Atomic force microscopy of differential weathering in real time
- Univ. of South Dakota, Vermillion, SD (United States). Dept. of Chemistry
Differential weathering of a rock sample was observed in-situ using atomic force microscopy (AFM). The sample contained fayalite intergrown with veins of magnetite and serpentine. Analyses consisted of polishing the sample with alumina and recording AFM scans periodically during subsequent exposure to nitric acid. Immediately after polishing, serpentine areas were recessed compared to fayalite and magnetite, which were similar in height. As weathering proceeded, both serpentine and magnetite areas protruded from the fayalite surface, and no significant change in the relative heights of magnetite and serpentine features was observed. This suggests that serpentine is less resistant to mechanical weathering than fayalite or magnetite but that serpentine and magnetite are both more resistant to chemical weathering than fayalite. Differential weathering rates between fayalite and magnetite, on the order of a few unit cells per minute, were determined in various nitric acid concentrations by measuring the difference in height between the two minerals as a function of time. A dissolution rate law for fayalite was determined by comparing the rates for different concentrations of nitric acid and assuming the dissolution of magnetite was negligible compared to that of fayalite. The rate law from this study is Rate = 7.7* [HNO[sub 3]][sup 0.45] nm/min which is in good agreement with previously reported rate laws for olivine dissolution.
- OSTI ID:
- 6975416
- Report Number(s):
- CONF-9404217-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 26:5; Conference: 27. annual conference of the North-Central Section of the Geological Society of America (GSA), Kalamazoo, MI (United States), 28-29 Apr 1994; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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