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Mineralization, alteration, and hydrothermal metamorphism of the ophiolite-hosted Turner-Albright sulfide deposit, southwestern Oregon

Journal of Geophysical Research

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Abstract

The Turner-Albright sulfide deposit, part of the Josephine ophiolite, formed on and below the seafloor during Late Jurassic volcanism at a back arc spreading center. Ore fluids were probably localized by faults which were active on the seafloor at the time of sulfide deposition. The uppermost massive sulfide formed on the seafloor at hydrothermal vents. The bulk of the sulfide mineralization formed below the seafloor within olivine basalt hyaloclastite erupted near the time of mineralization. Infiltration of hydrothermal fluid into the hyaloclastite altered the rock. The fluid responsible for the hydrothermal alteration was evolved seawater with low pH and Mg and high Fe. The average value of sulfide and the difference between sulfide and contemporaneous seawater sulfate values are similar to ophiolite-hosted sulfide deposits in Cyprus. Mudstone and clinopyroxene basalt above the sulfide horizons were not altered by the ore-transporting hydrothermal fluid, but these rocks were hydrothermally metamorphosed by altered seawater heated by deep circulation into hot oceanic crust. This subseafloor metamorphism produced a mineral assemblage typical of prehnite-pumpellyite facies metamorphism. Exchange with altered seawater increased the whole-rock ??18O of the basalts to values of 9.4-11.2%. -from Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Mineralization, alteration, and hydrothermal metamorphism of the ophiolite-hosted Turner-Albright sulfide deposit, southwestern Oregon
Series title:
Journal of Geophysical Research
Volume
93
Issue:
B5
Year Published:
1988
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research
First page:
4657
Last page:
4674
Number of Pages:
18