Solute profiles in soils, weathering gradients and exchange equilibrium/disequilibrium

White, A. F.; Schulz, M. S.; Stonestrom, D. A.; Vivit, D. V.; Fitzpatrick, J.; Bullen, T.

Abstract:

The spatial and temporal changes in hydrology and pore water elemental and 87/86Sr compositions were used to determine contemporary weathering rates in a 65 to 226 ky old soil chronosequence formed from granitic sediments deposited on marine terraces along coastal California. Cl-corrected Na, K and Si increased with depth denoting inputs from the weathering of plagioclase and K-feldspar. Solute 87/86Sr exhibited progressive mixing of sea water-dominated precipitation with inputs from less radiogenic plagioclase. Linear approximations to these weathering gradients were used to determine plagioclase weathering rates of between 0.38 and 8.9 ?? 10-15 moles m-2 s-1. The lack of corresponding weathering gradients for Ca and Sr indicated short-term equilibrium with the clay ion exchange pool which requires periodic resetting by natural perturbations to maintain continuity, in spite of soil composition changes reflecting the effects of long-term weathering. ?? 2008 The Mineralogical Society.

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Conference Paper

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70033138

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White, A. F.; Schulz, M. S.; Stonestrom, D. A.; Vivit, D. V.; Fitzpatrick, J.; Bullen, T.

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153

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English

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Mineralogical Magazine

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Solute profiles in soils, weathering gradients and exchange equilibrium/disequilibrium; 2008; Conference Paper; Mineralogical Magazine; White, A. F.; Schulz, M. S.; Stonestrom, D. A.; Vivit, D. V.; Fitzpatrick, J.; Bullen, T.