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<br /> <br />GEOCHEMICAL INVESTIGATION REPORT <br />PROPOSED LINE CAMP OPEN PIT ALLUVIAL GRAVEL MINE <br />MONTEZUMA COUNTY <br />DOLORES,COLORADO <br />BACKGROUND <br />Geology. <br />The proposed operation lies within alluvium of the Dolores River. Alluvial gravel exposed <br />along the river adjacent to the site comprises boulders, cobbles, and pebbles containing <br />about 90% andesite and latite, 5% orthoquartize and/or quartz sandstone, and less than <br />about 1% each of basalt, shale, non-andesitic and non-latitic conglomerates, siltstone, and <br />traces of greenstone (a rock assemblage composed of epidote, quartz and chlorite with <br />minor calcite). These rock names are based on field-scale observations, not microscopic or <br />chemically-based identifications. Rocks described in the literature typically are much <br />more inclusive and mineralogically specific. <br />The majority of alluvial gravel derive apparently from erosion of the San Juan volcanic <br />units. (This is parenthetically interesting because exposures of the San Juan volcanics <br />today do not erode into the Dolores River canyon, so must represent deposition of Dolores <br />River alluvial valley fill at a time when the volcanics extended more westerly, or prior to <br />uplift or stream capture that segregated the river from the volcanics.) Most of the other <br />rocks -the sandstones, shales, siltstones, and conglomerates -are from units exposed <br />along the canyon walls. <br />Mineral Deposits. <br />Base and precious metal mineral deposits occur in the Dolores River headwaters, near <br />Rico on Silver Creek and a few sites on the West Dolores River. A few greenstone <br />cobbles and iron-stained sandstone cobbles at the proposed Line Camp area appear to be <br />the only rocks related to mineral deposits in the headwaters. In general, rocks that would <br />be expected to be associated with mineralization and hydrothermal alteration of the type <br />found in the Dolores headwaters and the La Plata Mountains -rocks that might be <br />anticipated to be related to release of acid or toxic forming substances -are absent. <br />Manganese oxide coatings on all rock types persist near the water line of the river. During <br />a site inspection in March of this year, mineral salts were not especially evident. Mineral <br />