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Mineral and energy resource assessment maps of the Mount Katmai, Naknek, and western Afognak quadrangles, Alaska

January 1, 1994

On the basis of new geologic mapping and exploration geochemical studies, we have provided a mineral and energy resource assessment of the Mount Katmai, Naknek, and western Afognak quadrangles, Alaska. We delineate four tracts of ground that have metallic mineral resources. The mineral deposit types considered in each tract are summarized in table 4. Estimates of the number of undiscovered mineral deposits have been made for porphyry copper and polymetallic vein deposits. We estimate that one undiscovered porphyry copper deposit is present in the Katmai study area at the ten percent probability level. Although the sampling density may be too low to give an accurate estimate of the number of undiscovered polymetallic vein deposits, we suggest that, at a minimum, there is a five percent probability for five or more undiscovered polymetallic vein deposits in the Katmai study area. In addition, several areas have potential for undiscovered porphyry molybdenum, massive sulfide, and epithermal gold and mercury deposits.

Several placer gold claims have been filed in the area; one is still active. One claim, on American Creek, produced a small but unknown amount of gold. Several source areas for gold are identified in this study and would provide potential sources for gold in stream placer deposits given the right hydrologic conditions. Many of these sites in the Kulik Lake area have been prospected with only limited success. However, the upper reaches of lkagluik Creek and some areas of the Rainbow River in the central part of Katmai National Park may also contain undiscovered placer gold resources. Berryhill (1963) investigated the titanium-rich black sand beach placers along the coast of Bristol Bay at Egegik Bay and concluded that they did not constitute a resource for either titanium or gold.

Sand and gravel deposits are locally abundant (Riehle and Detterman, in press) and are adequate to supply local demand. No cinder resources have been delineated.

Energy potential evaluated during the study includes geothermal, oil and gas, and coal resources. A few warm springs were found, but no hot springs areas suitable for geothermal development exist within the study area. Better sites for geothermal resources have been identified on the Alaska Peninsula south of the study area (Smith and Shaw, 1975).

The potential for commercial accumulations of oil and gas in the Naknek, Mount Katmai, and western Afognak quadrangles is low. Area E1, in the Naknek quadrangle along Bristol Bay, has low potential for thermogenic oil and gas (Church, Detterman, and Wilson, 1989). In area E2, oil seeps are along the anticlinal structures both north and south of the Katmai study area. Studies by Magoon and Anders (1992) indicate that the oil is from lower Mesozoic sedimentary rocks. Surface exposures of the Naknek Formation have uniformly indicated poor reservoir characteristics where studied, both here and in the adjacent quadrangles, and the shallow depth of burial of the Naknek Formation probably would result in flushing of the reservoir by meteoric water if oil were present.

Coal seams as much as several meters in aggregate thickness crop out in Tertiary rocks in the Geographic Harbor area. Since these coal beds occur within withdrawn Federal lands, there has been no incentive to evaluate them as coal resources. Given different land accessibility and a local market, these beds could constitute a small marketable coal resource.