Abstract:

Clay minerals of Miocene sedimentary rock and river sediment samples were collected from the Ba River basin in Southern Central Vietnam to evaluate controlling factor on weathering in Miocene and the present time. The analysis results display that Miocene andesitic sedimentary rocks contain high smectite (average 72%) with moderate kaolinite (24%), while Miocene felsic sedimentary rocks consist of high kaolinite (65%) with moderate smectite (25%). River sediments are represented by moderate smectite (43%) and kaolinite (37%). Based on the formation and typical distribution of clay minerals in the Ba River basin can be caused by the occurrence of felsic intrusive rocks and eruptive rocks along with the weak tectonics and tropical East Asia monsoon climate during the Miocene and in the present time. This indicates that lithological composition of parent rocks and East Asian monsoon conditions are significant roles in controlling weathering process, while tectonics play only a subordinate role in the Ba River basin.