Placer-gold deposits of the Las Animas District, Sierra County, New Mexico

Economic geology of some selected mines in the Hillsboro and San Lorenzo quadrangles, Grant and Sierra counties, New Mexico

“…For the Hillsboro and Las Animas districts the principal publications have been those of Harley (1934), Kuellmer (1955), Dunn (1982Dunn ( , 1984, and Segerstrom and Antweiler (1975). The work in the district is supplemented by enlarged geologic maps that were prepared by the author as an outgrowth of the geologic mapping of the Hillsboro and San Lorenzo quadrangles in the early and mid-1970's (Hedlund, 1977a).…”

“…Gold production up to 1931 was about $7 million, using the prices at the time of production (Harley, 1934). The fissure veins yielded about 51,000 oz of gold (Harley, 1934) and the placer deposits about 110,000 oz (Segerstrom and Antweiler, 1975). This indicates that prior to 1931 about one-third of the former production came from the quartz-gold fissure veins.…”

“…Most of the underground mining was done prior to 1893. After the price of gold rose from $20.67 to $35.00 an ounce in 1933, there was renewed mining activity and the placer deposits yielded 15,200 oz of gold from 1932 to 1943 (Segerstrom and Antweiler, 1975). Many of the tailings from this operational period are still visible.…”

Background information to accompany folio of geologic, mineral resource, geochemical, aeromagnetic, and gravity maps of the Hillsboro and San Lorenzo quadrangles, Sierra and Grant Counties, New Mexico, with sections on geochemistry and geophysics

“…The mineral deposits of the Las Animas placer district in order of their past importance are of three main types: (I) the gold placers east of Copper Flat, (2) the gold-bearing fissure veins within the andesite about the Copper Flat stock, and (3) the porphyry copper mineralization within the quartz-monzonite stock of Copper Flat. The gold-bearing fissure veins within the andesite have yielded about 51,000 ounces of gold Segerstrom and Antweiler, 1975) total value of the past gold production has been $6,900,000 . More recently, and beginning about 1953, the quartz-monzonite stock of Copper Flat has been extensively drilled and a relatively lowgrade porphyry copper deposit has been defined.…”

“…Special studies include the mapping and economic appraisal of the gold placer deposits of the Las Animas placer mining district by Segerstrom and Antweiler (1975). The high-temperature pegmatites within the Rabb Park intrusion were studied by Kelley and Branson (I 947).…”