Timiskaming volcanism in the Kirkland Lake area, Ontario, Canada

Abstract

The petrography and chemistry of the Timiskaming volcanics of the Kirkland Lake area reveal three distinct yet intimately associated suites within a composite volcanic-sedimentary sequence. The initial phase of Timiskaming volcanism was characterized by calc-alkaline lavas; which are transitional between the later alkaline volcanics of the Timiskaming and the underlying calcic Keewatin greenstones. Flows of alkalic mafic trachytes and a variety of leucitic lavas and pyroclastic rocks are the latest differentiates represented. This occurrence of leucitic volcanics is the first reported anywhere in the Precambrian. Deposition of sedimentary rocks and intrusions of syenite and mafic syenites were contemporaneous with the period of volcanism, but intrusions of feldspar porphyry were post-Timiskaming.The major mineral constituents are augite, biotite, plagioclase, leucite, and their alteration products. Potash feldspar and hornblende occur in subsidiary amounts, and magnetite and apatite are the common accessory minerals. The chemical composition of this volcanic sequence is marked by high alkalies, A1203, and low SiOZ, P20,, and TiOz. The calc-alkaline and alkaline lavas are rich in Na20 and poor in K 2 0 and BaO, whereas the leucite lavas are high in K,O and BaO, and comparatively low in Na20.The Kirkland Lake sequence is compared with similar exotic, but less altered, lavas of more recent age in order to clarify further the nature of Timiskaming volcanism. The alkalic association of the Kirkland Lake area is similar to those occurring at a late stage in the volcanic cycle of modern volcanic arcs and along orogenic belts marginal to major continental masses.'Present address : Cominco, Exploration, 800-1 199

Evolution of the south-central part of the Archean Abitibi Belt, Quebec. Part I: Stratigraphy and paleogeographic model

“…There, the Timiskaming Group underlies a syncline bounded in the south by the Larder Lake break. According to Jensen (1 978a), the group is composed mainly of the debris derived from contemporaneous potassic and alkaline volcanic rocks (Cooke and Moorhouse 1969). Such debris is absent from the Timiskaming Group in Quebec.…”

Caractéristiques sédimentologiques, volcanologiques et structurales du bassin de Granada dans la ceinture de roches vertes de l'Abitibi (Québec) /

“…L'analyse des spectres des terres rares des intrusions porphyriques du bassin de Granada ( figure 3-8 (Cooke et Moorhouse, 1969 ;Capdevila et al, 1982 ;Ujike, 1985, Ben Othman et al, 1990. Les intrusions du bassin de Granada ont des teneurs en Yb variables entre 1,5 et 3,2 ppm ; des teneurs comparables à celles des roches volcaniques du Timiskaming analysées par Ujike, (1985) avec des teneurs variables en Yb comprises entre 1,4 et 3,3 ppm.…”

U–Pb ages and tectonic significance of late Archean alkalic magmatism and nonmarine sedimentation: Timiskaming Group, southern Abitibi belt, Ontario

“…The contacts that escaped shearing (Hamilton 1986) arr: at various locations unconformable with the underlying komatiitic to calcalkalic sequences (Thompson 1943(Thompson , 1946Hewitt 1963;Jackson 1988). The alkalic volcanic rocks have been subdivided into four main sequences generally comprising tuffaceous deposits 1 at the base, overlain by lava flows, followed by abundant I pyroclastic rocks and clastic sedimentary rocks (Cooke and Moorhouse 1969). The volcanic rocks comprise predominantly trachyte with lesser andesite, mafic trachyte, and (pseudo-) i leucitic volcanic rocks (Cooke and Moorhouse 1969).…”