The major,trace,and rare earth elements of the Duanjiapo(DJP)section in the south of the Loess Plateau,the Jiaxian(JX)section in the north,and the Jiuzhoutai(JZT)section in the west are studied.The results show that t...The major,trace,and rare earth elements of the Duanjiapo(DJP)section in the south of the Loess Plateau,the Jiaxian(JX)section in the north,and the Jiuzhoutai(JZT)section in the west are studied.The results show that the main elemental characteristics of loess in three profiles are consistent with the upper continental crust(UCC).In terms of trace elements,Th,Nb,Zr,Hf,Y,Cs,W,Cr,V,Li,and Pb show relative enrichment compared with UCC;Rb,Ba,Sr and Be exhibit relative depletion.The average ofΣREE is 171.91ppm with a negative anomaly forδEu and essentially no anomaly forδCe.The results of K_(2)O/Na_(2)O,Rb/Sr ratios,as well as the leaching co-efficient from three profiles,indicate DJP>JX>JZT,suggesting that DJP experiences the strongest weathering leaching effect.The chemical index of alteration(CIA)reveals that all three profiles of loess are in the primary stage of Ca and Na depletion.DJP is generally in the early to moderate stage of chemical weathering,while JX and JZT are both in the early stage.展开更多
The present research deals with the geochemical characteristics of the Holocene sediments from Alamdanga area, Chuadanga district, Bangladesh. Main goals of the study are to delineate source rock characteristics, degr...The present research deals with the geochemical characteristics of the Holocene sediments from Alamdanga area, Chuadanga district, Bangladesh. Main goals of the study are to delineate source rock characteristics, degree of chemical weathering and sorting processes and behavior of redox conditions during deposition of the sediments. Geochemical characteristics of the sediments show comparatively a wide variation in accordance with stratigraphy in their major element contents(e.g. Si O2 69.46–82.13, Al2O3 2.28–8.88 in wt%), reflecting the distinctive provenance and in part an unstable period in terms of tectonic activity. Geochemical classification of the sediments shows mostly sub-arkose with few sub-litharenites. Some major and trace elements display comprehensible correlation with Al2O3 confirming their possible hydraulic fractionation. The chemical index of alteration(CIA*), W* index, index of compositional variability(ICV), plagioclase index of alteration(PIA*) values and the ratio of Si O2/Al2O3, suggest low degrees of chemical weathering in the source areas as well as immature to moderately mature the sediments. The sediments suggest semi-arid climatic trends within oxic deltaic depositional conditions during the Holocene, at 3–12 ka. Whole rock geochemistry and discrimination diagrams demonstrate the continental signature derivatives, which might have been derived from the felsic to intermediate igneous rocks(granitic plutonic rocks) as well as from quartzose sedimentary/metamorphic provenance. These typical sources are present in a vast region of the Himalayan belt and catchment areas of Ganges. The tectonic setting of the sediments demarcates typically passive margin with slightly continental arc system.展开更多
随着光伏产业和新能源汽车产业的蓬勃发展,国内外锂资源需求持续增加,黏土型锂矿逐渐成为矿产勘查的重点。经地质调查,南漳县西部梁山组黏土岩存在锂的超常富集现象,具备形成独立锂矿床的潜力,而梁山组富锂黏土岩物源特征、沉积环境和...随着光伏产业和新能源汽车产业的蓬勃发展,国内外锂资源需求持续增加,黏土型锂矿逐渐成为矿产勘查的重点。经地质调查,南漳县西部梁山组黏土岩存在锂的超常富集现象,具备形成独立锂矿床的潜力,而梁山组富锂黏土岩物源特征、沉积环境和成矿规律的研究仍为空白。因此,有必要研究南漳县西部梁山组富锂黏土岩物源特征,以进一步揭示其源区地质特征,为后续找矿工作提供有效指导。经测定,南漳县西部梁山组富锂黏土岩样品Al_(2)O_(3)/TiO_(2)比值为14.45~37.69,平均值为27.68;K_(2)O/Al_(2)O_(3)比值为0.0017~0.0206,平均值为0.0098;Cr/Zr比值为0.1449~0.3519,平均值为0.2775。结果表明,黏土岩物源区主要为长英质岩石。La/Sc-Th/Co图解、Zr-TiO_(2)图解中,所有样品点均落在长英质物源区,显示物源的单一性。大多数样品的化学蚀变指数(Chemical Index of Alteration,CIA)、化学风化指数(Chemical Index of Weathering,CIW)均在90以上,说明源岩经历强烈化学风化作用。展开更多
氮肥施用是引起土壤酸化的主要原因之一,酸性环境促进紫色母岩的风化过程,并影响紫色母岩风化产物的理化性质,然而氮肥施用对风化产物的盐基离子和酸缓冲容量(pH Buffer Capacity,pHBC)的影响尚不明晰.因此,以蓬莱镇组(J_(3)p)紫色泥岩...氮肥施用是引起土壤酸化的主要原因之一,酸性环境促进紫色母岩的风化过程,并影响紫色母岩风化产物的理化性质,然而氮肥施用对风化产物的盐基离子和酸缓冲容量(pH Buffer Capacity,pHBC)的影响尚不明晰.因此,以蓬莱镇组(J_(3)p)紫色泥岩为研究对象,设置3组氮肥施用水平(280,560,840 kg/hm^(2))以及不施肥处理(CK),通过淋溶试验模拟母岩风化,以探明氮肥施用对紫色泥岩风化产物盐基离子及pHBC的影响.结果表明:与CK处理相比,氮肥施用处理下风化产物的化学蚀变指数(Chemical Index of Alteration,CIA)增加0.9%~4.7%,且风化产物的CIA随施肥水平的增加而呈现先增加后减小的趋势.氮肥施肥处理下风化产物的pHBC较CK处理降低4.0%~8.9%,且风化产物的pHBC随氮肥施用水平的增加呈现先减小后增加的趋势.风化产物的交换性盐基离子、水溶性盐基离子和盐基离子的淋失总量表现为:Ca^(2+)>Mg^(2+)>Na^(+)>K^(+),且风化产物的二价盐基离子(Ca^(2+)和Mg^(2+))含量远高于一价盐基离子含量(K^(+)和Na^(+)).基于多元线性逐步回归分析和结构方程模型分析结果表明:氮肥施用对风化产物水溶性K^(+)(R^(2)=0.75)和Na^(+)(R^(2)=0.99)含量存在显著负效应(p<0.05),而水溶性K^(+)和Na^(+)含量对风化产物pHBC(R^(2)=0.44)存在正效应,进而导致氮肥施用对风化产物pHBC存在负效应,这可能是氮肥施用影响风化产物pHBC的主要机制之一.研究结果表明:为了紫色土肥力的可持续发展,紫色土区域的氮肥施用量应小于280 kg/hm^(2).展开更多
化学蚀变指数（chemical index of alteration）最早作为判别源岩区化学风化程度的指标而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA=n（Al2O3）／[n（Al2O3）＋n（CaO^＊）＋n（Na2O）＋n（K2O）]×100...化学蚀变指数（chemical index of alteration）最早作为判别源岩区化学风化程度的指标而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA=n（Al2O3）／[n（Al2O3）＋n（CaO^＊）＋n（Na2O）＋n（K2O）]×100。CaO^＊代表硅酸盐中的CaO，n（CaO^＊）=n（CaO）-n（CO2，方解石）-O．5·n（CO2，白云石）-10／3·n（P2O5）。化学蚀变指数研究样品的选取极为重要，最佳岩性为细碎屑岩，需要清除成岩过程中钾交代作用的影响。用成分变异指数（ICV）来判别沉积再循环作用和沉积物成分被改造的程度。用A—CN—K三角图解来判别物源区的源岩性质和样品钾交代的特征及其风化趋势。宜昌三斗坪地区南华系CIA研究表明：该区南华系下统莲沱组下部的CIA值在50～65之间（干燥寒冷），上部为65～75之间（温暖潮湿）和顶部为55～60之间（干燥寒冷）；南华系上统南沱组的CIA值基本在60～65之间（干燥寒冷），近顶部两个样品的CIA值达70（温暖潮湿）。上述CIA值变化表明本区南华纪经历自老到新由冰期干燥寒冷-间冰期温暖潮湿-冰期干燥寒冷沉积环境的变化过程。本文据此提出了新的扬子古陆南华系新的划分和对比方案。展开更多
化学蚀变指数（chemical index of alteration）（CIA）最早作为判别源岩化学风化程度而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA={n（Al2O3）／[n（Al2O3）＋n（CaO^＊）＋n（Na2O）＋n（K2O）]}×10...化学蚀变指数（chemical index of alteration）（CIA）最早作为判别源岩化学风化程度而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA={n（Al2O3）／[n（Al2O3）＋n（CaO^＊）＋n（Na2O）＋n（K2O）]}×100。CaO^＊代表硅酸盐中的CaO，n（CaO^＊）=n（CaO）-n（CO2方解石）-n0．5×n（CO2白云石）-10／3xn（P2O5）。化学蚀变指数样品的选取极为重要，最佳岩性为细碎屑岩，并需清除成岩过程中钾交代作用的影响，以及采用成分变异指数（ICV）来判别沉积再循环作用和沉积物成分被改造的程度。使用A—CN—K三角图解判别物源区的源岩性质和样品钾交代的程度及其风化趋势。黔南-桂北地区南华系的CIA研究表明：该地区南华系下部的长安组其下部CIA值为60～65之间，中部为70～5，上部回落到65—70之间。南华系中部富禄组CIA值高，在85-95之间。南华系上部的南沱组CIA值再次回落到60—65的范围。上述CIA值的变化表明本区南华纪时期自老至新经历多次由干燥寒冷-温暖潮湿气候期的变化。本文据此提出扬子地块南华系新的划分、对比方案。展开更多
本文应用化学蚀变指数(CIA)方法,研究新疆库鲁克塔格地区新元古代地层,并探讨沉积时期的气候环境。贝义西组总体 CIA 值较低,介于51～56之间,具冰期环境特征。照壁山组 CIA 值为60左右,表明气候有所变暖。阿勒通沟组的CIA 值变化范围在4...本文应用化学蚀变指数(CIA)方法,研究新疆库鲁克塔格地区新元古代地层,并探讨沉积时期的气候环境。贝义西组总体 CIA 值较低,介于51～56之间,具冰期环境特征。照壁山组 CIA 值为60左右,表明气候有所变暖。阿勒通沟组的CIA 值变化范围在48～61之间,顶部突变为69～71,说明阿勒通沟期经历了另一次寒冷事件,并以温暖环境结束。其上的特瑞爱肯组 CIA 值介于49～53之间,说明第三次经历寒冷干燥的气候环境。扎莫克提组,育肯沟组和水泉组的 CIA 均值为65,反映温暖条件下的沉积环境。新元古代末期汉格尔乔克组 CIA 值下降为56,暗示第四次出现寒冷气候环境。以上特征表明新疆库鲁克塔格地区新元古代的气候环境出现四次冷热交替变化。其中尤为重要的是阿勒通沟组中下部应为寒冷气候环境,而顶部突变为温暖气候环境,因此该组反映了一次明确的从冷到暖的气候变化过程,可以作为贝义西冰期和特瑞爱肯冰期之间的另一次独立冰期。本文的研究成果从地球化学角度支持塔里木板块新元古代四次冰期的划分方案。通过与扬子板块新元古代冰期划分方案的对比,认为塔里木板块新元古代四次冰期的前三次均已在华南板块以冰期或寒冷环境沉积形式出现。展开更多
基金the National Natural Science Foundation of China(No.41561001,42271007).
文摘The major,trace,and rare earth elements of the Duanjiapo(DJP)section in the south of the Loess Plateau,the Jiaxian(JX)section in the north,and the Jiuzhoutai(JZT)section in the west are studied.The results show that the main elemental characteristics of loess in three profiles are consistent with the upper continental crust(UCC).In terms of trace elements,Th,Nb,Zr,Hf,Y,Cs,W,Cr,V,Li,and Pb show relative enrichment compared with UCC;Rb,Ba,Sr and Be exhibit relative depletion.The average ofΣREE is 171.91ppm with a negative anomaly forδEu and essentially no anomaly forδCe.The results of K_(2)O/Na_(2)O,Rb/Sr ratios,as well as the leaching co-efficient from three profiles,indicate DJP>JX>JZT,suggesting that DJP experiences the strongest weathering leaching effect.The chemical index of alteration(CIA)reveals that all three profiles of loess are in the primary stage of Ca and Na depletion.DJP is generally in the early to moderate stage of chemical weathering,while JX and JZT are both in the early stage.
文摘The present research deals with the geochemical characteristics of the Holocene sediments from Alamdanga area, Chuadanga district, Bangladesh. Main goals of the study are to delineate source rock characteristics, degree of chemical weathering and sorting processes and behavior of redox conditions during deposition of the sediments. Geochemical characteristics of the sediments show comparatively a wide variation in accordance with stratigraphy in their major element contents(e.g. Si O2 69.46–82.13, Al2O3 2.28–8.88 in wt%), reflecting the distinctive provenance and in part an unstable period in terms of tectonic activity. Geochemical classification of the sediments shows mostly sub-arkose with few sub-litharenites. Some major and trace elements display comprehensible correlation with Al2O3 confirming their possible hydraulic fractionation. The chemical index of alteration(CIA*), W* index, index of compositional variability(ICV), plagioclase index of alteration(PIA*) values and the ratio of Si O2/Al2O3, suggest low degrees of chemical weathering in the source areas as well as immature to moderately mature the sediments. The sediments suggest semi-arid climatic trends within oxic deltaic depositional conditions during the Holocene, at 3–12 ka. Whole rock geochemistry and discrimination diagrams demonstrate the continental signature derivatives, which might have been derived from the felsic to intermediate igneous rocks(granitic plutonic rocks) as well as from quartzose sedimentary/metamorphic provenance. These typical sources are present in a vast region of the Himalayan belt and catchment areas of Ganges. The tectonic setting of the sediments demarcates typically passive margin with slightly continental arc system.
文摘随着光伏产业和新能源汽车产业的蓬勃发展,国内外锂资源需求持续增加,黏土型锂矿逐渐成为矿产勘查的重点。经地质调查,南漳县西部梁山组黏土岩存在锂的超常富集现象,具备形成独立锂矿床的潜力,而梁山组富锂黏土岩物源特征、沉积环境和成矿规律的研究仍为空白。因此,有必要研究南漳县西部梁山组富锂黏土岩物源特征,以进一步揭示其源区地质特征,为后续找矿工作提供有效指导。经测定,南漳县西部梁山组富锂黏土岩样品Al_(2)O_(3)/TiO_(2)比值为14.45~37.69,平均值为27.68;K_(2)O/Al_(2)O_(3)比值为0.0017~0.0206,平均值为0.0098;Cr/Zr比值为0.1449~0.3519,平均值为0.2775。结果表明,黏土岩物源区主要为长英质岩石。La/Sc-Th/Co图解、Zr-TiO_(2)图解中,所有样品点均落在长英质物源区,显示物源的单一性。大多数样品的化学蚀变指数(Chemical Index of Alteration,CIA)、化学风化指数(Chemical Index of Weathering,CIW)均在90以上,说明源岩经历强烈化学风化作用。
文摘氮肥施用是引起土壤酸化的主要原因之一,酸性环境促进紫色母岩的风化过程,并影响紫色母岩风化产物的理化性质,然而氮肥施用对风化产物的盐基离子和酸缓冲容量(pH Buffer Capacity,pHBC)的影响尚不明晰.因此,以蓬莱镇组(J_(3)p)紫色泥岩为研究对象,设置3组氮肥施用水平(280,560,840 kg/hm^(2))以及不施肥处理(CK),通过淋溶试验模拟母岩风化,以探明氮肥施用对紫色泥岩风化产物盐基离子及pHBC的影响.结果表明:与CK处理相比,氮肥施用处理下风化产物的化学蚀变指数(Chemical Index of Alteration,CIA)增加0.9%~4.7%,且风化产物的CIA随施肥水平的增加而呈现先增加后减小的趋势.氮肥施肥处理下风化产物的pHBC较CK处理降低4.0%~8.9%,且风化产物的pHBC随氮肥施用水平的增加呈现先减小后增加的趋势.风化产物的交换性盐基离子、水溶性盐基离子和盐基离子的淋失总量表现为:Ca^(2+)>Mg^(2+)>Na^(+)>K^(+),且风化产物的二价盐基离子(Ca^(2+)和Mg^(2+))含量远高于一价盐基离子含量(K^(+)和Na^(+)).基于多元线性逐步回归分析和结构方程模型分析结果表明:氮肥施用对风化产物水溶性K^(+)(R^(2)=0.75)和Na^(+)(R^(2)=0.99)含量存在显著负效应(p<0.05),而水溶性K^(+)和Na^(+)含量对风化产物pHBC(R^(2)=0.44)存在正效应,进而导致氮肥施用对风化产物pHBC存在负效应,这可能是氮肥施用影响风化产物pHBC的主要机制之一.研究结果表明:为了紫色土肥力的可持续发展,紫色土区域的氮肥施用量应小于280 kg/hm^(2).
文摘化学蚀变指数（chemical index of alteration）最早作为判别源岩区化学风化程度的指标而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA=n（Al2O3）／[n（Al2O3）＋n（CaO^＊）＋n（Na2O）＋n（K2O）]×100。CaO^＊代表硅酸盐中的CaO，n（CaO^＊）=n（CaO）-n（CO2，方解石）-O．5·n（CO2，白云石）-10／3·n（P2O5）。化学蚀变指数研究样品的选取极为重要，最佳岩性为细碎屑岩，需要清除成岩过程中钾交代作用的影响。用成分变异指数（ICV）来判别沉积再循环作用和沉积物成分被改造的程度。用A—CN—K三角图解来判别物源区的源岩性质和样品钾交代的特征及其风化趋势。宜昌三斗坪地区南华系CIA研究表明：该区南华系下统莲沱组下部的CIA值在50～65之间（干燥寒冷），上部为65～75之间（温暖潮湿）和顶部为55～60之间（干燥寒冷）；南华系上统南沱组的CIA值基本在60～65之间（干燥寒冷），近顶部两个样品的CIA值达70（温暖潮湿）。上述CIA值变化表明本区南华纪经历自老到新由冰期干燥寒冷-间冰期温暖潮湿-冰期干燥寒冷沉积环境的变化过程。本文据此提出了新的扬子古陆南华系新的划分和对比方案。
文摘化学蚀变指数（chemical index of alteration）（CIA）最早作为判别源岩化学风化程度而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA={n（Al2O3）／[n（Al2O3）＋n（CaO^＊）＋n（Na2O）＋n（K2O）]}×100。CaO^＊代表硅酸盐中的CaO，n（CaO^＊）=n（CaO）-n（CO2方解石）-n0．5×n（CO2白云石）-10／3xn（P2O5）。化学蚀变指数样品的选取极为重要，最佳岩性为细碎屑岩，并需清除成岩过程中钾交代作用的影响，以及采用成分变异指数（ICV）来判别沉积再循环作用和沉积物成分被改造的程度。使用A—CN—K三角图解判别物源区的源岩性质和样品钾交代的程度及其风化趋势。黔南-桂北地区南华系的CIA研究表明：该地区南华系下部的长安组其下部CIA值为60～65之间，中部为70～5，上部回落到65—70之间。南华系中部富禄组CIA值高，在85-95之间。南华系上部的南沱组CIA值再次回落到60—65的范围。上述CIA值的变化表明本区南华纪时期自老至新经历多次由干燥寒冷-温暖潮湿气候期的变化。本文据此提出扬子地块南华系新的划分、对比方案。
文摘本文应用化学蚀变指数(CIA)方法,研究新疆库鲁克塔格地区新元古代地层,并探讨沉积时期的气候环境。贝义西组总体 CIA 值较低,介于51～56之间,具冰期环境特征。照壁山组 CIA 值为60左右,表明气候有所变暖。阿勒通沟组的CIA 值变化范围在48～61之间,顶部突变为69～71,说明阿勒通沟期经历了另一次寒冷事件,并以温暖环境结束。其上的特瑞爱肯组 CIA 值介于49～53之间,说明第三次经历寒冷干燥的气候环境。扎莫克提组,育肯沟组和水泉组的 CIA 均值为65,反映温暖条件下的沉积环境。新元古代末期汉格尔乔克组 CIA 值下降为56,暗示第四次出现寒冷气候环境。以上特征表明新疆库鲁克塔格地区新元古代的气候环境出现四次冷热交替变化。其中尤为重要的是阿勒通沟组中下部应为寒冷气候环境,而顶部突变为温暖气候环境,因此该组反映了一次明确的从冷到暖的气候变化过程,可以作为贝义西冰期和特瑞爱肯冰期之间的另一次独立冰期。本文的研究成果从地球化学角度支持塔里木板块新元古代四次冰期的划分方案。通过与扬子板块新元古代冰期划分方案的对比,认为塔里木板块新元古代四次冰期的前三次均已在华南板块以冰期或寒冷环境沉积形式出现。
