Strontium, hydrothermal systems and steady-state chemical weathering in active mountain belts

We compare model results with Sr fluxes and isotopic composition of riverine waters from the Southern Alps of New Zealand, an area that is frequently used as an example of a steady-state collisional orogen. As our model predicts, roughly 50% of Sr flux is from the weathering of calcite in the areas of highest uplift along the west-flank of the Southern Alps. This proportion decreases substantially (< 20% from calcite) in the areas of lower uplift east of the Southern Alps. Because chemical weathering rates are approximately a factor of two higher in the rapidly uplifting areas as compared to the more stable regions a significant portion of strontium flux from rivers on South Island of New Zealand is from the weathering of calcite.