Implications of Celsian in the Ruby Mountains, Elko County, Nevada

ABSTRACT
The BaÐfeldspar celsian [BaAl2Si2O8] has been found in
quartz-skarn-sulfide deposits at the American Beauty and Summit
View Mines in the Ruby Mountains, Nevada. The celsian is present
in quartz-skarn-polymetallic sulfide ores formed during Jurassic and
Tertiary phases of skarn formation. Well-shaped microcrystals of
celsian, along with sulfide minerals and apatite, fill cavities in quartz
and are related to a retrogressive hydrothermal mineral paragenesis
that took place during a final stage of contact-metamorphic mineralization
at temperatures of approximately 300¡C. Prismatic crystals
of celsian were subsequently fragmented and rounded during superposed
ductile deformation of the enclosing quartz and became part
of a Tertiary mylonitic fabric at the American Beauty Mine.
According to data reviewed from celsian localities worldwide,
celsian in association with other BaÐfeldspars and BaÐbearing micas
is believed to result from regional or contact metamorphism of VMS
(volcanogenic massive sulfide) or SEDEX (sedimentary-exhalative)
barite-bearing polymetallic and manganese deposits. Thus, celsian
should be considered as a prominent mineral-indicator of metamorphosed
BaÐbearing syngenetic mineralized rock. Formation of celsian
can be described by a simplified empirical stoichiometric reaction
that corresponds to specific metamorphic conditions associated
with desulfurization:
BaSO4 + Al2O3 + 2SiO2 = BaAl2Si2O8 + SO3
Barite Pelitic sediments or Celsian
appropriate aluminosilicate
minerals
The presence of celsian as a prominent phase in skarn in the
Ruby Mountains suggests that early Cambrian or Precambrian(?)
carbonate host rocks contained syngenetic barite-base metal mineralization
prior to the contact metamorphism that is associated with
emplacement of granite intrusions. This speculation is confirmed by
lead isotopic data that show distinct differences in lead-isotopic
compositions of galena from quartz-skarn-sulfide deposits (a narrow
range of 206Pb/204Pb between 18.2 and 18.6) versus temporally associated
igneous rocks (206Pb/204Pb values are greater than 19.2).
Therefore, the igneous rocks cannot be considered as a metal source
for the deposits. Use of a Òcelsian-indicatorÓ may help screen areas
for original pre-metamorphic, mainly syngenetic, barite occurrences
and may provide additional insight in the geological history of specific
mineralized areas.