|Seminar: Scott D. Anderson|
|Date: ||Tuesday, March 13, 2012|
|Time: ||1:00 PM|
|Location: ||217 Wallace Building|
|GRADUATE SEMINAR: GUEST SPEAKER|
1:00 pm TuEsday, MARCH 13, 2012
Rm. 217 Wallace Bldg
The Rice Lake greenstone belt, southeast Manitoba: magmatism, sedimentation and deformation along the accretionary margin of a
Mesoarchean continental terrane in the western Superior Province
Scott D. Anderson
Manitoba Geological Survey
The Rice Lake greenstone belt is situated at the western extent of the Uchi Domain of the
Archean Superior Province and is flanked to the north by the continental North Caribou Terrane
(NCT) and to the south by marine sedimentary rocks of the English River Subprovince (ERS).
Collectively, these tectonic entities record the opening and closing of an Archean ocean during a period of early Earth history thought to coincide with the birth of modern‐style plate tectonics. This talk will provide an overview of the regional evolution of the Rice Lake greenstone belt in light of new results from MGS geoscience investigations (20022011), and the Western Superior NATMAP and Lithoprobe projects (1996‐2003).
In Manitoba, the south margin of the NCT is bounded by the crustal‐scale Wanipigow Fault and includes vestiges of 3.0 Ga tonalitic basement rocks and an overlying 2.982.92 Ga platform‐rift sequence (Wallace assemblage), both of which are intruded by 2.942.90 continental‐arc plutons. The NCT also includes a locally preserved 2.892.85 Ga volcanic arc and arc‐rift complex (Garner assemblage), which likely formed in a marginal setting and was subsequently accreted to the NCT margin. Following an interval of apparent magmatic quiescence between 2.85 and 2.75 Ga, renewed convergence along the NCT margin generated 2.752.70 Ga continental‐arc plutons and a north‐verging 2.752.72 Ga subduction‐accretion complex (Uchi Domain) that records a transition from back‐arc (Bidou assemblage) to arc and arc‐rift (Gem assemblage) volcanism. The suture is marked by 2.712.70 Ga, fault‐bounded, fluvial‐alluvial basins (San Antonio assemblage) that locally overlie pronounced angular unconformities. Distal marine turbidites (Edmunds assemblage) of similar age onlap the south margin of the domain and record submarine fan sedimentation in response to uplift and erosion of the NCT margin during a short‐lived episode of crustal extension prior to the onset of collisional orogenesis. High‐grade metasedimentary rocks derived from 2.70 Ga turbidites in the ERS record 2.692.66 Ga regional metamorphism, deformation and anatexis associated with basin inversion and terminal collision with the continental Winnipeg River terrane. Deformation structures in the Uchi Domain and ERS evidence a complex deformation history that included synvolcanic
faulting (D1) and early‐orogenic thrust faulting (D2). Regional sinistral transpression (D3) related to continent collision gave way in the latest stages of convergence to dextral transcurrent shear deformation (D4‐D6) along crustal‐scale faults and major terrane boundaries. Crustal‐scale fluid flow within this accretionary orogenic system generated lode‐gold deposits in the Uchi Domain, which are currently the focus of significant mining and exploration activity in Manitoba and adjacent Ontario.
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