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
|Author(s)||Liu Zhifei1, Colin Christophe2, Huang Wei1, Le Khanh Phon3, Tong Shengqi1, Chen Zhong4, Trentesaux Alain5|
|Affiliation(s)||1 : Tongji Univ, State Key Lab Marine Geol, Shanghai 200092, Peoples R China.
2 : Univ Paris 11, Lab IDES, CNRS, UMR 8148, F-91405 Orsay, France.
3 : Hanoi Univ Min & Geol, Oil & Gas Fac, Hanoi, Vietnam.
4 : Chinese Acad Sci, S China Sea Inst Oceanol, Guangzhou 510301, Peoples R China.
5 : Univ Lille 1, FR 1818, UMR PBDS CNRS USTL 8110, F-59655 Villeneuve Dascq, France.
|Source||Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2007-05-11 , Vol. 8 , N. 5 , P. 1-18|
|WOS© Times Cited||160|
|Keyword(s)||clay minerals, major elements, chemical weathering, Pearl River, Red River, Mekong River|
|Abstract||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 K(2)O/(Na(2)O + 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, (87)Sr/(86)Sr 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.|