios of Pr/Ph, Pr/nC17 and Ph/nC18 the samples can be divided into three sub-groups approximately. The ratios of Pr/Ph in the three sub-groups A,B,C are 4.0-6.0, 6.0-6.5, 8.0-9.63 respectively, coinciding with the distribution pattern of hydrocarbon chromatogram. Theδ13C values of eleven oil samples range f rom-23 .53‰ to-26.24‰. A lot of scholars useδ13C (-2.6‰)as a boundary value to tell oils formed in marine environment from that in terrestrial. But geological data indicate that the samples are generated in terrestrial environment. According to the ratios of Pr/Ph, Pr/nC17 and Ph/nC18, the Chinese terrestrial petroleum can be classified into four types. TypeⅠ: The ratio of Pr/Ph is near 1.0 (0.87-1.39) with medium pristane and phytane content. The ratios of Pr/nC17 and Ph/nC18 are 0.18-0.61 and 0.15-0.77 respectively. It is generated in fresh-brackish lacustrine sediments. The majority of marine oils distribute in this range. Type Ⅱ: the ratio of Pr/Ph is less than 0.80(0.33-0.70), the phytane content is specially high, usually with predominant odd carbon numbers in lower carbon numbers, meanwhile the predominance of even carbon numbers in higher ones when phytane is regarded as a boundary. Type Ⅱ forms in saline lacustrine enviroment and some of marine crude oils formed in saline enviroment probably have this kind of characteristics. The ratio of Pr/Ph in Type Ⅲ is more than 2.50 (2.75-4.28) with very low content of isoprenoid and the ratios of Pr/nC17, Ph/nC18 are less than 0.85, 0.21 respectively. It is generated in river-lacustrine or swamp deposits. The environment of forming type Ⅳ is peaty-swamp or bog. The ratio of Pr/Ph is 7.23, while those of Pr/nC17, Ph/nC18 are 1.27, 0.18 respectively. Type Ⅲ and Type Ⅳ are similar in characteristics, however, there is a high content of isoprenoid in the latter. The value of C in the Chinese terrestrial petroleum distributes from -20‰to -32‰widely. Owing to the δ13C value of oils formed in salt lacustrine deposits and some of swamps is heavier than -26‰ as well, to authors opinion, it could not use the δ13C value (-26‰) to separate marine oils from terrestrial ones. However, on the basis of statistical probability, we can distinguish between fresh-brackish lacustrine and marine oils by using δ13C (-26‰) as a boundary value. This paper introduces a new graph which expresses the relationship between the ratio of Pr/Ph and the value of δ13C in determining the environments of oil formation. The different regions of the graphrespcct different geochemical environments in which variant types of crude oils are generated, such as Region Ⅰ: the fresh-brackish lacustrine, Ⅱ: the salt water lacustrine, Ⅲ: the river -lacustrine, Ⅳ: the peat-bog, Ⅴ: the marine.
1987, 5(1): 37-47.
Abstract:
Before the introduction of the Fourier transform infrared (FTIR) spectrum, X-ray diffraction was probably the best method for the identification and guantitatire analysis of clay mineral mixtures. But the method is limited by problems of the overlaying diffraction peaks and mineral orientation, particularly to the clay mineral. The dispersive infrared spectrum is also limited by the overlaying andi superposition of the bands of complex multicomponent systems. The introduction of the FTIR spectrum promises to improve the routine mineral analysis. This paper deals with the procedure of the sample preparation for the FT-IR differential spectrum and quantitative analysis of clay mineral mixture samples, and discusses the following problems: 1) It is generally accepted that the attainable maximum ratio of signal and noise the FTIR spectrum is determined by the digitization noise system of the minimum significant bit (LSB) in the analog/digital (A/D) converter. The signal/noise ratio(SNR) of a 100% line is formed by proportion, and then the final equation should be Here△vis the resolution ratio, γmax and γmin are the two opposite extremes of the observed wavenumber range, C is the cumulative number of scanning, b is the changing range in bits of the A/D converter, f is the safety margin between the largest measured signal and the saturation of the converter, and M is the ratio between the spectral intensity of measuring wavenumber and the mean value. According to this theory, the equations of the differential spectrometry and the differential quantitative method have been further confirmed in practice. 2) The mixed spectrum of kaolinite including trace illite is very similar to that of pure kaolinite because of the strong absorption of kaolinite. However, applying FTIR, we can use the computer to digitally subtract the known standard spectrum of kaolinite from the mixed spetrum so as to get the differential spectrum, which can now be identified as the illite spectrum, Chlorite and kaolinite spectra are very similar, too. We also obtained each pure spectrum from mixed spectrum by using the FTIR differential spectrum. 3) As mentioned above, we performed the quantitative analysis on clay mineral mixtures by using the FTIR differential spectrum. The results show that the relative stancard deviation of five clay mineral mixtures is less than 3%. The concentration of five absorbed frequancy measurement has an average error of only 0.2-0.5%. This study clearly proves that the FTIR differential spectrum is feasible for the clay mineral mixture.
Before the introduction of the Fourier transform infrared (FTIR) spectrum, X-ray diffraction was probably the best method for the identification and guantitatire analysis of clay mineral mixtures. But the method is limited by problems of the overlaying diffraction peaks and mineral orientation, particularly to the clay mineral. The dispersive infrared spectrum is also limited by the overlaying andi superposition of the bands of complex multicomponent systems. The introduction of the FTIR spectrum promises to improve the routine mineral analysis. This paper deals with the procedure of the sample preparation for the FT-IR differential spectrum and quantitative analysis of clay mineral mixture samples, and discusses the following problems: 1) It is generally accepted that the attainable maximum ratio of signal and noise the FTIR spectrum is determined by the digitization noise system of the minimum significant bit (LSB) in the analog/digital (A/D) converter. The signal/noise ratio(SNR) of a 100% line is formed by proportion, and then the final equation should be Here△vis the resolution ratio, γmax and γmin are the two opposite extremes of the observed wavenumber range, C is the cumulative number of scanning, b is the changing range in bits of the A/D converter, f is the safety margin between the largest measured signal and the saturation of the converter, and M is the ratio between the spectral intensity of measuring wavenumber and the mean value. According to this theory, the equations of the differential spectrometry and the differential quantitative method have been further confirmed in practice. 2) The mixed spectrum of kaolinite including trace illite is very similar to that of pure kaolinite because of the strong absorption of kaolinite. However, applying FTIR, we can use the computer to digitally subtract the known standard spectrum of kaolinite from the mixed spetrum so as to get the differential spectrum, which can now be identified as the illite spectrum, Chlorite and kaolinite spectra are very similar, too. We also obtained each pure spectrum from mixed spectrum by using the FTIR differential spectrum. 3) As mentioned above, we performed the quantitative analysis on clay mineral mixtures by using the FTIR differential spectrum. The results show that the relative stancard deviation of five clay mineral mixtures is less than 3%. The concentration of five absorbed frequancy measurement has an average error of only 0.2-0.5%. This study clearly proves that the FTIR differential spectrum is feasible for the clay mineral mixture.
1987, 5(1): 48-57.
Abstract:
By applying the methods of understanding unknown environments from known environments and the principle of uniformitarianism("the key to the past is in the present"), the relationship between characters of clay minerals in mudstone and depo-sitional environments is discussed in this paper. Thus the possible facies indicators in clay, such as microstructures, autogenetic clay minerals and assemblage of clay minerals, have been discovered. And it was tried to use them to indicate the depositional environments of some mudstone without obvious macroscopic facies indicators. First, the samples of different mudstone,which were collected from the same area and the same coal-bearing strata and which contained various facies fossils, were taken respectively to be representatives of seawater deposit, brackish deposit and fresh-water deposit. In order to contrast, additionally, several modern mud samples were taken from different modern enviornments in the Luan River system. Then, these samples of different environments were studied in detail by scanning electron microscope, X-ray diffraction and differential thermal analysis. The results of repeated contrast showed that following three aspect characteristics of clay minerals in the samples were closely related to depositional environments, probably, they were controlled by environmental conditions: 1.Orientation and fabric feature of clay In freshwater samples, the orientation of clay particles was better, flaky clay particles tended to arrange parallelly each other and showed a kind of parallel structure. While in marine and brackish samples, flaky clay particles accumulated in a jumble and showed somewhat flocculated, honeycomb, and cardhouse structures. The former probably reflects that the deposition of clay particles in freshwater,Which was short of electrolytes, was mainly controlled by hydrodynamic condition, and the suspended clay particles deposited as single flakes. The latter probably reflects that deposition of clay in seawater or brackish water, which were rich in electrolytes and microbes, was not only controlled by hydrodynamic condition, but also strongly influenced by coagulation, organism agglutination and flocculation, the suspended clay particles tend to deposit as aggregates of clay minerals. 2.Autogenetic clay minerals The observation of SEM showed that different autogenetic clay species existed in different environment samples. In the marine and brackish deposits the main autogenetic clay min ls are illite, montmorillonite and chlorite. But in freshwater deposits mainly is kaolinite. It indicates that the formation of autogenetic clay minerals arae controlled by physicochemical condition of water medium in depositional environments. So it promises to indicate environments by studying types of autogenetic clay minerals in mudstone. In the SEM photographay the identification of autogenetic clay minerals can be summarized as follows;(a) Mineral grain is complete and its edges and corners are clearly discernible and withoat any transported marks;(b) It generally formed in the pore and fossils cavity, its crystal size and arrangement were restricted by crystal space and out of relation to terrigenous clay grain;(c) Some autogenetic clay minerals transformated from other minerals, so it could be identified according to the relation between both of them. 3.Assemblage of clay minerals By utilizing X- ray diffraction and differential thermal analysis, SEM and chemical analysis, the relative content of each type of clay minerals in each sample has been estimated. The assemblage of clay minerals in freshwater environmental samples is distinct from seawater and brackish ones, for example, in brackish clay samples the main clay assemblage is illite-montmorillonite-kaolinite (arranged in sequence of relative content),and in freshwater clay samples the main clay assemblage is kaolinite-illite-montmorillonite. The causes for different clay assemblage might be the following: (a) From slightly acid, low salinity fresh water to basic, highly salinity seaw
By applying the methods of understanding unknown environments from known environments and the principle of uniformitarianism("the key to the past is in the present"), the relationship between characters of clay minerals in mudstone and depo-sitional environments is discussed in this paper. Thus the possible facies indicators in clay, such as microstructures, autogenetic clay minerals and assemblage of clay minerals, have been discovered. And it was tried to use them to indicate the depositional environments of some mudstone without obvious macroscopic facies indicators. First, the samples of different mudstone,which were collected from the same area and the same coal-bearing strata and which contained various facies fossils, were taken respectively to be representatives of seawater deposit, brackish deposit and fresh-water deposit. In order to contrast, additionally, several modern mud samples were taken from different modern enviornments in the Luan River system. Then, these samples of different environments were studied in detail by scanning electron microscope, X-ray diffraction and differential thermal analysis. The results of repeated contrast showed that following three aspect characteristics of clay minerals in the samples were closely related to depositional environments, probably, they were controlled by environmental conditions: 1.Orientation and fabric feature of clay In freshwater samples, the orientation of clay particles was better, flaky clay particles tended to arrange parallelly each other and showed a kind of parallel structure. While in marine and brackish samples, flaky clay particles accumulated in a jumble and showed somewhat flocculated, honeycomb, and cardhouse structures. The former probably reflects that the deposition of clay particles in freshwater,Which was short of electrolytes, was mainly controlled by hydrodynamic condition, and the suspended clay particles deposited as single flakes. The latter probably reflects that deposition of clay in seawater or brackish water, which were rich in electrolytes and microbes, was not only controlled by hydrodynamic condition, but also strongly influenced by coagulation, organism agglutination and flocculation, the suspended clay particles tend to deposit as aggregates of clay minerals. 2.Autogenetic clay minerals The observation of SEM showed that different autogenetic clay species existed in different environment samples. In the marine and brackish deposits the main autogenetic clay min ls are illite, montmorillonite and chlorite. But in freshwater deposits mainly is kaolinite. It indicates that the formation of autogenetic clay minerals arae controlled by physicochemical condition of water medium in depositional environments. So it promises to indicate environments by studying types of autogenetic clay minerals in mudstone. In the SEM photographay the identification of autogenetic clay minerals can be summarized as follows;(a) Mineral grain is complete and its edges and corners are clearly discernible and withoat any transported marks;(b) It generally formed in the pore and fossils cavity, its crystal size and arrangement were restricted by crystal space and out of relation to terrigenous clay grain;(c) Some autogenetic clay minerals transformated from other minerals, so it could be identified according to the relation between both of them. 3.Assemblage of clay minerals By utilizing X- ray diffraction and differential thermal analysis, SEM and chemical analysis, the relative content of each type of clay minerals in each sample has been estimated. The assemblage of clay minerals in freshwater environmental samples is distinct from seawater and brackish ones, for example, in brackish clay samples the main clay assemblage is illite-montmorillonite-kaolinite (arranged in sequence of relative content),and in freshwater clay samples the main clay assemblage is kaolinite-illite-montmorillonite. The causes for different clay assemblage might be the following: (a) From slightly acid, low salinity fresh water to basic, highly salinity seaw
1987, 5(1): 69-76.
Abstract:
The composition and microstructure of the bauxite deposits from Xiuwen County, Guizhou Province have been studied with JSM-35C scanning electron microscope and PV-9100 X-ray energy dispersive analyzer. The body of bauxite deposits in Xiuwen is in layered or lenticular structure with different size. The occurrence is gently. The bauxite bed is in median of congenial. Upper and lower parts of the bauxite bed are bauxitic clay in grey and compact texture, and downward, there is hematiteshale. The bauxitic clay and compact bauxite, oolitic bauxite soil bauxite and their transitional types are mainly dealt with in this paper. The bauxitic clay under bauxite bed is grey and compact. Its main component is kaolinite and the crystal is mainly scaly. From its microstructure, the kaolinite, seen under electro-micro-scope, is authigenic mineral in syngenetic stage of epicontinental sea sedimentation. In bauxite layer, there are compact bauxite, soil bauxite, oolitic bauxite and their transitional types. In their components, the diaspore is dominated, and the following are: beohmite, kaolinite, micagroup mineral and several kinds of terrigenous clastic sediments. According to the abrasion of the sediments, it is considered that the accumulation in bauxite layer is connected with the remove of the terrigenous sediments in a suort distance. The potassium is more high in compact bauxite. The crystal grain which contains some heavy metals, such as gold, silver and copper or several kinds of elements, has been found, the author considers that it is the result of absorption during sedimentation. The existence of the gold chloride proves that the bauxite bed may have undergone the process of high temperature or high pressure. In the inner part and matrix of the oolitic bauxite, the major component is diaspore, the minor components are kaolinite, mica-group mineral, a few boehmite and some of terrigenous clastic sediments. Several cross-sections of ooide and bean have been observed carefuly. Generally, there are four layers from core to outside. The main component in the core is kaolinite. In the component of the second and third layers, the diaspore is dominated. But the microstructure in the second and third layers is different. In the forth layer, the main component is kaolinite, its crystallinity is fine, but absorption is obvious and impure elements are varied. Most of soil bauxite are soft and their tenor is in high grade. They contain a lot of columnar pseudohexagonal crystal with complete shape and uniform size. In their microstructure, the character of secondary enrichment is obvious. There are many secondary holes in some of soil bauxite. The shapes and microstructures of these holes are varied. Most of holes are filled with complete macrocrystalline diaspore. In some of these holes, typical crystals of diaspore and gibbsite exist together. In a few holes, the indications of transform from clay to bauxite are obvious. The characters mentioned above indicate that the concentration of the bauxite is connected with leaching and downward enrichmcent.
The composition and microstructure of the bauxite deposits from Xiuwen County, Guizhou Province have been studied with JSM-35C scanning electron microscope and PV-9100 X-ray energy dispersive analyzer. The body of bauxite deposits in Xiuwen is in layered or lenticular structure with different size. The occurrence is gently. The bauxite bed is in median of congenial. Upper and lower parts of the bauxite bed are bauxitic clay in grey and compact texture, and downward, there is hematiteshale. The bauxitic clay and compact bauxite, oolitic bauxite soil bauxite and their transitional types are mainly dealt with in this paper. The bauxitic clay under bauxite bed is grey and compact. Its main component is kaolinite and the crystal is mainly scaly. From its microstructure, the kaolinite, seen under electro-micro-scope, is authigenic mineral in syngenetic stage of epicontinental sea sedimentation. In bauxite layer, there are compact bauxite, soil bauxite, oolitic bauxite and their transitional types. In their components, the diaspore is dominated, and the following are: beohmite, kaolinite, micagroup mineral and several kinds of terrigenous clastic sediments. According to the abrasion of the sediments, it is considered that the accumulation in bauxite layer is connected with the remove of the terrigenous sediments in a suort distance. The potassium is more high in compact bauxite. The crystal grain which contains some heavy metals, such as gold, silver and copper or several kinds of elements, has been found, the author considers that it is the result of absorption during sedimentation. The existence of the gold chloride proves that the bauxite bed may have undergone the process of high temperature or high pressure. In the inner part and matrix of the oolitic bauxite, the major component is diaspore, the minor components are kaolinite, mica-group mineral, a few boehmite and some of terrigenous clastic sediments. Several cross-sections of ooide and bean have been observed carefuly. Generally, there are four layers from core to outside. The main component in the core is kaolinite. In the component of the second and third layers, the diaspore is dominated. But the microstructure in the second and third layers is different. In the forth layer, the main component is kaolinite, its crystallinity is fine, but absorption is obvious and impure elements are varied. Most of soil bauxite are soft and their tenor is in high grade. They contain a lot of columnar pseudohexagonal crystal with complete shape and uniform size. In their microstructure, the character of secondary enrichment is obvious. There are many secondary holes in some of soil bauxite. The shapes and microstructures of these holes are varied. Most of holes are filled with complete macrocrystalline diaspore. In some of these holes, typical crystals of diaspore and gibbsite exist together. In a few holes, the indications of transform from clay to bauxite are obvious. The characters mentioned above indicate that the concentration of the bauxite is connected with leaching and downward enrichmcent.
1987, 5(1): 86-93.
Abstract:
This paper deals with how the inclusion is used in a new study field which is about the evaluation of oil-and-gas resources in cardonate areas. The authors put emphasis on the possibility of the inclusion application in the oil-and-gas prospect evaluation and some major problems which might be resolved by using the inclusion stuby method in the research of oil and gas resources. On the basis of the research on the oilandgas reservoirs and nonreservoirs of carbonate rocks in Hebei, Sichuan, Guizhou provinces and Guangxi Zhuang Autonomous Region, it has been proved that the inclusion can be formed in each stage of oil and gas accumulation and may be a fluid inclusion of gas and liquid phase, often seen in carbonate rocks, or an organic inclusion containing hydrocarbons. However, the organic inclusion can directly provide evidence for primary and secondary migration of hydrocarbons from carbonate rocks. In the oil and gas resource evaluation,it is possible to investigate the thermal history of petroleum genesis and the maturity of organic matter according to the type, feature, palaeotemperature, and gaseous-phase composition of inclusions. For example, the type of the inclusion from oil-bearing indication rocks in Pingquan, Hebei is mainly of the pure-liquid inclusion and fluid-hydrocarbon-bearing organic inclusion, and the homogenization temperature is 120-145℃. For another example, the type of the inclusion from carbonate minerals with a large amount of anthraxolite in Guangxi is mainly of the gas-liquid phase fluid inclusion, however, the organic inclusion in the minerals consists mainly of gaseous hydrocarbon and solid bitumen, and the homogenization temperature is 240-260℃. The analysis results show that the gaseous-phase compositions in inclusions are mainly H2O and CO2 in low stage of evolution, but CH4 is increasing along with the evolution development towards high stage. Taking the inclusion in Pingquan, Hebei, and Shang-lin, Guangxi as an example, its CH4/H2O + CO2 values are 0.0015 and 0.0075 (wt%) respectively. Moreover, the inclusion can be used to study the origin and estrapment conditions of oil and gas in order to obtain chemical compositions of ancient oil-field water,salinity,stable isotopes of C,H,O,oxidizing reduction potential,acidity,and fluid pressure parameters etc. May be determined by using inclusion study. For example,the liquid compositions of the inclusion from oil and gas reservoirs in Eastern Sichuan and Pingquan, Hebei are S-poor, but Cl, Na-rich, the fluid salinity is 13-14.5 wt%, and the D value of the mineralizing fluid in Eastern Sichuan is-29.27%,δ18O is+ 0.37‰, pH=7.2-7.6, these show that it is of palaeo-seawater character. The reduction parameter of the fluid is 1.0, indicating a reducing environment.
This paper deals with how the inclusion is used in a new study field which is about the evaluation of oil-and-gas resources in cardonate areas. The authors put emphasis on the possibility of the inclusion application in the oil-and-gas prospect evaluation and some major problems which might be resolved by using the inclusion stuby method in the research of oil and gas resources. On the basis of the research on the oilandgas reservoirs and nonreservoirs of carbonate rocks in Hebei, Sichuan, Guizhou provinces and Guangxi Zhuang Autonomous Region, it has been proved that the inclusion can be formed in each stage of oil and gas accumulation and may be a fluid inclusion of gas and liquid phase, often seen in carbonate rocks, or an organic inclusion containing hydrocarbons. However, the organic inclusion can directly provide evidence for primary and secondary migration of hydrocarbons from carbonate rocks. In the oil and gas resource evaluation,it is possible to investigate the thermal history of petroleum genesis and the maturity of organic matter according to the type, feature, palaeotemperature, and gaseous-phase composition of inclusions. For example, the type of the inclusion from oil-bearing indication rocks in Pingquan, Hebei is mainly of the pure-liquid inclusion and fluid-hydrocarbon-bearing organic inclusion, and the homogenization temperature is 120-145℃. For another example, the type of the inclusion from carbonate minerals with a large amount of anthraxolite in Guangxi is mainly of the gas-liquid phase fluid inclusion, however, the organic inclusion in the minerals consists mainly of gaseous hydrocarbon and solid bitumen, and the homogenization temperature is 240-260℃. The analysis results show that the gaseous-phase compositions in inclusions are mainly H2O and CO2 in low stage of evolution, but CH4 is increasing along with the evolution development towards high stage. Taking the inclusion in Pingquan, Hebei, and Shang-lin, Guangxi as an example, its CH4/H2O + CO2 values are 0.0015 and 0.0075 (wt%) respectively. Moreover, the inclusion can be used to study the origin and estrapment conditions of oil and gas in order to obtain chemical compositions of ancient oil-field water,salinity,stable isotopes of C,H,O,oxidizing reduction potential,acidity,and fluid pressure parameters etc. May be determined by using inclusion study. For example,the liquid compositions of the inclusion from oil and gas reservoirs in Eastern Sichuan and Pingquan, Hebei are S-poor, but Cl, Na-rich, the fluid salinity is 13-14.5 wt%, and the D value of the mineralizing fluid in Eastern Sichuan is-29.27%,δ18O is+ 0.37‰, pH=7.2-7.6, these show that it is of palaeo-seawater character. The reduction parameter of the fluid is 1.0, indicating a reducing environment.
1987, 5(1): 104-113.
Abstract:
There are at least dozens of modes to evaluate oil and gas resources. The selection of the evaluation methods must be based on the geologic conditions of a certain area, since the restrictive applicability of each method has been recognized. This paper summarized seven modes which are commonly used. 1. Geologic analigosm: It is known that the resource capacity of a sedimentary basin basically relys on geologic factors of the basin. So that area A should have the similar resource capacity to that of area B when area A and B have similar geologic conditions, even though area A and area B are respectively in early stage and mature stage of exploration. 2. Volume mode: This method lies estimating oil and gas resources of a sedimentary basin on the density parameters(i. e. oil and gas reserves in per unit volume Ton Cubic kilometer). 3. Average volume-velocity method. According to statistics, it is known that there is an increase of logarithmic linear function between the resource capacity of a sedimentary basin and its average volume-velocity. 4. Trap volume method: This is an important method to evaluate the resources in single trap, local structure system and trap group. 5. Material balance mode: This mode is based on that the algebraic sum of the volume variation of oil, gas and water should be zero within an oil and gas accumulation. 6. Montcalo model. This is a kind of statistical distribution models. 7. Oilfield-scale sequence mode: The whole scale, numbers and final reserves of an oilfield can be prodicted by the reserve survey of several giant oilfields and the sequence of their scale within the basin. According to different stages of exploration and geology of the study area, different method should be selected in resource evaluation.
There are at least dozens of modes to evaluate oil and gas resources. The selection of the evaluation methods must be based on the geologic conditions of a certain area, since the restrictive applicability of each method has been recognized. This paper summarized seven modes which are commonly used. 1. Geologic analigosm: It is known that the resource capacity of a sedimentary basin basically relys on geologic factors of the basin. So that area A should have the similar resource capacity to that of area B when area A and B have similar geologic conditions, even though area A and area B are respectively in early stage and mature stage of exploration. 2. Volume mode: This method lies estimating oil and gas resources of a sedimentary basin on the density parameters(i. e. oil and gas reserves in per unit volume Ton Cubic kilometer). 3. Average volume-velocity method. According to statistics, it is known that there is an increase of logarithmic linear function between the resource capacity of a sedimentary basin and its average volume-velocity. 4. Trap volume method: This is an important method to evaluate the resources in single trap, local structure system and trap group. 5. Material balance mode: This mode is based on that the algebraic sum of the volume variation of oil, gas and water should be zero within an oil and gas accumulation. 6. Montcalo model. This is a kind of statistical distribution models. 7. Oilfield-scale sequence mode: The whole scale, numbers and final reserves of an oilfield can be prodicted by the reserve survey of several giant oilfields and the sequence of their scale within the basin. According to different stages of exploration and geology of the study area, different method should be selected in resource evaluation.
1987, 5(1): 125-131.
Abstract:
Liaoning Province is located in the circum-Pacific volcanic belt where diastro-phic and volcanic activities occured repeatedly during Mesozoic and Tertiary, forming several hundreds of volcanic cones and mounds which occupy an area about 7,000km2. The total thickness of the volcanic rocks is 3,000 metres. They are classified into the lower Yanshan volcanic rock, upper Yanshan volcanic rock and Himalayan basalt according to the interrelation between their cyclothems of magmatic differentiation and the sediments of erupting intervals. There are usually sedimentary coal series of intervals interbedded in the volcanic rocks developed ia different geological times. The typical occurrence can be seen in some coal fields in Shuangtagou of Nanpiao, Shahezi of Changtu, Wenduhua of Tianshan and Fushun. All of these coalfields, surrounding rocks of central eruption, developed in the marginal belts of volcanos. It shows that the coal accumulation is controlled by the volcanic-structural mechanism. Thus, in origin, these coal series are sharply different from those usually seen in shallow-sea, offshore or inland environments. The coal accumulation in erupting intervals is affected by volcanic mechanism and sedimentation. It formed rapidly and was of the characters of volcanic and sedimentary rocks. Since such coals were generated merely during erupting intervals and their development space was restricted in the marginal belts of central eruption, the coal prospecting should be concentrated on the regions where volcanics developed well, i.e. on Yanshan Depression and Xinganling Foldbelt, which include the upper volcanic rock in the marginal belts of volcanos (Rock Units, No. 16-50, and 35 volcanic cones) about 16,000km2, the lower volcanic rock with an area about 2,000km2 and the Tertiary basaltic platform about 8,000km2. It is necessary to research into the distribution, reserve and buried depth of the coals formed in erupting intervals, especially in Liaoning Province where more coal resources are needed keenly. Effectively mining and utilizing of such coal resources are considered of important economic significance.
Liaoning Province is located in the circum-Pacific volcanic belt where diastro-phic and volcanic activities occured repeatedly during Mesozoic and Tertiary, forming several hundreds of volcanic cones and mounds which occupy an area about 7,000km2. The total thickness of the volcanic rocks is 3,000 metres. They are classified into the lower Yanshan volcanic rock, upper Yanshan volcanic rock and Himalayan basalt according to the interrelation between their cyclothems of magmatic differentiation and the sediments of erupting intervals. There are usually sedimentary coal series of intervals interbedded in the volcanic rocks developed ia different geological times. The typical occurrence can be seen in some coal fields in Shuangtagou of Nanpiao, Shahezi of Changtu, Wenduhua of Tianshan and Fushun. All of these coalfields, surrounding rocks of central eruption, developed in the marginal belts of volcanos. It shows that the coal accumulation is controlled by the volcanic-structural mechanism. Thus, in origin, these coal series are sharply different from those usually seen in shallow-sea, offshore or inland environments. The coal accumulation in erupting intervals is affected by volcanic mechanism and sedimentation. It formed rapidly and was of the characters of volcanic and sedimentary rocks. Since such coals were generated merely during erupting intervals and their development space was restricted in the marginal belts of central eruption, the coal prospecting should be concentrated on the regions where volcanics developed well, i.e. on Yanshan Depression and Xinganling Foldbelt, which include the upper volcanic rock in the marginal belts of volcanos (Rock Units, No. 16-50, and 35 volcanic cones) about 16,000km2, the lower volcanic rock with an area about 2,000km2 and the Tertiary basaltic platform about 8,000km2. It is necessary to research into the distribution, reserve and buried depth of the coals formed in erupting intervals, especially in Liaoning Province where more coal resources are needed keenly. Effectively mining and utilizing of such coal resources are considered of important economic significance.
