Clastic-hosted stratiform, vein/breccia and disseminated Zn-Pb-Ag deposits of the northwestern Brooks Range, AK: Are they different expressions of dewatering of the same source basin

Conference · Thu Apr 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5097394

Schmidt, J M ^[1]; Werdon, M B ^[2]

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1. Geological Survey, Anchorage, AK (United States)
2. Univ. of Alaska, Fairbanks, AK (United States). Dept. of Geology

Sphalerite and galena, with significant silver occur in 3 distinct types of mineralization hosted in Upper Devonian and Carboniferous clastic rocks of the northwestern Brooks Range. The best known are Zn-Pb-Ag massive sulfide deposits with variable pyrite, barite, and hydrothermal silifica hosted in Mississippian (to Pennsylvanian ) black siliceous shale and chert, and similar to shale-hosted Pb-Zn massive sulfide deposits worldwide. Zn-Pb-Ag breccias and veins are hosted in Upper Devonian to Lower Mississippian fine-grained quartzites and siltstone which stratigraphically underlie the massive sulfide-hosting units. The breccia-vein and disseminated occurrences are co-extensive with the rocks that host massive sulfide deposits, and with the western part of the Endicott Group clastic basin. Pb isotopic ratios of galena from all the deposits are remarkably uniform, and suggest a single Pb source. The authors genetic model suggests that all types are the result of dewatering of a single clastic source basin. Different mineralization styles are probably due to variable depths of emplacement (at or below the seafloor), thermal variations related to extensional thinning of the crust, and hydrologic flow out of the basin controlled by extensional thinning of the crust, and hydrologic flow out of the basin controlled by extensional faulting and permeability variations in local stratigraphy. The most likely sources for Zn and Pb are clay minerals within the lowermost (Hunt Fork Shale) portions of the western Endicott Group.

• OSTI ID: 5097394
• Report Number(s): CONF-9305259-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALASKA
GEOLOGIC DEPOSITS
GALENA
GEOCHEMISTRY
MINERALIZATION
GEOLOGY
SPHALERITE
CARBONIFEROUS PERIOD
DEVONIAN PERIOD
GEOLOGIC FORMATIONS
GEOLOGIC MODELS
HYDROTHERMAL SYNTHESIS
ISOTOPE RATIO
LEAD
LEAD ORES
MOUNTAINS
PARAGENESIS
SEDIMENTARY ROCKS
SILVER
SILVER ORES
ZINC
ZINC ORES
CHEMISTRY
DEVELOPED COUNTRIES
ELEMENTS
GEOLOGIC AGES
METALS
MINERALS
NORTH AMERICA
ORES
PALEOZOIC ERA
ROCKS
SULFIDE MINERALS
SYNTHESIS
TRANSITION ELEMENTS
USA
580000* - Geosciences