Overview of Results from the Greenstone ... - Geology Ontario

sheet flow facies, channelized sheet flow facies, lava channel facies, lava pond facies, lava lobe facies,
and distal pyroclastic and/or epiclastic facies. Worldwide, most Ni-Cu-PGE mineralization is hosted by
lava channels, channelized sheet flows and, rarely, within vent facies. Komatiite flow fields have never
been mapped directly, but komatiite volcanic facies have been interpreted to vary on the scale of an entire
flow field and also on the scale of individual flow units. This complexity of lava facies makes it difficult
to predict the locations of mineralized lava channel or channelized sheet flows, except that they most
often (but not always) occur at or near the bases of individual komatiite sequences. Our work suggests
that the identification of variations within barren volcanic facies is particularly important as it can
potentially vector toward ore-forming environments. As these types of deposits are usually found within
deformed Archean and Proterozoic greenstone belts, a multidisciplinary approach including geological
mapping, volcanic facies mapping, geophysical surveys, and geochemical studies are required to aid in
the exploration for these deposits and to facilitate the recognition of favourable volcanic sequences that
may host magmatic Ni-Cu-(PGE) sulphide mineralization.
GOLD MINERALIZATION SUBPROJECTS
Timmins Subproject
The Timmins–Porcupine gold camp is the largest lode gold camp in Earth’s Archean greenstone belts
(Witwatersrand aside). It hosts several deposits are dispersed over 35 km, and together produced 63.7
million ounces gold, which is far ahead of other districts in the province (Groves et al. 2005). These
deposits are distributed along the northern margin of an originally south-dipping Porcupine–Destor
deformation zone (PDDZ). Herein lies one of the structural anomalies to be resolved: Why the gold
deposits apparently lie in the footwall of this shear zone, contrary to other Archean gold camps such as
Val d’Or and Kalgoorlie? Other uncertainties concerning these gold deposits include the kinematics and
timings of deformations; the presence or absence of foliation predating the deposition of the Timiskaming
assemblage; the relative timing of the several generations of quartz-carbonate veins and styles that have
long been known (at least in general terms) in this camp; and the way in which an evolving orogenesis
determines the geometry and kinematics of coeval gold mineralization. Research carried out involved
mapping, and geochemical analysis of samples north of the PDDZ, principally in Tisdale, Hoyle and
Whitney townships. A structural scheme, with refinements to the stratigraphic column and
geochronology, has been constructed for the Timmins–Porcupine gold camp in order to develop the
constraints applying to these matters (Figure 26; Bateman et al. 2005).
Unconformities or disconformities have been identified between each assemblage (Ayer, Amelin et
al. 2002) mapped in the gold camp: between Tisdale and Deloro; between Porcupine and Tisdale; and a
long recognized unconformity between the Timiskaming and the Porcupine–Tisdale assemblages. Some
formations have been shown to be correlatives: the terms Beatty and Hoyle formations apply to turbidites
that occur in different parts of the camp, and have been shown to be of the same age (~2688 Ma). The age
of the albitite dikes at the McIntyre Mine has been confirmed at 2672.8±1.1 Ma, and a second albitite
dike and a porphyry intrusion in the vicinity of the Pamour Mine have ages of 2676.5±1.6 Ma and
2677.5±2.0 Ma, respectively, the latter being considerably younger than the 2685 to 2690 Ma age of the
other dated porphyries and the Krist formation. Geochemical sampling and analysis (compared with
unpublished Porcupine Joint Venture data) of basalts and komatiites have allowed the subdivision of the
Tisdale assemblage into 4 formations that have been traditionally defined on lithological and textural
grounds. These formations—the Hersey Lake komatiite (2 subgroups), Central formation (3 subgroups),
Vipond formation and Gold Centre formation—are distinguished on the basis of Fe total -MgO-TiO 2 -V-Zr-
Y-Ni-Cr-REE. Lavas in one Central formation subgroup show distinct boninitic affinities (Kerrich et al.
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