The ca. 2720 Ma Vermilion, Shebandowan, Winston Lake, and Manitouwadge greenstone
belts (VGB, SGB, WGB, and MGB, respectively) are located along the northern margin of the Wawa
subprovince. They are interpreted to have formed in broadly similar rifted arc to back-arc
environments, but their base and precious endowment and, in particular, their endowment in VMS
deposits, differ markedly. These difference is metal endowment reflect differences in their
metallogenic history that were examined by comparing their regional, belt-scale lithostratigraphy,
chemostratigraphy, petrogenesis and tectonic history constrained by new U-Pb zircon
geochronology.
The MGB is the most VMS-endowed and isotopically juvenile (Pb and Nd) greenstone belt.
It has a trace element chemostratigraphy that is consistent with a rifted arc to back-arc environment.
The trace element chemostratigraphy of the WGB is also consistent with a rifted-arc to back arc
geodynamic setting. The Winston Lake VMS deposits formed during early rifting of the arc and their
timing is tightly constrained at ca. 2720 Ma by U-Pb ages of the host felsic strata and post-VMS
Zenith gabbro. The Zn-dominated VMS mineralization formed from hydrothermal fluids that were
<300 ° and were possibly boiling in relatively shallow water.
The trace element chemostratigraphy of the VGB, SGB, and WGB indicates a plume-driven
rifted arc to back-arc geodynamic settings. The composition of VMS mineralization, lithofacies, and
alteration in these belts are consistent with a relatively shallower-water environment, which may
have compromised VMS formation. The high-Mg andesites that are typical of, but restricted to, the
SGB formed during compressional “hot” subduction, which resulted in the development of a thicker
arc crust. This thicker crust may have inhibited VMS formation, but favoured the formation of
magmatic sulphide and gold mineralization.
New detrital and magmatic zircon U-Pb geochronology allowed comparison and correlation
of lithostratigraphy and metallogeny between the greenstone belts. U-Pb ages within the VGB also
defined younger, Timiskaming-type volcanic and sedimentary strata that are coeval with similar
deposits in the SGB. These strata are spatially and temporally associated with gold mineralization in
both belts and are coeval with similar deformation and magmatic events in the WGB and along the
northern margin of the Wawa-Abitibi terrane. This indicates that the formation of Timiskaming-type
pull apart basins in the northern part of the Wawa-Abitibi terrane were synchronous, and earlier than
in the southern part, which is consistent with oblique convergence of the Wawa-Abitibi terrane onto
the Superior Province. Detrital zircon geochronology also revealed the presence of a >2720 Ma
iv
zircon population within the Timiskaming-type sedimentary strata of the SGB. This is consistent
with their derivation from the Wabigoon subprovince and suggests trans-terrane transport of detritus
in a foreland –type basin resulting from uplift of the Wabigoon subprovince during accretion of the
Wawa subprovince.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OSUL.10219/2081 |
| Date | 08 October 2013 |
| Creators | Lodge, Robert Wilfred David |
| Publisher | Laurentian University of Sudbury |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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