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Bulletin 37—Geology and mineral deposits of Lake Valley quadrangle, Grant, Luna, and Sierra Counties, New Mexico

By H. L. Jicha, Jr., 1954, reprinted 1980, 93 pp., 8 tables, 13 figs., 5 plates, 1 appendix, 1 index.

Lake Valley quadrangle is located about 15 mi north of Deming, in southwestern NM. The area is nearly flat in the southeast, but becomes increasingly rugged in the northwest and southwest, where locally the relief exceeds 1,000 ft.

One of the main structural features is the north-south trending Mimbres Range, a faulted anticlinal high which extends along the west side of the quadrangle as an extension from the Black Range anticline to the north. The Mimbres Mountains terminate at a regional fault which separates them from Cooks Range, a large faulted mass of Precambrian, Paleozoic, and Mesozoic rocks cut by intrusions, in the southwestern corner of the area. A third large structural feature is in Lake Valley fault block in the northeast, in which early and middle Paleozoic limestones and shales have been raised to the level of surrounding Tertiary volcanics. Lesser faults of general north-south and east-west trend are found in many areas, but are difficult to trace for any distance in the volcanic rocks.

Every geologic period, with the exception of the Triassic and Jurassic, is represented by at least one formation. Above the granitic Precambrian basement lies a series of Paleozoic and Mesozoic limestones, sandstones, and shales, represented completely only in Cooks Range. The Tertiary system is represented largely by volcanics, which cover about two-thirds of the area. The earliest series, made up of pyroxene andesites, is followed by pyroxene andesites and latites, which have been intruded by northeast-trending porphyry dikes. Later, quartz latite tuffs and rhyolitic flows were deposited on an erosion surface on the pyroxene andesites and latites. The rhyolites were succeeded by pyroxene andesites and basalts. During Tertiary time there were several periods of erosion and at least one period of faulting. A thick series of fanglomerates, the Santa Fe Formation, which covers a large part of the southern and western area of the quadrangle, was laid down probably in Pliocene or Pleistocene time. Uplift and erosion in Pleistocene and Recent time have yielded the present topography. Late gravels and alluvium were formed during the last erosion cycle.

The five mineralized areas in Lake Valley quadrangle are: the Lake Valley mining district, characterized by oxidized silver-manganese replacement deposits in the Lake Valley Limestone; the Macho mining district, which contains lead-silver vein deposits in pyroxene andesites; the Old Hadley–Graphic district, characterized by copper-lead-zinc-silver veins in pyroxene andesites; and the Cooks Peak and Jose districts, where lead-zinc-silver replacement deposits occur in the Silurian Fusselman Limestone. Lead-zinc deposits were being mined in the Cooks Peak district in 1951. Late in 1953 the Cooks Peak district was inactive, but preparations were being made to mine and concentrate manganese ores in the Lake Valley district, where manganese mining began again early in 1954. Several other smaller prospects also are known. The mineralization is believed to be of Tertiary age, since it occurs both in pyroxene andesites and in Paleozoic rocks. Masses of perlite have been found in the rhyolite flows.

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