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Ftining/Milling Plan <br />Exhibit D <br />k. <br />Information presented in the following exhibit describes <br />mining and milling operations conducted by Standard Metals Lor- <br />poration resulting in affected or disturbed acreage at the <br />~ Silverton site. <br />The San Juan Mountains of southwestern Colorado occupy an <br />area of 20,000 to 26,000 km2, consisting of a sequence of middle <br />to late Tertiary lavas and pyroclastic volcanic substrate up to <br />two kilometers thick. The volcanics unconformably overlie meta- <br />morphosed sediments, volcanics, and intrusive strata of Precambrian <br />age, as well as relatively undeformed sedimentary rocks of Paleozoic <br />and Mesozoic age. The majority of the Tertiary volcanics were <br />• erupted from caldera-type eruptive centers. To date, fourteen swch <br />caldera-structures have been identified. Significant economic <br />mineralization has been found associated with eight of these structures. <br />Two caldera centers in particular, the San Juan - Silverton center <br />in the west, and.the Uncompahgre - Lake City center to the east <br />dominated the structural and stratigraphic evolution o~ the Wesi;ern <br />San Juan Mountains. Joint resurgence of the San Juan and Uncompahgre <br />cal deras following eruption of the Sapinero Mesa tuff approximately <br />28 million years ago produced an elongate northeast trenching arch <br />enclosed by the caldera s. Within this arch an apical graben structure <br />was developed. This structure, the Eureka graben is the major struc- <br />tural control for mineralization in the Eureka mining district in <br />which the Sunnyside Mine is located. The northeast trending graben <br />. • <br />~. <br />/ T. <br />._ <br />