Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is ...Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is point out that the development of hercynian fracture-vuggy and filling succession of fracture-cave mineral was under the background of the mingling of low-temperature magma hydrotherm and the brine of upper strata. There are overlap or associate relations between generate of fluorite and buried dissolution or oil-gas migration. It was volume decreased 26.4% after calcite metasomatic by fluorite, this reaction made fluorite engender plentiful intergranular space. It’s created appreciable reservoir space. At same time, hydrotherm carried by fluorite generating could erode adjacent rock though fracture or fissure, forming irregular fracture-cave system, and also accompanied with hydrocarbon migration. The time of hydrocarbon migration and accumulation happened in late hercynian-indosinian is inosculates with the sedimentation time such as fluorite and several hydrothermal mineral.展开更多
Late Cretaceous lacustrine deposits in Songliao Basin provide a unique material to study the paleo-environment and paleoclimate of nomarine Cretaceous.Two large transgressions occurred during the Qingshankou and Nenji...Late Cretaceous lacustrine deposits in Songliao Basin provide a unique material to study the paleo-environment and paleoclimate of nomarine Cretaceous.Two large transgressions occurred during the Qingshankou and Nenjiang deposition times,the later of which was larger.Based on sedimentation,ostracode,TOC,HI,δ<sup>13</sup>C<sub>org</sub> and C/N from upper Yaojia Formation to Lower Nenjiang Formation in the eastern Songliao Basin。展开更多
The Kathmandu valley is an intermountain basin located at about 1300 and surounded by mountains around 2400m.Thick fluvio\|lacustrine sediments from late Pliocene to Quaternary are accumulated there under monsoon clim...The Kathmandu valley is an intermountain basin located at about 1300 and surounded by mountains around 2400m.Thick fluvio\|lacustrine sediments from late Pliocene to Quaternary are accumulated there under monsoon climate.We undertook palynological and sedimentological studies on 284\|m\|long drilled core that reaches the basement of the kathmandu basin,in order to clarify the paleoclimatic changes and their tectonic link with uplifting of the Himalayas..The core is lithologically divided into three members:sand predominant lower member (51m),slit and clay dominant middle member (182m) and organic silty clay predominant upper member (45m).We analyzed fossil pollens contained in muddy samples which were taken from the middle and upper member in every one meter interval.The pollen assemblage is characterized by predominance of \%Quercus,\%30%～80% of the all arboreal pollen.We inferred paleoclimatic changes on the basis of comparison between present vegetation and climate of Kathmandu valley and surrounded mountains and pollen diagram which we obtained.For the purpose of inference of paleoclimate,we used the following genera as climatic index:\%Pinus\% for cold climate, \%Quercus\% and \%Cyclobalanopsis\% for warm climate, Alnus for wet climate and Gramineae for dry climate.As the reference.we also examined amount of another eight genera,two family and all spores.The pollen diagram shows two pattern of paleoclimatic changes:oscillation pattern with seven times fluctuation of warm and cold climate in younger period (ca.115m in depth),and older less fluctuated pattern of warm climate.During the older period (209～215m in depth),one cold stage was recognized,and is characterized by predominance of Pinus and occurrence of Tsuga .展开更多
The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are main...The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are mainly hosted within a low-grade to medium-grade,dominantly submarine metamorphosed siliciclastic and carbonate sedimentary succession of the Neoproterozoic Shilu Group.Three facies types of metamorphosed BIFs,i.e.the oxide facies,the silicate-oxide facies and the sulfide-carbonate facies BIFs,are identified within the sixth sequence of the Shilu Group.The oxide facies BIF(i.e.the Fe-rich itabirites or ores)consists of alternating hematite-rich microbands with quartz-rich microbands;the silicate-oxide facies BIF(i.e.the Fe-poor itabirites or ores)comprises alternating millimeter-to a few tens meter-scale,magnetite-hematite-rich bands with calcsilicate-rich(garnet+actinolite+diopside+epidote+quartz)meso-to microbands;and the sulfide-carbonate facies BIF(i.e.the Co-Cu ores)contains alternating macro-to mesobands of Co-bearing pyrite and pyrrhotite,and chalcopyrite with mesobands of dolomite+calcite+diopside+quartz and/or chlorite+sericite+quartz.The blastooolitic,blastopelletoid blastocolloidal and blastopsammitic textures,and blasobedding structures which most likely represent primary sedimentation are often observed in these BIF facies.The interbedded host rocks with the BIFs mainly are the pyroxene-amphibole rocks and the banded or impure dolostones,and also contain banded or laminated structures,and lepido-gra-noblastic,nematoblastic and/or blastoclastic textures.Compositionally,the main host rocks,the pyroxene-amphibole rocks contain basic-intermediate SiO_2(~54.00 wt.%),CaO(~14.19 wt.%),MgO(~9.68 wt.%)and Al_2O_3(~8.49 wt.%)with a positive correlation between Al_2O_3 and TiO_2.The UCC-like Zr and Hf abundances,high Ba content andεNd(t)value(^-5.99)as well as the ratios of La/YbPAAS(0.17~1.00),δEuPAAS(0.88~1.12)andδCePAAS(0.93~1.13)commonly reveal that the protoliths to this type rocks are hydrogenic with a large contribution of terrigenous sediments and minor hydrothermal input.The high CaO+MgO+LOI contents and the extremely low trace element and REEconcentrations as well as the ratios of Y/Ho(44~45),δEuPAAS(1.13~1.57)andδCePAAS(0.69~0.98)reflect a marine origin with minor terrigenous materials for the banded or impure dolostones.Moreover,this type rocks also account for a negativeεNd(t)value(^-7.49).The oxide facies BIF is dominated by Fe_2O_3+FeO(~75.59wt.%)and SiO_2(~20.47 wt.%)with aεNd(t)value of^-6.10.The variable contents in Al_2O_3,TiO 2,K2O,Na2O,Zr,Hf and∑REE,and variable ratios of Y/Ho(24~39)andδEuPAAS(0.86~11.07)suggest the precursor sediments to this facies BIF are admixtures of sea-floor hydrothermal fluids and seawaters with minor involvement of detrital components.Compared to the oxide facies BIF,the silicate-oxide facies BIF is lower in Fe_2O_3+Fe O(~39.81wt.%)and Ba but higher in SiO_2(~42.54 wt.%),Al2O3(~3.60 wt.%),TiO_2(~0.19 wt.%),MgO(~1.12 wt.%),CaO(~9.06 wt.%),K_2O(~0.98 wt.%),Mn and Zr.The ratios of Y/Ho(25~34),La/YbPAAS(0.14-0.74)andδEuPAAS(0.91~1.12)most likely are linked to higher degree of detrital contamintants.While the sulfide-caronate facies BIF is main but variable in Fe_2O_3+Fe O(15.79~57.91 wt.%),SiO 2(0.54~61.52 wt.%),MgO(0.12~16.09wt.%),CaO(0.17~23.41 wt.%)and LOI(8.28-30.06 wt.%).The generally low contents in trace elements(including REE)except for an obvious enrichment in Pb,and the positive Ce anomalies(δCePAAS=1.04~1.95)and negative Pr anomalies(δPrPAAS=0.67~0.93),as well as the variable ratios ofδEuPAAS(0.72~1.71),La/YbPAAS(0.26~1.60)and Y/Ho(26~57)suggest that the precursors to the sulfide-carbonate facies BIF mainly are metalliferious sediments from deep-marine hydrotheral source with minor detrital components.The T2DM ages(ca.2.0 Ga)imply that the Shilu BIFs and interbedded host rocks contain a component with Paleoproterozoic crustal residence age due to a significant crustal accretion event at ca.2.0 Ga in Hainan Island.In connection with the petrographical and mineralogical relationship,we conclude that the precursor precipitates to the Shilu BIFs are variable degree of admixtures of the Fe-Co-Cu-(Si)-rich hydrothermal fluids and detrital components from seawater and fresh water carring continental landmass;whereas the protolith to the main interbedded host rocks,i.e.the pyroxene-amphibole rocks,most likely was terrigenous,fine-grained clastic-sediments but with significant input of hydrothermal fluids in a seawater environment.As a result,a continent marginal marine basin is proposed for deposition of the Shilu BIFs and interbedded host rocks.Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments.展开更多
水生植被和藻类作为湖泊生态系统的主要初级生产者,对湖泊生态系统具有重要作用。在气候变化和人类活动的双重作用下,湖泊富营养化加剧,水生植被退化,藻类水华频发。开展湖泊水生植被群落和藻类水华的长期观测可为湖泊生态系统水生植被...水生植被和藻类作为湖泊生态系统的主要初级生产者,对湖泊生态系统具有重要作用。在气候变化和人类活动的双重作用下,湖泊富营养化加剧,水生植被退化,藻类水华频发。开展湖泊水生植被群落和藻类水华的长期观测可为湖泊生态系统水生植被修复和藻类水华管控提供决策依据。本研究以太湖流域浅水湖泊长荡湖为研究区,基于1985-2021年的Landsat 5和8卫星数据,利用VBI(vegetation and bloom indices)草藻分类算法,开展了浮叶/挺水植被、沉水植被和藻类水华长时序时空演变分析。结果表明:36年来,长荡湖水生植被(包括浮叶/挺水植被和沉水植被)都呈现显著下降趋势,其中沉水植被下降趋势尤为明显,沉水植被从湖中心向岸边逐步退化,其覆盖度从1985年的75%下降至2021年的不足21%;自2011年起,长荡湖水生植被优势生活型从沉水植被转变为浮叶/挺水植被;2010年首次监测到水华发生,2020年和2021年连续两年均监测到湖中心有大面积水华。基于湖泊围网面积和气象数据分析发现,围网拆除是水生植被退化和优势生活型转变的主要因素。展开更多
文摘Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is point out that the development of hercynian fracture-vuggy and filling succession of fracture-cave mineral was under the background of the mingling of low-temperature magma hydrotherm and the brine of upper strata. There are overlap or associate relations between generate of fluorite and buried dissolution or oil-gas migration. It was volume decreased 26.4% after calcite metasomatic by fluorite, this reaction made fluorite engender plentiful intergranular space. It’s created appreciable reservoir space. At same time, hydrotherm carried by fluorite generating could erode adjacent rock though fracture or fissure, forming irregular fracture-cave system, and also accompanied with hydrocarbon migration. The time of hydrocarbon migration and accumulation happened in late hercynian-indosinian is inosculates with the sedimentation time such as fluorite and several hydrothermal mineral.
文摘Late Cretaceous lacustrine deposits in Songliao Basin provide a unique material to study the paleo-environment and paleoclimate of nomarine Cretaceous.Two large transgressions occurred during the Qingshankou and Nenjiang deposition times,the later of which was larger.Based on sedimentation,ostracode,TOC,HI,δ<sup>13</sup>C<sub>org</sub> and C/N from upper Yaojia Formation to Lower Nenjiang Formation in the eastern Songliao Basin。
文摘The Kathmandu valley is an intermountain basin located at about 1300 and surounded by mountains around 2400m.Thick fluvio\|lacustrine sediments from late Pliocene to Quaternary are accumulated there under monsoon climate.We undertook palynological and sedimentological studies on 284\|m\|long drilled core that reaches the basement of the kathmandu basin,in order to clarify the paleoclimatic changes and their tectonic link with uplifting of the Himalayas..The core is lithologically divided into three members:sand predominant lower member (51m),slit and clay dominant middle member (182m) and organic silty clay predominant upper member (45m).We analyzed fossil pollens contained in muddy samples which were taken from the middle and upper member in every one meter interval.The pollen assemblage is characterized by predominance of \%Quercus,\%30%～80% of the all arboreal pollen.We inferred paleoclimatic changes on the basis of comparison between present vegetation and climate of Kathmandu valley and surrounded mountains and pollen diagram which we obtained.For the purpose of inference of paleoclimate,we used the following genera as climatic index:\%Pinus\% for cold climate, \%Quercus\% and \%Cyclobalanopsis\% for warm climate, Alnus for wet climate and Gramineae for dry climate.As the reference.we also examined amount of another eight genera,two family and all spores.The pollen diagram shows two pattern of paleoclimatic changes:oscillation pattern with seven times fluctuation of warm and cold climate in younger period (ca.115m in depth),and older less fluctuated pattern of warm climate.During the older period (209～215m in depth),one cold stage was recognized,and is characterized by predominance of Pinus and occurrence of Tsuga .
文摘The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are mainly hosted within a low-grade to medium-grade,dominantly submarine metamorphosed siliciclastic and carbonate sedimentary succession of the Neoproterozoic Shilu Group.Three facies types of metamorphosed BIFs,i.e.the oxide facies,the silicate-oxide facies and the sulfide-carbonate facies BIFs,are identified within the sixth sequence of the Shilu Group.The oxide facies BIF(i.e.the Fe-rich itabirites or ores)consists of alternating hematite-rich microbands with quartz-rich microbands;the silicate-oxide facies BIF(i.e.the Fe-poor itabirites or ores)comprises alternating millimeter-to a few tens meter-scale,magnetite-hematite-rich bands with calcsilicate-rich(garnet+actinolite+diopside+epidote+quartz)meso-to microbands;and the sulfide-carbonate facies BIF(i.e.the Co-Cu ores)contains alternating macro-to mesobands of Co-bearing pyrite and pyrrhotite,and chalcopyrite with mesobands of dolomite+calcite+diopside+quartz and/or chlorite+sericite+quartz.The blastooolitic,blastopelletoid blastocolloidal and blastopsammitic textures,and blasobedding structures which most likely represent primary sedimentation are often observed in these BIF facies.The interbedded host rocks with the BIFs mainly are the pyroxene-amphibole rocks and the banded or impure dolostones,and also contain banded or laminated structures,and lepido-gra-noblastic,nematoblastic and/or blastoclastic textures.Compositionally,the main host rocks,the pyroxene-amphibole rocks contain basic-intermediate SiO_2(~54.00 wt.%),CaO(~14.19 wt.%),MgO(~9.68 wt.%)and Al_2O_3(~8.49 wt.%)with a positive correlation between Al_2O_3 and TiO_2.The UCC-like Zr and Hf abundances,high Ba content andεNd(t)value(^-5.99)as well as the ratios of La/YbPAAS(0.17~1.00),δEuPAAS(0.88~1.12)andδCePAAS(0.93~1.13)commonly reveal that the protoliths to this type rocks are hydrogenic with a large contribution of terrigenous sediments and minor hydrothermal input.The high CaO+MgO+LOI contents and the extremely low trace element and REEconcentrations as well as the ratios of Y/Ho(44~45),δEuPAAS(1.13~1.57)andδCePAAS(0.69~0.98)reflect a marine origin with minor terrigenous materials for the banded or impure dolostones.Moreover,this type rocks also account for a negativeεNd(t)value(^-7.49).The oxide facies BIF is dominated by Fe_2O_3+FeO(~75.59wt.%)and SiO_2(~20.47 wt.%)with aεNd(t)value of^-6.10.The variable contents in Al_2O_3,TiO 2,K2O,Na2O,Zr,Hf and∑REE,and variable ratios of Y/Ho(24~39)andδEuPAAS(0.86~11.07)suggest the precursor sediments to this facies BIF are admixtures of sea-floor hydrothermal fluids and seawaters with minor involvement of detrital components.Compared to the oxide facies BIF,the silicate-oxide facies BIF is lower in Fe_2O_3+Fe O(~39.81wt.%)and Ba but higher in SiO_2(~42.54 wt.%),Al2O3(~3.60 wt.%),TiO_2(~0.19 wt.%),MgO(~1.12 wt.%),CaO(~9.06 wt.%),K_2O(~0.98 wt.%),Mn and Zr.The ratios of Y/Ho(25~34),La/YbPAAS(0.14-0.74)andδEuPAAS(0.91~1.12)most likely are linked to higher degree of detrital contamintants.While the sulfide-caronate facies BIF is main but variable in Fe_2O_3+Fe O(15.79~57.91 wt.%),SiO 2(0.54~61.52 wt.%),MgO(0.12~16.09wt.%),CaO(0.17~23.41 wt.%)and LOI(8.28-30.06 wt.%).The generally low contents in trace elements(including REE)except for an obvious enrichment in Pb,and the positive Ce anomalies(δCePAAS=1.04~1.95)and negative Pr anomalies(δPrPAAS=0.67~0.93),as well as the variable ratios ofδEuPAAS(0.72~1.71),La/YbPAAS(0.26~1.60)and Y/Ho(26~57)suggest that the precursors to the sulfide-carbonate facies BIF mainly are metalliferious sediments from deep-marine hydrotheral source with minor detrital components.The T2DM ages(ca.2.0 Ga)imply that the Shilu BIFs and interbedded host rocks contain a component with Paleoproterozoic crustal residence age due to a significant crustal accretion event at ca.2.0 Ga in Hainan Island.In connection with the petrographical and mineralogical relationship,we conclude that the precursor precipitates to the Shilu BIFs are variable degree of admixtures of the Fe-Co-Cu-(Si)-rich hydrothermal fluids and detrital components from seawater and fresh water carring continental landmass;whereas the protolith to the main interbedded host rocks,i.e.the pyroxene-amphibole rocks,most likely was terrigenous,fine-grained clastic-sediments but with significant input of hydrothermal fluids in a seawater environment.As a result,a continent marginal marine basin is proposed for deposition of the Shilu BIFs and interbedded host rocks.Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments.
文摘水生植被和藻类作为湖泊生态系统的主要初级生产者,对湖泊生态系统具有重要作用。在气候变化和人类活动的双重作用下,湖泊富营养化加剧,水生植被退化,藻类水华频发。开展湖泊水生植被群落和藻类水华的长期观测可为湖泊生态系统水生植被修复和藻类水华管控提供决策依据。本研究以太湖流域浅水湖泊长荡湖为研究区,基于1985-2021年的Landsat 5和8卫星数据,利用VBI(vegetation and bloom indices)草藻分类算法,开展了浮叶/挺水植被、沉水植被和藻类水华长时序时空演变分析。结果表明:36年来,长荡湖水生植被(包括浮叶/挺水植被和沉水植被)都呈现显著下降趋势,其中沉水植被下降趋势尤为明显,沉水植被从湖中心向岸边逐步退化,其覆盖度从1985年的75%下降至2021年的不足21%;自2011年起,长荡湖水生植被优势生活型从沉水植被转变为浮叶/挺水植被;2010年首次监测到水华发生,2020年和2021年连续两年均监测到湖中心有大面积水华。基于湖泊围网面积和气象数据分析发现,围网拆除是水生植被退化和优势生活型转变的主要因素。
