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Ferricrete, manganocrete, and bog iron occurrences with selected sedge bogs and active iron bogs and springs in the ... (1831 words) |
 | Ferricretes (stratified iron and manganese oxyhydroxide-cemented sedimentary deposits) are one indicator of the geochemical baseline conditions as well as the effect that weathering of mineralized rocks had on water quality in the Animas River watershed prior to mining. |
| Thus, by knowing where ferricrete is preserved in the watershed today, land-management agencies have an indication of (1) where metal precipitation from weathering of altered rocks has occurred in the past, and (2) where this process is ongoing and may confound remediation efforts. |
| Ferricrete is one indicator of pyrite oxidation and acid rock drainage that have been ongoing in this region since the late Pleistocene. |
| ESTIMATING PRE-MINING WATER QUALITY USING FERRICRETE (465 words) |
| Ferricrete terraces mapped and radiocarbon-dated as Holocene age, discovered along many of these streams appear to be the result of acid rock drainage from sulfide mineral weathering, and suggest that streams in these watersheds may not have met aquatic or human health, water quality criteria prior to mining. |
| Based on an empirical trace metal relationship between the terrace deposits of ferricrete in Fisher and Daisy Creeks and the modern iron oxyhydroxide precipitates presently forming in the streams, the longitudinal dissolved metal and pH continuum that existed along these streams before any mining disturbance occurred can be reconstructed. |
| For each ferricrete sampling location along the stream, the precipitate metal value is substituted by the ferricrete value in the equation to calculate the composition and pH of the paleo-stream. |
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