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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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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
3.
青藏高原古岩溶的性质、发育时代和环境特征 总被引：7，自引：0，他引：7
青藏高原目前多处所见岩溶地貌主要属第三纪古岩溶之地下部分经后期剥蚀而出露于地表的，风化壳红土和洞穴次生化学沉积等古岩溶相关沉积也多以残留形态出露在已经发生解体的高原主夷平面的南和东南缘，风化壳红土中所含粘粒部分的主要化学成分为SiO2,Al2O3和Fe2O3；粘土矿物多属“伊利石-高岭石”型组合，少数样品属“高岭石-伊利石”型组合，据硅酸系数和粘土矿物组合判断，古岩溶风化壳红土的发育阶段处在化学风化的初期，但由于目前所见红土仅反映当时风化壳剖面根部的化学风化状况，故其较弱的风化指数仍能间接指示古岩溶发育时期湿热的地表环境，扫描电镜观测结果亦表明，风化壳红土中石英砂的表面结构特征以化学溶蚀形成的为主，机械侵蚀形成的为辅，反映了高原风化壳红土垢长期残留特征，对应风化壳发育时期的湿热环境。 相似文献
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Salt exposures and weathering residuum on several salt diapirs in different geographic/climatic settings were studied. Anhydrite,
gypsum, hematite, calcite, dolomite, quartz, and clay minerals are the main constituents of the weathering residuum covering
the salt diapirs in various thicknesses. Erosion rates of residuum as well as of rock salt exposures were measured at selected
sites for a period of 5 years by plastic pegs as benchmarks. Recorded data were standardized to a horizontal surface and to
long-term mean precipitation. For the rock salt exposures the following long-term denudation rates were determined of 30–40 mm a−1 for coastal diapirs and up to 120 mm a−1 for mountain salt diapirs. Long-term mean superficial denudation rate measured on weathering residuum of low thickness reached
3.5 mm a−1 on coastal diapirs. The total denudation rate estimated for the thin residuum is close to 4–7 mm a−1 based on apparent correlation with the uplift rate on Hormoz and Namakdan diapirs. Denudation of rock salt exposures is much
faster compared to parts of diapirs covered by weathering residuum. The extent of salt exposures is an important factor in
the morphological evolution of salt diapirs as it can inhibit further expansion of the diapir. Salt exposures produce huge
amounts of dissolved and clastic load, thus affecting the surrounding of the diapir. 相似文献
5.
黑龙江省北部风化壳的形成及其对砂金成矿的作用 总被引：2，自引：0，他引：2
黑龙江省北部风化壳的形成及其对砂金成矿的作用宋长春张宝林（中国科学院长春地理研究所，长春１３００２１）关键词风化壳砂金次生长大储集体黑龙江省北部地区第三纪准平原化过程形成了广布的风化壳，在部分区段风化壳中储集有大量的金质，表现出明显的金及伴生元素地球... 相似文献
6.
关中平原420-350 ka BP的古土壤与环境 总被引：3，自引：0，他引：3
通过对关中平原双竹村剖面、寇家坡剖面以及蓝田田家坡剖面、三官庙剖面、长安四府村剖面和宝鸡马家塬剖面黄土沉积中第4层古土壤的分析，发现西安、长安、蓝田和宝鸡中更新世中期发育的第4层古土壤已转变成为风化壳，厚度变化在3．5～3．7m之间。它由4层组成，最上部的第1层是发育好的红棕色粘化层(Bts)，第2层是具有铁质胶膜的风化淋滤黄土层(Cs)，第3层是不含铁质胶膜的风化淋滤黄土层(Cl)，第4层是CaCO3结核层(Ck)。对风化剖面中CaCO3含量、pH值、黏土含量，元素Sr、Fe2O3和Al2O3分析，表明该风化剖面受到了较强烈的风化淋溶和黏土化作用，并指示当时的风化淋滤深度明显超出了土壤粘化层的厚度。粘化层中黏土胶膜具亚热带土壤胶膜特征，具超微晶粒结构，由新生的蒙脱石、高岭石和伊利石微晶粒构成，明显定向排列，这是其具有光性的原因。风化壳型古土壤的发育表明，在距今42．35万年前后，黄土高原东南部盛行亚热带气候。这一古土壤剖面构型为Bts-Cs-Cl-Ck-C，它发育时的年平均温度和降水量分别约为16℃和1000mm，比现代关中平原高约30℃和400mm。 相似文献
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