Lead, copper, molybdenum, and zinc geochemical anomalies south of the Summitville district, Rio Grande County, Colorado

Preliminary report on the geology of hydrothermally altered areas within the upper Alamosa River basin, Colorado

“…Finally, geochemical sampling of highly altered rock in the Summitville and IABC basins (Sharp and Gualtieri, 1968) show extensive lead anomalies in both areas with smaller anomalies of copper, molybdenum, and zinc. However, traces to appreciable amounts of gold and silver were also detected (<0.1 ppm Au; <0.5 ppm Ag) in altered rocks from the Summitville area, whereas these metals were not detected in samples from the IABC basins.…”

“…The style of alteration, the occurrence of anomalous copper, lead, zinc, and the intimate association with a porphyritic quartz monzonite intrusion spurred substantial exploration activity in the Alum Creek area, specifically as a porphyry copper-molybdenum target. However, the IABC basins were considered poor exploration targets for gold and silver (Sharp and Gualtieri, 1968) because concentrations of these metals in over 200 samples were below analytical detection limits (< 0.1 ppm and <0.5 ppm, respectively). The presence of trace to appreciable amounts of both metals in altered rocks in the Summitville area (Fisher age alteration) is an important distinction between the IABC basins (Conejos age alteration), where altered rocks are apparently devoid of these metals.…”

The architecture of the porphyry-metal system as a prospecting stratagem in the Southern Rocky Mountains

“…Structural but not genetic association (Whitney, 1977) of mineralized rocks with calderas is a prominent congruous property of the San Juan Mountains segment of the southern Rocky Mountains province Lipman and others, 1973;Steven and Lipman, 1976;Steven and others, 1974b). Identification of the Platoro caldera mineralized rocks with the other mineralized rocks of the San Juan Mountain^ is well established geologically (Lipman and Steven, 1971;Steven and Ratte, 1960) and further documented by chemical analyses (Fischer and others, 1968;Fisher and Leedy, 1973;Sharp and Gualtieri, 1976;Steven and others, 1969).…”

“…Published descriptions of the Platoro caldera sample set (Sharp andGualtieri, 1968, 1976;Lipman, 1975) do not include the mineralogical data needed to identify, sample by sample, with the petrographic alteration zones of Crater Creek (table 2). However, calcium and magnesium contents of Crater Creek samples group distinctively ( fig.…”

Journal of Research of the U. S. Geological Survey, 1974, volume 2, issue 4

“…The western, southern, and eastern periphery of the younger caldera localized repeated faulting and intrusive and extrusive igneous activity after the caldera was filled, and the adjacent rocks were extensively altered during several episodes of hydrothermal activity related to emplacement of different intrusive bodies. Major amounts of copper-gold-silver ore were deposited in the Summitville district (Steven and Ratte',I960) late in this period of postsubsidence igneous activity, and anomalous concentrations of various metals are known at other places around the altered and intruded periphery (Calkin, 1967;Sharp and Gualtieri, 1968). Gold-silver veins have also been worked along radial fissure zones in the Stunner-Gilmore district (not shown in fig.…”