CONSTRAINTS FROM FLUID-INCLUSION DATA ON THE ORIGIN OF THE JUBILEE
CARBONATE-HOSTED Zn-Pb DEPOSIT, CAPE BRETON, NOVA SCOTIA*
GUOXIANG CHI, MARTINE M. SAVARD and YVON HÉROUX
Geological Survey of Canada, Quebec Geoscience Centre, P.O. Box 7500, Sainte-Foy, Quebec G1V 4C7
* Geological Survey of Canada contribution number 31794.
Abstract
Aqueous (Aq) and hydrocarbon (HC) fluid inclusions were studied in fibrous calcite (pre-ore),
sphalerite, and coarse, anhedral calcite (syn- to post-ore) of the Jubilee Zn-Pb
deposit, Cape Breton, Nova Scotia. The deposit is hosted by a limestone breccia at the top
of the Macumber Formation (limestones) and under the Carrolls Corner Formation (evaporites). Aq inclusions from
different minerals have similar temperatures of first melting (- 62.1 to -46.7 C), indicating a H2O-NaCl-CaCl2
compositional system. Salinities (wt%), NaCl/(NaCl + CaCl2) weight ratios, and temperatures of
homogenization (Th) of Aq inclusions range from 21 to 27%, 0.16 to 0.73, and 53 to
79 C for fibrous calcite, 15 to 24%, 0.26 to 0.64, and 59 to 228 C for sphalerite, and 12 to 24%, 0.17 to 0.72, and
66 to 224 C for anhedral calcite. The Th -salinity correlation suggests that a high-temperature, high-salinity fluid
first mixed with a low-temperature, high-salinity fluid, then mixed with a fluid of low temperature
and salinity. HC inclusions coexist with Aq inclusions. The Th of HC inclusions ranges from 34 to
89 C for fibrous calcite, 46 to 87 C for sphalerite, and 31 to 238 C for anhedral calcite. Fluid pressures estimated
from the intersection of isochores of coexisting Aq and HC inclusions ranges from 175 to 363 bars
for the fibrous calcite, and from 160 to 398 bars for the anhedral calcite. The microthermometric data suggest that
the Jubilee deposit formed from a hot, metal-carrying brine in a shallow environment (probably less than 1500
m) characterized by a low background temperature. Hydrocarbons migrated into the limestone breccia
before the mineralizing event, reacted with oxidized sulfur derived from the evaporites, and produced a
reservoir of reduced sulfur available for mineralization when the metal-carrying brine migrated through.
Keywords: Zn-Pb deposit, carbonates, aqueous fluid inclusions, hydrocarbon fluid inclusions, basinal
brines, Jubilee, Cape Breton, Nova Scotia.