1991 Vol. 9, No. 2
column
Display Method:
1991, 9(2): 1-15.
Abstract:
Shallow sea deposit or deep sea deppsit? two different opinions about its origin had been put forward since Wufeng Formation was named in 1931. Researching the cross-section of Wufeng Formation again in Lunshan mountain of Jurong county, Jiangsu Province, in 1989, the authors found profuse Fadiolarians in silicilith and volcanic rock intercalated between silicilith layers, which provides evidences for volcanicism, oringin of the silicilith, and tectonic evolution during Wufeng Age. Thicker than 6.33m which divided into 26 layers, containing abundant radiolarians and graptolithines and spongioid spicules but not benthons, the formation of Upper Ordovician Series is mainly composed of dark thinlayered chertlith and siliceous shale, intercalated more than 97 layers (0.1 to 7cm thick per layer) of yellow mudded volcanic rock as well as a little lava. With the primary composition ranging from neutrality to neutral-basicity to alkaline-neutrality, the volcanic rock consists principally of neutral crystal-vitrie tuff and volcanic dust tuff with a little ignimbrite and andesitic lava and autoclastic- lavaflow- pyroclastic, all of which had illitized, vermiculitized and chloritized.The frequency of volcanic eruption was 8 to 18 times per ma., with the feature of approximately symmetric normal-distribution. According to its thickness and size, the ejecta is of remote origin, and the craters, which spread probably along both grand intraplate extension fault and the top of the uplifted upper mantle, are located at the southeast and the south 300 to 520km or so to Lunshan Mountain, with a little lava from the east dozens of kilometers to Lunshan Mountain.The REE's geochemical characteristic of volcanic rock is similar to that of neutral extrusive-rock related to continental-crust-derived alkaline femic rock, which indicates that the volcanic eruption originated from continental-crust-estension of the continental margin. With a few clastic spongioids and other powdered organisms and a little microcrysialline quartz, the content of the radiolarians and their fragments is about 20-30% in the radiolarian-chertlith.Beside illite, its main component, the siliceous shale-contains a small amount of volcanic-glass pieces and volcanogenic heavy minerals.the silicilith comprises trace elements, such as plentiful Ba, Ti and P as well as poor Sr and Ca, some of which change regularly with the sequence of strata. And the higher the content of radiolarians and silica, the larger the quantity of δ18O (SMOW) in the rocks.The difference of temperature calculated by δ18O is 30℃.So the silicilith was deposited under the condition of the shallow-sea gradually turned into deep sea and the volcanic rock was decomposed, therefore, SiO2in the seawater was considerably increased, and siliceous organisms such as radiolarians, remains of which composed siliceous ooze, reproduced in large amounts.Consequently, opal-A in the skeletons of the radiolarians and other siliceous organ. isms was dissloved and precipitated again, and then crystallized into opal-CT lepispheres which, by burial diagenesie, became fibrous chalcedony and microcrystalline quartz and the formation of bedded chertlith was followed.The cause of this formation is called volcano-organogenic mechanism. The distributive pattern of the radiolarian-silici-lite and the intercalated volcanic rock layers as well as all other deposited substances in the whole region at Wufeng Age prove that, during Late Ordovician epoch, the continental-plate-margin of Lower Yangtzi was extended so fiercely that its crust was thinned to sink and the sea water got deeper and deeper from the east to the west, which formed the marine tectonic and geographical framework put in order from tidal flat to shelf to continental- slope ( including depression) to deep sea basin. And richly distribution radiolarian-silicilith in the vast west area of Maoshan Mountain to Yangzhou line became a blocked and uncompensated small deep sea basin and extended far westernly.The collision between North China Plate and Yangtzi Plat
Shallow sea deposit or deep sea deppsit? two different opinions about its origin had been put forward since Wufeng Formation was named in 1931. Researching the cross-section of Wufeng Formation again in Lunshan mountain of Jurong county, Jiangsu Province, in 1989, the authors found profuse Fadiolarians in silicilith and volcanic rock intercalated between silicilith layers, which provides evidences for volcanicism, oringin of the silicilith, and tectonic evolution during Wufeng Age. Thicker than 6.33m which divided into 26 layers, containing abundant radiolarians and graptolithines and spongioid spicules but not benthons, the formation of Upper Ordovician Series is mainly composed of dark thinlayered chertlith and siliceous shale, intercalated more than 97 layers (0.1 to 7cm thick per layer) of yellow mudded volcanic rock as well as a little lava. With the primary composition ranging from neutrality to neutral-basicity to alkaline-neutrality, the volcanic rock consists principally of neutral crystal-vitrie tuff and volcanic dust tuff with a little ignimbrite and andesitic lava and autoclastic- lavaflow- pyroclastic, all of which had illitized, vermiculitized and chloritized.The frequency of volcanic eruption was 8 to 18 times per ma., with the feature of approximately symmetric normal-distribution. According to its thickness and size, the ejecta is of remote origin, and the craters, which spread probably along both grand intraplate extension fault and the top of the uplifted upper mantle, are located at the southeast and the south 300 to 520km or so to Lunshan Mountain, with a little lava from the east dozens of kilometers to Lunshan Mountain.The REE's geochemical characteristic of volcanic rock is similar to that of neutral extrusive-rock related to continental-crust-derived alkaline femic rock, which indicates that the volcanic eruption originated from continental-crust-estension of the continental margin. With a few clastic spongioids and other powdered organisms and a little microcrysialline quartz, the content of the radiolarians and their fragments is about 20-30% in the radiolarian-chertlith.Beside illite, its main component, the siliceous shale-contains a small amount of volcanic-glass pieces and volcanogenic heavy minerals.the silicilith comprises trace elements, such as plentiful Ba, Ti and P as well as poor Sr and Ca, some of which change regularly with the sequence of strata. And the higher the content of radiolarians and silica, the larger the quantity of δ18O (SMOW) in the rocks.The difference of temperature calculated by δ18O is 30℃.So the silicilith was deposited under the condition of the shallow-sea gradually turned into deep sea and the volcanic rock was decomposed, therefore, SiO2in the seawater was considerably increased, and siliceous organisms such as radiolarians, remains of which composed siliceous ooze, reproduced in large amounts.Consequently, opal-A in the skeletons of the radiolarians and other siliceous organ. isms was dissloved and precipitated again, and then crystallized into opal-CT lepispheres which, by burial diagenesie, became fibrous chalcedony and microcrystalline quartz and the formation of bedded chertlith was followed.The cause of this formation is called volcano-organogenic mechanism. The distributive pattern of the radiolarian-silici-lite and the intercalated volcanic rock layers as well as all other deposited substances in the whole region at Wufeng Age prove that, during Late Ordovician epoch, the continental-plate-margin of Lower Yangtzi was extended so fiercely that its crust was thinned to sink and the sea water got deeper and deeper from the east to the west, which formed the marine tectonic and geographical framework put in order from tidal flat to shelf to continental- slope ( including depression) to deep sea basin. And richly distribution radiolarian-silicilith in the vast west area of Maoshan Mountain to Yangzhou line became a blocked and uncompensated small deep sea basin and extended far westernly.The collision between North China Plate and Yangtzi Plat
1991, 9(2): 25-33.
Abstract:
The contents of most trace elements, especially B, Ga and Zr, in Bauxite of China, are higher thanthe means of that in the Crust, but those of Cu, Ba, Rb, Sc etc. are lower. Compared with othertquntries, the bauxite of China is obviously richer in Zr, Ga, Sr, Ba, B, Ni, Cu, Nb, poorer in Cr,V etc.The contents of more active elements (such as B, Sr, Ba, Rb) distribute in a wide range and thefrequency decreases quickly with the increase of the contents.The contents of stable Zr, Cr and Ga are nearlyof normal distribution. The gibbsitic bauxite formed by weathering of basalt in south-eastern China obviously reflects the fea-tures of basalt, that is rich in Cr, Co, Sc and poor in Zr, Ni. The diasporitic bauxites formed bysedimentation in different areas also have their own features, those on Yangtzi platform rich in Ga; insouthwestern Guan脚and south-eastern Yunan rich in Zr, Cr; in Kangdian axis of earth rich in V, Zr;on North China platform rich in B, Sr, Ba, Ni. From north to south the contents of V and Cr are in thetendency of increasing. The contents of trace elements in bauxite is related to basal rocks, one of the reason is that some basalrocks are the source rocks, or the two have similar mother rocks, the other is that the movement of some e1-ements takes place due to ground water in diagenesis and supergenesis.The content of Ga in bauxite decreases with the time passing.C1and P1 bauxite are rich in Ar, Cr andV.C2 bauxite rich in B, Zr, Sr.The wntents of trace elements in Mz bauxite are low, in Kz bauxite, Crcontent is very high, and those of Zr, Co and V are high. In different rocks, the ratios of pairs of tracx elements or with the content of A12203 are different be-cause of their different geochemical properties, sources and formations of the rocks. According to the distribution of trace elements and their ratio in bauxite, compared with basal rock, itfound that the gibbsitic bauxite in southeastern China inherited the feature of its mother rock (basal basalt)in trace elements, withe the relative contents of Zr, Cr, Ga, and Ga/A1203value; the sedimentary baux-ites in Xiuwen, Tuanzi and Zhangjiaquan mainly originate from their basal rock: those in Pinguo, Xiaoyiand Xinzhan mainly from Al-silicate of acient continents.
The contents of most trace elements, especially B, Ga and Zr, in Bauxite of China, are higher thanthe means of that in the Crust, but those of Cu, Ba, Rb, Sc etc. are lower. Compared with othertquntries, the bauxite of China is obviously richer in Zr, Ga, Sr, Ba, B, Ni, Cu, Nb, poorer in Cr,V etc.The contents of more active elements (such as B, Sr, Ba, Rb) distribute in a wide range and thefrequency decreases quickly with the increase of the contents.The contents of stable Zr, Cr and Ga are nearlyof normal distribution. The gibbsitic bauxite formed by weathering of basalt in south-eastern China obviously reflects the fea-tures of basalt, that is rich in Cr, Co, Sc and poor in Zr, Ni. The diasporitic bauxites formed bysedimentation in different areas also have their own features, those on Yangtzi platform rich in Ga; insouthwestern Guan脚and south-eastern Yunan rich in Zr, Cr; in Kangdian axis of earth rich in V, Zr;on North China platform rich in B, Sr, Ba, Ni. From north to south the contents of V and Cr are in thetendency of increasing. The contents of trace elements in bauxite is related to basal rocks, one of the reason is that some basalrocks are the source rocks, or the two have similar mother rocks, the other is that the movement of some e1-ements takes place due to ground water in diagenesis and supergenesis.The content of Ga in bauxite decreases with the time passing.C1and P1 bauxite are rich in Ar, Cr andV.C2 bauxite rich in B, Zr, Sr.The wntents of trace elements in Mz bauxite are low, in Kz bauxite, Crcontent is very high, and those of Zr, Co and V are high. In different rocks, the ratios of pairs of tracx elements or with the content of A12203 are different be-cause of their different geochemical properties, sources and formations of the rocks. According to the distribution of trace elements and their ratio in bauxite, compared with basal rock, itfound that the gibbsitic bauxite in southeastern China inherited the feature of its mother rock (basal basalt)in trace elements, withe the relative contents of Zr, Cr, Ga, and Ga/A1203value; the sedimentary baux-ites in Xiuwen, Tuanzi and Zhangjiaquan mainly originate from their basal rock: those in Pinguo, Xiaoyiand Xinzhan mainly from Al-silicate of acient continents.
1991, 9(2): 44-54.
Abstract:
Calcisponge reefs are well developed in the Upper Permian Changxing Formation carbonate platform,The exposed reefs are mainly distributed along three belts: The first is located on the east margin of the plat-form and develops rimming framework reefs. The second is on the border of open and drowned platforms.mainly comprises longitudinal framework reefs.The third is composed of bafflestone point reefs located with-in the platform. The framework reef complexes have undergone four diagenetic stages:(1)The depositional stage aremainly submarine cementation and blue-algae binding.The former is limited to the reef core facies, relatedto high water energy and upwelling current. The latter is well developed in the reef- core facies of thelongitudinal or point framework reef complexes within the platform. (2) Submarine phreatic cementation and evaporating dolomitization are the main diageneses of the early burial stage, mainly occurred in theback-reef bank and flat fades (both the rimming reefs and the reefs within the platform)，and less can befound in the reef-core fades. (3) Mid-burial diagenesis closely related to the T2 T3 regional surface ofunconformity. Meteoric water mixed with underground water and caused dissolusion and dolomitization.(4) Deep burial diageneses are cracking. microkarst, coarse dolomite and calcite cementation. Thehydrothermal solution flown up and dissolved along crevices and stylolites ( which were well developed)，formed the microkarsts, and them hydrothermal dolomite and calcite filled in the microkarsts and crevices. Secondary pores was well developed during the mid and deep-burial diagenetic stages caused by crack-ing, mined water dissolusion and dolomitization, and hydrothermal solution dissolusion(nticrokarst)，made the framework reef complexes be a significant oil reservoir. The bafflestone point reefs contain very much calcic- mud, framework structure hadn’t formed,compaction is the main diagenesis through early-and mid-burial stages.Because of the poor porosity, andfew crevices and stylolites, the mixed water and hydrothermal solution have little influence during mid-anddeEp-bural stages, the baftlestone reefs are no significant oil reservoir. The diagenesis of the reef complexes is obviously controlled by the sedimentary facies and thetectionics. The regional tectonic movement, faults and T2 T3 unconformity surface, play an importantpart in mid-and deep-burial diagenesis. Synsedimentary faults controlled the distribution of the reef com-plezes, and acted as the pathways of mined water and hydrothermal solution at mid to deep-burial stages,so the active diagenesis of the framework reef complexes is closely related to the faults.
Calcisponge reefs are well developed in the Upper Permian Changxing Formation carbonate platform,The exposed reefs are mainly distributed along three belts: The first is located on the east margin of the plat-form and develops rimming framework reefs. The second is on the border of open and drowned platforms.mainly comprises longitudinal framework reefs.The third is composed of bafflestone point reefs located with-in the platform. The framework reef complexes have undergone four diagenetic stages:(1)The depositional stage aremainly submarine cementation and blue-algae binding.The former is limited to the reef core facies, relatedto high water energy and upwelling current. The latter is well developed in the reef- core facies of thelongitudinal or point framework reef complexes within the platform. (2) Submarine phreatic cementation and evaporating dolomitization are the main diageneses of the early burial stage, mainly occurred in theback-reef bank and flat fades (both the rimming reefs and the reefs within the platform)，and less can befound in the reef-core fades. (3) Mid-burial diagenesis closely related to the T2 T3 regional surface ofunconformity. Meteoric water mixed with underground water and caused dissolusion and dolomitization.(4) Deep burial diageneses are cracking. microkarst, coarse dolomite and calcite cementation. Thehydrothermal solution flown up and dissolved along crevices and stylolites ( which were well developed)，formed the microkarsts, and them hydrothermal dolomite and calcite filled in the microkarsts and crevices. Secondary pores was well developed during the mid and deep-burial diagenetic stages caused by crack-ing, mined water dissolusion and dolomitization, and hydrothermal solution dissolusion(nticrokarst)，made the framework reef complexes be a significant oil reservoir. The bafflestone point reefs contain very much calcic- mud, framework structure hadn’t formed,compaction is the main diagenesis through early-and mid-burial stages.Because of the poor porosity, andfew crevices and stylolites, the mixed water and hydrothermal solution have little influence during mid-anddeEp-bural stages, the baftlestone reefs are no significant oil reservoir. The diagenesis of the reef complexes is obviously controlled by the sedimentary facies and thetectionics. The regional tectonic movement, faults and T2 T3 unconformity surface, play an importantpart in mid-and deep-burial diagenesis. Synsedimentary faults controlled the distribution of the reef com-plezes, and acted as the pathways of mined water and hydrothermal solution at mid to deep-burial stages,so the active diagenesis of the framework reef complexes is closely related to the faults.
1991, 9(2): 63-70.
Abstract:
This paper, taking the palaeosoils in Upper Guantao Formation, Gudong oilfield as an example, discusses mainly three questions about fluvial palaeosoils. 1.Several identification criterias in cores data were summarized, that is, Ⅰ.in a palaeosoil profile, the vertical changing of sediments colour is sequential, the vertical changing of percentage of many components is regular, the sedimentary structures disappear gradually upwards, and the diagenetic degree decreases gradually upwards; Ⅱ.original roots; Ⅲ.calcite glaebule; Ⅳ.mud crack; Ⅴ.palaeosoil profiles are situated in the uppermost part of fluvial rhythmic profiles. 2.The maturity of a concrete palaeosoil profile was influenced directly by five factors, ie.climate, original sediments, topography, biomass and time, however, the development of palaeosoil in a thick (e.g, thicker than 100 m) profile of fluvial sediments was controlled by three geologic actions, i.e., crust movements, river channel changing, and flooding. 3. Palaeosoil can be used as a zonation marker of fluvial deposits because there is little difference of palaeosoil development in the region of a palaeoriver system.Two steps are finished to get the application of Gudong palaeosoils on the correlation of the fluvial deposits in Upper Guantao Formation, GuDong oilfield.The first is to build a controlling framework for correlation of formations by using the difference between palaeosoil sets and non-palaeosoil sets as a zonation marker, and the second is to make a detailed correlation in polaeosoil sets by using the cyclicity of its maturity as zonation marker. At last, the paper discusses briefly the remaining questions about identification and application of fluvial palaeosoils.
This paper, taking the palaeosoils in Upper Guantao Formation, Gudong oilfield as an example, discusses mainly three questions about fluvial palaeosoils. 1.Several identification criterias in cores data were summarized, that is, Ⅰ.in a palaeosoil profile, the vertical changing of sediments colour is sequential, the vertical changing of percentage of many components is regular, the sedimentary structures disappear gradually upwards, and the diagenetic degree decreases gradually upwards; Ⅱ.original roots; Ⅲ.calcite glaebule; Ⅳ.mud crack; Ⅴ.palaeosoil profiles are situated in the uppermost part of fluvial rhythmic profiles. 2.The maturity of a concrete palaeosoil profile was influenced directly by five factors, ie.climate, original sediments, topography, biomass and time, however, the development of palaeosoil in a thick (e.g, thicker than 100 m) profile of fluvial sediments was controlled by three geologic actions, i.e., crust movements, river channel changing, and flooding. 3. Palaeosoil can be used as a zonation marker of fluvial deposits because there is little difference of palaeosoil development in the region of a palaeoriver system.Two steps are finished to get the application of Gudong palaeosoils on the correlation of the fluvial deposits in Upper Guantao Formation, GuDong oilfield.The first is to build a controlling framework for correlation of formations by using the difference between palaeosoil sets and non-palaeosoil sets as a zonation marker, and the second is to make a detailed correlation in polaeosoil sets by using the cyclicity of its maturity as zonation marker. At last, the paper discusses briefly the remaining questions about identification and application of fluvial palaeosoils.
1991, 9(2): 78-85.
Abstract:
1. There are eight types of sediment in Tieshan Harbour: clay (mud), silty clay, sandy clay, clayey sand, fine-middle sand, middle-coarse sand, coarse sand, sandy gravel (Fig.2).Generally, sediments appear stripped idstribution and parellel to the coast. Contents of heavy minerals in surface sediment tend to decrease from to sea shore with the increase of water depth, and the heavy minerals are named as turmaline-zircon-ilmenite assemblage, which characterized by high content of turmaline and the ratio of turmaline plus zircon to ilmenite is above 1.0. 2. Foraminifera and ostracoda are abundant in the sediment. Species diversity and foraminifera number increase from shore with the increase of water depth, three assemblage zone can be divided: 7) Ammonia beccarii vars.assemblage zone, distributed in intertidal zone; 2) A.beccarii vars-Brizalina striatula assemblage zone in subtidal zone (water depth 0-10m); 3) Schackoinellaglobosa-A.compressiuscula assemblage zone in the water depth 10-20m. 3. Based on micropaleontology and lithology and 14C dating, four sedimentary fades can be indentified from lower to upper: 1) continental depositional stratum formed in the Pleistocene Epoch; 2) fresh water-marshy fades formed in the Early-Holocene (1000-8000B.P.); 3) marine-continental transitional fades formed in the Middle- Holocene ( 8000- 6000B. P. ) ; 4) shallow- sea fades formed in the Middle-Late-Holocene (6000-present). 4. Sediments in Tieshan Harbour are mainly derived from the erosion of Beihai Formation and Zhanjiang Formation by wind, wave, tidal and surface water.
1. There are eight types of sediment in Tieshan Harbour: clay (mud), silty clay, sandy clay, clayey sand, fine-middle sand, middle-coarse sand, coarse sand, sandy gravel (Fig.2).Generally, sediments appear stripped idstribution and parellel to the coast. Contents of heavy minerals in surface sediment tend to decrease from to sea shore with the increase of water depth, and the heavy minerals are named as turmaline-zircon-ilmenite assemblage, which characterized by high content of turmaline and the ratio of turmaline plus zircon to ilmenite is above 1.0. 2. Foraminifera and ostracoda are abundant in the sediment. Species diversity and foraminifera number increase from shore with the increase of water depth, three assemblage zone can be divided: 7) Ammonia beccarii vars.assemblage zone, distributed in intertidal zone; 2) A.beccarii vars-Brizalina striatula assemblage zone in subtidal zone (water depth 0-10m); 3) Schackoinellaglobosa-A.compressiuscula assemblage zone in the water depth 10-20m. 3. Based on micropaleontology and lithology and 14C dating, four sedimentary fades can be indentified from lower to upper: 1) continental depositional stratum formed in the Pleistocene Epoch; 2) fresh water-marshy fades formed in the Early-Holocene (1000-8000B.P.); 3) marine-continental transitional fades formed in the Middle- Holocene ( 8000- 6000B. P. ) ; 4) shallow- sea fades formed in the Middle-Late-Holocene (6000-present). 4. Sediments in Tieshan Harbour are mainly derived from the erosion of Beihai Formation and Zhanjiang Formation by wind, wave, tidal and surface water.
1991, 9(2): 93-98.
Abstract:
Shouchang Basin is an accumulation basin of volcanic sandstone, which located in Shouchang, Zhejiang province, substrata of which is Henshan group of fluvial sediments (Lewer Cretaceous) and the upper is Shouchang group of lacastrine deposit (Upper Jurrasic), both of them are sandstones of low quartz contents, the former is charactrized by plagioclase and lithoclast, and the later is mainly ortheclase and lithoclast. It is the different compositions which led to the different diagenesis of the two groups.Undertaken high temparature and pressure (i.e. above 200@@ and less than 3 kb.), Henshan group undergone early diagenesis with the feature of laumontite formed by hydration; but Shouchang group undergoue late diagenesis characterized by albite formed by dehydration.Diagenetic zonation is obviously in the basin. Diagenetic processes are based on the different mineral compositions and characters of the two groups.In the early diagenetic stage, because of the lack of quartz, primary pores are mainly damaged by compaction, pressur solution, hydration and the regrowth of quarty and feldspar, filling of carbonate can also destroy the primary pores.But the secondary pores can be formed by dehydration and dissolution during late diagentic stage which made the strata be a potential reservoir of oil and gas.
Shouchang Basin is an accumulation basin of volcanic sandstone, which located in Shouchang, Zhejiang province, substrata of which is Henshan group of fluvial sediments (Lewer Cretaceous) and the upper is Shouchang group of lacastrine deposit (Upper Jurrasic), both of them are sandstones of low quartz contents, the former is charactrized by plagioclase and lithoclast, and the later is mainly ortheclase and lithoclast. It is the different compositions which led to the different diagenesis of the two groups.Undertaken high temparature and pressure (i.e. above 200@@ and less than 3 kb.), Henshan group undergone early diagenesis with the feature of laumontite formed by hydration; but Shouchang group undergoue late diagenesis characterized by albite formed by dehydration.Diagenetic zonation is obviously in the basin. Diagenetic processes are based on the different mineral compositions and characters of the two groups.In the early diagenetic stage, because of the lack of quartz, primary pores are mainly damaged by compaction, pressur solution, hydration and the regrowth of quarty and feldspar, filling of carbonate can also destroy the primary pores.But the secondary pores can be formed by dehydration and dissolution during late diagentic stage which made the strata be a potential reservoir of oil and gas.
1991, 9(2): 106-113.
Abstract:
A complete series of short side chain steroids (C20-C26) have first been identified in the crude oil and source rock of saline lake facies from Jinxian Sag of North China by GC / MS and the biological origin and geochemical significance of these compounds are dicussed. The short side chain steroid compounds identified include: (a) steranes, which have m/ z 217 or m/z218 base peak in its mass spectrum but the length of their side chain at C-20 position are different (fig.2). (b) 4-methyl and 4, 4-dimethyl pregnanes and homopregnanes (Fig.3). (c) sterenes, whichs molecular weight are 2 units less than the carbons number corresponding steranes and have m / z 281 base peak or characteristic peak on their mass spectrum.lt can be inferred that the position of double bond is on the D ring (Fig.4). There are some geochemical phenomena accompaning the occurrence of short side chain steroids. The content of n?alkanes is lower and the content of lower carbon number is much more than the higher (∑C21-/ ∑C22+= 3.66), and the major peak is C16, there is a higher concentration of C23, C24and C25isoprenoid hydrocarbons (peak K, L and M in Fig.5) Besides higher concentration of pristane and phytane. It is proposed that the high concentrations of isoprenoid hydrocarbons and low carbon number n-alkanes are the result of bacterial input. It is intresting that in our samples the content of short side chain steroids (c20-C26) is much higher than the C27-C29 steranes. the occurrence of a series of short side chain steroids is considered to be the products of some halophilic bacterial activities and, the high concentration of γ- cerane provides another evidence. Furthermore, it has been noticed that the common C21-pregnanes and C22-homopregnanes are dominated in the short side chain steriods.They should be the derivatives from some microorganisms especially from pregnant sterone and pregnant sterol in the halophilic bacteria. As for the origin of all short side chain steroids, however, bacteria (fat discomposition bacteria) degradation leading to side chain rupture of normal steranes could not be excluded. There is nearly not the long side chain hopanes above C30but a high content of C30hopane.It shows that bacterial degradation may result a vanishing of long side chain hopanes and relative richment of C30opane, and indicates shows the existence of the bacterial degradation. In short, the input of organic matter are mainly derived from bacteria and algal, and the original organic matter had experienced a bacterial reconstruction.Therefore, the existence of short side chain steroids and some accompaning marker compounds reflects a hypersaline and component reducing depositional envi- ronment and bacterial biodegradation of some biological precursor molecules.
A complete series of short side chain steroids (C20-C26) have first been identified in the crude oil and source rock of saline lake facies from Jinxian Sag of North China by GC / MS and the biological origin and geochemical significance of these compounds are dicussed. The short side chain steroid compounds identified include: (a) steranes, which have m/ z 217 or m/z218 base peak in its mass spectrum but the length of their side chain at C-20 position are different (fig.2). (b) 4-methyl and 4, 4-dimethyl pregnanes and homopregnanes (Fig.3). (c) sterenes, whichs molecular weight are 2 units less than the carbons number corresponding steranes and have m / z 281 base peak or characteristic peak on their mass spectrum.lt can be inferred that the position of double bond is on the D ring (Fig.4). There are some geochemical phenomena accompaning the occurrence of short side chain steroids. The content of n?alkanes is lower and the content of lower carbon number is much more than the higher (∑C21-/ ∑C22+= 3.66), and the major peak is C16, there is a higher concentration of C23, C24and C25isoprenoid hydrocarbons (peak K, L and M in Fig.5) Besides higher concentration of pristane and phytane. It is proposed that the high concentrations of isoprenoid hydrocarbons and low carbon number n-alkanes are the result of bacterial input. It is intresting that in our samples the content of short side chain steroids (c20-C26) is much higher than the C27-C29 steranes. the occurrence of a series of short side chain steroids is considered to be the products of some halophilic bacterial activities and, the high concentration of γ- cerane provides another evidence. Furthermore, it has been noticed that the common C21-pregnanes and C22-homopregnanes are dominated in the short side chain steriods.They should be the derivatives from some microorganisms especially from pregnant sterone and pregnant sterol in the halophilic bacteria. As for the origin of all short side chain steroids, however, bacteria (fat discomposition bacteria) degradation leading to side chain rupture of normal steranes could not be excluded. There is nearly not the long side chain hopanes above C30but a high content of C30hopane.It shows that bacterial degradation may result a vanishing of long side chain hopanes and relative richment of C30opane, and indicates shows the existence of the bacterial degradation. In short, the input of organic matter are mainly derived from bacteria and algal, and the original organic matter had experienced a bacterial reconstruction.Therefore, the existence of short side chain steroids and some accompaning marker compounds reflects a hypersaline and component reducing depositional envi- ronment and bacterial biodegradation of some biological precursor molecules.
1991, 9(2): 121-126.
Abstract:
The concept tempestites is currently used at home and abroad which's original word is "tempest", but the usuage of "tempest"is not as often as "storm"in metorology.The word storm, which emphasized catastrophic charicter, means cyclone (tornado, typhone, oneway windstorn) and its flow speed is just as the same as sound speed. Cyclone can promote and influence ocean water in the track area to form vortex with the same track as cyclone itself.But the cyclone can not form sediments directly from sands in ocean wates, it can only affects the sediments of coceanwater by seperation, sorting transportation, so the name of " tempestities" is not suitable. Cyclone is only one of the factors of vortex forming, its life is short and the track is not steady. The function of wind is emphasized when tempesites is named, but the function of oceanwater can't be seen in it, this problem is worth to discuss. In addition, the theory which whirling currents can transport sands from coast (intertidal zone) into the ocean for tens to one hundred kilometres far is analyzed and observed actually, it indicated that the en-ergy of whirling currents is weak and can't be signifcant sediments transporting factor.
The concept tempestites is currently used at home and abroad which's original word is "tempest", but the usuage of "tempest"is not as often as "storm"in metorology.The word storm, which emphasized catastrophic charicter, means cyclone (tornado, typhone, oneway windstorn) and its flow speed is just as the same as sound speed. Cyclone can promote and influence ocean water in the track area to form vortex with the same track as cyclone itself.But the cyclone can not form sediments directly from sands in ocean wates, it can only affects the sediments of coceanwater by seperation, sorting transportation, so the name of " tempestities" is not suitable. Cyclone is only one of the factors of vortex forming, its life is short and the track is not steady. The function of wind is emphasized when tempesites is named, but the function of oceanwater can't be seen in it, this problem is worth to discuss. In addition, the theory which whirling currents can transport sands from coast (intertidal zone) into the ocean for tens to one hundred kilometres far is analyzed and observed actually, it indicated that the en-ergy of whirling currents is weak and can't be signifcant sediments transporting factor.
1991, 9(2): 16-24.
Abstract:
By using graphic analysis to study carbonate and terrigenous clastic sediments of the western Hunan and eastern Guizhou provinces, the different dynamic factors uneiital carbonate sequences in this area are studied especially. With the analysis, the ooidalpisolitic grainstone, oncolitic packstone and intraclastic gram and tidal dominated environments are discussed.Furthermore, the characten and gravity flow sediments are analyzed, and the sedimentary mechanics of st is idscussed. Particularly, the authors studied the hummocky cross-stratifie in tempestite sequence. Which was to be the product of unidirectional back-flow of gradient current- formed by storm interpays with storm wave action, this bed-form is a transitional type betwwen syn ripples with straight crest and the upper flat bed- form of gradient currents.Pale rent sis of Cambrian contour currents in studied area indicates the paleocurrent flown from NE to S and along the edge of the basin. Four ki difterent veruend es are recognized, which includes the shallowing-upward cycles, and minor" transgoressive regressive pulses. Lateral distribution of facies may indicates paleogeograp ter diferent periods: a gentle slope consists of algal mound during the early Cambrian and a steep slope consists of ooidal shoal in the middle Cambrian.The sedimentary dynamics of the mentioned slope is suggested: (1) wavy and tidal action that affected the shore belt; (2) storm events that influenced the shore and shelf environments; ( 3) sliding and gravity flow that developed across to the shoreline; (4) contour current that flowed along the slope and parallelled to the shoreline. Comparision of minor cycles suggests that the dynamic factors controlling these cycles may be derived from the block faulting. The regressive sequence of basinal edge was controlled by the.interaction of plate spreading, sealevel changing and the developing of carbonate itself.
By using graphic analysis to study carbonate and terrigenous clastic sediments of the western Hunan and eastern Guizhou provinces, the different dynamic factors uneiital carbonate sequences in this area are studied especially. With the analysis, the ooidalpisolitic grainstone, oncolitic packstone and intraclastic gram and tidal dominated environments are discussed.Furthermore, the characten and gravity flow sediments are analyzed, and the sedimentary mechanics of st is idscussed. Particularly, the authors studied the hummocky cross-stratifie in tempestite sequence. Which was to be the product of unidirectional back-flow of gradient current- formed by storm interpays with storm wave action, this bed-form is a transitional type betwwen syn ripples with straight crest and the upper flat bed- form of gradient currents.Pale rent sis of Cambrian contour currents in studied area indicates the paleocurrent flown from NE to S and along the edge of the basin. Four ki difterent veruend es are recognized, which includes the shallowing-upward cycles, and minor" transgoressive regressive pulses. Lateral distribution of facies may indicates paleogeograp ter diferent periods: a gentle slope consists of algal mound during the early Cambrian and a steep slope consists of ooidal shoal in the middle Cambrian.The sedimentary dynamics of the mentioned slope is suggested: (1) wavy and tidal action that affected the shore belt; (2) storm events that influenced the shore and shelf environments; ( 3) sliding and gravity flow that developed across to the shoreline; (4) contour current that flowed along the slope and parallelled to the shoreline. Comparision of minor cycles suggests that the dynamic factors controlling these cycles may be derived from the block faulting. The regressive sequence of basinal edge was controlled by the.interaction of plate spreading, sealevel changing and the developing of carbonate itself.
1991, 9(2): 34-43.
Abstract:
Block halite had been found in three test-wells from the upper Majiagou Formation of Ordovician in eastern Ordos.There are four layers of bedded halite whichs'thickness is 114 to 157m, and serverat thin layers of anhydrite and dolomite interbedded in it, the content of pure salt is about 90 percent. The dlomite and anhydrite have different characters above and below the block halite. The dolomites above have obvious shallow-water depositional features; but the dolomites below are characterized by deepwater depositional features. There are four types of halite: black opaque matrix, black transparent crystals,.white transparent crystals and reddish transparent crystals.The most common is the third type followed by the fourth.The first two contain much more anhydrite, and the fourth contains more KCl. The block halite is composed by many cycles which consist of penesaline, saline and hypersaline sediments in vertical. The first is made up of dolomite and anhydrite; the second, dolomite and anhydrite and salt; the third, anhydrite and salt (often reddish crytal salt).Anhydrite with thickness less than 10cm usually 2-4cm is often found in hah'te.Vertically, the thickness of pure salt is less than 1 m. The block halite was formed in a short period and a deep water environment, but the dolomite and anhydrite above it have obvious shallowwater depositional features, it indicated that the forming of halite had filled the geomorphological depression. The occurrence of halite is significant for survey of KCl-bearing salt deposits and gas pool.
Block halite had been found in three test-wells from the upper Majiagou Formation of Ordovician in eastern Ordos.There are four layers of bedded halite whichs'thickness is 114 to 157m, and serverat thin layers of anhydrite and dolomite interbedded in it, the content of pure salt is about 90 percent. The dlomite and anhydrite have different characters above and below the block halite. The dolomites above have obvious shallow-water depositional features; but the dolomites below are characterized by deepwater depositional features. There are four types of halite: black opaque matrix, black transparent crystals,.white transparent crystals and reddish transparent crystals.The most common is the third type followed by the fourth.The first two contain much more anhydrite, and the fourth contains more KCl. The block halite is composed by many cycles which consist of penesaline, saline and hypersaline sediments in vertical. The first is made up of dolomite and anhydrite; the second, dolomite and anhydrite and salt; the third, anhydrite and salt (often reddish crytal salt).Anhydrite with thickness less than 10cm usually 2-4cm is often found in hah'te.Vertically, the thickness of pure salt is less than 1 m. The block halite was formed in a short period and a deep water environment, but the dolomite and anhydrite above it have obvious shallowwater depositional features, it indicated that the forming of halite had filled the geomorphological depression. The occurrence of halite is significant for survey of KCl-bearing salt deposits and gas pool.
1991, 9(2): 55-62.
Abstract:
Aksu and Keping in northwest Tarim Basin are the areas with perfect outcrops of Lower Palaeozoic strata. This paper mainly deals with Cambrian and Ordovician carbonate strata on the western side of Aksu-Karshgar high way for the study of sedimentary environments and development of the strata. The Cambrian and Ordovician strata are a series of dark-carbonate formations, with total thickness of about 1341m The Cambrian system consists mainly of dark dolostones accompanied with intraclast limestone, sandstone and mudstone, the thickness is 541m. The Lower Ordovician series was deposited continuously after the Cambrian system, and the Upper Ordovician series was lacuna. The lower part of Lower Ordovician series are massive dolostone, upwards there are successively limestone, biotic limestone and intraclast limestone. The Middle Ordovician series is interbedded limestone, siltstone and mudstone, and the total thickness is 800m.The strata can be divided into 8 groups and two types of sedimentary models according to their carbonate minerals, crystal grainsi, texture, organisms and inraclasts. The sedimentary environment was developed from subtidal zone to supratidal zone of carbonate plateform of semienclosed bay and then into open shallow marine continental shelf.The Cambrian system was a tidal environment that undergone two cycles of regressions. The Ordovician system was once a larger transgression. During the Cambrian, the sea water body was shallow, the temprature was higher and the environment was calm, a large quantity of carbonate deposited in the semienclosed restricted bay.The salinity of sea water at that time was favourable for the development of hypersaline stromatolithic algae, which were flat-top, continuously-upwarping algal mat mainly developed in the supratidal zone.Stromatolite with fracture was developed mostly in the Upper-Middle Cambrian, moreover, edgewise and gravel clastic dolostones were also deposited in the same period.However, with continuous development of stromatolite, main deposits were massive silica-contained dolostone in the early Ordovician.From the upper part of Lower Ordovician the environment had changed greatly, at first deposits are algal limestone that consists of algal grains, granules, thrombolites which formed in turbulent water; continuously upwards are the deposits of orthoceras limestone which formed from high-energy subtidal to shallow-water environments; the top of this series are very thick black shales with pyrite nodules. The Upper Ordovician series is interbedded bioclastic intraclast limestone, siltstone and mudstone with typical thin laminated nodule limestone and huge wave ripples of flowing water, representing a transition from turbulent, open shallow sea to continental shelf. Up to then all strata had risen and the sedimention of platform in this area had ceased. The datas of elements, stable isotopes, compositions of clay minerals were also employed for discussing the conditions of sedimentary medium in this paper.
Aksu and Keping in northwest Tarim Basin are the areas with perfect outcrops of Lower Palaeozoic strata. This paper mainly deals with Cambrian and Ordovician carbonate strata on the western side of Aksu-Karshgar high way for the study of sedimentary environments and development of the strata. The Cambrian and Ordovician strata are a series of dark-carbonate formations, with total thickness of about 1341m The Cambrian system consists mainly of dark dolostones accompanied with intraclast limestone, sandstone and mudstone, the thickness is 541m. The Lower Ordovician series was deposited continuously after the Cambrian system, and the Upper Ordovician series was lacuna. The lower part of Lower Ordovician series are massive dolostone, upwards there are successively limestone, biotic limestone and intraclast limestone. The Middle Ordovician series is interbedded limestone, siltstone and mudstone, and the total thickness is 800m.The strata can be divided into 8 groups and two types of sedimentary models according to their carbonate minerals, crystal grainsi, texture, organisms and inraclasts. The sedimentary environment was developed from subtidal zone to supratidal zone of carbonate plateform of semienclosed bay and then into open shallow marine continental shelf.The Cambrian system was a tidal environment that undergone two cycles of regressions. The Ordovician system was once a larger transgression. During the Cambrian, the sea water body was shallow, the temprature was higher and the environment was calm, a large quantity of carbonate deposited in the semienclosed restricted bay.The salinity of sea water at that time was favourable for the development of hypersaline stromatolithic algae, which were flat-top, continuously-upwarping algal mat mainly developed in the supratidal zone.Stromatolite with fracture was developed mostly in the Upper-Middle Cambrian, moreover, edgewise and gravel clastic dolostones were also deposited in the same period.However, with continuous development of stromatolite, main deposits were massive silica-contained dolostone in the early Ordovician.From the upper part of Lower Ordovician the environment had changed greatly, at first deposits are algal limestone that consists of algal grains, granules, thrombolites which formed in turbulent water; continuously upwards are the deposits of orthoceras limestone which formed from high-energy subtidal to shallow-water environments; the top of this series are very thick black shales with pyrite nodules. The Upper Ordovician series is interbedded bioclastic intraclast limestone, siltstone and mudstone with typical thin laminated nodule limestone and huge wave ripples of flowing water, representing a transition from turbulent, open shallow sea to continental shelf. Up to then all strata had risen and the sedimention of platform in this area had ceased. The datas of elements, stable isotopes, compositions of clay minerals were also employed for discussing the conditions of sedimentary medium in this paper.
1991, 9(2): 71-77.
Abstract:
Field work proves that the modern dry playas in the Kenteyi Playa lake of Qaidan Basin have been under gone two main formation courses: 1) Subfluvial sedimentary process in common saline lakes.Their mechanical sediments mainly consists of suspended fine particles, fluvial and aeolian, dispersed or interbedded in salt-bearing beds; 2) subaerial sedimentary and/ or remaking process on playas after drying.Aeolian dust adhesion sedimentation develops at the beginning of this stage, then coarser sands deposit, with aeolian erosion in some case. While the playa are dissolved and remade by rain and evaporation so the mechanical sediments and evaporite deposits are mixed, the earlier and the latter materials get together in one bed, formed the dry playa sequence. By grain-size analysis and correlation, the clastic sediments in the modern saline lakes and playas have clearly different distribution characteristics: The former has a single peak frequence curve, spread out, consists mainly of fine and poor sorted sediments (silts and clays); And the latter is a very complicated poly-peak frenquence curve, which can be generally devided into two parts, a coarser one and a finer one.The coarser one has a relatively steep cumulative curve with a "median" range 0-2Φ and well sorted.Its frequence curve is left-side skewed. These features stand for aeolian sand sediments, which are the added part after drying the finer one is similar to the curve of the modern saline drying.The finer one is similar to the curve of the modern saline 5Φ.So they are the original sediments formed in common saline lakes before dry ing.It is clear that the grain-size distribution characteristics is a good indicator to indentify playa sequence. Using the results got above from modern samples, some dry playa sequences are revealed which can be correlated horizontally in the different sections.Potash deposits (such as polyhalite ) and K+-rich interstital brines just occur at these dry playa intervals. It proves that potash accumulation is closely related to dry playas, and it shows that the grain-size analysis method can be used in prospection potash deposits. Grain-size analysis firsthand datas have been delt with by a computer in order to use and interpret easily, and the result shows that the datas of saline lake elastics are generally approximated to one population still; but the datas of dry playa sediments to two or more sub-populations, indicating that they derived from more than one sedimentary processes. That is identical with geological observation and discussion above.
Field work proves that the modern dry playas in the Kenteyi Playa lake of Qaidan Basin have been under gone two main formation courses: 1) Subfluvial sedimentary process in common saline lakes.Their mechanical sediments mainly consists of suspended fine particles, fluvial and aeolian, dispersed or interbedded in salt-bearing beds; 2) subaerial sedimentary and/ or remaking process on playas after drying.Aeolian dust adhesion sedimentation develops at the beginning of this stage, then coarser sands deposit, with aeolian erosion in some case. While the playa are dissolved and remade by rain and evaporation so the mechanical sediments and evaporite deposits are mixed, the earlier and the latter materials get together in one bed, formed the dry playa sequence. By grain-size analysis and correlation, the clastic sediments in the modern saline lakes and playas have clearly different distribution characteristics: The former has a single peak frequence curve, spread out, consists mainly of fine and poor sorted sediments (silts and clays); And the latter is a very complicated poly-peak frenquence curve, which can be generally devided into two parts, a coarser one and a finer one.The coarser one has a relatively steep cumulative curve with a "median" range 0-2Φ and well sorted.Its frequence curve is left-side skewed. These features stand for aeolian sand sediments, which are the added part after drying the finer one is similar to the curve of the modern saline drying.The finer one is similar to the curve of the modern saline 5Φ.So they are the original sediments formed in common saline lakes before dry ing.It is clear that the grain-size distribution characteristics is a good indicator to indentify playa sequence. Using the results got above from modern samples, some dry playa sequences are revealed which can be correlated horizontally in the different sections.Potash deposits (such as polyhalite ) and K+-rich interstital brines just occur at these dry playa intervals. It proves that potash accumulation is closely related to dry playas, and it shows that the grain-size analysis method can be used in prospection potash deposits. Grain-size analysis firsthand datas have been delt with by a computer in order to use and interpret easily, and the result shows that the datas of saline lake elastics are generally approximated to one population still; but the datas of dry playa sediments to two or more sub-populations, indicating that they derived from more than one sedimentary processes. That is identical with geological observation and discussion above.
1991, 9(2): 86-92.
Abstract:
As the study of the open estuary, Fe, Mn, Ca, Mg elements concentration, source and geochemistry characteristics in sediments are discussed in detail. The results are as follows: 1) Fe, Mn, Mg in sediments of Hangzhou estuary are higher and Ca is lower than that in sediments of the Prydz estuary and Antractics, the average value of Fe, Mn, Mg and Ca are 3. 76%, 0. 074%, 1.73%and 3.08% respectively.It shows that the characteristics of high Ca and Mg in sediments of the studying area. 2) The horizontal distribution of Fe, Mn and Ca, Mg in sediments are both the same and different.The distribution law of Fe, Mn, Ca and Mg are as follows: Fe, Mn increase from estuary tothe centre of estuary and decrease from Nanwei mouth to the centre of the estuary, the distribution of Fe, Mn tongue into centre of estuary; There are also two tongues of Ca with 30°30 'north latitude as boundary line; The distribution of Mg is more complex than that Fe, Mn, Ca, there are three thongues from Qiantangjiang runoff, Shoushan island and the dilute water of Yongjiang to the centre of the area respectively. 3) Fe, Mn, Mg in sediments exist in fine sediments, and Fe, Mn came mainly from movement of the dilute water of Yongjiang and Qiantangjiang runoff and controlled by clay; Mg came mainly from the absorption of clay to Mg2+in sea water and effected by the salinity of overlying water; Ca of south area came mainly from Qiantangjiang runoff and the weathering of rock in the coastal area and probably came mainly from biological shells and deposition of inorganic chemistry in north area. 4) The relation of elements in north area are stronger obviously than that in south, especially, except for correlation between Fe and Mn, Mg, there are no correlation in the south.It shows that the sources and exist forms of elements in south sediments are more complex than that in the north. 5) The study of the correlation between ratio of elements (Mg / Ca) in sediments shows that Mg / Ca in sediments increases from the mouth to the near shore and there is positive correlation between the organic carbon in sediments and Mg / Ca, it is found that there are bitter spar on manily section, it shows that the reaction of original calcium cabonate in sediments with Mg2+in seawater was processed
As the study of the open estuary, Fe, Mn, Ca, Mg elements concentration, source and geochemistry characteristics in sediments are discussed in detail. The results are as follows: 1) Fe, Mn, Mg in sediments of Hangzhou estuary are higher and Ca is lower than that in sediments of the Prydz estuary and Antractics, the average value of Fe, Mn, Mg and Ca are 3. 76%, 0. 074%, 1.73%and 3.08% respectively.It shows that the characteristics of high Ca and Mg in sediments of the studying area. 2) The horizontal distribution of Fe, Mn and Ca, Mg in sediments are both the same and different.The distribution law of Fe, Mn, Ca and Mg are as follows: Fe, Mn increase from estuary tothe centre of estuary and decrease from Nanwei mouth to the centre of the estuary, the distribution of Fe, Mn tongue into centre of estuary; There are also two tongues of Ca with 30°30 'north latitude as boundary line; The distribution of Mg is more complex than that Fe, Mn, Ca, there are three thongues from Qiantangjiang runoff, Shoushan island and the dilute water of Yongjiang to the centre of the area respectively. 3) Fe, Mn, Mg in sediments exist in fine sediments, and Fe, Mn came mainly from movement of the dilute water of Yongjiang and Qiantangjiang runoff and controlled by clay; Mg came mainly from the absorption of clay to Mg2+in sea water and effected by the salinity of overlying water; Ca of south area came mainly from Qiantangjiang runoff and the weathering of rock in the coastal area and probably came mainly from biological shells and deposition of inorganic chemistry in north area. 4) The relation of elements in north area are stronger obviously than that in south, especially, except for correlation between Fe and Mn, Mg, there are no correlation in the south.It shows that the sources and exist forms of elements in south sediments are more complex than that in the north. 5) The study of the correlation between ratio of elements (Mg / Ca) in sediments shows that Mg / Ca in sediments increases from the mouth to the near shore and there is positive correlation between the organic carbon in sediments and Mg / Ca, it is found that there are bitter spar on manily section, it shows that the reaction of original calcium cabonate in sediments with Mg2+in seawater was processed
1991, 9(2): 99-105.
Abstract:
In the past the studies on the "petroporphyrins" usually deal with single samples or several non-related single samples, few attention had been payed to suites of samples from the same reservoir-system or co-generic oils from the same basin, but only systematic study can reveal the true maturational progress of these biomarkers. In order to study geochemical characteristics of petroporphyrins, 19 samples of crude oils and source rocks from western Liaohe Basin have been systematically investigated (See Table). 1. Formation of rock-porphyrins in the Paleogene from western Liaohe Basin had undergone four stages.Contents of porphyrins are less than Ippm in the first stage (less than 1800m) and increased rapidly during stage two (1800-2350m), decreased quickly in the third sta (2350-2800m), and little in stage four (more than 2800m) (See Fig.2). Changes of rock-porphyrins contents with burial depth coincident with the changes of total hydrocarbons conternts in profile. The best porphyrins-generating zone occurs in 1800-2800m and as the same with of total hydrocarbons generation ( See Fig. 1).It provided that porphyrin is an effective geochemical index during low maturity of petroleum. 2.Demetallized porphyrins in the crude oil of S4 section from Gaosheng 1-6-14 well include DPEP (M-l) series (72.4%) and Rhodo-ETIO (M-l) series (27.6%) (See Fig.4).In the crude oil of S3 section from Gaosbeng 3- 7- 9 well, demetallized porphyrins are Rhodo-DPEP ( 30. 8% ), Rhodo-ETIO (20%), Rhodo-Di-DPEP (13.1%), Di-DPEP (16.3%), DPEP (12.6%) and ETIO (7.2%) (See fig.5), Correlation of oil and oil indicated that the crued oils from Gaosheng 1-6-14 and 3-7-9 wells probably come from different oil-source area, and the maturity of the former maybe higher than the latter. GC of saturated hydrocarbons of three samples in the area confirmed that the maturity of crude oil and source rock from S3 section of Gao-3 fault block was obviously lower than the crude oil from S4 section of Gao-1 fault block. (See Fig.3 and 6). 3.The case is rare at home and abrood that porphyrins are dominated by Rhodo-prphyrins as occured in crude oil of Gaosheng 3-7-9 well.This feature is similar to that of low-maturity consistent oil formd in fresh water deposit. 4.By the comparisons of metalloporphyrins in the source rock from Dujiatai oil field with the crude oils from Gaosheng oil field, it is suggested that the source rock of Du-65 well contains a little VO-ETIO series and VO-rhodo-DPEP series ( See Fig. 8) besides Ni- porphyrins. It indicated the difference of hydrocarbons source rocks between Dujiatai and Gaosheng oil field.
In the past the studies on the "petroporphyrins" usually deal with single samples or several non-related single samples, few attention had been payed to suites of samples from the same reservoir-system or co-generic oils from the same basin, but only systematic study can reveal the true maturational progress of these biomarkers. In order to study geochemical characteristics of petroporphyrins, 19 samples of crude oils and source rocks from western Liaohe Basin have been systematically investigated (See Table). 1. Formation of rock-porphyrins in the Paleogene from western Liaohe Basin had undergone four stages.Contents of porphyrins are less than Ippm in the first stage (less than 1800m) and increased rapidly during stage two (1800-2350m), decreased quickly in the third sta (2350-2800m), and little in stage four (more than 2800m) (See Fig.2). Changes of rock-porphyrins contents with burial depth coincident with the changes of total hydrocarbons conternts in profile. The best porphyrins-generating zone occurs in 1800-2800m and as the same with of total hydrocarbons generation ( See Fig. 1).It provided that porphyrin is an effective geochemical index during low maturity of petroleum. 2.Demetallized porphyrins in the crude oil of S4 section from Gaosheng 1-6-14 well include DPEP (M-l) series (72.4%) and Rhodo-ETIO (M-l) series (27.6%) (See Fig.4).In the crude oil of S3 section from Gaosbeng 3- 7- 9 well, demetallized porphyrins are Rhodo-DPEP ( 30. 8% ), Rhodo-ETIO (20%), Rhodo-Di-DPEP (13.1%), Di-DPEP (16.3%), DPEP (12.6%) and ETIO (7.2%) (See fig.5), Correlation of oil and oil indicated that the crued oils from Gaosheng 1-6-14 and 3-7-9 wells probably come from different oil-source area, and the maturity of the former maybe higher than the latter. GC of saturated hydrocarbons of three samples in the area confirmed that the maturity of crude oil and source rock from S3 section of Gao-3 fault block was obviously lower than the crude oil from S4 section of Gao-1 fault block. (See Fig.3 and 6). 3.The case is rare at home and abrood that porphyrins are dominated by Rhodo-prphyrins as occured in crude oil of Gaosheng 3-7-9 well.This feature is similar to that of low-maturity consistent oil formd in fresh water deposit. 4.By the comparisons of metalloporphyrins in the source rock from Dujiatai oil field with the crude oils from Gaosheng oil field, it is suggested that the source rock of Du-65 well contains a little VO-ETIO series and VO-rhodo-DPEP series ( See Fig. 8) besides Ni- porphyrins. It indicated the difference of hydrocarbons source rocks between Dujiatai and Gaosheng oil field.
1991, 9(2): 114-120.
Abstract:
Dongpu Depression was one of the rifts in eastern China which accumulated sequences of salts and oil source rocks over 2, 000m in thickness during the Oligocene.Every sequence consists of lots of rhythms of 1 -5m thick which comprises light yellow transparent halite and grey-black mudstone interbedded with white laminated gypsum or brown oil shale. A model of deep-water saline lake is given in which the salts and the dark mudstones are deposited at the same time. Mudstones rich in organic matter were proved to be significant source rocks for oil and gas. It is important for the source rocks to deposit that the deep-water saline lake was layered by salinities: the upper part is brackish and aerobic, suitable for organisms living; in contrast the lower one is bitter and anoxic-the best environment for organic matter accumulation and preservation.The Corgof the mudstones deposited in the deep-water saline lake is over 1% and up to 4.4%. The middle and lower parts of Jidic Formation (Miocene) in narthern Tarim Basin, is consist of grey-green mudstones, brown siltstones and shell-shaped gypsums and dispersed granular halites.The sediments were probably formed in a movible shallow saline and aerobic lake, i.e.playa.Corgis only 0.3-0.7% in mudstone, but the interbedded sandstone has intensive showing of oil which implied that the the mudstone is the potential source rock. It was discovered that organic matter in the deep-water saline lake facies comprises a series of 17β 21β hopanes, and the corresponding shallow-one contains 17 (21) hopenes, which indicates that the reduction in sediments of the deep-water saline lake is stronger than that of the shallow one. Bitumen ratio (chloroform extracts / organic carbon) of the immature source rocks of the deep-water salt lake facies in Dongpu Depression is about 7% which is higher than the normal ones, the contents of total hydrocarbon are about 500 ppm.This may be due to the seal ability of the halites to keep the liquid hydrocarbons from leakage. But the bitumen ratio and the content of total hydrocarbon are only 3.37% and 100.93 ppm respectively in the potential source rocks of playa facies of Jidic Formation in Tarim Basin.It can be explained as the bad preservation in the playa sequences. In conclusion, the source rocks of the deep-water saline lake facies are rich in organic matter and able to generate great amounts of oil and gas, and those of the shallow-water saline lake facies have certain potential in hydrocarbon generation.
Dongpu Depression was one of the rifts in eastern China which accumulated sequences of salts and oil source rocks over 2, 000m in thickness during the Oligocene.Every sequence consists of lots of rhythms of 1 -5m thick which comprises light yellow transparent halite and grey-black mudstone interbedded with white laminated gypsum or brown oil shale. A model of deep-water saline lake is given in which the salts and the dark mudstones are deposited at the same time. Mudstones rich in organic matter were proved to be significant source rocks for oil and gas. It is important for the source rocks to deposit that the deep-water saline lake was layered by salinities: the upper part is brackish and aerobic, suitable for organisms living; in contrast the lower one is bitter and anoxic-the best environment for organic matter accumulation and preservation.The Corgof the mudstones deposited in the deep-water saline lake is over 1% and up to 4.4%. The middle and lower parts of Jidic Formation (Miocene) in narthern Tarim Basin, is consist of grey-green mudstones, brown siltstones and shell-shaped gypsums and dispersed granular halites.The sediments were probably formed in a movible shallow saline and aerobic lake, i.e.playa.Corgis only 0.3-0.7% in mudstone, but the interbedded sandstone has intensive showing of oil which implied that the the mudstone is the potential source rock. It was discovered that organic matter in the deep-water saline lake facies comprises a series of 17β 21β hopanes, and the corresponding shallow-one contains 17 (21) hopenes, which indicates that the reduction in sediments of the deep-water saline lake is stronger than that of the shallow one. Bitumen ratio (chloroform extracts / organic carbon) of the immature source rocks of the deep-water salt lake facies in Dongpu Depression is about 7% which is higher than the normal ones, the contents of total hydrocarbon are about 500 ppm.This may be due to the seal ability of the halites to keep the liquid hydrocarbons from leakage. But the bitumen ratio and the content of total hydrocarbon are only 3.37% and 100.93 ppm respectively in the potential source rocks of playa facies of Jidic Formation in Tarim Basin.It can be explained as the bad preservation in the playa sequences. In conclusion, the source rocks of the deep-water saline lake facies are rich in organic matter and able to generate great amounts of oil and gas, and those of the shallow-water saline lake facies have certain potential in hydrocarbon generation.
