1994 Vol. 12, No. 3
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Display Method:
1994, 12(3): 1-11.
Abstract:
The Sinian ( Precambrian ) chert formation occurs at Gusui,western Guangdong Province,southern China,and is an integral part of the source strata of the Hetai gold field. The presence of the chert formation offers an excellent opportunity to evaluate the possible hydrothermal system and its role in the formation of the.source strata. The Precambrian chert from Gusui is characterized by bedded, laminated,massive and pseudobrecciated structures, and the depletion of TiO2,AI2O3and most trace elements. However, it is enriched in Ba,As, Sb, Hg and Se,which are considered as diagnostic elements of hydrothermal sediments. In the Al一Fe一Mn ternary diagram,it falls into the“hydrothermal field ". Correspondence analysis and factor analysis reveal that many elements show up in the factor that represents the leaching of country rocks by hydrothermal solution,and is the very characteristic element association of the geochemically anomalous South China basement. REE are characterized by a low total content and a gradually increasing NASC一normalized value with increasing atomic number of REE, ranging between the upper and the lower limits of typical hydrothermal deposits.The petrologic and geochemical evidences suggest a hydrothermal origin for the chert. It may have formed in a Precambrian rift or extension zone developed within the Yunkai marginal geosyncline.with a fault system linkihg to an unknown heat source at depth.
The Sinian ( Precambrian ) chert formation occurs at Gusui,western Guangdong Province,southern China,and is an integral part of the source strata of the Hetai gold field. The presence of the chert formation offers an excellent opportunity to evaluate the possible hydrothermal system and its role in the formation of the.source strata. The Precambrian chert from Gusui is characterized by bedded, laminated,massive and pseudobrecciated structures, and the depletion of TiO2,AI2O3and most trace elements. However, it is enriched in Ba,As, Sb, Hg and Se,which are considered as diagnostic elements of hydrothermal sediments. In the Al一Fe一Mn ternary diagram,it falls into the“hydrothermal field ". Correspondence analysis and factor analysis reveal that many elements show up in the factor that represents the leaching of country rocks by hydrothermal solution,and is the very characteristic element association of the geochemically anomalous South China basement. REE are characterized by a low total content and a gradually increasing NASC一normalized value with increasing atomic number of REE, ranging between the upper and the lower limits of typical hydrothermal deposits.The petrologic and geochemical evidences suggest a hydrothermal origin for the chert. It may have formed in a Precambrian rift or extension zone developed within the Yunkai marginal geosyncline.with a fault system linkihg to an unknown heat source at depth.
1994, 12(3): 21-28.
Abstract:
The data of δ18O and δ13C were measured fromplanktoric forarninifera for 4 species and benthic foraminifen for 2 species in piston core 8KL of the South China Sea(S. C. S.).The oxygen isotope records of planktoric and benthic foraminifen can be recognized stage 1~6 distinctly. A research on biostratigraphy of the planktonic forams indicated that the last appearance datum(LAD)of Globigerinoides ruber(pink) occured at oxygen isotope stage 5. 5(≈120ka). The curvres of planktonic carbon isotope composition clearly recorded two lightest events at 128ka (stage 5/6) and 12ka(stage 1/2),especially for 128ka. This phenomenon was discoverd in different cores such as SCS 15A and 15B in the southern part of S. C. S.,37KL in the northern part of S. C. S. and V 19一30 in the East Pacific Ocean as well as the cores in Mexico Gulf. Therefore,the two events might be existed in the whole ocean. Due to the lighter δ13C value was recorded in deeper planktomic furams, so it can be infered that the two lightest events refleeted on existence of welling watermasses from intermediate and bottom waters in transitional duration from glaciation interglaciation. In terms of the oxygen siotope records from planktonic forams, the dewelling water depth of planktonic foraminifera species from shallower to deeper was G. Tuber (pink ),G. Tuber and G. sacculifer in turn. Based on oxygen isotope geostratigraphic scale,the sedimentary rates and fluxes were calculated for each stage. The results show that the sedimental rates and fluxes are 2. 7cm/ka and 17. 6g/m2·yr for stage 1;1. 9cm/ka and 16. Og/m2·yr for stage 5;6. 7cm/ka and 57. 3g/m2·yr for stage 6,7. 2cm/ka and 59. Og/m2·yr for the last glaciation (stage 2,3,9).All in all,the sedimentary rates and fluxes in glacial times were much greater than that in interglacial ages.
The data of δ18O and δ13C were measured fromplanktoric forarninifera for 4 species and benthic foraminifen for 2 species in piston core 8KL of the South China Sea(S. C. S.).The oxygen isotope records of planktoric and benthic foraminifen can be recognized stage 1~6 distinctly. A research on biostratigraphy of the planktonic forams indicated that the last appearance datum(LAD)of Globigerinoides ruber(pink) occured at oxygen isotope stage 5. 5(≈120ka). The curvres of planktonic carbon isotope composition clearly recorded two lightest events at 128ka (stage 5/6) and 12ka(stage 1/2),especially for 128ka. This phenomenon was discoverd in different cores such as SCS 15A and 15B in the southern part of S. C. S.,37KL in the northern part of S. C. S. and V 19一30 in the East Pacific Ocean as well as the cores in Mexico Gulf. Therefore,the two events might be existed in the whole ocean. Due to the lighter δ13C value was recorded in deeper planktomic furams, so it can be infered that the two lightest events refleeted on existence of welling watermasses from intermediate and bottom waters in transitional duration from glaciation interglaciation. In terms of the oxygen siotope records from planktonic forams, the dewelling water depth of planktonic foraminifera species from shallower to deeper was G. Tuber (pink ),G. Tuber and G. sacculifer in turn. Based on oxygen isotope geostratigraphic scale,the sedimentary rates and fluxes were calculated for each stage. The results show that the sedimental rates and fluxes are 2. 7cm/ka and 17. 6g/m2·yr for stage 1;1. 9cm/ka and 16. Og/m2·yr for stage 5;6. 7cm/ka and 57. 3g/m2·yr for stage 6,7. 2cm/ka and 59. Og/m2·yr for the last glaciation (stage 2,3,9).All in all,the sedimentary rates and fluxes in glacial times were much greater than that in interglacial ages.
1994, 12(3): 37-46.
Abstract:
The Shangdan fault zone is the most important tectonic boundary within the Qinling orogen during the Phanerozic. A large volume of sedimentary rocks,which formed in the subduction process of north and south qnling plates,is preserved in the zone. Conglomerate is the facies which is believed to be closely related to orogenesis. Different sorts of conglomerate are produced in distinct tectonic settings. Heihe conglomerate within the Shangdan zone was considered to be Mollasse of basal conglomerate in previous studies, and accordingly served as a crucial piece of evidence supporting the inferrence that the Qinlin orogenic belt was built during the Caledonian period. However,this study shows that Heihe conglomerates is actually fore一arc deposits in the process of plate subduction and can not be interpreted as product resulting from plate collison. Heihe conglomerate can be divided into six different facies and two distinct facies associations.Most facies were deposited from debris flows and density一modified grainflows, and conglomeratic beds show clear evidence of laminar flow. The others represent gravelly high一density turbidites.Grading is well developed in conglomerate beds,including inverse, inverse一to一normal, and normal,but structureless or massive beds are also common. Some of gravity flows probably underwent flow transformation,for instance,certain debris flows might originate from turbidity currents. It is proved that all the conglomerate formed in a subaqueous environments. This conclusion is mainly based upon the analyses of internal sedimentary structures of conglomerates and their close association with turbidites. Two distinct facies associations actually build two independent conglomerate lenticular bodies in space. Association I consists predominantly of clast一supported conglomerate with abundant are derived materials, and pyroclastic rocks are clearly coexisting. It is believed that Association I was deposited from lahar which flowed from volcanic island to a foreare basin. Matrix一supported conglomerate is characteristic of Association Ⅱ and obviously interlayered with fine to medium grained turbidites. Especially,the two associations occurred separately,indicating that they were typically two independent subaqueous apron deposit. Different factors controlled the development of the two distinct aprons. Volcanic eruptions were the main cause of initiation of lahar which produced Association I,while faulting triggered the occurrence of submarine gravity flows which brought about formation of Assocition Ⅱ. A direct relationship exists between sedimentation of conglomerate and co一existing lithofacies and evolution of Danfeng ophiolites. Sedimentary sequence conformably overlies volcanic rocks of southern arcflank of the inferred arc and is approximately concurrent with arc development.Conglomerate,together with other lithofacies, was evidently fore一are basin fills and resulted from coeval subduction tectonism. The two associations occurred in different parts of basin and therefore possessed distinct facies sequences. Heihe area was marked by occurrence of small一scale apron deposits instead of well一developed large一scale submarine fans, reflecting an unstable tectonic sedimentary environment at that time.
The Shangdan fault zone is the most important tectonic boundary within the Qinling orogen during the Phanerozic. A large volume of sedimentary rocks,which formed in the subduction process of north and south qnling plates,is preserved in the zone. Conglomerate is the facies which is believed to be closely related to orogenesis. Different sorts of conglomerate are produced in distinct tectonic settings. Heihe conglomerate within the Shangdan zone was considered to be Mollasse of basal conglomerate in previous studies, and accordingly served as a crucial piece of evidence supporting the inferrence that the Qinlin orogenic belt was built during the Caledonian period. However,this study shows that Heihe conglomerates is actually fore一arc deposits in the process of plate subduction and can not be interpreted as product resulting from plate collison. Heihe conglomerate can be divided into six different facies and two distinct facies associations.Most facies were deposited from debris flows and density一modified grainflows, and conglomeratic beds show clear evidence of laminar flow. The others represent gravelly high一density turbidites.Grading is well developed in conglomerate beds,including inverse, inverse一to一normal, and normal,but structureless or massive beds are also common. Some of gravity flows probably underwent flow transformation,for instance,certain debris flows might originate from turbidity currents. It is proved that all the conglomerate formed in a subaqueous environments. This conclusion is mainly based upon the analyses of internal sedimentary structures of conglomerates and their close association with turbidites. Two distinct facies associations actually build two independent conglomerate lenticular bodies in space. Association I consists predominantly of clast一supported conglomerate with abundant are derived materials, and pyroclastic rocks are clearly coexisting. It is believed that Association I was deposited from lahar which flowed from volcanic island to a foreare basin. Matrix一supported conglomerate is characteristic of Association Ⅱ and obviously interlayered with fine to medium grained turbidites. Especially,the two associations occurred separately,indicating that they were typically two independent subaqueous apron deposit. Different factors controlled the development of the two distinct aprons. Volcanic eruptions were the main cause of initiation of lahar which produced Association I,while faulting triggered the occurrence of submarine gravity flows which brought about formation of Assocition Ⅱ. A direct relationship exists between sedimentation of conglomerate and co一existing lithofacies and evolution of Danfeng ophiolites. Sedimentary sequence conformably overlies volcanic rocks of southern arcflank of the inferred arc and is approximately concurrent with arc development.Conglomerate,together with other lithofacies, was evidently fore一are basin fills and resulted from coeval subduction tectonism. The two associations occurred in different parts of basin and therefore possessed distinct facies sequences. Heihe area was marked by occurrence of small一scale apron deposits instead of well一developed large一scale submarine fans, reflecting an unstable tectonic sedimentary environment at that time.
1994, 12(3): 56-66.
Abstract:
Siace the diagenetic carbonate is siliciclastic rocks was rather common in world range. The relationship between the diagenetic carbonate and organic matter decarboxy group is very closely,Since the relationship between formation of its secondary pore and organic resolve H+ also is very closely. Its s important that diagenetic carbonate controled the reservoirs of oil and gas.The cemention of carbonate make primary pore completely filled up. The cemention of carbonate is not the same as compaction,press一solution. As the cempaction,press一solution as well as cemention of carbonate is the damage factors of the reservoir,but it's volume is reduced snout 1/2,however cemention of carbonate is also the damage of the reservoir under volcum is not changed. Therefore underwent solution later. It' s possible that formation of many secondary pore, it is improved character. Therefore, cemention of carbonate prived matters basis formated secondary pore later. At a time,organic matter can formated organic acid,with,underwent resolved into H+,with not only can made carbonate of cemention to formated secondary soluton pore, but it also can made clastic feldspar,and lithoclast of deposition to formated seconddary soluted pore,largely changed character of the reservoir. As large decarboxylation and resolved forated priori to organic mature.Therefore the corrlation of migration,accumulation of the oil and gas later and formated prior to cemention of carbonate,secondary pore. On the one hand it can provides good thoroughfare after migration of oil and gas. On the other hand,it also can provides condition of seal (cemenion of carbonate ) in terms of worked for FS Depression,Auther good proved that some researched above bear fruit. Finally,author provided that if decarboxylation is leading, after organic matter tranfered into organic acid. Then Ca 2+, Mg2+ and Fe2+ ion in clastic rock pore flow was more than liquid with,CO2, which underwent decarboxylation of }ganic acid,or qual. Then it can formated cemention of carbonaze,primary pore was choked up. If above assume is quite the, contrary. First of allformated the,cemention of carbonate,then surplus liquid with CO2 can nnis solution of the carbonte to formated many secondary pore(formated diagjnetic trap) If resole H+of organic acid is leading.Then it can make carbonate and cemention of carbonate soluton and solution of clastic minerals to formated many secondary pore.
Siace the diagenetic carbonate is siliciclastic rocks was rather common in world range. The relationship between the diagenetic carbonate and organic matter decarboxy group is very closely,Since the relationship between formation of its secondary pore and organic resolve H+ also is very closely. Its s important that diagenetic carbonate controled the reservoirs of oil and gas.The cemention of carbonate make primary pore completely filled up. The cemention of carbonate is not the same as compaction,press一solution. As the cempaction,press一solution as well as cemention of carbonate is the damage factors of the reservoir,but it's volume is reduced snout 1/2,however cemention of carbonate is also the damage of the reservoir under volcum is not changed. Therefore underwent solution later. It' s possible that formation of many secondary pore, it is improved character. Therefore, cemention of carbonate prived matters basis formated secondary pore later. At a time,organic matter can formated organic acid,with,underwent resolved into H+,with not only can made carbonate of cemention to formated secondary soluton pore, but it also can made clastic feldspar,and lithoclast of deposition to formated seconddary soluted pore,largely changed character of the reservoir. As large decarboxylation and resolved forated priori to organic mature.Therefore the corrlation of migration,accumulation of the oil and gas later and formated prior to cemention of carbonate,secondary pore. On the one hand it can provides good thoroughfare after migration of oil and gas. On the other hand,it also can provides condition of seal (cemenion of carbonate ) in terms of worked for FS Depression,Auther good proved that some researched above bear fruit. Finally,author provided that if decarboxylation is leading, after organic matter tranfered into organic acid. Then Ca 2+, Mg2+ and Fe2+ ion in clastic rock pore flow was more than liquid with,CO2, which underwent decarboxylation of }ganic acid,or qual. Then it can formated cemention of carbonaze,primary pore was choked up. If above assume is quite the, contrary. First of allformated the,cemention of carbonate,then surplus liquid with CO2 can nnis solution of the carbonte to formated many secondary pore(formated diagjnetic trap) If resole H+of organic acid is leading.Then it can make carbonate and cemention of carbonate soluton and solution of clastic minerals to formated many secondary pore.
1994, 12(3): 76-81.
Abstract:
During Hercynian一Indosinian Epoch,Western Qinling Mt. was located on the margin of Palaeotethys where developed three time rift一faultings developed(1. Devonian,2. Carboniferous,3. Permian一Triassic )that caused the strata distributed in the form of belts and shallow一water and deep一water sediments appeared at intervals on the plane. Every rift一faulting can be divided into three stages; rift一faulting stage,calm stage and compressional stage. During rift一faulting stage carbonate plateform rifted and depressed,deep一water trough basins were formed. Depositional sequence from shallow to deep water contains several layers of olistro一gravity current sediments which consist chiefly of olistromes, debris flow deposits and turbidites. Its compositions are not complex,mainly coming from adjacent plateform and their provenances are linear not point. It is spectacular that giant carbonate olistoliths were formed that are several tens of meters to one thousand meters in diameter. During calm stage the basin was gradually filled to form up一shallowing sequence. During compressional stage the sediments of thousands of meter in basins were compressed and folded to deposite piedmont molase facies and continental一oceanic alternative facies. The alteration of rift一faulting and compressive stages made rift一faulting happened periodicalvy. Synsedimentary faults are the main structure which controlled olistro一gravity current complex sediments.
During Hercynian一Indosinian Epoch,Western Qinling Mt. was located on the margin of Palaeotethys where developed three time rift一faultings developed(1. Devonian,2. Carboniferous,3. Permian一Triassic )that caused the strata distributed in the form of belts and shallow一water and deep一water sediments appeared at intervals on the plane. Every rift一faulting can be divided into three stages; rift一faulting stage,calm stage and compressional stage. During rift一faulting stage carbonate plateform rifted and depressed,deep一water trough basins were formed. Depositional sequence from shallow to deep water contains several layers of olistro一gravity current sediments which consist chiefly of olistromes, debris flow deposits and turbidites. Its compositions are not complex,mainly coming from adjacent plateform and their provenances are linear not point. It is spectacular that giant carbonate olistoliths were formed that are several tens of meters to one thousand meters in diameter. During calm stage the basin was gradually filled to form up一shallowing sequence. During compressional stage the sediments of thousands of meter in basins were compressed and folded to deposite piedmont molase facies and continental一oceanic alternative facies. The alteration of rift一faulting and compressive stages made rift一faulting happened periodicalvy. Synsedimentary faults are the main structure which controlled olistro一gravity current complex sediments.
1994, 12(3): 91-98.
Abstract:
With the further exploration work,more and more natural gases have been found m eastern fault basins of Songliao region,such as Shiwu fault basin,Dehui fault basin,Fulongquan fault basin and Ying一Xing fault basin etc. Based on the abundant geochemical data of the gases,the genetic types of the natural gas and the correlation of gas/rock in these basins have been studied.The main conclusions are drawn as follows; 1)The natural gases are generally hydrocarbon gases. Methane ranges from 75~96%,and heavier gases are totally about 0. 73~10. 6500,containing various amount of nitxogen (N2 1~ 2000)and a little carbon dioxide (C02). These gases are chemically dry with C1/C2-C5 generally larger than 0. 95. 2)Four kinds of genetic types of natural gas have been subdivided by using the data of carbon isotopes. ①Sapropelic一type gas;The isotopes of C1 and C2 are relatively lighter,i,e.,δ13C1一48. 08‰ and δ13C2一35. 95‰. The gas associated with oil,indicating that this kind of gas was derived from hydrogen一rich type kerogens during the mature stage of hydrocarbon generation. ② The lower mature humic一type gas:δ13C1一46一一99‰,δ13C2一26. 58一一29. 73‰. The carbon isotope of ethane is heavier than一29‰ witch is usually an indicator of humic一type gas.The gas it is with lighter isotope of methane indicates that it is generated from oxygen一rich type Hf kerogen at the lower mature stage. ③ The post一mature humic一type gas:with δ13C1>一30‰ and δ13C2>一27‰,was found predominantly in the relatively deep levels (Ka一basement). Besides methane,ethane,propane etc,there are also a little hydrogen ( H2 ) and helium ( He).The gas with heavier isotope of methane commonly interpreted as post一mature humic一type gas. .Mixed一type gas with δ13C1一32~一42‰ and δ13C2一26~一33‰,is the mast aboundant gas type in these fault basins. Some of the sampled gases contain mercury which is usually an indicator of humic一type gas. Considering the geological setting, the author believe that this kind of gas is possibly either the product of the type I kerogen or a mixture of sapropelic一type gas and humic一type gas. 3)The correlations of gas/gas and gas/rock have been done by studying the data of the light hydrocarbon (C1~C2),hydrocarbons absorbed by source rocks, the relation between carbon isotope and vitrinite reflectance and the other geological data,in orger to determine the source rocks. It is suggested that these gases,whether they occur in the Quantou depressed Formation or in the Denglouku Formation and underlying farlted Formation,are all derived from lower Cretaceous coal一bearing measure of the fault basin fill(K1d一K1sh),not from Qingshankou depressed formation.
With the further exploration work,more and more natural gases have been found m eastern fault basins of Songliao region,such as Shiwu fault basin,Dehui fault basin,Fulongquan fault basin and Ying一Xing fault basin etc. Based on the abundant geochemical data of the gases,the genetic types of the natural gas and the correlation of gas/rock in these basins have been studied.The main conclusions are drawn as follows; 1)The natural gases are generally hydrocarbon gases. Methane ranges from 75~96%,and heavier gases are totally about 0. 73~10. 6500,containing various amount of nitxogen (N2 1~ 2000)and a little carbon dioxide (C02). These gases are chemically dry with C1/C2-C5 generally larger than 0. 95. 2)Four kinds of genetic types of natural gas have been subdivided by using the data of carbon isotopes. ①Sapropelic一type gas;The isotopes of C1 and C2 are relatively lighter,i,e.,δ13C1一48. 08‰ and δ13C2一35. 95‰. The gas associated with oil,indicating that this kind of gas was derived from hydrogen一rich type kerogens during the mature stage of hydrocarbon generation. ② The lower mature humic一type gas:δ13C1一46一一99‰,δ13C2一26. 58一一29. 73‰. The carbon isotope of ethane is heavier than一29‰ witch is usually an indicator of humic一type gas.The gas it is with lighter isotope of methane indicates that it is generated from oxygen一rich type Hf kerogen at the lower mature stage. ③ The post一mature humic一type gas:with δ13C1>一30‰ and δ13C2>一27‰,was found predominantly in the relatively deep levels (Ka一basement). Besides methane,ethane,propane etc,there are also a little hydrogen ( H2 ) and helium ( He).The gas with heavier isotope of methane commonly interpreted as post一mature humic一type gas. .Mixed一type gas with δ13C1一32~一42‰ and δ13C2一26~一33‰,is the mast aboundant gas type in these fault basins. Some of the sampled gases contain mercury which is usually an indicator of humic一type gas. Considering the geological setting, the author believe that this kind of gas is possibly either the product of the type I kerogen or a mixture of sapropelic一type gas and humic一type gas. 3)The correlations of gas/gas and gas/rock have been done by studying the data of the light hydrocarbon (C1~C2),hydrocarbons absorbed by source rocks, the relation between carbon isotope and vitrinite reflectance and the other geological data,in orger to determine the source rocks. It is suggested that these gases,whether they occur in the Quantou depressed Formation or in the Denglouku Formation and underlying farlted Formation,are all derived from lower Cretaceous coal一bearing measure of the fault basin fill(K1d一K1sh),not from Qingshankou depressed formation.
1994, 12(3): 106-113.
Abstract:
In this paper,formation and evolution of bicyclic sesquiterpane in wooden coal from Nanning Basin are studied by means of pyrolysis. Besides of the peralent method which heats a certain number of raw samples at different temperature, a new one which heats only one sample step by step from the low to the high temperature was used. The fist series experiment is called Y series and the second one is called Z series. The Y series represented the thermal evolution of comprehensive primary organic matter,and the Z sereis represented the pyrolysis of kerogen,the two series of constracting experiments had born much information. On the m/z 123 mass chromatogram seven bicyclic sesquiterpane compounds are determined.Peak 1,2,3 are pentamethyl一naphthalene,drimane and pentamethyl一naphthalene respectively which molecules are C15H28, and Peak 4,5,6,7 are ethyl,tetramethyl一naphthalene,ethyl, tetramethyl一naphthalene,homodrimane and ethyl,tetramethyl一naphthalene which molecules are C16H30 There were many differences between Y and Z sereis experiments. 1n Y series, the seven compounds were all present at the temperature below 300℃, compound No. 2,3,6,7 were present at 350℃,the one No. 2,6,7 were present at 400℃ and no this kind of compounds appeared at the temperature higher than 4000C.Peak 6 was the main in the raw sample, peak 7 was the main in the range of 250一300℃ and peak 6 was the main in range of 350一400'C .Peak 1,4,5 reduced throughout in the whole process and disappeared at 350℃.Peak 7 riled at the temperature below 300℃ and reduced then. In pace whith the temperaure rising, the others reduced at fist and riled then,Peak 3 maintained about the same at the temperature below 300℃ and reduced at 3500C and disappeared at 400℃.In Z series, the bicyclic sesquiterpanes were mainly compound 2,6,7.Compound No. 7 was the main one in the range of 250一300℃ and No. 6 is the main at 350℃.1n pace whith the temperature rising, peak 2,6 became higher and peak 7 reduced. No bicyclic sesquiterpanes were present at 400'C.On the basis of above analysis, two ways of bicyclic sesquiterpanes were defined. Compound No. 1,3,4,5 and a little of one No. 2,6,7 were generated probably from organic matzer of non一kerogen,and the ones No. 2,6,7 were formed mainly from kerogen. It is considered generally that drimane/homodrimane ratio increases gradually with thermal evolution,so it is can be used as a maturation index.But the experiment showed that the ratio decreased gradually till 300℃ and then increased at the higher temperature,so it is not a good maturation index,the other maturation parameters are not either. Only the drimane/pentamethyl一naphthalene(compound No. 1)ratio increased linearly along with temperature rising, and it can be used as a good maturation index.
In this paper,formation and evolution of bicyclic sesquiterpane in wooden coal from Nanning Basin are studied by means of pyrolysis. Besides of the peralent method which heats a certain number of raw samples at different temperature, a new one which heats only one sample step by step from the low to the high temperature was used. The fist series experiment is called Y series and the second one is called Z series. The Y series represented the thermal evolution of comprehensive primary organic matter,and the Z sereis represented the pyrolysis of kerogen,the two series of constracting experiments had born much information. On the m/z 123 mass chromatogram seven bicyclic sesquiterpane compounds are determined.Peak 1,2,3 are pentamethyl一naphthalene,drimane and pentamethyl一naphthalene respectively which molecules are C15H28, and Peak 4,5,6,7 are ethyl,tetramethyl一naphthalene,ethyl, tetramethyl一naphthalene,homodrimane and ethyl,tetramethyl一naphthalene which molecules are C16H30 There were many differences between Y and Z sereis experiments. 1n Y series, the seven compounds were all present at the temperature below 300℃, compound No. 2,3,6,7 were present at 350℃,the one No. 2,6,7 were present at 400℃ and no this kind of compounds appeared at the temperature higher than 4000C.Peak 6 was the main in the raw sample, peak 7 was the main in the range of 250一300℃ and peak 6 was the main in range of 350一400'C .Peak 1,4,5 reduced throughout in the whole process and disappeared at 350℃.Peak 7 riled at the temperature below 300℃ and reduced then. In pace whith the temperaure rising, the others reduced at fist and riled then,Peak 3 maintained about the same at the temperature below 300℃ and reduced at 3500C and disappeared at 400℃.In Z series, the bicyclic sesquiterpanes were mainly compound 2,6,7.Compound No. 7 was the main one in the range of 250一300℃ and No. 6 is the main at 350℃.1n pace whith the temperature rising, peak 2,6 became higher and peak 7 reduced. No bicyclic sesquiterpanes were present at 400'C.On the basis of above analysis, two ways of bicyclic sesquiterpanes were defined. Compound No. 1,3,4,5 and a little of one No. 2,6,7 were generated probably from organic matzer of non一kerogen,and the ones No. 2,6,7 were formed mainly from kerogen. It is considered generally that drimane/homodrimane ratio increases gradually with thermal evolution,so it is can be used as a maturation index.But the experiment showed that the ratio decreased gradually till 300℃ and then increased at the higher temperature,so it is not a good maturation index,the other maturation parameters are not either. Only the drimane/pentamethyl一naphthalene(compound No. 1)ratio increased linearly along with temperature rising, and it can be used as a good maturation index.
1994, 12(3): 120-129.
Abstract:
The Tertiary mud diapir of Ying Ge Hai Basin is an extraordinary geological body. Its formation influenced other fluid generation,migration and accmulation as well as plastic mud flow.Mud diapir is an independent and integrated system or compartment for hydrocarbon generation,migration and accumulation,in which the hydrocarbon and fluid migration and accumulation aswell as the plastic mud flow all have close relation with the formation and destruction of the top compartment seal,i. e.,The broken or unbroken top compartment seals can control and determine the migration and accumulation mechanism and models of hydrocarbon fluid and plastic mud. The paper has concluded that two different kinds of hydrocarbon migration and accumulation mechanisms or models can be used as guidlines for the mud diapir deposit exploration.
The Tertiary mud diapir of Ying Ge Hai Basin is an extraordinary geological body. Its formation influenced other fluid generation,migration and accmulation as well as plastic mud flow.Mud diapir is an independent and integrated system or compartment for hydrocarbon generation,migration and accumulation,in which the hydrocarbon and fluid migration and accumulation aswell as the plastic mud flow all have close relation with the formation and destruction of the top compartment seal,i. e.,The broken or unbroken top compartment seals can control and determine the migration and accumulation mechanism and models of hydrocarbon fluid and plastic mud. The paper has concluded that two different kinds of hydrocarbon migration and accumulation mechanisms or models can be used as guidlines for the mud diapir deposit exploration.
1994, 12(3): 136-142.
Abstract:
During the一marine comprehensive investigation of the Central South China Basin(12一20。N )from the October 1983 to June 1984,38 sediment cores were obtained by the piston一sampler. The cores are generally not longer than 4m. The paleomagnetic measurement of 5 sediment cores selecting from the continental slope and deep plain has been carried out. The result shows:(1)all cores are mainly positive polarity and belong to Brunhes epoch;(2)the magnetostratigraphic differences exist between the slope cores and deep plain cores. The lower of slope cores reveals the existence of negative magnetic excursion. The chronology of the excursion has been stuffed by various methods, such as 14C,Th一230,δ18O and CaC03%,etc. We got two satisfying cycle curves of δ18O and CaC03% in the slope cores. In comparison with the magnetostratigraphy and Quaternary geochronology from the neighbour borehole of Tianyang Lake,it can be seen that the nagative polarity section of studied slope cores is in the lower stage 3 of δ18O and CaC03% curves .its stratum is approximately equal to that located Mungo magnetic excursion in the borehole from Tianyang Lake.
During the一marine comprehensive investigation of the Central South China Basin(12一20。N )from the October 1983 to June 1984,38 sediment cores were obtained by the piston一sampler. The cores are generally not longer than 4m. The paleomagnetic measurement of 5 sediment cores selecting from the continental slope and deep plain has been carried out. The result shows:(1)all cores are mainly positive polarity and belong to Brunhes epoch;(2)the magnetostratigraphic differences exist between the slope cores and deep plain cores. The lower of slope cores reveals the existence of negative magnetic excursion. The chronology of the excursion has been stuffed by various methods, such as 14C,Th一230,δ18O and CaC03%,etc. We got two satisfying cycle curves of δ18O and CaC03% in the slope cores. In comparison with the magnetostratigraphy and Quaternary geochronology from the neighbour borehole of Tianyang Lake,it can be seen that the nagative polarity section of studied slope cores is in the lower stage 3 of δ18O and CaC03% curves .its stratum is approximately equal to that located Mungo magnetic excursion in the borehole from Tianyang Lake.
1994, 12(3): 12-20.
Abstract:
Ganqi profile with a length of 13 km is located by a road from Mianyang to Pinwu .Started at Guixi grain depot and ended at limekiln of Shawozi. The Devonian of Longmenshan belongs to shallow sea and shallow water deposits .The clastic rocks of lower part of low一Devonian overlay unconformly on the lightly metamorphic siltstone and silty slate of lower一middle Silurian. Middle part of low一Devonian to lower part of mid一Devonian are charcteraized by interbedded clastic and carbonate rocks. Upper part of mid一Devonian and up一Devonian are entirely carbonate deposits. The marine carbonates of Devonian from Ganxi profile are determined serially for Sr, C, O isotopes and Na,Sr,Mn、Al、Fe, Mn trace elements as well as cathodolumines feature. Sr and C isotope stratigraphic curves of marine carbonates of Devonian are first set up some conclusions are as follows. 1. Based on studies of trace element and C,O isotopes most samples of marine carbonate and brachiopods fossil have the same strorium and carbon isotopic features as they deposited. 2. Sr and C isotope stratigraphic curves of Devonian marine carbonates and fossils from Ganxi profile are familiar with the function curves of geological age (B. N. Popp et al 1986;W. H. Barke, 1982;L. R. Kump and Garrets.1986).They implicates that Sr and C isotopic compositions of marine carbonates and fossil are controlled by globe factors(but C isotopic composition is superimposed influence of regional geological process)and have significance on statigraphic correlation. 3. C and O isotopic components of marine carbonates vary obviously at geological boundaries and can be used as subsidiary criteria for stratigraphic division. 4. When deposited,marine carbonates formed by organism or non一organism have no detectable fractionation of strontium isotope.
Ganqi profile with a length of 13 km is located by a road from Mianyang to Pinwu .Started at Guixi grain depot and ended at limekiln of Shawozi. The Devonian of Longmenshan belongs to shallow sea and shallow water deposits .The clastic rocks of lower part of low一Devonian overlay unconformly on the lightly metamorphic siltstone and silty slate of lower一middle Silurian. Middle part of low一Devonian to lower part of mid一Devonian are charcteraized by interbedded clastic and carbonate rocks. Upper part of mid一Devonian and up一Devonian are entirely carbonate deposits. The marine carbonates of Devonian from Ganxi profile are determined serially for Sr, C, O isotopes and Na,Sr,Mn、Al、Fe, Mn trace elements as well as cathodolumines feature. Sr and C isotope stratigraphic curves of marine carbonates of Devonian are first set up some conclusions are as follows. 1. Based on studies of trace element and C,O isotopes most samples of marine carbonate and brachiopods fossil have the same strorium and carbon isotopic features as they deposited. 2. Sr and C isotope stratigraphic curves of Devonian marine carbonates and fossils from Ganxi profile are familiar with the function curves of geological age (B. N. Popp et al 1986;W. H. Barke, 1982;L. R. Kump and Garrets.1986).They implicates that Sr and C isotopic compositions of marine carbonates and fossil are controlled by globe factors(but C isotopic composition is superimposed influence of regional geological process)and have significance on statigraphic correlation. 3. C and O isotopic components of marine carbonates vary obviously at geological boundaries and can be used as subsidiary criteria for stratigraphic division. 4. When deposited,marine carbonates formed by organism or non一organism have no detectable fractionation of strontium isotope.
1994, 12(3): 29-36.
Abstract:
This paper has discussed volumes and mass of each period sedimentary strata in North China platform .The constitution of rocks has been calculated and compared with other main platform in the world. The sedimentary cover of North China plateform is composed of one/thind carbonate and two/thinds terrigenous rocks. The constitution of rocks is similar to Laurasia and North China platform. But there are poor evaporite and extensive distrubution of carbonate. Compared with the earthy s sedimentary shell, North China Platform is characterized by that terrigenous rock is rich in clastic rock(41 percent of grass rock volum ) and percentage of argillaceous rock is low(26. 7 percent of grass rock volum). However,Character of constitute of rocks of each sedimentary time is greatly different from each other, which is determined by special history of geological development in North China Platform. Periodically tectonic and thermal event changed the resource of sedimentary rock and rate of sedimentation. It makes mass, volume constitution of rocks change with tectonic cycle, and is main base of variation of constitute,volume,mass. Only in Longer period of geological time,will the influence of recycling of sediment be obvious. Because the influence of tectonic一thermal event is averaged in this case. The influence of recycling of sediment also exist in the stable period of tectonic activity .Only considering tectonic event and recycling of sediment can we realize the variation of the constitute of sedimentary rocks and mass. Simulating calculation shows that the 90% of sedimentary rock in North China Platform have been recycled during the period of sedimentary cover development which indicates that it is main recycling of sedimentary rocks during sedimentary cover development.
This paper has discussed volumes and mass of each period sedimentary strata in North China platform .The constitution of rocks has been calculated and compared with other main platform in the world. The sedimentary cover of North China plateform is composed of one/thind carbonate and two/thinds terrigenous rocks. The constitution of rocks is similar to Laurasia and North China platform. But there are poor evaporite and extensive distrubution of carbonate. Compared with the earthy s sedimentary shell, North China Platform is characterized by that terrigenous rock is rich in clastic rock(41 percent of grass rock volum ) and percentage of argillaceous rock is low(26. 7 percent of grass rock volum). However,Character of constitute of rocks of each sedimentary time is greatly different from each other, which is determined by special history of geological development in North China Platform. Periodically tectonic and thermal event changed the resource of sedimentary rock and rate of sedimentation. It makes mass, volume constitution of rocks change with tectonic cycle, and is main base of variation of constitute,volume,mass. Only in Longer period of geological time,will the influence of recycling of sediment be obvious. Because the influence of tectonic一thermal event is averaged in this case. The influence of recycling of sediment also exist in the stable period of tectonic activity .Only considering tectonic event and recycling of sediment can we realize the variation of the constitute of sedimentary rocks and mass. Simulating calculation shows that the 90% of sedimentary rock in North China Platform have been recycled during the period of sedimentary cover development which indicates that it is main recycling of sedimentary rocks during sedimentary cover development.
1994, 12(3): 47-55.
Abstract:
The Ordovician in north China platform consists of marinecarbonate rocks .As oil and gas resrvoirs. They are formed by the combination of sedimentation. tectonism and diagenesis. Three sets of reservoir were formed duringgeo history .The first type of reservoir region is paleo一weathered and teached rocks .They occur in the centrat part of Ordos Mesozoic and Cenozoic fault depressions in east of the Taihang montain which distributed from the 109. 3 E to the 39 N area The second type of the reservoir are deep fault rock solution zones. which are mostly developed along Yanshan or Himalaya fault zone. They mainly occur in the sourth一western margin .The third type of reservoir is evaporating strand flat solution reservoir .which mainly occours in the central一eastern part of the Ordos. The three resaervoirs can be divided into five types and their occurrences can be determined. 1. The ordivician dolomite reservoirs formed by the sedimentation. 2. Then dolomite and solution collapse reservoir formed by the sedimentation and the Caledonian tectonism .3. The carbonate rock reservoir formed bt the sedimention and the Indosinian一Yanshan tectonisms. 4. The carbonate rock reservoir formed by the sedimentation and the multiple cyclic tectonism. 5. The solution pore and cavity doiomite reservoir formed by the sedimentation一diagenesis and Huaiyuen teotonism .The practices of the oil and gas exploration and production have prvoren that the oil reserrvoir can be formed be formed by the combination of the ordivician carbonate rock reservoirs and the Mesozoic一Cenozoic hydrocarbon .It is important to study the ordivician carbonate rock reservoirs to the hydrocarbon exploration of the Ordos.
The Ordovician in north China platform consists of marinecarbonate rocks .As oil and gas resrvoirs. They are formed by the combination of sedimentation. tectonism and diagenesis. Three sets of reservoir were formed duringgeo history .The first type of reservoir region is paleo一weathered and teached rocks .They occur in the centrat part of Ordos Mesozoic and Cenozoic fault depressions in east of the Taihang montain which distributed from the 109. 3 E to the 39 N area The second type of the reservoir are deep fault rock solution zones. which are mostly developed along Yanshan or Himalaya fault zone. They mainly occur in the sourth一western margin .The third type of reservoir is evaporating strand flat solution reservoir .which mainly occours in the central一eastern part of the Ordos. The three resaervoirs can be divided into five types and their occurrences can be determined. 1. The ordivician dolomite reservoirs formed by the sedimentation. 2. Then dolomite and solution collapse reservoir formed by the sedimentation and the Caledonian tectonism .3. The carbonate rock reservoir formed bt the sedimention and the Indosinian一Yanshan tectonisms. 4. The carbonate rock reservoir formed by the sedimentation and the multiple cyclic tectonism. 5. The solution pore and cavity doiomite reservoir formed by the sedimentation一diagenesis and Huaiyuen teotonism .The practices of the oil and gas exploration and production have prvoren that the oil reserrvoir can be formed be formed by the combination of the ordivician carbonate rock reservoirs and the Mesozoic一Cenozoic hydrocarbon .It is important to study the ordivician carbonate rock reservoirs to the hydrocarbon exploration of the Ordos.
1994, 12(3): 67-75.
Abstract:
Porosity formed by the dissolution of unstable framework grains is one of the most important genetic types of secondary porosity,and feldspar is found to be the most extensive ones of the unstable framework grains. Songliao and Liaohe basins are two large petroliferous inland basins of Mesozoic and Cenozoic,in which has been constructed a clastic rock formation with great thickness.In sandstone there is above 20% unstable feldspar fragments,which is the requisite condition for the development of the secondary porosity. But it has been studied that the FGD of the grains, may not cause the increase of the reservoir permeability of the sandstone(Siebert,1984). The dissolution of a unit volume of feldspar may produce 0. 66 volume of Kaolinite and 0. 33 volume of quartz (Sullivan,1991).Therefore.only when the dissolved materials are transferred after dissolution the porosity of the sandstone can be effectively increased. This paper is based on analyzing the state of thermodynamics of feldspar dissolution process.The SEM,X一diffraction,oxygen and carbon stable isotopes, etc. analytical methods are adopted in research of the controlling factors of feldspar dissolution in Cretaceous sandstone in the region of Songliao basin and Palaeogene sandstone in the Liaohe basin. Through research,the author indicates that favors to development degree of feldspar dissolution are dependent on:(1)the organic and inorganic reaction time;(2)the characteristics and fluid condition of pore water;(3)the primary porosity of sandstone,and(4)the temperature and pressure,etc. These factors play different roles in different types of feldspar. The most important parameters are fluid condition,type and abundance of organic acid in fluid .which were closely related with the evolution of clay mineral and organic material in the diagenesis of mudstone.
Porosity formed by the dissolution of unstable framework grains is one of the most important genetic types of secondary porosity,and feldspar is found to be the most extensive ones of the unstable framework grains. Songliao and Liaohe basins are two large petroliferous inland basins of Mesozoic and Cenozoic,in which has been constructed a clastic rock formation with great thickness.In sandstone there is above 20% unstable feldspar fragments,which is the requisite condition for the development of the secondary porosity. But it has been studied that the FGD of the grains, may not cause the increase of the reservoir permeability of the sandstone(Siebert,1984). The dissolution of a unit volume of feldspar may produce 0. 66 volume of Kaolinite and 0. 33 volume of quartz (Sullivan,1991).Therefore.only when the dissolved materials are transferred after dissolution the porosity of the sandstone can be effectively increased. This paper is based on analyzing the state of thermodynamics of feldspar dissolution process.The SEM,X一diffraction,oxygen and carbon stable isotopes, etc. analytical methods are adopted in research of the controlling factors of feldspar dissolution in Cretaceous sandstone in the region of Songliao basin and Palaeogene sandstone in the Liaohe basin. Through research,the author indicates that favors to development degree of feldspar dissolution are dependent on:(1)the organic and inorganic reaction time;(2)the characteristics and fluid condition of pore water;(3)the primary porosity of sandstone,and(4)the temperature and pressure,etc. These factors play different roles in different types of feldspar. The most important parameters are fluid condition,type and abundance of organic acid in fluid .which were closely related with the evolution of clay mineral and organic material in the diagenesis of mudstone.
1994, 12(3): 82-90.
Abstract:
Usually,sedimentary facies is denominated by determining the nature. There are different facies analysis results to the same beds by different researchers. In the study area,the main types of sedimentary facies have been denominated. Through field fades analysising, four important facies factors have been introduced in this paper. The logic judge method is on the basis of expert system' s thought. The basic principal is utilizing sedimentary facies expert' s knowlege and analysising progress on Tc1一Tc2 of East Sichuan. Four factors, including lithology,tectonic, structure and fossil are given to computer, the computer can judge the type of facies through the judging sequence. The fuzzy comprehensive judgement method is on the basis of fuzzy mathematics. The factor set theory has been built when the computer gets the facies expert's experience and judging knowlege. Then,different weight factor must be given to four main factors.In order to build fuzzy set theory,the computer will judge the facies through comparing four given factors in judging matrix. The different judging method can be used through main menu, then answer the computer's question,imput different facies sign.at last, computer can glve the most possible facies and explains. Comparing cores analyses. the result of computer explain is close to the nature. The sedimentary facies work will be developed from determining the nature to the amount. The computer will play a more and more important role in sedimentary facies analysis.
Usually,sedimentary facies is denominated by determining the nature. There are different facies analysis results to the same beds by different researchers. In the study area,the main types of sedimentary facies have been denominated. Through field fades analysising, four important facies factors have been introduced in this paper. The logic judge method is on the basis of expert system' s thought. The basic principal is utilizing sedimentary facies expert' s knowlege and analysising progress on Tc1一Tc2 of East Sichuan. Four factors, including lithology,tectonic, structure and fossil are given to computer, the computer can judge the type of facies through the judging sequence. The fuzzy comprehensive judgement method is on the basis of fuzzy mathematics. The factor set theory has been built when the computer gets the facies expert's experience and judging knowlege. Then,different weight factor must be given to four main factors.In order to build fuzzy set theory,the computer will judge the facies through comparing four given factors in judging matrix. The different judging method can be used through main menu, then answer the computer's question,imput different facies sign.at last, computer can glve the most possible facies and explains. Comparing cores analyses. the result of computer explain is close to the nature. The sedimentary facies work will be developed from determining the nature to the amount. The computer will play a more and more important role in sedimentary facies analysis.
1994, 12(3): 99-105.
Abstract:
The aromatic hydrocarbon fraction of 4 Quaternary cores from Chaidamu Basin was analysed by GC一MS. As a result,a series of long chain fatty acid ethyl esters(C15一C34 ) were first found.Their mass spectrum characteristics are that base peak is m/z 88 and characteristic ion is m/z 101、157,M+,M+一43. These ion existence were confirmed by fragmenting analyses of fatty acid ethyl esters. Distribution of the carbon number of fatty acid ethyl esters in studied samples is from C15 to C34 maximizing at C28 with a strong even to odd carbon number preference. we believe occurrence of fatty acid ethyl esters in studied samples may be related to biochemical process. Fatty acid ethyl esters of Quaternary sediments in Chaidamu Basin may play an important part in formation of biogas in this region.
The aromatic hydrocarbon fraction of 4 Quaternary cores from Chaidamu Basin was analysed by GC一MS. As a result,a series of long chain fatty acid ethyl esters(C15一C34 ) were first found.Their mass spectrum characteristics are that base peak is m/z 88 and characteristic ion is m/z 101、157,M+,M+一43. These ion existence were confirmed by fragmenting analyses of fatty acid ethyl esters. Distribution of the carbon number of fatty acid ethyl esters in studied samples is from C15 to C34 maximizing at C28 with a strong even to odd carbon number preference. we believe occurrence of fatty acid ethyl esters in studied samples may be related to biochemical process. Fatty acid ethyl esters of Quaternary sediments in Chaidamu Basin may play an important part in formation of biogas in this region.
1994, 12(3): 114-119.
Abstract:
The Tertiary are saline sediment in western part of Qaidam Basin. The source rocks of oil contain much of carbonate and some strata even contain halite and mirabilite. The concentration of chlorine is higher in rocks. The composition and distribution of biomarkers have a close relationship with their sedimentary environment. The increasing of salinity in sedimentry environment can restrain the transformation from Tm to Ts. In addition,the formation of Ts may relative to some aquatic organism in saline facies. Sterane parameter of C27/C28十C29 ratios which can reperesent the input information of organism have a positive relationship with the concentration of Cl一Show that because of dry climate, the supplying of higher plants decrence,the salinity incrence in water and some aquatic organism which can living in saline water may incrence. Many publications have shown that the hopane parameter of C31S/R ratio and the sterane parameter of C29ββ/aa十ββ ratio both can reflect the maturity degree of source rocks and oils. But in Qaidam Basin,when the concentrations of carbonate is lower than 25%,both of the C31S/R ration and the C29ββ/aa十ββ ration have a pesitive relationship with the concentrations of carbonate,when the concentrations of carbonate is higher than 25%,both of the parameters have a negative relationship with the concentrations of carbonate. Show that the higher amount of carbonate have a restricted effection on the isomerisation of sterane and hopane.
The Tertiary are saline sediment in western part of Qaidam Basin. The source rocks of oil contain much of carbonate and some strata even contain halite and mirabilite. The concentration of chlorine is higher in rocks. The composition and distribution of biomarkers have a close relationship with their sedimentary environment. The increasing of salinity in sedimentry environment can restrain the transformation from Tm to Ts. In addition,the formation of Ts may relative to some aquatic organism in saline facies. Sterane parameter of C27/C28十C29 ratios which can reperesent the input information of organism have a positive relationship with the concentration of Cl一Show that because of dry climate, the supplying of higher plants decrence,the salinity incrence in water and some aquatic organism which can living in saline water may incrence. Many publications have shown that the hopane parameter of C31S/R ratio and the sterane parameter of C29ββ/aa十ββ ratio both can reflect the maturity degree of source rocks and oils. But in Qaidam Basin,when the concentrations of carbonate is lower than 25%,both of the C31S/R ration and the C29ββ/aa十ββ ration have a pesitive relationship with the concentrations of carbonate,when the concentrations of carbonate is higher than 25%,both of the parameters have a negative relationship with the concentrations of carbonate. Show that the higher amount of carbonate have a restricted effection on the isomerisation of sterane and hopane.
1994, 12(3): 130-135.
Abstract:
Based on the analysis of mathematical concept and geometric transformation .the author consider that the decorrelation stretch can selectively exaggerate the least correlated part of thermal multispectral image information,and enhance the spectral contrast of different ground materials. It is one of the effective methods to enhance the highly correlated images. The information of a thermal infrared multispectral image mainly include two parts:surface temperature and emissivity. In principle .the surface temperature is the dominant information. For the temperature of terrestrial surface is commonly less than 30℃.the thermal infrared multispectral image data are always highly correlated from one channel to the next. It is unfavourable for the extraction and analysis of the thematically geological information. The decorrelation stretch,which tend to increase the saturation and affect the hues little,is usful in exaggerating the poorly correlated emissivity information of thermal infrared rnultispectral image data,rather than the highly correlated surface temperature information. The paper presents the effectiveness of decorrelation stretch image with an example in extracting lithostratigraphical information by use of the information about the composition ( i. e.emissivity),rather than the surface temperature.
Based on the analysis of mathematical concept and geometric transformation .the author consider that the decorrelation stretch can selectively exaggerate the least correlated part of thermal multispectral image information,and enhance the spectral contrast of different ground materials. It is one of the effective methods to enhance the highly correlated images. The information of a thermal infrared multispectral image mainly include two parts:surface temperature and emissivity. In principle .the surface temperature is the dominant information. For the temperature of terrestrial surface is commonly less than 30℃.the thermal infrared multispectral image data are always highly correlated from one channel to the next. It is unfavourable for the extraction and analysis of the thematically geological information. The decorrelation stretch,which tend to increase the saturation and affect the hues little,is usful in exaggerating the poorly correlated emissivity information of thermal infrared rnultispectral image data,rather than the highly correlated surface temperature information. The paper presents the effectiveness of decorrelation stretch image with an example in extracting lithostratigraphical information by use of the information about the composition ( i. e.emissivity),rather than the surface temperature.
