Seminar

Silicate weathering is a fundamentally important process to remove CO₂ from the atmosphere. This, coupled with other processes in the carbon cycle, has helped regulate climate over multimillion-year timescales through a strong negative feedback mechanism. Southeast Asia theoretically features some of the highest global weathering rates due to the hot and humid tropical climate and the continuous supply of fresh silicate material via the active tectonics; however, Southeast Asian rivers remain poorly studied. Riverine lithium isotopic values provide a direct tracer on silicate weathering processes due to how Li fractionates during silicate weathering; however, the direct utility of Li isotopes remains unclear, with ongoing debates about how local weathering conditions impact riverine δ⁷Li values. Here we present δ⁷Li isotopic, elemental and clay mineralogical compositions from Hong Kong, the Mariana Islands and Malaysia Borneo to examine how local factors (i.e., lithology and tectonic setting) affects riverine geochemistry. Overall, our geochemical data reflects the differences between the local weathering regimes in our sampling regions. For example, the δ⁷Li values between Hong Kong and the Mariana Islands show large variations and this can be attributed to differences in the local tectonic setting. This work provides a solid groundwork for further studies to understand the impact that Southeast Asia has towards both global silicate weathering fluxes and the oceanic Li budget.

Additional information: Mr. Chris Tsz Long CHEUNG, ctlc@connect.hku.hk