Carbonate versus silicate weathering in the Raikhot watershed within the High Himalayan Crystalline Series

Major ion chemistry of the Yarlung Tsangpo–Brahmaputra river: Chemical weathering, erosion, and CO2 consumption in the southern Tibetan plateau and eastern syntaxis of the Himalaya

“…Roughly 80-90% of all Ca 2+ and Mg 2+ are derived from the weathering of these carbonates. This result supports previous studies (Blum et al, 1998;Jacobson et al, 2003) which demonstrate that in active tectonic environments, weathering fluxes are often dominated by carbonate weathering processes, even when there is little or no carbonate rock exposed within the catchment. Surprisingly however, hydrothermal inputs from the Himalayan geothermal belt and evaporite weathering in the arid western portion of the Yarlung basin provide significant inputs to many tributaries of the TsangpoBrahmaputra and may strongly affect solute budgets of these streams.…”

“…These types of calcite vein systems have been identified in other tectonically active areas (Koons et al, 1998;Chamberlain et al, 2002;Jacobson et al, 2002) and are thought to form through the development of hydrothermal vein systems. Because calcite dissolution rates are several orders of magnitude faster than plagioclase (Chou et al, 1989;Blum and Stillings, 1995), even small quantities of calcite in veins can exert significant control on Ca 2+ and Sr 2+ fluxes (Blum et al, 1998;Chamberlain et al, 2005). As a result, vein calcite may be an important contributor to cation budgets in Yarlung Tsangpo.…”

Chemical weathering in the Krishna Basin and Western Ghats of the Deccan Traps, India: Rates of basalt weathering and their controls

“…The maximum Ca contribution from carbonates is ϳ29% for the rivers used in calculation This is unlike granites/ gneiss watersheds, where Ca supply from such minor phases are reported to be more significant (Blum et al, 1998;White et al, 1999;Oliva et al, 2004). This difference is attributable to high Ca in basalts, relative ease of their weathering, and their relatively low carbonate content.…”

“…It has been shown in some of the earlier studies on granite watersheds (Blum et al, 1998;White et al, 1999;Jacobson et al, 2002;Oliva et al, 2004) that Ca-rich minor phases such as calcite, apatites, and Ca-rich silicates present in these rocks can be a major source of Ca to rivers draining them. The role of such phases in contributing to Ca budget of Deccan rivers is evaluated below.…”

Chemical weathering under mid- to cool temperate and monsoon-controlled climate: A study on water geochemistry of the Songhuajiang River system, northeast China

“…Blum et al (1998) found that carbonates provide more than 90% of the weathering-yield Ca even though carbonates represent only about 1% of fresh glacial till. It was estimated that this result was valid for a period of 55 ka, and then the mechanical exposure of the rock and the flux derived from carbonate will decrease while the flux derived from silicate weathering will increase (Viers et al, 2004).…”