Alkaline Rocks and Carbonatites of the World

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Cardiff And Faraday Townships

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Occurrence number: 
031-00-093
Country: 
Canada
Region: 
Ontario
Location: 
Longitude: -78, Latitude: 45.03

The area divides into the Haliburton-Hastings Highland complex of gneisses in the northwest and the Hastings basin of lower grade sedimentary rocks, principally limestones and pelitic schists and gneisses, in the southeast. The structure is dominated by the Cheddar granite batholith in the southeast, the Cardiff plutonic complex of granitic and syenitic sills and metasedimentary gneisses in north Cardiff Township, and the Faraday granite sheet in north Faraday Township. In Cardiff Township nepheline syenites occur in a southward-dipping syenitized zone of mixed gneisses flanking the southward-dipping Faraday granite sheet. The nepheline-bearing rocks are gneissic and are variable in mineralogy both across and along the strike. They are conformable with the associated metasediments and syenitic gneisses, but they also intrude and replace metasediments and metagabbros and are themselves intruded and replaced by alkaline syenite. The nepheline gneisses consist essentially of nepheline and albite or oligoclase, with microcline and microcline perthite sometimes present. Biotite, hastingsite, aegirine and magnetite are important mafics in some varieties; garnet, scapolite and corundum are characteristic accessories, with minor accessories including idocrase, muscovite, sphene, tourmaline, apatite, zircon, sodalite, cancrinite, fluorite, calcite and zeolites. At the Bentley-Siddon Lakes area in Faraday Township, the Faraday gabbro is cut by ijolite and nordmarkite and altered to garnet- hastingsite-hedenbergite-sodic plagioclase plus or minus scapolite and nepheline assemblages with corona textures in a rock which has been termed an "alkaline skarn" (Mitchell, S.L., 1976). Mylonitized nepheline syenite gneisses occur in Faraday Township (Hewitt, 1959, p. 29 and 1961, pp. 58-63). It has been suggested that fluorite-calcite-apatite veins that flank the Cardiff plutonc complex may be carbonatitic.

Economic: 
There were numerous mining operations for uranium in the area, the deposits generally being marginal to the major granite-syenite complexes in close spatial association to the belt of nepheline gneisses; the type of mineralization is variable (Hewitt, 1959, p. 50). Deposits of apatite, corundum, feldspar, fluorite, garnet, graphite, mica, allanite, molybdenite, arsenic, dolomite and talc have been examined, but are not worked. Marble was quarried for a number of years near Bancroft and used to decorate several Canadian public buildings.
References: 
HEWITT, D.F. 1957. Haliburton-Bancroft area. Ontario Department of Mines, Map No. 1957b. HEWITT, D.F. 1959. Geology of Cardiff and Faraday Townships. Annual Report, Ontario Department of Mines, 66(3): 1-82. HEWITT, D.F. 1961. Nepheline syenite deposits of southern Ontario. Annual Report, Ontario Department of Mines, 69(8): 1-194. MITCHELL, S.L. 1976. Structure and petrology of the Bentley-Siddon Lakes area, Bancroft, Ontario with special reference to rocks of alkalic affinity. Unpublished M. Sc. thesis, University of Waterloo, Canada
Fig. 50 Cardiff and Faraday Townships (after Hewitt, 1957, Map No. 1957b).
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