Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana

Details Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana

Mar 1990

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990gecoa..54..683d&link_type=abstract

Geochimica et Cosmochimica Acta, vol. 54, Issue 3, pp.683-698

Mathematics

Logic

3

Scientific paper

Fluid inclusions and graphite are intimately associated in quartz veins that cut high grade metamorphic rocks in the Black Hills, South Dakota, and at the Crystal Graphite Mine in the southwestern Ruby Range, Montana. Measured fluid inclusion compositions and volumetric properties were compared with calculated compositions of graphite-saturated fluids and with estimates of metamorphic P-T conditions and carbon isotope ratios of graphite were measured to evaluate possible sources of carbon in veinforming fluids. Fluid inclusions from the two areas contrast markedly in their reliability as recorders of metamorphic fluid compositions and metamorphic conditions. The 13 C of graphite associated with the veins indicates that the source of carbon was also different in the two areas. In the Black Hills veins, fluid inclusions are dominantly H 2 O---CO 2 mixtures with 24-96 mol% CO 2 and a maximum of ~5 mol% N 2 and ~ 13 mol% CH 4 . Isochores for the highest density inclusions pass near estimated peak metamorphic conditions (550°-600°C, 4.5-6.5 kbar) and fluid inclusion compositions are compatible with thermodynamic predictions for fluids in equilibrium with graphite in the stated P - T range at geologically reasonable f O 2 .Graphite in a 12-cm wall-rock alteration zone adjacent to one of the veins has uniform 13 C of -20.8 ± 0.2%., indicating that carbon in the vein-forming fluid was derived largely from reduced organic carbon. In the Ruby Range, peak metamorphic conditions were higher-- ~750°-850°C, 5-8 kbar. In contrast to the Black Hills veins, fluid inclusions are almost all CO 2 ---CH 4 mixtures (with unknown N 2 content). Many contain > 20 equivalent mol% CH 4 and mixed H 2 O---CO 2 inclusions were observed in only one sample. Inclusions in one vein have ~ 84-97 mol% CH 4 . Virtually all inclusion compositions are incompatible with computed graphite equilibria and inclusion isochores likewise do not pass through estimated metamorphic conditions. The density and composition of most, if not all, inclusions have been modified subsequent to original trapping, possibly through H 2 O loss. The range of 13 C values of vein graphites (-5.8 to -8.6%.) is nearly indistinguishable from values for graphite in dolomitic marble near the veins (-4.8 to -7.1%.). Carbon was probably mobilized through devolatilization reactions in the marble and precipitated as 13 C-rich graphite in the veins at fairly constant temperature and from fluid of fairly constant composition.

Affiliated with

Also associated with

No associations

Rating

Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluid inclusion and carbon isotope studies of quartz-graphite veins, Black Hills, South Dakota, and Ruby Range, Montana will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1887248