Publication Type:

Journal Article

Authors:

Tomlinson, Kirsty Y.; Davis, Donald W.; Percival, John A.; Hughes, David J.; Thurston, Phil C.

Source:

Precambrian ResearchPrecambrian Research, Elsevier, Amsterdam, International, Volume 114, Number 3-4, p.295-325 (2002)

ISBN:

0301-9268

Keywords:

absolute age, alteration, Archean, back-arc basins, basement, basins, Canada, Canadian Shield, dates, eastern canada, felsic composition, genesis, granites, Greenstone Belts, high-field-strength elements, igneous rocks, intrusions, mafic composition, magma contamination, magmatism, major elements, Mesoarchean, metals, metamorphic belts, Metamorphic rocks, metasomatism, nesosilicates, North America, Ontario, orthosilicates, plutonic rocks, plutons, Precambrian, rare earths, silicates, Sm/Nd, superior province, supracrustals, Trace elements, U/Pb, volcanic rocks, VOLCANISM, Wabigoon Belt, zircon, zircon group, zoning

Abstract:

The central Wabigoon Subprovince of the western Superior Province contains Mesoarchean granitoid and supracrustal rocks (3.01-2.83 Ga) and 2.78-2.69 Ga granitoid plutons and supracrustal sequences. It is a key area for understanding the relationship between greenstone belts and surrounding granitoid rocks that may have acted as basement. The Obonga Lake greenstone belt contains two distinct assemblages: (1) a Ta>Nb>Th. They have epsilon (sub Nd) values of +0.7 to +2.4. A dacitic unit in the northern assemblage has high La/Yb, high Sr/Y, low Nb, Y and heavy REE and is interpreted to represent a mantle-modified slab melt similar to adakites in Cenozoic arcs. The associated enriched basalts may represent melts from the mantle wedge modified by slab melt (adakitic) metasomatism, or they may represent an enriched (OIB-like) asthenospheric source. Rocks of the southern assemblage mostly show Th and light REE enrichment and negative Nb and Ta anomalies. Low epsilon (sub Nd) values (down to -0.9) can be modelled through contamination of a mafic liquid by 3.3-3.2 Ga sialic crust, although rocks of that age have not been observed. Suggested Mesoarchean basement to the southern assemblage may therefore have had a complex history spanning several hundred million years. The southern assemblage volcanism may have occurred in a continental arc to continental back-arc system where crustal recycling played an important role. Abstract Copyright (2002) Elsevier, B.V.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2002-030836<br/>Obonga Lake greenstone belt<br/>Onaman-Tashota Terrane<br/>Sturgeon Lake-Savant Lake Belt