Lac Tio

Quebec, Canada

Main commodities: Ti Fe
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The Lac Tio or Tio deposit is located within the Allard Lake district, Quebec, some 40 km inland from Havre St Pierre on the northern shore of the St Lawrence seaway.

The deposit lies within the 145 x 32 to 48 km Allard Lake Massif anorthosite, which parallels the Gulf of St Lawrence, and comprises the southeastern lobe of the Havre St. Pierre Complex which is composed of an anorthosite-mangerite-charnockite-granite suite. This complex is the largest of several anorthositic masses occurring at intervals in the the central Grenville Orogen of the south-eastern part of the Precambrian shield in a line trending NE from the Ontario-Quebec border to the Labrador coast.

The Grenville Orogen forms the leading or south-eastern edge of the Canadian Shield. It is characterised by extensive re-working of older crust, high metamorphic grade and ductile deformation with NW-directed tectonic transport, and a retrogressive sequence of thrusting which youngs to the south-east. The Orogen is divided into three composite zones, the para-autochthonous North-western Zone, the allochthonous polycyclic Central Zone and the allochthonous monocyclic South-eastern Zone.

The Havre St. Pierre Complex and the other members of the NE-SW string of anorthositic masses distributed along the Grenville Orogen fall within the Central Zone, or "Interior Magmatic Belt". The Central Zone is composed of 1.68 to 1.63 Ga granulitic and granitic orthogneisses and paragneisses, a 1.30 Ga syenite-granite complex and scattered 1.08, 0.99 and 0.97 Ga granites. It was transported north-westward over a granulite-grade mylonitic zone that undulates around south-easterly and north-easterly axes with an apparent displacement of at least 200 km and has undergone three pulses of north-west directed thrusting and high grade metamorphism during the periods 1190 to 1140, 1080 to 1020 and 1000 to 990 Ma.

The Havre St. Pierre Complex suite was emplaced during an extensional event that followed the 1190-1140 Ma compressional pulse, and includes a late phase dated at 1062 Ma. A pegmatite that cuts the Allard Lake Massif anorthosite, but is cut by ore of the Lac Tio deposit, has a K-Ar age of 1025 Ma. The Allard Lake Massif lobe mainly comprises pure (>95% plagioclase) anorthosite, and minor leuconorite. Both lithologies contain antiperthitic andesine, hypersthene, hemoilmenite and biotite in variable proportions. Whole-rock normative compositions are in the range An37-48Or4-7, with 1000-1200 ppm Sr, 200-500 ppm Ba, and <5 ppm Rb. Locally, distinct, small-scale (tens of metres thick) zones of labradorite anorthosite-leuconorite (An66-74Or1-3, 350-550 ppm Sr, <50-100 ppm Ba), which are cut by dykes of the host andesine anorthosite. The anorthosite is also invaded by sheets of hemo-ilmenite and magnetite rich (containing 2 to 5 wt% P2O5, ~4-10 wt% TiO2), mafic to ultramafic rock mapped as oxide-rich norite or ferrodiorite which occur as steeply dipping sheets as much as 6 km long and 1 km thick.

The Lake Tio deposit is a massive, coarse grained, sub-horizontal igneous sheet more than 60 m thick intruded into the anorthosite. It is essentially composed of coarse, platy 10 x 10 x 2 mm crytstals of coarse ilmenite (75%) containing exsolved hematite (25%) intergrowths. This ore contains 32 to 36% TiO
2. Minor constituents of the ore include magnetite, sulphides, apatite, hercynitic spinel and zircon. Magnetite is less abundant than the sulphides, which here include several Ni-Co minerals.

The gangue minerals are predominatly plagioclase, pyroxene, biotite, pyrite, pyrrhotite and chalcopyrite. Locally, the modal proportion of sulphides reaches 2 %.

The Tio ore deposit is a subhorizontal, massive ilmenite intrusion dissected by normal faults into the Main, Northwest and Cliff deposits.

The orebody is divided into three layers or zones: i). the upper zone, composed of massive ferrian ilmenite, ii). the intermediate zone, alternating layers of massive to semi-massive ferrian ilmenite and anorthosite, and iii). the lower zone of massive ferrian ilmenite.

The Main deposit measures 1097 m north-south by 1036 m east-west, with an average thickness of around 110 m, dipping 10°E. The Northwest deposit forms a 7 to 60 m thick band of massive ilmenite alternating with anorthosite, gently dipping to the east. It is separated from the Main deposit by a late normal fault. The Cliff deposit forms a hill that overlooks the Tio Mine, and has an ellipsoidal shape. Both the Main and Northwest deposits are mined.

The Main deposit contains at least of 125 Mt of ore with a mean composition of 34.2% TiO
2, 27.5% FeO, 25.2% Fe2O3, 4.3% SiO2, 3.5 Al2O3, 3.1% MgO, 0.9% CaO, 0.1% Cr2O3, and 0.41% V2O5.

The Northwest deposit contains 5 Mt @ 37.4% Fe and 32.32% TiO

The Cliff deposit comprises 8.4 Mt @ 39.2% Fe and 33.9% TiO

Since 1950, QIT has extracted an estimated 60 Mt of ore @ 38.8% Fe and 33.6% TiO

This summary is predominantly drawn from the Natural Resources Canada and Quebec Natural Resources websites, Dymek R. F. (2001) and other sources.

The most recent source geological information used to prepare this summary was dated: 2007.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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