A study of the mafic and ultramafic rocks in the Queensborough area, eastern Ontario.

The amphibolite-ultramafic belt in the southern Grimsthorpe Domain, eastern Ontario, is interpreted to be part of a Mesoproterozoic ophiolite sequence, herein named the Queensborough Ophiolite Complex. The Queensborough Ophiolite Complex is bounded to the east by the intrusive contact of the Elzevir Tonalite Batholith, to the west by the Queensborough Fault Zone (new name proposed herein) and to the south by the Moira Lake Fault Zone. The rock succession comprises up to 800 m thick of ultramafic rocks consisting of assemblages of serpentine, talc, chlorite, carbonate, anthophyllite, and actinolite/tremolite. Structurally overlying (up dip of) the ultramafic rocks is a belt of amphibolite rocks at least three kilometres thick, and consists mostly of meta-gabbros with very minor mafic meta-volcanics and unsystematically distributed mafic dykes. The meta-volcanics are fine-grained, massive actinolite-plagioclase rocks, and may show pillow structures. The meta-gabbros are coarse- to medium-grained, massive to sheared rocks, and comprise mostly of actinolite/tremolite and plagioclase. The mafic dykes are fine- to coarse-grained, actinolite-plagioclase rocks, generally having biotite in their mineralogy. The dykes have two distinct textures; a massive to lineated texture, or a feather-amphibolite texture. Chemically, the mafic rocks of the Queensborough Ophiolite Complex show fractional crystallization patterns indicative of olivine, plagioclase, orthopyroxene and clinopyroxene. The nearby presence of the large Elzevir Tonalite batholith suggests the Queensborough Complex was formed in a back-arc basin. The lack of any subduction component in the meta-volcanic chemistry suggests the basin was associated with a young subduction zone. (Abstract shortened by UMI.)Dept. of Geology and Geological Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .H375. Source: Masters Abstracts International, Volume: 34-02, page: 0685. Adviser: T. E. Smith. Thesis (M.Sc.)--University of Windsor (Canada), 1994