ISBN:

Keywords:

Abstract:

The Garson deposit is one of several deformed magmatic Ni-Cu-platinum group element (PGE) deposits in the South Range of the 1.85 Ga Sudbury structure. The deposits occur along the southeast limb of the folded Sudbury Igneous Complex (SIC), at the contact between the SIC basal norite and underlying Paleoproterozoic metabasalt and metasedimentary rocks of the Huronian Supergroup. At the Garson deposit inclusion-rich breccia and disseminated Ni-Cu-PGE sulfide ores are hosted by steeply south-dipping shear zones and splays that underwent two major ductile deformation events (D (sub 1) and D (sub 2) ). D (sub 1) is characterized by a steeply, south-dipping, S (sub 1) foliation and a down-dip L (sub 1) mineral stretching lineation defined by ferrotschermakite in metabasalt and by magnesiohornblende in norite. Coexisting ferrotschermakite and oligoclase in metabasalt indicate amphibolite facies conditions during D (sub 1) . The shear zones formed along or near the SIC-Huronian contact during the 1.7-1.6 Ga Mazatzal-Labradorian Orogeny. They formed as layer-parallel, north-dipping, north-over-south thrusts in response to flexural slip during buckling of the SIC. As the general transport direction was from south to north during the Mazatzal-Labradorian Orogeny, the D (sub 1) shear zones are back-thrusts with opposite transport direction. The thrusts imbricated the SIC, underlying Huronian rocks, and ore zones, and emplaced slivers of Huronian rocks and metabreccia into the overlying norite. In contrast to the D (sub 1) shear zones at Garson, the Thayer Lindsley and the regional South Range shear zones, which transgress the SIC-Huronian contact at a high angle, formed as moderately SE-dipping reverse shear zones as a result of localization of folding-induced strain near the hinge zone in order to accommodate further flattening and tightening of the SIC with progressive D (sub 1) shortening. Together with the southeast limb of the SIC, the D (sub 1) shear zones were overturned into their present steep southerly dips and were reactivated as south-over-north shear zones either later during the Mazatzal-Labradorian Orogeny or during the 1.5-1.45 Ga Chieflakian event, which was coeval with accretion of juvenile Andean-style, calc-alkaline magmatic arcs along the entire southeastern margin of Laurentia. During this D (sub 2) reactivation event, S (sub 1) was transposed and locally preserved in crenulations bounded by a S (sub 2) chloritic shear foliation, which has a strong down-dip L (sub 2) mineral chlorite lineation and parallel L (sub 2) ductile slickenlines. Abstract Copyright (2012) Elsevier, B.V.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2012-049635<br/>backthrust faults<br/>Garson Mine<br/>Labradorian Orogeny<br/>South Range