1 Introduction Sichuan Basin is basically a salt brine reservoir,large closed and semi-closed artesian sedimentary basin with an area of 200,000 Km2 in southeast China.During the forming and evolution of the basin,it ...1 Introduction Sichuan Basin is basically a salt brine reservoir,large closed and semi-closed artesian sedimentary basin with an area of 200,000 Km2 in southeast China.During the forming and evolution of the basin,it has been affected by展开更多
The evolution characteristics of Gejiu granites.Yunnan Province are described in terms of theirPetrology,especially their trace elements and REE geochemistry The three major types of Gejiu granites:porphyritic biotite...The evolution characteristics of Gejiu granites.Yunnan Province are described in terms of theirPetrology,especially their trace elements and REE geochemistry The three major types of Gejiu granites:porphyritic biotite monzonitic granite(stageⅠ),medium-coarse-grained biotite-K-feldspar granite(stage Ⅱ)and two-mica alkali-feldspar granite(stage Ⅲ)are thought to have been formed successively from the samegranite magma source through fractional crystallization(Rayliegh fractionation),because linear correlationsare found between log(Rb/Sr)-log Sn,log(Rb/Ba)-log Sn,log(Rb/Ba)-log(Rb/Sr),log La-log Sr,log Ce-log Sr,log Eu-log Sr,etc In addition.the characteristics of REE distribution patterns in these three major types ofgranites also reflect the magmatic differentiation features of Gejiu granites.Of the three major types,the twomica alkali-feldspar granite of stage Ⅲ nuderwent the strongest differentiation,and thus has the closestgenetic relationship with the Gejiu tin-polymetallic ore deposit Such tin-polymetal mineralized granites arecharacterized by high Rb/Sr and Rb/Ba ratios,low K/Rb and ∑Ce/∑Y ratios and remarkable Eu depletion.展开更多
Two comparative simulation experiments(a normal atmospheric-pressure opening system and a 20 MPa closed system)were conducted to study the geochemical evolution of n-alkane,sterane,and terpane biomarkers in the proces...Two comparative simulation experiments(a normal atmospheric-pressure opening system and a 20 MPa closed system)were conducted to study the geochemical evolution of n-alkane,sterane,and terpane biomarkers in the process of oil cracking into gas under different pressures.With an initial experimental temperature set at 300°C,the temperature was increased to 650°C at a heating rate of 30°C/h.The products were tested every 50°C starting at 300°C,and a pressure of 20 MPa was achieved using a water column.The low-maturity crude oil sample was from the Paleogene system in the Dongying sag in eastern China.The threshold temperature obtained for the primary oil cracking process in both pressure systems was 450°C.Before the oil was cracked into gas,some components,including macromolecular n-alkanes,were cracked into medium-or small-sized n-alkanes.The secondary oil cracking of heavy hydrocarbon gases of C2–5to methane mainly occurred between 550°C to 650°C,and the parameters Ln(C1/C2)and Ln(C1/C3),as well as the dry coefficients,increased.Overpressure inhibited the oil cracking process.In the 20 MPa system,the oil conversion rate decreased,the temperature threshold for gas generation rose,and oil cracking was inhibited.Compared with the normal pressure system,high-carbon n-alkanes and other compounds in the 20 MPa pressure system were reserved.Furthermore,the parameters∑C21-/∑22+,Ln(C1/C2),and Ln(C1/C3),as well as the dry coefficients,decreased within the main temperature range.During secondary oil cracking(550°C to 600°C),the Ph/nC18and Pr/nC17decreased.High pressure influenced the evolution of the biomarkers Ts and Tm,C31homohopane,C29sterane,and their related maturity parameters to different extents during oil cracking under different temperature ranges.展开更多
To reveal the geochemical characters of water coproduced with coalbed gas and shallow groundwater,water samples were collected from 12 wells of coalbed methane and 7 wells of shallow groundwater.The pH,CODMn,fCO2,tota...To reveal the geochemical characters of water coproduced with coalbed gas and shallow groundwater,water samples were collected from 12 wells of coalbed methane and 7 wells of shallow groundwater.The pH,CODMn,fCO2,total dissolved solids （TDS）,total hardness,and concentrations of metasilicic acid,sodium and kalium,calcium ion,magnesium ion,ammonium iron,bicarbonate ion,carbonate,chloride,sulfate ion,nitrate ion,fluoride,lithium,zinc,nickel,manganese,iron,boron,barium,etc.of the samples were measured.Research results showed the following：（1） Concentrations of TDS,chloride,fluoride,sodium and kalium,ammonium,iron,and barium in the water coproduced with coalbed gas exceeded the national standards of China; however,physical,chemical,and biological properties of shallow groundwater could meet the national standard.（2） The water produced from coalbed contained mainly Na-Cl·HCO3,with average TDS of 4588.5 ppm,whereas shallow groundwater contained a mixture of chemicals including Na.Mg.Ca-HCO3·SO4 and Na.Mg-HCO3·SO4,with average TDS of 663.8 ppm.（3） In general,it was observed that bicarbonate and sodium accumulated in a reducing environment and deeper system,while depletion of hydrogen ions and dissolution of sulfate,calcium,and magnesium occurred in a redox environment and shallow system.（4） Sodium and kalium,ammonium,chloride,and bicarbonate ions were the main ions found in the study area.展开更多
Mount Cameroon volcano has erupted several times in the 20 th Century with documented eruptions in 1909,1922,1954,1959,1982,1999 and 2000.Evidence of historic volcanism is represented by several older lava flows and l...Mount Cameroon volcano has erupted several times in the 20 th Century with documented eruptions in 1909,1922,1954,1959,1982,1999 and 2000.Evidence of historic volcanism is represented by several older lava flows and lahar deposits around the flanks of the volcano.This study aims to assess the evolution of Mount Cameroon volcanism through its eruptive history via interpretation of mineralogical,whole rock geochemical and Pb,Sr,Nd isotope data generated from historic and recent lava flows.In this study,samples were collected from the 1959,1982,1999 and 2000 eruptions and from several historic eruption sites with unknown eruption dates.Evaluation of major and trace element data demonstrates that Mount Cameroon is geotectonically associated with within-plate Ocean Island Basalt Settings.More than 90%of the studied historic lavas(n=29)classify as tephrites and basanites whereas the modern lavas(n=38)are predominantly trachybasalts,demonstrating evolution from primitive to evolved lavas over time typically in response to fractional crystallization.Petrographically,the lavas are porphyritic with main mineral phases being olivine,clinopyroxene,plagioclase feldspars and Fe-Ti-Cr oxides.The 1982 lavas are predominantly aphyric and dominated by lath-shaped flow-aligned plagioclase in the groundmass.Olivine chemistry shows variable forsterite compositions from Fo60-89.Clinopyroxenes vary from diopside through augite to titanaugite with chemical composition ranges from Wo45En32Fs7 to Wo51En47Fs17.Plagioclase feldspars vary from labradorite(An567 O)to bytownite(An80-87).For the Fe-Ti-Cr oxides,calculated ulvospinel component shows a wide variation from ulv38-87.CIPW-normative classification on the Di-Ol-Hy-Qz-Ne system shows that all Mount Cameroon lavas are nepheline-normative(Ne ranges from4.20 wt.%to 11.45 wt.%).Radiogenic isotope data demonstrate that Mount Cameroon lavas are HIMU(or high μ=238U/204Pb),characterized by 206Pb/204Pb=20.19-20.46,207Pb/204Pb=15.63-15.69,208Pb/204Pb=40.01-40.30,87Sr/86Sr=0.70322-0.70339(εsr=-21.37 to-18.96)and 143 Nd/144 Nd=0.51276-0.51285(εNd=+2.29 to+4.05).The historic lavas show stronger HIMU signature relative to the modern lavas,suggesting evolution towards less HIMU signatures over time.This study has revealed that Mount Cameroon volcanism has evolved from primitive magmas characterized by stronger HIMU signatures with high 206/204Pb and 208/204Pb isotopes,low SiO2 and high Mg,Ni,Cr content towards lower HIMU signatures with relatively higher SiO2,lower Mg,Cr and Ni compositions.The geochemical and isotopic changes,which account for the evolution of magmatism on Mount Cameroon occur over long periods of time because all the modern lavas erupted within the last 100 years are isotopically homogeneous,with very limited variation in SiO2 compositions.展开更多
Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle.Based on the density functional theory(DFT)and the the climbing image nudged elastic band(CI-N...Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle.Based on the density functional theory(DFT)and the the climbing image nudged elastic band(CI-NEB)method,we performed first-principles calculations of diffusion characteristics of helium in perfect aragonite crystal under high pressure to 40 GPa.Our results show that He diffusion behaviors are controlled by pressure,temperature and crystal size.The activation energy increases,and the diffusion coefficients decrease significantly under high pressure.Ea[100]increases from 176.02 kJ/mol to 278.75 kJ/mol,and Ea[001]increases from 195.89 kJ/mol to 290.43 kJ/mol,with pressure increasing from 20 GPa to 40 GPa.At 700 K,the diffusion coefficients at 40 GPa is 7 orders of magnitude lower than that at 20 GPa;and at 1000 K it decrease 5 orders of magnitude.To ensure that at least 90%helium is not lost,we synthesized the temperature obtained from cooling and heating processes and derive the'stable temperature range'for helium in aragonite.The obtained results show that the stable temperature range is 22-76℃at 0 GPa and 641-872℃at 40 GPa,for the crystal of 100-2000μm size.Besides,the travel time of helium in aragonite under high pressure increases rapidly with pressure increasing.Our calculations indicate that helium can be quantitatively retained in aragonite in the deep mantle as long as the temperature is in the'stable temperature range'.These results have certain implications for exploring the evolution of mantle and the storage of helium within it.展开更多
基金supported by China Geological Survey Projects(1212010011803, 121201103000150011)
文摘1 Introduction Sichuan Basin is basically a salt brine reservoir,large closed and semi-closed artesian sedimentary basin with an area of 200,000 Km2 in southeast China.During the forming and evolution of the basin,it has been affected by
文摘The evolution characteristics of Gejiu granites.Yunnan Province are described in terms of theirPetrology,especially their trace elements and REE geochemistry The three major types of Gejiu granites:porphyritic biotite monzonitic granite(stageⅠ),medium-coarse-grained biotite-K-feldspar granite(stage Ⅱ)and two-mica alkali-feldspar granite(stage Ⅲ)are thought to have been formed successively from the samegranite magma source through fractional crystallization(Rayliegh fractionation),because linear correlationsare found between log(Rb/Sr)-log Sn,log(Rb/Ba)-log Sn,log(Rb/Ba)-log(Rb/Sr),log La-log Sr,log Ce-log Sr,log Eu-log Sr,etc In addition.the characteristics of REE distribution patterns in these three major types ofgranites also reflect the magmatic differentiation features of Gejiu granites.Of the three major types,the twomica alkali-feldspar granite of stage Ⅲ nuderwent the strongest differentiation,and thus has the closestgenetic relationship with the Gejiu tin-polymetallic ore deposit Such tin-polymetal mineralized granites arecharacterized by high Rb/Sr and Rb/Ba ratios,low K/Rb and ∑Ce/∑Y ratios and remarkable Eu depletion.
基金supported by the National Natural Science Foundation of China(Grant Nos.40802026&41272140)Shandong Province Natural Science Foundation(Grant No.ZR2011DM004)
文摘Two comparative simulation experiments(a normal atmospheric-pressure opening system and a 20 MPa closed system)were conducted to study the geochemical evolution of n-alkane,sterane,and terpane biomarkers in the process of oil cracking into gas under different pressures.With an initial experimental temperature set at 300°C,the temperature was increased to 650°C at a heating rate of 30°C/h.The products were tested every 50°C starting at 300°C,and a pressure of 20 MPa was achieved using a water column.The low-maturity crude oil sample was from the Paleogene system in the Dongying sag in eastern China.The threshold temperature obtained for the primary oil cracking process in both pressure systems was 450°C.Before the oil was cracked into gas,some components,including macromolecular n-alkanes,were cracked into medium-or small-sized n-alkanes.The secondary oil cracking of heavy hydrocarbon gases of C2–5to methane mainly occurred between 550°C to 650°C,and the parameters Ln(C1/C2)and Ln(C1/C3),as well as the dry coefficients,increased.Overpressure inhibited the oil cracking process.In the 20 MPa system,the oil conversion rate decreased,the temperature threshold for gas generation rose,and oil cracking was inhibited.Compared with the normal pressure system,high-carbon n-alkanes and other compounds in the 20 MPa pressure system were reserved.Furthermore,the parameters∑C21-/∑22+,Ln(C1/C2),and Ln(C1/C3),as well as the dry coefficients,decreased within the main temperature range.During secondary oil cracking(550°C to 600°C),the Ph/nC18and Pr/nC17decreased.High pressure influenced the evolution of the biomarkers Ts and Tm,C31homohopane,C29sterane,and their related maturity parameters to different extents during oil cracking under different temperature ranges.
基金funded by the National Science and Technology Major Project (2011ZX05060-005 2009ZX05039-003)
文摘To reveal the geochemical characters of water coproduced with coalbed gas and shallow groundwater,water samples were collected from 12 wells of coalbed methane and 7 wells of shallow groundwater.The pH,CODMn,fCO2,total dissolved solids （TDS）,total hardness,and concentrations of metasilicic acid,sodium and kalium,calcium ion,magnesium ion,ammonium iron,bicarbonate ion,carbonate,chloride,sulfate ion,nitrate ion,fluoride,lithium,zinc,nickel,manganese,iron,boron,barium,etc.of the samples were measured.Research results showed the following：（1） Concentrations of TDS,chloride,fluoride,sodium and kalium,ammonium,iron,and barium in the water coproduced with coalbed gas exceeded the national standards of China; however,physical,chemical,and biological properties of shallow groundwater could meet the national standard.（2） The water produced from coalbed contained mainly Na-Cl·HCO3,with average TDS of 4588.5 ppm,whereas shallow groundwater contained a mixture of chemicals including Na.Mg.Ca-HCO3·SO4 and Na.Mg-HCO3·SO4,with average TDS of 663.8 ppm.（3） In general,it was observed that bicarbonate and sodium accumulated in a reducing environment and deeper system,while depletion of hydrogen ions and dissolution of sulfate,calcium,and magnesium occurred in a redox environment and shallow system.（4） Sodium and kalium,ammonium,chloride,and bicarbonate ions were the main ions found in the study area.
文摘Mount Cameroon volcano has erupted several times in the 20 th Century with documented eruptions in 1909,1922,1954,1959,1982,1999 and 2000.Evidence of historic volcanism is represented by several older lava flows and lahar deposits around the flanks of the volcano.This study aims to assess the evolution of Mount Cameroon volcanism through its eruptive history via interpretation of mineralogical,whole rock geochemical and Pb,Sr,Nd isotope data generated from historic and recent lava flows.In this study,samples were collected from the 1959,1982,1999 and 2000 eruptions and from several historic eruption sites with unknown eruption dates.Evaluation of major and trace element data demonstrates that Mount Cameroon is geotectonically associated with within-plate Ocean Island Basalt Settings.More than 90%of the studied historic lavas(n=29)classify as tephrites and basanites whereas the modern lavas(n=38)are predominantly trachybasalts,demonstrating evolution from primitive to evolved lavas over time typically in response to fractional crystallization.Petrographically,the lavas are porphyritic with main mineral phases being olivine,clinopyroxene,plagioclase feldspars and Fe-Ti-Cr oxides.The 1982 lavas are predominantly aphyric and dominated by lath-shaped flow-aligned plagioclase in the groundmass.Olivine chemistry shows variable forsterite compositions from Fo60-89.Clinopyroxenes vary from diopside through augite to titanaugite with chemical composition ranges from Wo45En32Fs7 to Wo51En47Fs17.Plagioclase feldspars vary from labradorite(An567 O)to bytownite(An80-87).For the Fe-Ti-Cr oxides,calculated ulvospinel component shows a wide variation from ulv38-87.CIPW-normative classification on the Di-Ol-Hy-Qz-Ne system shows that all Mount Cameroon lavas are nepheline-normative(Ne ranges from4.20 wt.%to 11.45 wt.%).Radiogenic isotope data demonstrate that Mount Cameroon lavas are HIMU(or high μ=238U/204Pb),characterized by 206Pb/204Pb=20.19-20.46,207Pb/204Pb=15.63-15.69,208Pb/204Pb=40.01-40.30,87Sr/86Sr=0.70322-0.70339(εsr=-21.37 to-18.96)and 143 Nd/144 Nd=0.51276-0.51285(εNd=+2.29 to+4.05).The historic lavas show stronger HIMU signature relative to the modern lavas,suggesting evolution towards less HIMU signatures over time.This study has revealed that Mount Cameroon volcanism has evolved from primitive magmas characterized by stronger HIMU signatures with high 206/204Pb and 208/204Pb isotopes,low SiO2 and high Mg,Ni,Cr content towards lower HIMU signatures with relatively higher SiO2,lower Mg,Cr and Ni compositions.The geochemical and isotopic changes,which account for the evolution of magmatism on Mount Cameroon occur over long periods of time because all the modern lavas erupted within the last 100 years are isotopically homogeneous,with very limited variation in SiO2 compositions.
基金supported by National Natural Science Foundation of China(Grant Nos.42394114,41573121,42174115)Open Foundation of the United Laboratory of High-Pressure Physics and Earthquake Science(Grant No.2019HPPES06).
文摘Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle.Based on the density functional theory(DFT)and the the climbing image nudged elastic band(CI-NEB)method,we performed first-principles calculations of diffusion characteristics of helium in perfect aragonite crystal under high pressure to 40 GPa.Our results show that He diffusion behaviors are controlled by pressure,temperature and crystal size.The activation energy increases,and the diffusion coefficients decrease significantly under high pressure.Ea[100]increases from 176.02 kJ/mol to 278.75 kJ/mol,and Ea[001]increases from 195.89 kJ/mol to 290.43 kJ/mol,with pressure increasing from 20 GPa to 40 GPa.At 700 K,the diffusion coefficients at 40 GPa is 7 orders of magnitude lower than that at 20 GPa;and at 1000 K it decrease 5 orders of magnitude.To ensure that at least 90%helium is not lost,we synthesized the temperature obtained from cooling and heating processes and derive the'stable temperature range'for helium in aragonite.The obtained results show that the stable temperature range is 22-76℃at 0 GPa and 641-872℃at 40 GPa,for the crystal of 100-2000μm size.Besides,the travel time of helium in aragonite under high pressure increases rapidly with pressure increasing.Our calculations indicate that helium can be quantitatively retained in aragonite in the deep mantle as long as the temperature is in the'stable temperature range'.These results have certain implications for exploring the evolution of mantle and the storage of helium within it.
