Abstract

Info

Title:: Effects of Lithology on Chemical Weathering: Comparison of Granite and Andesite in Subtropical Climate

Author(s):: SUN Ming-zhao; QU Shu-yi; LI Lai-feng; LI Le; WU Wei-hua; 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, Jiangsu, China; 2. Key Laboratory of Surficial Geochemistry of Ministry of Education, Nanjing University, Nanjing 210023, Jiangsu, China

Keywords:: chemical weathering; lithology; granite; andesite; silicate; carbonate; subtropical; Yunnan

Abstract:: Silicate weathering, which is known as earth’s thermostat, affects earth’s long-term climate change. There are many factors to control the silicate weathering rate, including lithology, vegetation, climate and tectonics. A small area of tens of square kilometers near Beihai wetland of Tengchong city, Yunnan province, was selected to discuss the effects of lithology on the silicate weathering rate. The area develops two kinds of lithology, including granite and andesite; the granite and andesite watersheds have the same tectonics, climate and vegetation conditions. Based on the above situations, 4 river water and 1 rain water samples in Beihai wetland were collected to carry out the calculation of water chemical mass balance. The results show that the average values of the contribution of atmospheric inputs, silicate weathering and carbonate weathering to major cations in sampling watershed are 8.1%, 76.5% and 16.0%, respectively; the average values of silicate and carbonate weathering rates are 5.68, 9.96 t·km^-2·a^-1, the atmospheric CO₂ consuming rates are 2.68×10⁵, 0.29×10⁵ mol·km^-2·a^-1; the weathering rates of granite and andesite are 3.22, 8.14 t·km^-2·a^-1, respectively. The weathering rate of andesite is 2.5 times than that of granite, indicating that the effects of lithology on silicate weathering are dominant under the same conditions of vegetation, climate and tectonics.