Timmins District Geology

The Timmins District is underlain by Archean (i.e. greater than 2.5 billion year old) rocks of the Superior Province of the Canadian Shield. In the north part of the district that comprises the Hudson Bay and James Bay lowlands, Archean rocks are unconformably overlain by Phanerozoic sedimentary rocks. In the south part of the district, Archean rocks are unconformably overlain by Proterozoic sedimentary rocks.

The Archean rocks can be subdivided into four categories which are generally distinguished by the subprovince in which they occur:

• Abitibi Subprovince rocks, which contain the east-trending Abitibi and Swayze greenstone belts, where much of the exploration and mining activity has taken place;
• Wawa Subprovince rocks, which contain the east-trending Wawa greenstone belt and the Mishibishu greenstone belt, where gold, diamond and base metal exploration and mining activity occurs as well as historic;
• Quetico Subprovince rocks, north of the Abitibi Subprovince, which are predominantly sedimentary and minor intrusive rocks; and
• Sachigo Subprovince rocks, west of the sedimentary cover rocks of the Hudson Bay and James Bay lowlands, consist of relatively small, isolated greenstone belts enclosed by extensive granitic and gneissic rocks.

In the immediate Timmins area, the Abitibi subprovince is subdivided into 9 assemblages with ages ranging from the youngest, the Timiskaming assemblage sedimentary rocks that range in age from 2676 to 2670 Ma to Deloro assemblage rocks dated at 2730 to 2724 Ma. Timiskaming sediments were deposited unconformably on deep water turbidite sediments of the Porcupine assemblage. Coeval with the Porcupine sediments are the “Krist” felsic fragmental rocks dated at 2687 Ma. The Krist is considered to be the extrusive equivalent to the quartz feldspar porphyries in the Timmins area of similar age. Underlying Tisdale assemblage rocks have an age of 2710 to 2706 Ma and consist predominantly of mafic to felsic volcanic rocks and are further subdivided into a series of mine sequence formations. The Tisdale assemblage rocks, particularly mafic volcanic rocks with high iron tholeiitic affinity are the most productive for gold mineralization. Variolitic lavas of the Vipond Formation in the Tisdale assemblage provide useful volcanostratigraphic marker horizons. Deloro assemblage rocks immediately underlie the Tisdale assemblage and consist of mafic to felsic volcanic rocks with minor banded iron formation and clastic sediments near the top of the sequence.

The Shaw dome is a structural feature south of Timmins that juxtaposes iron formation and Deloro assemblage rocks against Tisdale assemblage komatiitic rocks, yielding deposits of magmatic massive sulphide and nickel mineralization. Coincident with the north boundary of the Shaw dome, the Porcupine Destor Fault is a major structural feature that is spatially related to many of the Timmins gold deposits.

Of significance for volcanogenic-hosted massive sulphides (VMS) is the Kidd Munro assemblage that ranges in age from 2719 to 2711 Ma and is host to the giant Kidd Creek Mine. Lesser amounts of VMS mineralization has been mined from the younger Blake River assemblage around Kamiskotia.
In the Wawa area, Archean aged diamonds are attracting exploration efforts whereas the area has traditionally yielded large quantities of iron ore and lesser amounts of gold from the Michipicoten greenstone belt. The Hawk, Wawa and Catfish assemblages comprise the Michipicoten greenstone belt and range in age from 2.89 to 2.7 Ga.

In the far north part of the district, Phanerozoic sedimentary rocks underlie the James Bay and Hudson Bay lowlands. These rocks are intruded by Jurassic aged kimberlites that host the Victor diamond mine. Also in the far north, small greenstone belts of the Sachigo subprovince are the location of recent discoveries of volcanic-hosted, and magmatic massive sulphide mineralization.

Historically, the district has been a major producer of both gold and base metals. In the immediate vicinity of Timmins, over 68 million ounces of gold have been mined. Copper and zinc ore is mined at the Kidd Creek Mine and refined at the Kidd Creek Metallurgical Site. The komatiite-hosted Redstone Mine and the gabbro-hosted Montcalm Mine are producing nickel, copper and cobalt.
Near Wawa, gold continues to be mined but Ontario iron ore production ended in 1998 with the closure of Algoma’s MacLeod Mine.

Industrial mineral production includes Rio Tinto Mineral Inc.’s talc operations at Penhorwood Mine west of Timmins and Agrium’s phosphate mine at Kapuskasing.

Exploration is continuing for gold, base metals and industrial minerals in traditionally productive areas and a focus on diamond exploration extends from Wawa through the Kapuskasing Structural Zone to Attawapiskat on the west side of James Bay.

The following table shows claim staking activity and exploration expenditures in the Timmins District since 1997.

Summary of claims activities in the Timmins District, 1997 - 2007

annual value of work filed for assessment work credits in the Timmins Resident Geologist Office

The map below depicts the general geology of the Timmins District.