The Seaman Gulch area is located approximately 20
miles east of Redding, California and is part of the
eastern Klamath lithotectonic belt.
Rock units of the area are chiefly mafic and silicic
volcanics of island arc affinity and shale that are Permian
to Triassic in age. Volcanic rocks of Tertiary and
Quaternary age unconformably overlie the pre-Tertiary
rocks. All pre-Tertiary rocks have been altered by hydro-thermal
and(or) metamorphic processes.
Stratabound epigenetic mineralization is hosted by
metadacitic pyroclastics of the Bully Hill Rhyolite. The
hypogene sulfide minerals present are pyrite, sphalerite,
chalcopyrite, tetrahedrite-tennantite and galena. Minor
amounts of supergene chalcocite are found. These sulfides
occur as disseminations, stringer veinlets, massive pods
and an irregular network around pyroclastic fragments.
Controls that localized the occurrences of sulfides are
intrusive rock-country rock contacts, permeability and
porosity of pyroclastic rocks, faults, and fractures. The
gangue mineralogy of the stringer veinlets consists of
quartz, carbonate, and anhydrite. The distribution of
sulfide minerals is zoned vertically and from bottom to top
as follows: pyrite - chalcopyrite as disseminations and
stringer veinlets; pyrite - sphalerite - chalcopyrite as
disseminations, stringer veinlets, and networks; and pyrite
- sphalerite - chalcopyrite - tetrahedrite-tennantite -
galena as disseminations, stringer veinlets, and massive
pods. Hydrothermal alteration assemblages are chloritic
alteration, quartz - white mica alteration, propylitic
alteration, silicification, argillic alteration, and
carbonate alteration. These alteration assemblages display
both vertical and lateral zonations. A central zone of
chloritic alteration grades laterally into propylitic
alteration, and upward into quartz-white mica alteration.
The quartz - white mica alteration in turn grades laterally
into propylitic alteration. Argillic alteration and
carbonate alteration are genetically related but slightly
later events that overprint the earlier assemblages.
The mineralization in the Seaman Gulch area is similar
to the stockwork zone that underlies Kuroko-type volcano-genic
massive sulfide deposits. The sulfides and their
associated products of hydrothermal alteration were deposited
during submarine geothermal activity that was
operative during the latest Permian time.
The economic potential of the Seaman Gulch area is
considered to be low because of the paucity of base metalbearing
sulfides, their occurrence as chiefly
disseminations and veinlets, and the restricted distribution
of economic assays.