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<br />silver-lead ore; most of it was produced prior to 1900. Production is not recorded <br />for several small mines in the Chief Mountain area near Frisco. nor for a gold <br />placer southwest of Silverthorne. The Primitive Area contains 24 patented mining <br />claims totaling 190 acres. Adjoining parts of the study area contain an additional <br />24'patented claims totaling 126 acres. <br /> <br />Geologic studies and the search for evidence of mineralization entaiied many <br />hundreds of miles of foot traverses over the range and the collection and analysis <br />of a total of 1,212 rock and stream-sediment samples. Visible evidence of mineral <br />deposits in the range is sparse, although many of the faults or fracture zones <br />contain quartz or carbonate veins or veinlets. A few fractures or veins contain <br />visible ore minerals in small amounts. but the great bulk of them do not. and <br />many are nothing more than slightly iron-stained fractured granite or migmatite. <br />Nevertheless. a great many of the fractures are highly anomalous geochemically. <br />Collectively. the anomalies include a remarkably large suite of metals; copper. <br />lead. zinc, gold, silver, molybdenum. bismuth, arsenic, antimony, cadmium, mer- <br />cury, and tin. The contents of such metals in the major anomalous fracture zones <br />is orders of magnitude greater than in the granite and migmatite country rock <br />between the fracture zones. <br /> <br />The geochemical anomalies record the passage of metal-bearing solutions <br />through the fracture system of the range. This occurred during or after the latest <br />major uplift in late Tertiary time. Thus the anomalies are not related to mineral- <br />ization episodes that created the ore deposits in the nearby mining districts of <br />Climax. Leadville, and Gilman. but they are younger. No localized source for <br />them. such as an intrusive body. is evident in either the geology or the magnetic <br />features of the range. No areas of altered rocks exist to suggest the presence of <br />such deposits. The anomalies are concluded to have been formed by metal-bear- <br />ing solutions that diffused into the fault system in small quantity from great <br />depth. probably at the time of scattered igneous activity in west-central Colorado <br />10 to 12 million years ago. The Frontal fault was the master conduit, and any <br />ore deposits that might have been formed at this time are likely to be on or near <br />it. and east of the Primitive Area. as at the Boss mine. Evidence of mineraliza- <br />tion along this fault is greatest in the area between Boulder and South Willow <br />Creeks and is weak from Slate Creek northward. <br /> <br />In summary, the Gore Range-Eagles Nest Primitive Area contains no known <br />ore deposits, and no geologic evidence exists to indicate a likelihood of hidden <br />deposits beneath it, even though many fractures are geochemically anomalous. <br />Chances for the existence of deposits increase eastward from the Primitive Area <br />toward the Frontal fault in the southern half of the area. <br /> <br />The Primitive Area has no potential whatever for coal. oil, or gas, and no-or <br />very low-potential for nonmetallic minerals. East of the Primitive Area, a poten- <br />tial for fluorspar exists in the sedimentary rocks beyond the Frontal fault, al- <br />though only two deposits. or marginal quality, are known there now. On the west <br />side of the range. structures favorable for oil and gas exist but are untested. Test <br />holes in similar rocks 20 miles or more away were nonproductive." <br /> <br />1347 <br /> <br />15 <br />