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

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. Exceptmore » 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.« less
Authors:
;
Publication Date:
OSTI Identifier:
6005226
Report Number(s):
CONF-8510489-
Journal ID: CODEN: GAAPB
Resource Type:
Conference
Resource Relation:
Journal Name: Geol. Soc. Am., Abstr. Programs; (United States); Journal Volume: 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28-31 Oct 1985
Research Org:
Geological Survey, Denver, CO (USA)
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 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; MAGNESIUM COMPOUNDS; MATERIALS; MINERALS; NORTH AMERICA; ORES; ORGANIC COMPOUNDS; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; PALEOZOIC ERA; RADIOACTIVE MATERIALS; RADIOACTIVE MINERALS; ROCKS; SEDIMENTARY ROCKS; SILICON COMPOUNDS; SILICON OXIDES; SULFATE MINERALS; SULFATES; SULFIDE MINERALS; SULFIDES; SULFUR COMPOUNDS; TRANSITION ELEMENT COMPOUNDS; URANIUM MINERALS; USA 050100* -- Nuclear Fuels-- Reserves, Exploration, & Mining; 580300 -- Mineralogy, Petrology, & Rock Mechanics-- (-1989)