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

Albitite dikes are crosscut by gold-bearing veins in the Hollinger–McIntyre Mine (Burrows et al.
1993) and give a maximum age for the bulk of vein quartz gold mineralization. An albitite dike, which
postdates the Cu-Au-Ag-Mo porphyry-style ore body hosted by the Pearl Lake porphyry at depth in the
McIntyre Mine, provided an age of 2673+6/–4 Ma (Corfu et al. 1989). In order to further refine the timing
of gold mineralization in Timmins, additional zircons were collected from this sample and now have
provided a more precise age of 2672.8±1.1 Ma (#13: Table 1, Figure 4E). This age is within error of the
2671.5±1.9 Ma age for an inter-mineral lamprophyre dike cutting early replacement-style gold
mineralization (Lightning zone) at the Holloway Mine and demonstrates that there is more than one age
for Abitibi orogenic gold deposits (Ropchan et al. 2002). Albitite dikes were also observed to intrude
sedimentary rocks and ultramafic volcanic rocks near the Destor–Porcupine deformation zone in Whitney
Township (E. Barr, Placer Dome (CLA) Ltd., Porcupine Joint Venture, personal communication, 2004).
An 8 m wide albitite dike cutting ultramafic volcanic rocks in this area yielded an age of 2676.5±1.6 Ma
(#20: Table 1, Figure 5F). This age is within error of the Pamour porphyry age of 2677±2.0 Ma, but is
slightly older than the McIntyre albitite dike.
LATE TECTONIC INTRUSIONS
Late-tectonic intrusions range in age from about 2670 to 2660 Ma and occur throughout the SAGB
(Heather, 1998; Davis et al. 2000). They are typically massive and occur within batholiths and the
greenstones. They consist of “Algoman” biotite granite, pegmatite and biotite-muscovite S-type granite.
The only geochronology from this type of intrusion within the study area is an age of 2663.3±3.3. Ma
from “porphyritic granitoid” of the Prosser stock in southwestern Prosser Township (Bleeker, Parrish and
Sager-Kinsman 1999). An age of 2662±4 Ma from a massive biotite granite in Desrosiers Township
(Heather 2001) occurs within the Algoman Somme pluton within the Kenogamissi batholith and extends
into the southwestern corner of the study area (see Figure 2). On the Quebec side of the Abitibi, the latest
Archean intrusions are the flat-lying, garnet-bearing, Pressiac and Lamotte monzonite intrusions which
have been dated at 2660 Ma (Chown, Harrap and Moukhsil 2002).
Structural Framework
GEOPHYSICAL INTERPRETATIONS OF GREENSTONE BELT
ARCHITECTURE AT DEPTH
Reflection Seismic Interpretation
Pre-existing and new Discover Abitibi geophysical data have improved our understanding of lithological
and structural features at depth. The new Discover Abitibi reflection survey is the first seismic survey in
the Abitibi where the acquisition parameters were designed to allow imaging of near-surface,
economically important structures and stratigraphy. The Discover Abitibi reflection seismic profiles thus
provide direct insight into the architecture of the greenstone belt, particularly in the Timmins region
(Reed, Snyder and Salisbury 2005). The base of the greenstone belt is imaged at about 8 km depth in the
northern part of the North Timmins–Crawchest seismic line (Reed, Snyder and Salisbury 2005). Major
lithologic contacts such as the Tisdale – Kidd–Munro assemblages contact in central Tully Township and
unconformable contacts such as the Kidd–Munro – Porcupine assemblages contact in Kidd Township are
imaged. Splayed reflectors suggest the presence of numerous thrust duplex structures. Major faults such
as the North Branch of the Porcupine–Destor deformation zone are also imaged. Both the South Timmins
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