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COLORADO

The Lost Mine on Slate Mountain

GEOLOGY OF THE AREA

The Sawatch Range of central Colorado stretches nearly 80 miles in a north-northwest direction from Monarch Pass to the Eagle River, just southwest of Vail. Rising up 12,550 feet, New York Mountain is the northernmost peak of the Sawatch chain. It broods just north of the 13,365-foot mountain known as Gold Dust Peak. The northern terminus of the Sawatch Range is drained by two major stream systems. These include the Lake Creek watershed and the Brush Creek watershed.

The northern prong of the Sawatch Range consists of an uplifted core of ancient Precambrian metamorphic basement rock intruded by 1.7 billion year old foliated granites and younger 1.4 billion year old anorogenic granites. The Precambrian core of the Sawatch Range is girdled by a band of Cambrian to Mississippian-age sediments which forms the lower foothills of the range. Pennsylvanian to Permian red beds crop out west and northwest of the Sawatch Range and lap up against the mountain front in many areas. Younger Triassic to Cretaceous clastic sedimentary rocks occur just west of New York Mountain.

 

The Fulford area on Brush Creek is dominated by a large Laramide porphyry intrusion surrounded by Mesozoic and Paleozoic sedimentary rocks. The Laramide intrusion crops out at the head of Brush Creek, near New York Mountain. It cuts through Mississippian limestones, Pennsylvanian-Permian red beds, and Triassic to Cretaceous clastic sedimentary rocks.

Mineralization in the Fulford District consists of both veins and replacement deposits containing native gold, argentite, chalcopyrite, galena, and pyrite. Polymetallic veins and fracture fillings occur around and within the Laramide porphyry intrusion located at the head of Brush Creek, near New York Mountain. There are also replacement deposits on New York Mountain that are likewise associated with the intrusion. These replacement bodies are emplaced within Mississippian carbonate rocks. Like most of the great gold-producing districts in Colorado, the deposits at Fulford consist of hypabyssal polymetallic veins and replacement deposits associated with either Laramide or mid-Tertiary intrusive systems.

PROSPECTING POTENTIAL

The northern terminus of the Sawatch Range presents the modern-day prospector with wonderful possibilities for future mineral strikes. First of all, the country is extremely rugged and difficult to negotiate. The mountains are prone to landslides and avalanches and have taken a toll on those who wander their slopes. Consider the Buck Rogers party in 1849 and Arthur Fulford's demise on New York Mountain in 1892. And yet, it is entirely possible that a hidden vein or mine portal still exists in the area. After all, new silver strikes were made in the area in 1912 and 1913, some 20 years after the initial rush in the 1890's.

Prospectors may want to focus on the Laramide porphyry intrusion at the head of Brush Creek and the surrounding sedimentary rocks. Particular attention should be paid to the carbonate formations as they are favorable sites for the

emplacement of skarn deposits and replacement bodies. Prospectors may also want to focus on the various shale formations in the area as these may have been misidentified as "slates" by Buck Rogers back in 1849. Prospectors should also concentrate on the scoured and abraded slopes of New York Mountain, especially those lying directly above large deposits of talus and landslide debris. These talus piles may also conceal a vein or mine portal so they should not be overlooked. Prospectors should probably search the rugged slopes of the mountains just below treeline in the area extending from Gold Dust Peak northward to New York Mountain and then northwestward to Porphyry Mountain. They may also want to search the northeastern slopes of the mountains above Lake Creek as rumors of a lost mine in that area also exist. A metal-detector may be useful in the search for gold-bearing float in the talus deposits and boulder fields on New York Mountain.