|Title||Current Research Part A / Recherches en cours partie A|
|Licence||Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences.|
|Author||Geological Survey of Canada|
|Source||Geological Survey of Canada, Paper no. 87-1A, 1987, 946 pages, https://doi.org/10.4095/122469 Open Access|
|Media||paper; on-line; digital|
|Related||This publication contains the
|Subjects||economic geology; geochemistry; geochronology; geophysics; marine geology; paleontology; fossil fuels; surficial geology/geomorphology; regional geology; stratigraphy; structural geology|
|Released||1987 01 01; 2013 09 10|
|Abstract||A subcircular, 300-km-diameter region of high-grade metamorphic rocks, the Ashuanipi complex, occurs in the southeastern corner of the Superior Province. Older migmatitic gneisses and younger
homogeneous granitoids are recognized. The migmatites consist of an older sequence of metasedimentary and rare, probably metavolcanic mafic rocks. Variably migmatitic tonalite occurs as sheets of 1-2000 m width within the supracrustal sequence. The
migmatites are eut by both foliated and massive tonalites and by the most abundant rock type, garnet-orthopyroxene-biotite diatexite. Later intrusions include orthopyroxene-biotite diatexite, granite and syenite, the latter locally with nepheline.
Structures trend dominantly northwest and have moderate to steep northeasterly dips suggesting regional homoclinal geometry. Folds of migmatitic layering, involving at least some of the diatexites, are open and upright, with gentle to moderate
plunge. Several large, inward-dipping aval structures may either be fold inte,ference structures or deformed magma chambers. Assemblages of garnet-orthopyroxene-biotite-plagioclase-Kjeldspar-quartz occur throughout the region indicating uniform
granulite facies conditions. With the exception of some Late granites and syenites, all rock types contain orthopyroxene. Encouraging gold assays were obtained from a sulphide-rich schist at the contact between metasedimentary and mafic gneisses.