TY - JOUR
T1 - Mineralogy of rare occurrences of precious-metal-enriched massive sulfide in the Voisey's Bay Ni-Cu-Co ovoid deposit, Labrador, Canada
AU - Kelvin, Michelle A.
AU - Sylvester, Paul J.
AU - Cabricnt, Louis J.
PY - 2011/12
Y1 - 2011/12
N2 - The Voisey's Bay Ovoid Ni-Cu-Co magmatic sulfide deposit, Labrador, is generally poor in precious metals (Pt, Pd, Ag, Au), but unusual occurrences with elevated levels (Pt + Pd > 0.5 ppm) are present. We present a quantitative description of the precious-metal mineralogy of four such occurrences within massive sulfides. The four samples, all from near the center of the Ovoid, were examined by SEM-based Mineral Liberation Analysis for characterization of precious-metal minerals. Distributions of precious metals among the major sulfide minerals were estimated using mass-balance calculations based on bulk assays of the samples and the proportions and compositions of the minerals. The results indicate that the majority of precious metals are present as discrete mineral phases including sperrylite, froodite, michenerite, Au-Ag alloy, volynskite, stützite and acanthite, whereas minor to moderate amounts of Pt, Pd, Ag and Au are found in solid solution in pyrrhotite, pentlandite, chalcopyrite and galena. The precious-metal minerals are normally associated with pentlandite, galena, chalcopyrite, pyrrhotite and magnetite, and rarely with breithauptite (NiSb), altaite (PbTe), other precious-metal minerals and native bismuth. With the exception of sperrylite, which is coarse grained and liberated easily by electric pulse disaggregation, the precious-metal minerals are most commonly found as fine inclusions in pentlandite and galena, and less so as larger attachments. The associations are consistent with previously reported precious-metal mineral data from a hornblende gabbro dyke of the Southeast Extension Zone at Voisey's Bay, demonstrating similar modes of crystallization, which are likely related to crystallization of a highly differentiated sulfide magma in both areas. Processing of Pt from sperrylite and perhaps Pd from froodite could be achieved in ores with a mineralogy similar to the samples described here by grinding, and gravity or flotation methods, but the Au-Ag alloy, volynskite and stützite would likely be too fine to recover as discrete grains for Ag and Au concentration. Instead, the Ag and Au could be recovered as a by-product of Ni-Cu-Co processing of the pentlandite and chalcopyrite, which are the major hosts of the Ag and Au minerals.
AB - The Voisey's Bay Ovoid Ni-Cu-Co magmatic sulfide deposit, Labrador, is generally poor in precious metals (Pt, Pd, Ag, Au), but unusual occurrences with elevated levels (Pt + Pd > 0.5 ppm) are present. We present a quantitative description of the precious-metal mineralogy of four such occurrences within massive sulfides. The four samples, all from near the center of the Ovoid, were examined by SEM-based Mineral Liberation Analysis for characterization of precious-metal minerals. Distributions of precious metals among the major sulfide minerals were estimated using mass-balance calculations based on bulk assays of the samples and the proportions and compositions of the minerals. The results indicate that the majority of precious metals are present as discrete mineral phases including sperrylite, froodite, michenerite, Au-Ag alloy, volynskite, stützite and acanthite, whereas minor to moderate amounts of Pt, Pd, Ag and Au are found in solid solution in pyrrhotite, pentlandite, chalcopyrite and galena. The precious-metal minerals are normally associated with pentlandite, galena, chalcopyrite, pyrrhotite and magnetite, and rarely with breithauptite (NiSb), altaite (PbTe), other precious-metal minerals and native bismuth. With the exception of sperrylite, which is coarse grained and liberated easily by electric pulse disaggregation, the precious-metal minerals are most commonly found as fine inclusions in pentlandite and galena, and less so as larger attachments. The associations are consistent with previously reported precious-metal mineral data from a hornblende gabbro dyke of the Southeast Extension Zone at Voisey's Bay, demonstrating similar modes of crystallization, which are likely related to crystallization of a highly differentiated sulfide magma in both areas. Processing of Pt from sperrylite and perhaps Pd from froodite could be achieved in ores with a mineralogy similar to the samples described here by grinding, and gravity or flotation methods, but the Au-Ag alloy, volynskite and stützite would likely be too fine to recover as discrete grains for Ag and Au concentration. Instead, the Ag and Au could be recovered as a by-product of Ni-Cu-Co processing of the pentlandite and chalcopyrite, which are the major hosts of the Ag and Au minerals.
KW - Genetic model
KW - Labrador
KW - Mass balance
KW - Ni-cu-co deposit
KW - Precious metals
KW - Precious-metal deportment
KW - Precious-metal recovery
KW - Specialized analytical methods
KW - Specialized sample preparation
KW - Voisey's bay
UR - http://www.scopus.com/inward/record.url?scp=84859418769&partnerID=8YFLogxK
U2 - 10.3749/canmin.49.6.1505
DO - 10.3749/canmin.49.6.1505
M3 - Article
AN - SCOPUS:84859418769
SN - 0008-4476
VL - 49
SP - 1505
EP - 1522
JO - Canadian Mineralogist
JF - Canadian Mineralogist
IS - 6
ER -