Chemical denudation rates of the western Canadian orogenic belt: the Stikine terrane

摘要: We report in this paper major element and Sr isotopic ratio analyses for 19 rivers draining the Stikine Province Western Canadian Cordillera. Dissolved solutes, suspended sediments river sands were analyzed. The aim of is to calculate chemical denudation rates uplifted accretionary prism, mainly dominated by volcanics volcanic-derived sedimentary rocks. features are their dilute character excess Ca, Mg dissolved load with regards Na. Molar Ca/Na ratios from 2 14, mean value 5.4, observed although region silicate Suspended show close 0.4. Isotopically, most investigated display lower compared load, which very unusual. To account cations, three different hypotheses tested an inversion method allowing us determine origin each solute. first scenario assumes that Ca due dissolution unradiogenic carbonates. second supposes base cations derived preferential Ca- Mg-rich minerals, such as amphiboles. In third scenario, all solutes assumed weathering. cationic weathering silicates, imprecise, order 2–5 tons/km2/year two hypotheses. If taken into account, between 9 15 tons/km2/year. On a global scale, these numbers among lowest found basaltic They however be consistent law established rocks showing rate linearly correlated runoff depend on temperature according Arrhenius law. complex assemblage volcanic subduction/collision geological context thus respond similarly other provinces world. This does not seem true associated CO2 consumption rates. abundance sulfate ions possibly oxidative sulfides, may indeed provide non-negligible part protons necessary Within Canada, geologic province one whose silicates weather at high rate. weatherabilty highest follows: granites