Sultan Mountain mine, western San Juan Mountains, Colorado: A fluid inclusion and stable isotope study

Journal Article · Tue Jan 01 00:00:00 EST 1991 · Economic Geology (plus the Bulletin of the Society of Economic Geologists); (United States)

DOI:https://doi.org/10.2113/gsecongeo.86.4.768· OSTI ID:6954571

Musgrave, J A ^[1]; Thompson, T B ^[2]

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1. Los Alamos National Lab., NM (United States)
2. Colorado State Univ., Fort Collins, CO (United States). Dept. of Earth Resources

The Sultan Mountain (SM) mine, in the western San Juan Mountains of Colorado, has produced Cu-Pb-Zn-Ag-Au ores from the mid-1870s until the 1950s. Production was from veins filling faults and fissures along the southern margin of the Silverton caldera. The principal host rock to the veins is a quartz monzonite stock. Five periods of hypogene mineralization have been recognized: (1) early quartz-pyrite; (2) quartz-pyrite; (3) rhodochrosite-siderite; (4) main ore-stage chalcopyrite, tetrahedrite, galena, sphalerite, and gold; and (5) quartz-fluorite. Evidence of open-space filling (banding, crustification, vugs) is widespread. Heating studies of fluid inclusions in quartz, rhodochrosite-siderite, sphalerite, and fluorite indicate temperatures were approximately 200 C for stages 1 to 4 and 186 C for stage 5. Stages 1, 2, and 4 show evidence of boiling. Crushing studies indicate that high-pressure gas, probably CO[sub 2], is present in the fluid inclusions. Freezing point depression estimates of salinity, corrected for CO[sub 2], indicate a range of 13.6 to 1.3 wt percent NaCl equiv. These data together with P-V-T data for saline solutions and P[sub CO[sub 2]] = 38 bars give a minimum depth of formation of 600 m. The [delta][sup 18]O values suggest hydrothermal fluids were predominantly composed of meteoric water which underwent isotopic exchange with the quartz monzonite. Carbon isotope data are inconclusive as to the source of the carbon. The [delta][sup 34]S values for sulfides suggest a Paleozoic evaporite source for most of the sulfur. Geologic and geochemical studies suggest a model of SM ore deposition in which predominantly meteoric hydrothermal solutions, restricted mostly to the SM area, scavenged metals from the Precambrian basement and the Tertiary volcanic and intrusive rocks. The primary mechanism of precipitation of the ore was an increase in pH as a result of boiling.

• OSTI ID: 6954571
• Journal Information: Economic Geology (plus the Bulletin of the Society of Economic Geologists); (United States), Vol. 86; ISSN 0361-0128
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COLORADO
GEOLOGIC DEPOSITS
GEOCHEMISTRY
COPPER ORES
EXPERIMENTAL DATA
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GOLD ORES
INCLUSIONS
ISOTOPE RATIO
LEAD ORES
MINERALOGY
ORIGIN
PARAGENESIS
RESERVOIR ROCK
SILVER ORES
ZINC ORES
CHEMISTRY
DATA
DEVELOPED COUNTRIES
INFORMATION
NORTH AMERICA
NUMERICAL DATA
ORES
USA
580000* - Geosciences