Paragenesis and conditions of formation of ore minerals from metalliferous breccia pipes, N. Arizona

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6005226

Wenrich, K J; Pratt, L M

Ore deposits within N. Arizona breccia pipes are currently being exploited for U, but at various times during the past century Cu, Pb, Zn, and Ag were mined. These pipes formed as solution-collapses within the Mississippian Redwall Ls and stopped upward through overlying strata. The principal ore minerals are: uraninite, chalcopyrite, chalcocite, tennantite-tetrahedrite, galena, sphalerite, millerite, gersdorffite, siegenite, and molybdenite. Common gangue minerals are marcasite, pyrite, barite, dolomite, calcite and quartz. Marcasite and pyrite appear to have formed prior to the ore minerals, followed closely by chalcopyrite. The Ni and Co phases also appear to be early: gersdorffite crystals are rimmed by later galena. Tennantite-tetrahedrite formed later than both galena and sphalerite; uraninite, the latest ore mineral, consisting fills interstices. Primary fluid inclusions in dolomite, quartz, and sphalerite show filling temperatures from 80 to 145/degree/C and high salinities, averaging 15 wt% NaCl (eq). Secondary inclusions in sphalerite have consistently higher filling temperatures from 105 to 173/degree/C, but similar salinities. Rock-Eval pyrolysis of pyrobitumen yields little or no volatile hydrocarbons (S/sub 1/=0-0.2 mg/gm), but large amounts of pyrolytic hydrocarbons (S/sub 2/=105-216 mg/gm). Temperatures of maximum pyrolytic yield are relatively low (424-430/degree/C), suggesting temperatures did not exceed 150/degree/C following pyrobitumen emplacement. Except for uraninite, the breccia pipes are similar to Mississippi Valley-type (MVT) deposits in mineralogy, fluid-inclusion filling temperatures and salinities, and associated organic material. Because MVT deposits do not host U minerals, a possible two-stage mineralization history of the pipes is suggested, the first by a MVT brine and perhaps a second forming the uraninite.

• Research Organization: Geological Survey, Denver, CO (USA)
• OSTI ID: 6005226
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28-31 Oct 1985
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
ARIZONA
URANIUM ORES
MINERALIZATION
MINERALOGY
BARITE
BRINES
CHALCOPYRITE
DOLOMITE
GALENA
GEOLOGIC HISTORY
GEOTHERMOMETRY
HYDROCARBONS
INCLUSIONS
LIMESTONE
MISSISSIPPIAN PERIOD
PARAGENESIS
PYRITE
QUARTZ
SPHALERITE
URANINITES
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM SULFATES
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER SULFIDES
FEDERAL REGION IX
GEOLOGIC AGES
IRON COMPOUNDS
IRON SULFIDES
LEAD COMPOUNDS
LEAD SULFIDES
MAGNESIUM CARBONATES
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MATERIALS
MINERALS
NORTH AMERICA
ORES
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PALEOZOIC ERA
RADIOACTIVE MATERIALS
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ROCKS
SEDIMENTARY ROCKS
SILICON COMPOUNDS
SILICON OXIDES
SULFATE MINERALS
SULFATES
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
URANIUM MINERALS
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