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Helicopter Electromagnetic And Magnetic Survey Of The Upper Animas River Watershed; Application To Abandoned Mine Land Studies
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 17th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, Feb 2004, cp-186-00012
Abstract
A helicopter electromagnetic and magnetic (HEM) survey has been done as part of an abandoned<br>mine land study. An important aspect of this study is to estimate ground water flow paths in the surface<br>and subsurface (bedrock). The apparent conductivity and total field magnetic maps from the HEM<br>survey are used to identify geologic features that can influence ground water flow. The most easily<br>understood studied ground water flow paths are near surface streams and flow through alluvial or<br>colluvial deposits. The HEM data indicates parts of the upper Animas River where bedrock ground<br>water flow may be important. Interestingly the other two major drainages (Cement and Mineral Creek)<br>are not associated with geophysical responses that indicate deep structures. High apparent conductivities<br>near one mine waste pile suggest near surface flow paths and a source for high dissolved solids where<br>high sulfide mill tailings have been removed after the HEM survey. The youngest dacite-rhyolite<br>intrusives show different types of magnetic and electrical properties that may have implications for the<br>occurrence of acid generating lithologies. Apparent conductivity maps suggest a northwest trending<br>structural zone along Cement creek that may control ground water flow. Total field magnetic data<br>suggest northwest trending structures that cross the Silverton Caldera ring fracture system.