Climatic and tectonic controls on weathering in south China and Indochina Peninsula: Clay mineralogical and geochemical investigations from the Pearl, Red, and Mekong drainage basins
Climatic and tectonic controls on weathering in south China and Indochina Peninsula: Clay mineralogical and geochemical investigations from the Pearl, Red, and Mekong drainage basins
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DOI：
10.1029/2006gc001490
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发表时间：
2007-05-11
影响因子：
3.5
通讯作者：
Trentesaux, Alain
中科院分区：
文献类型：
--
作者：
Liu, Zhifei;Colin, Christophe;Trentesaux, Alain
[1]从珠江、红河和湄公河流域采集的93个泥质样品的粘土矿物学、主要元素地球化学和Sr、Nd同位素分析结果表明，尽管东南亚地区气候条件相似，但这些地区的化学风化程度不同。高岭石/伊利石比值、伊利石化学指数和伊利石结晶度可作为化学风化强度的指标。这些矿物学指标结合K2 O/（Na 2 O + CaO）摩尔比、化学蚀变指数（CIA）和从主量元素结果观察到的风化趋势表明，珠江流域硅酸盐风化作用强烈，湄公河流域硅酸盐风化作用中等至强烈，红河流域硅酸盐风化作用中等。虽然在化学风化和迁移过程中，我们的河流沉积物中Sr Nd（0）值不太可能发生显著变化，但Sr-87/Sr-86比值受高Sr矿物（如斜长石（富含Na和Ca））的各种化学风化状态控制，从珠江、湄公河到红河盆地呈线性下降趋势。研究结果表明，华南和中南半岛半岛的风化侵蚀过程主要受构造因素的控制，而不是温暖的季风气候和强降水的影响。青藏高原东缘和红河断裂系的构造活动和河流下切作用造成的强烈物理侵蚀是红河和湄公河流域低地原生矿物含量高的原因。
[1] Results of clay mineralogy, major element geochemistry, and Sr and Nd isotopes in 93 argillaceous samples collected from drainage basins of the Pearl, Red, and Mekong rivers reveal different degrees of chemical weathering in Southeast Asia despite similar climate conditions across these regions. The kaolinite/illite ratio, illite chemistry index, and illite crystallinity can be used as indicators of chemical weathering intensity. These mineralogical proxies combined with the K2O/(Na2O + CaO) molar ratio, chemical index of alteration (CIA), and weathering trends observed from major element results indicate intensive silicate weathering in the Pearl River basin, moderate to intensive in the Mekong River basin, and moderate in the Red River basin. Although a significant modification of epsilon Nd(0) values in our riverine sediments during chemical weathering and transport is unlikely, Sr-87/Sr-86 ratios are controlled by various states of chemical weathering of high-Sr minerals such as plagioclase (rich in Na and Ca) with a linear decrease trend from the Pearl, Mekong, to Red river basins. Our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south China and Indochina Peninsula. Strong physical erosion caused by tectonic activities and river incision along the eastern margin of the Tibetan Plateau and along the Red River fault system is responsible for high contents of primary minerals in the lowlands of Red and Mekong river basins.