Weathering has always been a concerned around the world,as the first and most important step in the global cycle of elements,which leads to the fractionation of isotopes on the scale of geological age.The Middle Ordov...Weathering has always been a concerned around the world,as the first and most important step in the global cycle of elements,which leads to the fractionation of isotopes on the scale of geological age.The Middle Ordovician Majiagou Formation in Daniudi area of the Ordos Basin had experienced weathering for>130 Myr.Through thin section observation,major and trace element analysis,carbon,oxygen,and magnesium isotopes composition analysis,the dolomitization modes and weathering of ancient dolo-mite in Daniudi area were analyzed in detail.The results showed that the Sabkha and brine-reflux dolomitization modes had developed,and the Mg isotopes in different layers of the karst crust were fractionated by various factors.The vertical vadose zone was affected by weathering,the Mg isotope of dolomite(δ^(26)Mgdol)showed a downward decreasing trend;the horizontal underflow zone was controlled by diagenesis and formation fluid,δ^(26)Mgdol showed a vertical invariance and negative;the main reason for Mg isotope fractionation in the deep slow-flow zone was the brine-reflux dolomitization mode during early burial period,which showed a vertical downward increase.Finally,the Mg isotope characteristic data of the ancient weathering crust were provided and the process of Mg isotope frac-tionationinthekarstcrust was explained.展开更多
Based on drill core and thin section observation,major geochemical element analysis and con-ventional well log analysis,this study summarizes the characteristics and thickness of weathering crust of Pennsylvanian volc...Based on drill core and thin section observation,major geochemical element analysis and con-ventional well log analysis,this study summarizes the characteristics and thickness of weathering crust of Pennsylvanian volcanic rocks(Carboniferous)in Shixi area,Junggar Basin.The weathering crust is identified and divided into three types according to the petrological characteristics and well log interpretations in Shixi area,and the isopach of weathering crust is mapped.The results show that:(1)With the increase of depth,the weathering weakens,and the rocks become less fractured with decreased porosity;(2)the weathering crust of the Upper Carboniferous volcanic rocks can be divided into strongly weathered and mildly weathered layers in Shixi area;(3)the weathering crust is relatively thicker in Dinan uplift and Shixi uplift.This study provides research basis for further evaluation of Upper Carboniferous volcanic reservoir,and will benefit for well location deployment and potential oilfield development in the Shixi area.展开更多
Cements are widely developed in clastic rock-originated weathering crust(CWC)reservoirs in the Kexia region along the northwestern margin of the Junggar Basin and significantly affect reservoir physical properties and...Cements are widely developed in clastic rock-originated weathering crust(CWC)reservoirs in the Kexia region along the northwestern margin of the Junggar Basin and significantly affect reservoir physical properties and oil and gas distribution in this area.Focusing on the CWC reservoirs at the top of both the Permian Jiamuhe Formation and the Triassic Karamay Formation,this study analyzed the types and characteristics of cements in the reservoirs and explored their effects on reservoir physical properties based on thin sections,SEM images,XRD results,and tests of physical properties.The main results are as follows.The cements in the CWC reservoirs in Kexia region mainly consist of carbonate minerals(41.5%),clay minerals(27.8%)and zeolite minerals(30%),as well as small amount of siliceous minerals.Among them,the carbonate minerals are dominated by siderite and calcite,the clay minerals mainly include kaolinite,interstratified illite/smectite(I/S)and chlorite,and the zeolite minerals primarily comprise heulandite and laumontite.These different types of multiphase cements are generally paragenetic or associated and affect reservoir physical properties to different degrees.Specifically,the carbonate and clay cements of the early diagenetic stage reduced the reservoirs’average porosity from 21%to 15%.The dissolution of some carbonate and zeolite cements in the early A substage of the middle diagenetic stage restored the average porosity to 18%,and the cementation in the late A substage decreased the average porosity to 13%again,of which about 4%was reduced by carbonate cements.The average porosity of the CWC reservoirs gradually decreased to the current value of approximately 10%in the B substage of the middle diagenetic stage.The impact of cementation on the CWC reservoirs can reach as far as 70 m below the unconformity.Moreover,the types and contents of cements vary with their depth below the unconformity surface,leading to the development of multiple zones with high cement content and the differentiated oil and gas distribution.展开更多
The genetic analysis of the deep-buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarimbasin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have under...The genetic analysis of the deep-buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarimbasin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have undergone along term of modification. Secondly, the rocks are deeply buried with depths of 3800-7000 m in the Tarim basin. Theprimary reservoir properties formed in the deposition have been strongly modified during the deep burial process.Concurrently, the different burial depths in different areas result in diversities of burial temperature, pressure,underground water, hydrochemistry and various physicochemical changes, which further lead to differences in thediagenetic type, diagenetic property, diagenetic degree and their impacts on the reservoir properties. The LowerPaleozoic Cambrian and Ordovician carbonate reservoirs in the Tarim basin can be grouped into four types, i.e.,paleo-weathered-crust reservoirs, reef reservoirs, buried karst reservoirs and dolomite reservoirs. This paper presents adetailed discussion on the vertical and horizontal distribution characteristics, morphological division, reservoir propertiesand the efficiency in accumulating hydrocarbons of the paleo-weathered-crust type. Furthermore, its genesis is alsoanalyzed. We proposed that the composition of the carbonate rocks, the tectonic movement with associated fractures andfissures, the paleomorphology and paleoclimate, the sea level fluctuation, and the protection of the pores and fissures bythe deep burial diagenesis and burial dissolution are the main factors controlling the formation of thepaleo-weathered-crust reservoirs. We also consider that the petroleum exploration of the Lower Paleozoic carbonaterocks should be focused on the paleo-weathered-crust reservoirs.展开更多
Microbes were cultured from the samples at various depths in a weathering profile of RE-bearing granite in Gonghe RE mine, Guangdong Province. The cultured microbes, existing at a depth of 0 2～12 m and being more ple...Microbes were cultured from the samples at various depths in a weathering profile of RE-bearing granite in Gonghe RE mine, Guangdong Province. The cultured microbes, existing at a depth of 0 2～12 m and being more plentiful within 3 m in the profile,include bacteria (Bacillus,Enterobacter, Escherichia, Alkaligenes, Neisseria, Staphylococcus and anaerobic bacteria such as Clostridium), fungi (Aspergillus niger, Aspergillus flavus, Penicillium, Mucor and Saccharomycete) and actinomyces. Experiments were made under room temperature by using solutions of the cultured microbes and their metabolites, compared with distilled water and the culture solution without microbes, to leach RE from the sample of the weathering crust. The results are shown by the experiments: (1) The mixed microbes cultured from the profile and their metabolites increase the quantity of RE leached from the sample and reduce the pH of the solutions. (2) The ability to leach RE from the sample varies with various microbes, decreasing in a sequence of fungi (Mucor, saccharomycete, Aspegillus and Penicillium), zymotic bacilli (Enterobacter, Escherichia etc.), Staphylococcus, zymotic Bacillus, actinomyces and Alkaligenes. (3) The RE leached with bacteria is mainly related to the pH value of the solutions influenced by the metabolites of the bacteria; whereas that leached with fungi is mainly related to the adsorption and imbibition of RE by the fungi and the complexing of RE with their metabolites. (4) Compared with that leached with ammonium sulfate, the fractionation of the RE leached with microbes is characterized by higher δ Ce , lower δ Eu and lower ratios of N La/Sm and N Gd/Yb . The result of the fractionation of RE accords with the distribution of RE in the various layers of a profile of weathering crust of granite in South China. The experimental results indicate that microbes and their metabolites should play a positive role in the mobilization, migration and fractionation of RE in the weathering crust in South China.展开更多
A new type of rare earth elements (REEs) deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ΣRE2O3 0.065%–1.086%. This ty...A new type of rare earth elements (REEs) deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ΣRE2O3 0.065%–1.086%. This type of REEs deposit was widely distributed with steady horizon and thickness of 3–4 m. The ore-bearing weathering crust (kaolinite) of the three discovered REEs deposits belonged to the third episode of the Emeishan basalt eruption. The new type of REEs deposit was suggested that basalt (tuff) weathering could lead to the en- richment of the rare earth elements. Therefore, it is of important economic significance to explore REEs deposits in the weathering crust of basalt (tuffs) in Yunnan, Guizhou, and Sichuan Provinces.展开更多
The Cenozoic evolution history of Guizhou Province, which is located on the southeastem flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread...The Cenozoic evolution history of Guizhou Province, which is located on the southeastem flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread on the Yunnan-Guizhou Plateau may bear critical information about their evolution history. This work firstly determined the ages of four red weathering crusts in eastern, central and northern Guizhou. The material used in fission track dating is well-crystallized quartz occurring in many in-situ weathering crusts of carbonate rocks. The results showed that the fission track ages of quartz vary over a wide range from 1 to 25 Ma in the four profiles, significantly younger than the ages of the Triassic and Cambrian parent rocks. In combination with the evolution history of the regional geology during the period from 25 to 1 Ma, the ages of quartz can exclude the possibility that the origin of quartz has nothing to do with primary clastic minerals in parent rocks, authigenesis during diagenesis and hydrothermal precipitation or replacement by volcanic activities. It is deduced that the well-crystallized quartz was precipitated from Si-rich weathering fluids during the weathering process of carbonate rocks. The recorded ages of quartz from the four profiles are consistent with the episodes of the planation surfaces on the Qinghai-Tibet Plateau, the forming stages of red soil in the tropics of South China, the tectonically stable periods in Guizhou, and the ages of weathering in other parts of the world during the Cenozoic era. That is to say, the ages of authigenic quartz dated by the fission track method are well feasible and credible.展开更多
Microbes were cultured and identified from the samples collected at various depths in 4 weathering profiles of REE\|bearing granites in Gonghe, Guangdong. The microbes were found existing at the depth of 0-5 m in all ...Microbes were cultured and identified from the samples collected at various depths in 4 weathering profiles of REE\|bearing granites in Gonghe, Guangdong. The microbes were found existing at the depth of 0-5 m in all the profiles. The main microbes include coccus (Staphylococcus, Streptococcus), bacillus (Bacillus, Clostridium and Escherichia Coli), actinomyces and fungi (Saccharomycete, Penicillium, Fusarium, Aspergillus Aiger and Mucor). The number of colonies decreases downwards in the profiles. Experimental studies show that all the microbes used in the experiment can accelerate downward migration of REE in the experimental tubes. The ability to accelerate the migration of REE decreases in a sequence of fungi→actinomyces→bacillus→coccus. The microbes can change the modes of occurrence of REE in the weathering crust. The coccus, bacillus and actinomyces can increase the amounts of REE in ion state, whereas the fungi have a stronger ability to form organic compounding REE and accumulate REE than the bacteria do.展开更多
Through the analysis of core descriptions,well-logs,seismic data,geochemical data and structural settings of the volcanic rock of the Yingcheng Formation in the Xujiaweizi fault depression,Songliao Basin,and the geolo...Through the analysis of core descriptions,well-logs,seismic data,geochemical data and structural settings of the volcanic rock of the Yingcheng Formation in the Xujiaweizi fault depression,Songliao Basin,and the geological section of the Yingcheng Formation in the southeast uplift area,this work determined the existence of volcanic weathering crust exists in the study area.The identification marks on the volcanic weathering crust can be recognized on the scale of core,logging,seismic,geochemistry,etc.In the study area,the structure of this crust is divided into clay layer,leached zone,fracture zone and host rocks,which are 5-118 m thick(averaging 27.5 m).The lithology of the weathering crust includes basalt,andesite,rhyolite and volcanic breccia,and the lithofacies are igneous effusive and extrusive facies.The volcanic weathering crusts are clustered together in the Dashen zone and the middle of the Xuzhong zone,whereas in the Shengshen zone and other parts of the Xuzhong zone,they have a relatively scattered distribution.It is a major volcanic reservoir bed,which covers an area of 2104.16 km^2.According to the geotectonic setting of the Songliao Basin,the formation process of the weathering crust is complete.Combining the macroscopic and microscopic features of the weathering crust of the Yingcheng Formation in Xujiaweizi with the logging and three-dimensional seismic sections,we established a developmental model of the paleo uplift and a developmental model of the slope belt that coexists with the sag on the Xujiaweizi volcanic weathering crust.In addition,the relationship between the volcanic weathering crust and the formation and distribution of the oil/gas reservoir is discussed.展开更多
Soil degradation, including rocky desertification,of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understa...Soil degradation, including rocky desertification,of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock(marls). Atmospheric inputs from dust were also detected.展开更多
Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust wou...Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust would usually consume more than ten meters to several tens of meters of thickness of parent rocks. The knowledge of how to identify the homogeneity of parent rocks is essential to understand the formation mechanism of weathering crust in karst regions,especially that of thick-layered red weathering crust. In this work the grain-size analyses have demonstrated that the three profiles studied are the residual weathering crust of carbonate rocks and further showed that there objectively exists the heterogeneity of parent rocks in the three studied weathering crusts. The heterogeneity of parent rocks can also be reflected in geochemical parameters of major elements, just as the characteristics of frequency plot of grain-size distribution.Conservative trace element ratios Zr/Hf and Nb/Ta are proven to be unsuitable for tracing the heterogeneity of parent rocks of weathering crust, but its geochemical mechanism is unclear. The authors strongly suggest in this paper that the identification of the homogeneity of parent rocks of weathering crust in karst regions is of prime necessity.展开更多
The fieldwork and experiments indicate that the red weathering crust, which developed on the limestone of Tibet Plateau and its eastern district, is a component of common planation surface of karst. The evidences are ...The fieldwork and experiments indicate that the red weathering crust, which developed on the limestone of Tibet Plateau and its eastern district, is a component of common planation surface of karst. The evidences are as follows: (1) They distributed in transverse continuity and often covered on the summit plane of hills. They correspond with a certain geomorphologic surface, for example, near Lijiang of Yunnan, there are summit planes of little undulation, the red weathering crust of large area distributed on the summit plane, and there are also many dolines and closed depressions up to hundreds of meters in diameter. (2) According to the situation of karst development, the soil loss made the fine sediments to be washed away through the crack in the district which vertical process developed well. Therefore, even if in the most active district of karst process, the weathering crust of continuous heavy layer can not be formed only if there existed a certain undulation. The organic soil and redizina can only be formed, and their main types of soil profile are AF\|D and A\|D. The thick weathering crust is only observed on the karst plane nearby base\|level of erosion. (3) The existence of terra rossa indicates the humid tropical/subtropical environment. The study results show that the component of red weathering crust on the limestone generally had the character of high content of clay particles(<2μm) and the weak process of silicon losing and aluminium concentration comparing with typical terra rossa. These characters indicate that its forming environment was humid and eluviation was weak. This situation only existed in the peneplain environment where groundwater was shallow and drainage condition was not very well. In a word, the forming time of thick weathering crust in the limestone district corresponded with the period of peneplain, and the forming altitude height was near the base level of erosion. So the red weathering crust of limestone had the significance of geomorphologic stage. These knowledges were important for assessing of the degree of Tibet Plateau uplift by the use of red weathering crust.展开更多
The chief aim of this study is to investigate the chemical weathering process of the weathering crust in Great Wall Station region of China (in Fildes Peninsula), Antarctica by the method of sedimentology. CW,SW,GW,TW...The chief aim of this study is to investigate the chemical weathering process of the weathering crust in Great Wall Station region of China (in Fildes Peninsula), Antarctica by the method of sedimentology. CW,SW,GW,TW,WE weathering crusts developed on volcanic clastic rock, gray aptitic basalt with tuff or basaltic bedrock. On change of minerals, geochemical behaviors of elements, migration and enrichment regularities of elements, Correlation between element geochemical behaviors, change of weathering potential of rocks in chemical weathering process are studied by us. We can see that the sequence fo weathering strengths of the abovementioned sections, from high to low, should reflected in TW, GW, CWand SWF and basical correspond with that calculated from the enrichment and differentiation indexes.展开更多
Weathering crust of carbonate rocks refers to the terra rossa formation, which is derived from limestone, dolomite and transitional rocks between the two. Terra rossa is widespread in the tropical and subtropical area...Weathering crust of carbonate rocks refers to the terra rossa formation, which is derived from limestone, dolomite and transitional rocks between the two. Terra rossa is widespread in the tropical and subtropical areas over the world. It is also well distributed in southern China, such as Yunnan. Guizhou Sichuan, Hunan, Guangxi and other provinces. Its thickness is generally 7-8展开更多
The results of REE leached by some organic acids with various concentrations and water/rock ratios for different durations from a mixed sample of the weathering crust of a granite in Gonghe, Guangdong, China, showed t...The results of REE leached by some organic acids with various concentrations and water/rock ratios for different durations from a mixed sample of the weathering crust of a granite in Gonghe, Guangdong, China, showed that: 1) the contents of REE leached increase with increasing concentrations of the organic acids; 2) the contents of REE leached by 0.01 mol/L organic acids increase with increasing water/rock ratio; 3) the interaction between the organic acids and the samples enhances the pH value of the medium and the contents of REE leached tend to increase with decreasing pH value; and 4) compared with those leached by ammonia sulfate, the REE leached by the organic acids are characterized by a weaker negative Ce anomaly, a stronger negative Eu anomaly, and lower (La/Sm)\-N and (Gd/Yb)\-N ratios, indicating that the organic acids have made contributions to the fractionation of REE in the weathering crust.展开更多
Surfactants were proposed to be added into magnesium sulfate solution to improve the leaching process of weathered crust elution-deposited rare earth ores(WREOs).Effects of surfactants and their concentration on the s...Surfactants were proposed to be added into magnesium sulfate solution to improve the leaching process of weathered crust elution-deposited rare earth ores(WREOs).Effects of surfactants and their concentration on the seepage of leaching solutions and the leaching efficiency of rare earth(RE)and aluminum(Al)were investigated,and the leaching kinetics,the mass transfer process,the adhesion work and the adhesion work reduction factor were analyzed to reveal its strengthening leaching mechanism.The results show that cetyltrimethylammonium bromide(CTAB)has a better strengthening effect on the leaching process than dodecyl trimethyl ammonium bromide(DTAB),sodium dodecyl sulfate(SDS),sodium oleate and oleic acid.In the presence of 0.04%CTAB in 0.2 mol/L solution,the permeability coefficient of WREOs increases from 0.945×10^(-5)to 1.640×10^(-5)cm·s^(-1),and the leaching efficiency of RE increases from 80%to 90%,confirming the promotion of surfactants on the leaching process of WREOs.Kinetic analysis shows that the leaching process conforms to the inner diffusion control model,and the leaching kinetics equations of RE and Al related to CTAB content are obtained.Mass transfer discussion shows a smaller height equivalent to theoretical plate(HETP)of RE and Al at CTAB content of 0.04%,suggesting the higher mass transfer efficiency here.According to the interfacial properties of leaching solutions,the calculated adhesion work and the adhesion work reduction factor further demonstrate the strengthening leaching effect of CTAB on the leaching process of WREOs.展开更多
基金supported by the National Natural Science Foundation of China(42072177)National Natural Science Foundation of China(U19B6003)Frontier Project of Chinese Academy of Sciences(XDA14010201).
文摘Weathering has always been a concerned around the world,as the first and most important step in the global cycle of elements,which leads to the fractionation of isotopes on the scale of geological age.The Middle Ordovician Majiagou Formation in Daniudi area of the Ordos Basin had experienced weathering for>130 Myr.Through thin section observation,major and trace element analysis,carbon,oxygen,and magnesium isotopes composition analysis,the dolomitization modes and weathering of ancient dolo-mite in Daniudi area were analyzed in detail.The results showed that the Sabkha and brine-reflux dolomitization modes had developed,and the Mg isotopes in different layers of the karst crust were fractionated by various factors.The vertical vadose zone was affected by weathering,the Mg isotope of dolomite(δ^(26)Mgdol)showed a downward decreasing trend;the horizontal underflow zone was controlled by diagenesis and formation fluid,δ^(26)Mgdol showed a vertical invariance and negative;the main reason for Mg isotope fractionation in the deep slow-flow zone was the brine-reflux dolomitization mode during early burial period,which showed a vertical downward increase.Finally,the Mg isotope characteristic data of the ancient weathering crust were provided and the process of Mg isotope frac-tionationinthekarstcrust was explained.
基金Supported by 14th Five-year Major Project of CNPC(No.2021DJ0206).
文摘Based on drill core and thin section observation,major geochemical element analysis and con-ventional well log analysis,this study summarizes the characteristics and thickness of weathering crust of Pennsylvanian volcanic rocks(Carboniferous)in Shixi area,Junggar Basin.The weathering crust is identified and divided into three types according to the petrological characteristics and well log interpretations in Shixi area,and the isopach of weathering crust is mapped.The results show that:(1)With the increase of depth,the weathering weakens,and the rocks become less fractured with decreased porosity;(2)the weathering crust of the Upper Carboniferous volcanic rocks can be divided into strongly weathered and mildly weathered layers in Shixi area;(3)the weathering crust is relatively thicker in Dinan uplift and Shixi uplift.This study provides research basis for further evaluation of Upper Carboniferous volcanic reservoir,and will benefit for well location deployment and potential oilfield development in the Shixi area.
基金supported by the Shandong Province Natural Science Foundation of China(Grant no.ZR2021MD077)the National Major Science and Technology Project of China(Grant no.2017ZX05001-001-006).
文摘Cements are widely developed in clastic rock-originated weathering crust(CWC)reservoirs in the Kexia region along the northwestern margin of the Junggar Basin and significantly affect reservoir physical properties and oil and gas distribution in this area.Focusing on the CWC reservoirs at the top of both the Permian Jiamuhe Formation and the Triassic Karamay Formation,this study analyzed the types and characteristics of cements in the reservoirs and explored their effects on reservoir physical properties based on thin sections,SEM images,XRD results,and tests of physical properties.The main results are as follows.The cements in the CWC reservoirs in Kexia region mainly consist of carbonate minerals(41.5%),clay minerals(27.8%)and zeolite minerals(30%),as well as small amount of siliceous minerals.Among them,the carbonate minerals are dominated by siderite and calcite,the clay minerals mainly include kaolinite,interstratified illite/smectite(I/S)and chlorite,and the zeolite minerals primarily comprise heulandite and laumontite.These different types of multiphase cements are generally paragenetic or associated and affect reservoir physical properties to different degrees.Specifically,the carbonate and clay cements of the early diagenetic stage reduced the reservoirs’average porosity from 21%to 15%.The dissolution of some carbonate and zeolite cements in the early A substage of the middle diagenetic stage restored the average porosity to 18%,and the cementation in the late A substage decreased the average porosity to 13%again,of which about 4%was reduced by carbonate cements.The average porosity of the CWC reservoirs gradually decreased to the current value of approximately 10%in the B substage of the middle diagenetic stage.The impact of cementation on the CWC reservoirs can reach as far as 70 m below the unconformity.Moreover,the types and contents of cements vary with their depth below the unconformity surface,leading to the development of multiple zones with high cement content and the differentiated oil and gas distribution.
文摘The genetic analysis of the deep-buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarimbasin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have undergone along term of modification. Secondly, the rocks are deeply buried with depths of 3800-7000 m in the Tarim basin. Theprimary reservoir properties formed in the deposition have been strongly modified during the deep burial process.Concurrently, the different burial depths in different areas result in diversities of burial temperature, pressure,underground water, hydrochemistry and various physicochemical changes, which further lead to differences in thediagenetic type, diagenetic property, diagenetic degree and their impacts on the reservoir properties. The LowerPaleozoic Cambrian and Ordovician carbonate reservoirs in the Tarim basin can be grouped into four types, i.e.,paleo-weathered-crust reservoirs, reef reservoirs, buried karst reservoirs and dolomite reservoirs. This paper presents adetailed discussion on the vertical and horizontal distribution characteristics, morphological division, reservoir propertiesand the efficiency in accumulating hydrocarbons of the paleo-weathered-crust type. Furthermore, its genesis is alsoanalyzed. We proposed that the composition of the carbonate rocks, the tectonic movement with associated fractures andfissures, the paleomorphology and paleoclimate, the sea level fluctuation, and the protection of the pores and fissures bythe deep burial diagenesis and burial dissolution are the main factors controlling the formation of thepaleo-weathered-crust reservoirs. We also consider that the petroleum exploration of the Lower Paleozoic carbonaterocks should be focused on the paleo-weathered-crust reservoirs.
文摘Microbes were cultured from the samples at various depths in a weathering profile of RE-bearing granite in Gonghe RE mine, Guangdong Province. The cultured microbes, existing at a depth of 0 2～12 m and being more plentiful within 3 m in the profile,include bacteria (Bacillus,Enterobacter, Escherichia, Alkaligenes, Neisseria, Staphylococcus and anaerobic bacteria such as Clostridium), fungi (Aspergillus niger, Aspergillus flavus, Penicillium, Mucor and Saccharomycete) and actinomyces. Experiments were made under room temperature by using solutions of the cultured microbes and their metabolites, compared with distilled water and the culture solution without microbes, to leach RE from the sample of the weathering crust. The results are shown by the experiments: (1) The mixed microbes cultured from the profile and their metabolites increase the quantity of RE leached from the sample and reduce the pH of the solutions. (2) The ability to leach RE from the sample varies with various microbes, decreasing in a sequence of fungi (Mucor, saccharomycete, Aspegillus and Penicillium), zymotic bacilli (Enterobacter, Escherichia etc.), Staphylococcus, zymotic Bacillus, actinomyces and Alkaligenes. (3) The RE leached with bacteria is mainly related to the pH value of the solutions influenced by the metabolites of the bacteria; whereas that leached with fungi is mainly related to the adsorption and imbibition of RE by the fungi and the complexing of RE with their metabolites. (4) Compared with that leached with ammonium sulfate, the fractionation of the RE leached with microbes is characterized by higher δ Ce , lower δ Eu and lower ratios of N La/Sm and N Gd/Yb . The result of the fractionation of RE accords with the distribution of RE in the various layers of a profile of weathering crust of granite in South China. The experimental results indicate that microbes and their metabolites should play a positive role in the mobilization, migration and fractionation of RE in the weathering crust in South China.
基金the Major State Basic Research Development Program of China (2006CB403202)the Doctoral Discipline Foundation of Guizhou University
文摘A new type of rare earth elements (REEs) deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ΣRE2O3 0.065%–1.086%. This type of REEs deposit was widely distributed with steady horizon and thickness of 3–4 m. The ore-bearing weathering crust (kaolinite) of the three discovered REEs deposits belonged to the third episode of the Emeishan basalt eruption. The new type of REEs deposit was suggested that basalt (tuff) weathering could lead to the en- richment of the rare earth elements. Therefore, it is of important economic significance to explore REEs deposits in the weathering crust of basalt (tuffs) in Yunnan, Guizhou, and Sichuan Provinces.
基金This work was granted by the National Natural Science Foundation of China(Nos.40371012 and 49833002).
文摘The Cenozoic evolution history of Guizhou Province, which is located on the southeastem flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread on the Yunnan-Guizhou Plateau may bear critical information about their evolution history. This work firstly determined the ages of four red weathering crusts in eastern, central and northern Guizhou. The material used in fission track dating is well-crystallized quartz occurring in many in-situ weathering crusts of carbonate rocks. The results showed that the fission track ages of quartz vary over a wide range from 1 to 25 Ma in the four profiles, significantly younger than the ages of the Triassic and Cambrian parent rocks. In combination with the evolution history of the regional geology during the period from 25 to 1 Ma, the ages of quartz can exclude the possibility that the origin of quartz has nothing to do with primary clastic minerals in parent rocks, authigenesis during diagenesis and hydrothermal precipitation or replacement by volcanic activities. It is deduced that the well-crystallized quartz was precipitated from Si-rich weathering fluids during the weathering process of carbonate rocks. The recorded ages of quartz from the four profiles are consistent with the episodes of the planation surfaces on the Qinghai-Tibet Plateau, the forming stages of red soil in the tropics of South China, the tectonically stable periods in Guizhou, and the ages of weathering in other parts of the world during the Cenozoic era. That is to say, the ages of authigenic quartz dated by the fission track method are well feasible and credible.
基金ThisworkwasgrantedbytheNaturalScienceFoundationofGuangdongProvince China !(GrantNo .96 0 0 42 )
文摘Microbes were cultured and identified from the samples collected at various depths in 4 weathering profiles of REE\|bearing granites in Gonghe, Guangdong. The microbes were found existing at the depth of 0-5 m in all the profiles. The main microbes include coccus (Staphylococcus, Streptococcus), bacillus (Bacillus, Clostridium and Escherichia Coli), actinomyces and fungi (Saccharomycete, Penicillium, Fusarium, Aspergillus Aiger and Mucor). The number of colonies decreases downwards in the profiles. Experimental studies show that all the microbes used in the experiment can accelerate downward migration of REE in the experimental tubes. The ability to accelerate the migration of REE decreases in a sequence of fungi→actinomyces→bacillus→coccus. The microbes can change the modes of occurrence of REE in the weathering crust. The coccus, bacillus and actinomyces can increase the amounts of REE in ion state, whereas the fungi have a stronger ability to form organic compounding REE and accumulate REE than the bacteria do.
基金supported by the National Natural Science Fund Project(grant No.41430322)the National Basic Research Program of China(grant No.2009CB219306)the Open Fund of the State Key Laboratory Base of Unconventional Oil and Gas Accumulation and Exploitation,Northeast Petroleum University(grant No.2010DS670083-201301)
文摘Through the analysis of core descriptions,well-logs,seismic data,geochemical data and structural settings of the volcanic rock of the Yingcheng Formation in the Xujiaweizi fault depression,Songliao Basin,and the geological section of the Yingcheng Formation in the southeast uplift area,this work determined the existence of volcanic weathering crust exists in the study area.The identification marks on the volcanic weathering crust can be recognized on the scale of core,logging,seismic,geochemistry,etc.In the study area,the structure of this crust is divided into clay layer,leached zone,fracture zone and host rocks,which are 5-118 m thick(averaging 27.5 m).The lithology of the weathering crust includes basalt,andesite,rhyolite and volcanic breccia,and the lithofacies are igneous effusive and extrusive facies.The volcanic weathering crusts are clustered together in the Dashen zone and the middle of the Xuzhong zone,whereas in the Shengshen zone and other parts of the Xuzhong zone,they have a relatively scattered distribution.It is a major volcanic reservoir bed,which covers an area of 2104.16 km^2.According to the geotectonic setting of the Songliao Basin,the formation process of the weathering crust is complete.Combining the macroscopic and microscopic features of the weathering crust of the Yingcheng Formation in Xujiaweizi with the logging and three-dimensional seismic sections,we established a developmental model of the paleo uplift and a developmental model of the slope belt that coexists with the sag on the Xujiaweizi volcanic weathering crust.In addition,the relationship between the volcanic weathering crust and the formation and distribution of the oil/gas reservoir is discussed.
基金supported by the National Environmental Research Council of the UK(Grant Nos.NE/N007530/1 and NE/N007603/1)the National Science Foundation of China(Grant No.41571130042)
文摘Soil degradation, including rocky desertification,of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock(marls). Atmospheric inputs from dust were also detected.
基金This work was jointly supported by the Knowledge-Innovation Project of the Institute of Geochemistry,the“Westerm Light”Program sponsored by the Chinese Academy of Sciencesthe National Natural Science Foundation of China grants 49833002,40273015 and 40371012.
文摘Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust would usually consume more than ten meters to several tens of meters of thickness of parent rocks. The knowledge of how to identify the homogeneity of parent rocks is essential to understand the formation mechanism of weathering crust in karst regions,especially that of thick-layered red weathering crust. In this work the grain-size analyses have demonstrated that the three profiles studied are the residual weathering crust of carbonate rocks and further showed that there objectively exists the heterogeneity of parent rocks in the three studied weathering crusts. The heterogeneity of parent rocks can also be reflected in geochemical parameters of major elements, just as the characteristics of frequency plot of grain-size distribution.Conservative trace element ratios Zr/Hf and Nb/Ta are proven to be unsuitable for tracing the heterogeneity of parent rocks of weathering crust, but its geochemical mechanism is unclear. The authors strongly suggest in this paper that the identification of the homogeneity of parent rocks of weathering crust in karst regions is of prime necessity.
文摘The fieldwork and experiments indicate that the red weathering crust, which developed on the limestone of Tibet Plateau and its eastern district, is a component of common planation surface of karst. The evidences are as follows: (1) They distributed in transverse continuity and often covered on the summit plane of hills. They correspond with a certain geomorphologic surface, for example, near Lijiang of Yunnan, there are summit planes of little undulation, the red weathering crust of large area distributed on the summit plane, and there are also many dolines and closed depressions up to hundreds of meters in diameter. (2) According to the situation of karst development, the soil loss made the fine sediments to be washed away through the crack in the district which vertical process developed well. Therefore, even if in the most active district of karst process, the weathering crust of continuous heavy layer can not be formed only if there existed a certain undulation. The organic soil and redizina can only be formed, and their main types of soil profile are AF\|D and A\|D. The thick weathering crust is only observed on the karst plane nearby base\|level of erosion. (3) The existence of terra rossa indicates the humid tropical/subtropical environment. The study results show that the component of red weathering crust on the limestone generally had the character of high content of clay particles(<2μm) and the weak process of silicon losing and aluminium concentration comparing with typical terra rossa. These characters indicate that its forming environment was humid and eluviation was weak. This situation only existed in the peneplain environment where groundwater was shallow and drainage condition was not very well. In a word, the forming time of thick weathering crust in the limestone district corresponded with the period of peneplain, and the forming altitude height was near the base level of erosion. So the red weathering crust of limestone had the significance of geomorphologic stage. These knowledges were important for assessing of the degree of Tibet Plateau uplift by the use of red weathering crust.
文摘The chief aim of this study is to investigate the chemical weathering process of the weathering crust in Great Wall Station region of China (in Fildes Peninsula), Antarctica by the method of sedimentology. CW,SW,GW,TW,WE weathering crusts developed on volcanic clastic rock, gray aptitic basalt with tuff or basaltic bedrock. On change of minerals, geochemical behaviors of elements, migration and enrichment regularities of elements, Correlation between element geochemical behaviors, change of weathering potential of rocks in chemical weathering process are studied by us. We can see that the sequence fo weathering strengths of the abovementioned sections, from high to low, should reflected in TW, GW, CWand SWF and basical correspond with that calculated from the enrichment and differentiation indexes.
文摘Weathering crust of carbonate rocks refers to the terra rossa formation, which is derived from limestone, dolomite and transitional rocks between the two. Terra rossa is widespread in the tropical and subtropical areas over the world. It is also well distributed in southern China, such as Yunnan. Guizhou Sichuan, Hunan, Guangxi and other provinces. Its thickness is generally 7-8
基金ThisworkwasgrantedbytheNaturalScienceFoundationofGuangdongProvince China (GrantNos.96 0 0 42 990 2 32 )
文摘The results of REE leached by some organic acids with various concentrations and water/rock ratios for different durations from a mixed sample of the weathering crust of a granite in Gonghe, Guangdong, China, showed that: 1) the contents of REE leached increase with increasing concentrations of the organic acids; 2) the contents of REE leached by 0.01 mol/L organic acids increase with increasing water/rock ratio; 3) the interaction between the organic acids and the samples enhances the pH value of the medium and the contents of REE leached tend to increase with decreasing pH value; and 4) compared with those leached by ammonia sulfate, the REE leached by the organic acids are characterized by a weaker negative Ce anomaly, a stronger negative Eu anomaly, and lower (La/Sm)\-N and (Gd/Yb)\-N ratios, indicating that the organic acids have made contributions to the fractionation of REE in the weathering crust.
基金Financial supports for this work from National Natural Science Foundation of China(Nos.22078252 and 52274266)the Graduate Education Innovation Foundation of Wuhan Institute of Technology(No.CX2021463)the Young Top-notch Talent Cultivation Program of Hubei Province are greatly appreciated.
文摘Surfactants were proposed to be added into magnesium sulfate solution to improve the leaching process of weathered crust elution-deposited rare earth ores(WREOs).Effects of surfactants and their concentration on the seepage of leaching solutions and the leaching efficiency of rare earth(RE)and aluminum(Al)were investigated,and the leaching kinetics,the mass transfer process,the adhesion work and the adhesion work reduction factor were analyzed to reveal its strengthening leaching mechanism.The results show that cetyltrimethylammonium bromide(CTAB)has a better strengthening effect on the leaching process than dodecyl trimethyl ammonium bromide(DTAB),sodium dodecyl sulfate(SDS),sodium oleate and oleic acid.In the presence of 0.04%CTAB in 0.2 mol/L solution,the permeability coefficient of WREOs increases from 0.945×10^(-5)to 1.640×10^(-5)cm·s^(-1),and the leaching efficiency of RE increases from 80%to 90%,confirming the promotion of surfactants on the leaching process of WREOs.Kinetic analysis shows that the leaching process conforms to the inner diffusion control model,and the leaching kinetics equations of RE and Al related to CTAB content are obtained.Mass transfer discussion shows a smaller height equivalent to theoretical plate(HETP)of RE and Al at CTAB content of 0.04%,suggesting the higher mass transfer efficiency here.According to the interfacial properties of leaching solutions,the calculated adhesion work and the adhesion work reduction factor further demonstrate the strengthening leaching effect of CTAB on the leaching process of WREOs.
