Projects per year
Regolith formed on both lithologies is highly leached of most labile elements, although Mg and K are less depleted in the granitic than in the volcaniclastic profiles, reflecting residual biotite in the granitic regolith not present in the volcaniclastics. Profiles of both lithologies that terminate at bedrock corestones are less weathered at depth, near the rock-regolith interfaces. Mg fluxes in the volcaniclastics derive primarily from dissolution of chlorite near the rock-regolith interface and from dissolution of illite and secondary phases in the upper regolith, whereas in the granitic profile, Mg and K fluxes derive from biotite dissolution. Long-term mineral dissolution rates and weathering fluxes were determined by integrating mass losses over the thickness of solid-state weathering fronts, and are therefore averages over the timescale of regolith development. Resulting long-term dissolution rates for minerals in the volcaniclastic regolith include chlorite: 8.9 x 10-14 mol m-2 s-1, illite: 2.1 x 10-14 mol m-2 s-1 and kaolinite: 4.0 x 10-14 mol m-2 s-1. Long-term weathering fluxes are several orders of magnitude lower in the granitic regolith than in the volcaniclastic, despite higher abundances of several elements in the granitic regolith. Contemporary weathering fluxes were determined from net (rain-corrected) solute profiles and thus represent rates over the residence time of water in the regolith. Contemporary weathering fluxes within the granitic regolith are similar to the long-term fluxes. In contrast, the long-term fluxes are faster than the contemporary fluxes in the volcaniclastic regolith. Contemporary fluxes in the granitic regolith are generally also slightly faster than in the volcaniclastic. The differences in weathering fluxes over space and time between these two watersheds indicate significant lithologic control of chemical weathering mechanisms and rates.
- Cabot Institute
- chemical weathering
- critical zone
- soil formation
Buss, H. L., Scholl, M., White, A. F. & Shanley, J.
1/10/91 → …
Chemical weathering of volcanic rocks in the tropics: Using small scale studies to determine the mechanisms, rates and impacts of perturbationsAuthor: Moore, O., 14 Nov 2017
Supervisor: Sherman, D. (Supervisor) & Buss, H. (Supervisor)
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)