共查询到20条相似文献，搜索用时 411 毫秒
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本文利用电镜扫描方法 (SEM)对比分析了南极乔治王岛无冰区海滩沉积、冰碛物以及阿德雷岛湖泊沉积等典型沉积环境中的石英砂表面结构特征 ,得出了乔治王岛各典型沉积环境中石英砂表面结构特征的颗粒频率曲线。结果表明 :不同沉积环境下的石英砂颗粒表面结构特征具有相似性 ,这主要和南极地区广泛发育的冰川作用有关 ,同时 ,它们也有各自典型的特征组合 ,这些典型特征组合的不同反映了石英砂后期的搬运历史和沉积环境的差异。本文还依据石英砂表面特征的颗粒出现频率 ,利用聚类分析方法对研究区内三级海岸阶地上的沉积物和一个未知成因的样品进行了沉积环境的判别分析 ,结果证明石英砂微形貌特征可以作为南极地区沉积环境识别的有效手段 相似文献
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The karst landforms distributed on the Qinghai-Xizang (Tibet) Plateau can be genetically classed with the Tertiary underground karst, which were gradually exhumed to the surface with the uplift of the plateau during Quaternary period. The relative deposits of the Tertiary palaeokarst processes, such as the residuum and speleothem, were discovered recently in the southern and southeastern fringe areas of the plateau, where has geological-currently been disintegrated by the headward erosion processes of the modern river systems. The major chemical components of the clay portion of the residuum consist mainly of SiO2C, Al2CO3 and Fe2O3. The clay minerals composition of the clay portion belongs to illite-kaolinite pattern for most of the residuum samples, and kaolinite-illite pattern for a few of the samples. It can be judged from the silicic acid index and the clay minerals composition that the formation of the residuum of the Plateau was in its initial phase. However, such a lower chemical weathering index only reflected the weathering degree in the bottom or lower parts of the lateritic weathering crust. The relatively intensive chemical weathering processes of the surface layers of the lateritic weathering crust could be logically speculated. The surface feature textures of quartz grains in the residuum were formed mainly by the chemical erosion, which revealed a long-term humid-tropical environment when the residuum and the palaeokarst formed. 相似文献
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Prakash K. Shrivastava Rajesh Asthana Sandip K. Roy Ashit K. Swain Amit Dharwadkar 《Polar Science》2012,6(2):165-182
The scientific study of quartz grains is a powerful tool in deciphering the depositional environment and mode of transportation of sediments, and ultimately the origin and classification of sediments. Surface microfeatures, angularity, chemical features, and grain-size analysis of quartz grains, collectively reveal the sedimentary and physicochemical processes that acted on the grains during different stages of their geological history. Here, we apply scanning electron microscopic (SEM) analysis to evaluating the sedimentary provenance, modes of transport, weathering characteristics, alteration, and sedimentary environment of selected detrital quartz grains from the peripheral part of two epi-shelf lakes (ESL-1 and ESL-2) of the Schirmacher Oasis of East Antarctica. Our study reveals that different styles of physical weathering, erosive signatures, and chemical precipitation variably affected these quartz grains before final deposition as lake sediments. Statistical analysis (central tendencies, sorting, skewness, and kurtosis) indicates that these quartz-bearing sediments are poorly sorted glaciofluvial sediments. Saltation and suspension seem to have been the two dominant modes of transportation, and chemical analysis of these sediments indicates a gneissic provenance. 相似文献
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Gregory A. Pope 《自然地理学》2013,34(4):315-338
While most research on quartz weathering has focused primarily on surface textures and morphologies, very little is known about the internal weathering of quartz. This study demonstrates that internal weathering is ubiquitous in quartz. Internal weathering is measured in terms of porosity, which represents mass loss from the quartz grain, hence silica lost through dissolution. Mass loss calculated from porosity suggests higher-than-expected rates of quartz dissolution in the terrestrial environment. Internal weathering occurs through various grain defects, and is classified into several forms (in decreasing order of frequency): fractures, enlarged grain boundaries, holes, and networks. These features may be distinguished from occasional artifact voids left by laboratory procedures. The most intensely weathered grains exhibit large fractures and extensive networks, and occasionally contain secondary weathering products within the void areas. The presence of internal weathering in quartz supports field and laboratory observations of particle comminution in sediment transport systems, and can account for at least part of the production of silt- and clay-sized quartz. Given the potentially large surface area afforded by these internal defects, internal weathering plays an important role in the generation of quartz particles and dissolved silica, and presents a new avenue of study for the generation of secondary porosity in detrital sediments. [Key words: geomorphology, quartz, silica, weathering.] 相似文献
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萨拉乌苏河流域末次间冰期 古土壤化学风化与古气候 总被引：7，自引：0，他引：7
内蒙萨拉乌苏河流域米浪沟湾剖面末次间冰期发育5 层古土壤。对这5 层古土壤的形 态特征、粒度、扫描电镜及化学风化等分析结果表明: (1) 这些古土壤具有与华北现代褐土相 似的形态特征; (2) 粘化率中部高和石英颗粒表面硅质溶蚀-沉淀现象表明古土壤层中发生过 风化成壤作用; (3) 用K2O/Na2O、Al2O3/Na2O、MnO/Al2O3、CIA 及A-CN-K 图解与华北现代 褐土作对比分析, 发现它们的化学风化特征极为相似; (4) 用气温及降水量与CIA 值的回归 关系方程, 得出5 层古土壤发育时期的水热状况确与华北现代的暖温带半湿润季风性气候大 致相同或更显暖湿。形态特征、粒度、石英颗粒表面特征和化学风化特征等多个方面具备了 与现代华北褐土类似的化学风化成壤特征, 证明这些古土壤是在与华北相似的暖温带半湿润 季风性气候条件下形成的。 相似文献
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The property, age and formation environment of the palaeokarst in Qinghai-Xizang Plateau 总被引：1，自引：0，他引：1
The karst landforms distributed on the Qinghai-Xizang (Tibet) Plateau can be genetically classed with the Tertiary underground
karst, which were gradually exhumed to the surface with the uplift of the plateau during Quaternary period. The relative deposits
of the Tertiary palaeokarst processes, such as the residuum and speleothem, were discovered recently in the southern and southeastern
fringe areas of the plateau, where has geological-currently been disintegrated by the headward erosion processes of the modern
river systems. The major chemical components of the clay portion of the residuum consist mainly of SiO2, A12O3 and Fe2O3. The clay minerals composition of the clay portion belongs to illite-kaolinite pattern for most of the residuum samples,
and kaoliniteillite pattern for a few of the samples. It can be judged from the silicic acid index and the clay minerals composition
that the formation of the residuum of the Plateau was in its initial phase. However, such a lower chemical weathering index
only reflected the weathering degree in the bottom or lower parts of the lateritic weathering crust. The relatively intensive
chemical weathering processes of the surface layers of the lateritic weathering crust could be logically speculated. The surface
feature textures of quartz grains in the residuum were formed mainly by the chemical erosion, which revealed a long-term humid-tropical
environment when the residuum and the palaeokarst formed. 相似文献
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Vatche P. Tchakerian 《自然地理学》2013,34(4):347-369
Geomorphological and sedimentological analysis of aeolian deposits, combined with scanning electron microscopy (SEM) of quartz-grain surface characteristics, suggest six dune-building episodes during late Quaternary time in the southern Mojave Desert, California. The aeolian units accumulated largely in response to the lowering of water levels in lake basins and a consequent increase in fine sediment availability, and to stronger and more persistent winds, associated with rapidly changing environmental conditions. Peak dune deposition is believed to have taken place during the middle Holocene Altithermal between around 7.5 and 5 ka, a period characterized by greater aridity than the present. SEM analysis of the quartz surface textures indicates that mechanical and especially chemical weathering processes play a significant role in the post-depositional modification of aeolian sediments. Such evidence permits paleoenvironmental reconstruction during and since deposition, and a basis for the relative dating of aeolian sequences. Discriminant analysis using grain-size parameters, combined with principal components analysis of the SEM data from quartz-grain surfaces, is an effective analytical tool for distinguishing between spatially and temporally distributed aeolian deposits. [Key words: aeolian geomorphology, granulometry, quartz grain surface microfeatures, scanning electron microscopy, multivariate statistical analysis.] 相似文献
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本文从孢粉组成及石英砂表面形态角度研究了滇东南几种土壤的沉积环境及其演变，并研究了土壤粘粒矿物特性及化学组成特点。结果表明，土壤除受着目前成土因子作用外，沉积古环境及其演变对土壤发育特性及矿物学化学组成也有深刻的影响。 相似文献
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辽东古元古代变质硼矿床是我国最重要的硼矿资源,然而由于该区物质组成多样,构造演化复杂的特点,导致对于硼矿的物质来源、构造环境及成矿过程的认识存在很大差异。目前多数学者认为辽东硼矿床经历了早期的盐湖硼酸盐沉积阶段及晚期构造热事件引起的变质作用阶段。当前的研究认为古元古代辽东地区处于活动大陆边缘,且发育大量的钙碱性岩浆活动,这与第三纪以来的大型硼酸盐沉积矿床形成的构造环境及岩浆活动相似。结合现代盐湖体系下的硼酸盐沉淀物理化学条件讨论辽东地区古元古代沉积硼酸盐特征,根据硼同位素组成探讨物质来源及构造环境,发现辽东地区的硼矿床存在钠硼解石、硬硼钙石两种硼酸盐的沉积,硼同位素组成显示其硼源应来源于俯冲板块下蛇纹石及海相沉积物的脱水作用释放的硼,这种硼随钙碱性岩浆活动及热液活动在局限海盆中蒸发形成含水硼酸盐。 相似文献
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我国内陆沙漠与海岸沙丘石英颗粒表面结构的对比研究 总被引：6，自引：3，他引：6
本文通过扫描电镜分析，对我国内陆沙漠与海岸抄丘石英颗粒表面结构进行了对比研究。研究认为，无论是内陆沙漠砂或海岸沙丘砂，其石英颗粒都具有较好的磨圆度，表面有碟形坑、麻坑及ＳｉＯ＿２沉淀物等代表风成环境的典型特征；此外，还叠加有代表原生沙物质来源于水下环境的Ｖ型撞击坑、撞击沟等痕迹。然而，受环境尤其是气候影响，其表面结构特征仍有差异，表现在内陆干旱区大陆性气候的沙漠砂的风成机械作用和化学沉淀作用，都要比沿海湿润季风性气候的海岸沙丘砂强烈；但海岸沙丘砂的化学溶蚀作用却比内陆沙漠砂要明显。同属海岸抄丘环境，其石英颗粒表面结构特征表现为北方温带海岸沙丘砂的机械作用痕迹强；而南方热带海岸沙丘砂的化学作用痕迹发育，但机械作用痕迹并非少见，仍然十分明显。 相似文献
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通过孢子花粉、石英砂颗粒和土壤微形态学分析,研究北亚热带江淮地区白浆化土壤的发生学特性。白浆化土壤下部土体经历了暖温带森林草原景观和亚热带草原景观,为高能化学环境。在母质沉积后,经历了褐土化过程或其他物质堆积,经过一定时期的沉积间断后,堆积新物质,随着气候的变化,成土环境演变为现代气候类型,属亚热带森林草原环境。淀积层也源于黄土状物质,风化程度更强,白浆层则为后期堆积物,不具备高能化学环境。淀积层在高能环境下,存在次生粘化和淀积粘化作用。 相似文献
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利用电镜扫描的方法分析了南极阿德雷岛Y2湖企鹅粪土沉积层中石英砂微形貌的特征,发现在企鹅粪含量高的沉积层中石英砂表面具有明显的碗状溶蚀坑等化学溶蚀特征,这一溶蚀特征在Y2湖企鹅粪含量低的沉积层和研究区的其他未受企鹅粪影响的沉积环境中均未明显出现。为了揭示这一特殊化学溶蚀现象的作用机制,根据Y2湖企鹅粪土沉积层自然沉积环境,通过条件实验确定在实验室内使用酸性较高的氟溶液(1mol.L-1HF溶液)对石英砂进行溶蚀实验,通过对比分析发现,实验室模拟条件下可以得到与企鹅粪土沉积层中石英砂相近的表面微形貌特征,这表明它们是在相似的过程中形成的。企鹅粪土沉积层酸性高氟环境中可能存在的HF酸化学溶蚀作用是形成企鹅粪土层中石英砂表面特有溶蚀坑的主要原因。在南极特殊的自然条件下碗状溶蚀坑与企鹅粪之间存在一定的因果关系,从而使石英砂的表面微形貌分析成为南极企鹅生态研究的一种新的辅助手段。 相似文献
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在对南极长城站地区西湖水化学组成影响因素分析的基础上，利用化学风化反应平衡方程，对西湖水化学组成的影响因子进行了定量化分析评价。研究表明，影响西湖水化学组成的主要因素是大气降水、化学风化过程和海洋物质的叠加效应。西湖水中Ｃａ和Ｍｇ元素主要来源于陆地原生矿物的化学风化，尤其是碳酸盐风化；Ｎａ和Ｋ元素则主要来源于海洋物质的叠加效应。硅（铝）酸盐风化产生的元素量对湖水的贡献率较小，反映出在南极低温条件下化学风化尚停留在硅（铝）酸盐脱盐基阶段。 相似文献
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Climatic implications of hydrologic changes in two lake catchments on the central Tibetan Plateau since the last glacial 总被引：1，自引：0，他引：1
The numerous and widespread lakes of the Tibetan Plateau (TP) constitute the largest group of alpine lakes on Earth. Some of the lakes are fed mainly by glacier meltwater and others by precipitation and groundwater. Past changes in the environments of these lakes differed because of differences in lake hydrological regimes and the complex pattern of climate change on the TP. Here we present records of scanning XRF, inorganic carbon (IC) concentration n-alkanoic acid average chain length (ACL) and percent aquatic inputs (Paq) in sediment cores from two non-glaciated lakes on the central TP (Dagze Co and Jiang Co), which span the past 19,000 years. We used these measures to investigate past changes in catchment hydrology, climate and environment. Variations in the concentration of Ti and other lithogenic elements at the two sites were influenced mainly by surface runoff, which is supported by the variation of IC, Ca/(Al, Ti, Fe) (reflecting authigenic carbonate precipitation), Rb/Sr (a chemical weathering proxy), and ACL and Paq. We attribute variations in surface runoff to changes in the precipitation/evaporation ratio, caused by the pattern of climate change on the central TP since the late Pleistocene. During the late Pleistocene, stronger runoff (indicated by higher Ti, higher Rb/Sr and Paq, lower IC, Ca/(Al, Ti, Fe) and ACL) likely resulted from lower temperatures. Lower runoff during the Holocene may reflect intensified evaporation caused by higher temperatures. Comparison with records from glaciated lakes in the region reveals opposite trends in catchment hydrology. Overall, our results suggest that since the late Pleistocene the central TP was influenced mainly by the Indian Summer Monsoon. 相似文献
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YOSHIHIDE OHTA 《Polar research》1985,3(1):49-67
Two types of basic igneous rocks have been mapped in the middle Hecla Hoek succession in the area between St. Jonsfjorden and Isfjorden, central western Spitsbergen: the metadiabase-gabbros from the calc-argillo-volcanic formation and the Trollheimen volcanics from the quartzite-shale formation; both formations are older than the Eocambrian tilloid formation. The former has diabasic and gabbroic textures and occurs as thin discontinuous lensoid masses, while the latter exhibits definite extrusive structures with large amounts of pyroclastics and tuffs and relatively small amounts of solid lavas with abundant amygdules. Both basic rocks have been metamorphosed under the greenschist facies conditions, characterized by actinolite-epidote-biotite-albite assemblage.
The metadiabase-gabbros are moderate-high Fe tholeiites and the Trollheimen volcanics are mainly Na-alkaline, accompanied by a small amount of calk alkaline rocks. The immobile minor and trace element contents indicate that the metadiabase-gabbros are oceanic, similar to the MORB, while those of the Trollheimen volcanics show non-oceanic chemical characteristics and occur in shallow marine, shelf-shelfedge sediments.
The calc-argillo-volcanic formation reveals a shallow marine sedimentary environment and this does not conform with the oceanic nature of the metadiabase-gabbros, occurring in the formation. To overcome this disagreement, an idea of changing tectonic position is postulated to bring a shallow marine sedimentary regime onto a mid-oceanic tectonic zone. This hypothesis supports the concept of active consuming margin tectonics of the Svalbard Caledonides and explains, for example, the occurrence of the high-P metamorphic rocks in the western part of the present area. 相似文献
The metadiabase-gabbros are moderate-high Fe tholeiites and the Trollheimen volcanics are mainly Na-alkaline, accompanied by a small amount of calk alkaline rocks. The immobile minor and trace element contents indicate that the metadiabase-gabbros are oceanic, similar to the MORB, while those of the Trollheimen volcanics show non-oceanic chemical characteristics and occur in shallow marine, shelf-shelfedge sediments.
The calc-argillo-volcanic formation reveals a shallow marine sedimentary environment and this does not conform with the oceanic nature of the metadiabase-gabbros, occurring in the formation. To overcome this disagreement, an idea of changing tectonic position is postulated to bring a shallow marine sedimentary regime onto a mid-oceanic tectonic zone. This hypothesis supports the concept of active consuming margin tectonics of the Svalbard Caledonides and explains, for example, the occurrence of the high-P metamorphic rocks in the western part of the present area. 相似文献
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油田开发区水体的非点源石油污染试验研究——以胜利油田为例 总被引：4，自引：0，他引：4
本文通过对胜州油田开发区内水体非点污染源的土壤水文类型进行了划分,估算了各非点污染源的油类侵蚀量及其对石油入海通量的贡献。进行了以小流域为单元的非点污染源油类侵蚀的计算,确立了4个重点发生区,提出控制与管理必须以小流域为单元的流域综合治理。 相似文献
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巴丹吉林沙漠沙山区径流与地下水补给条件 总被引：1，自引：0，他引：1
在全球高差最大的巴丹吉林沙漠沙山斜坡上发现了沙漠区罕见的因大气降水而产生的地表超渗径流,地表径流侵蚀,缓渗径流及因地下径流出露而产生的地表径流--风沙混合物理沉积与化学沉积(次生盐).根据电镜观察,能谱分析,化学分析和粒度分析等资料,研究了径流化学沉积物的矿物和化学组成,风积沙和径流--风沙混合物理沉积物的粒度组成,径流类型及沙山区水分平衡,降水对地下水与湖水的补给机制.超渗径流的出现表明,虽然该区降水量少,但存在能够为地下水提供补给来源的较强有效降雨过程.径流,径流--风沙混合物理沉积和化学沉积等六项科学指标从深层次上充分证明,该区降水通过入渗至少达到了沙山的下部,完全能够对地下水构成有效补给.细粒层相对的隔水性是该区地下径流出露于地表的原因.沙山区确实存在令人惊奇的水分正平衡,即在大气降水在经过蒸发和蒸腾等消耗之后,每年还有约134648.4 t/km2水补给了地下水和湖水,成为湖水的重要补给来源之一.沙山区能够产生有效降水,植被稀少蒸腾量少,沙层入渗率高和沙层受蒸发影响深度很小是该区水分出现正平衡和大气降水能够补给地下水的四个条件,也是导致该沙漠区有众多湖泊发育的主要条件. 相似文献