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Importance of mechanical disaggregation in chemical weathering in a cold alpine environment, San Juan Mountains, Colorado

Geological Society of America Bulletin

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Abstract

Weathering of welded tuff near the summit of Snowshoe Mountain (3660 m) in southwestern Colorado was studied by analyzing infiltrating waters in the soil and associated solid phases. Infiltrating waters exhibit anomalously high potassium to silica ratios resulting from dissolution of a potassium-rich glass that occurs as a trace phase in the rock. In laboratory experiments using rock from the field site, initial dissolution generated potassium-rich solutions similar to those observed in the field. The anomalous potassium release decreased over time (about 1 month), after which the dominant cation was calcium, with a much lower potassium to silica ratio. The anomalous potassium concentrations observed in the infiltrating soil solutions result from weathering of freshly exposed rock surfaces. Continual mechanical disaggregation of the rock due to segregation freezing exposes fresh glass to weathering and thus maintains the source of potassium for the infiltrating water. The ongoing process of creation of fresh surfaces by physical processes is an important influence on the composition of infiltrating waters in the vadose zone.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Importance of mechanical disaggregation in chemical weathering in a cold alpine environment, San Juan Mountains, Colorado
Series title:
Geological Society of America Bulletin
Volume
111
Issue:
2
Year Published:
1999
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
304
Last page:
314
Number of Pages:
11