Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Francon Quarry - Orleans (Eastview)


Occurrence number: 
Longitude: -75.55, Latitude: 45.47

This large quarry in massive Ottawa limestone contains carbonatite dykes that occupy regionally developed shatter zones at intervals of 50-100 m. They parallel a set of normal faults trending approximately east-west. The largest dyke, the most northerly, ranges in thickness from 1.2 to 0.3 m. The dyke has a 1-2 cm wide, fine-grained margin and a massive to slightly flow-banded interior containing phenocrysts and xenocrysts. The phenocrysts include two generations of phlogopite and apatite up to 1 cm diameter and a wide range of xenocrysts derived from the Precambrian basement. The matrix, which is essentially carbonate, is fine-grained and varies from vesicular to trachytic. Chemical analyses indicate the carbonate to be dolomitic with high tenors of La, Ce, Nb, Mo and Sr. The larger Precambrian xenoliths are silica under-saturated and sodic. This is the Eastview occurrence of Tuttle and Gittins (1966, p. 528).

K-Ar on phlogopite gave 190 Ma (Hon, 1970 - quoted in Bolton and Liberty, 1972, p. 22), but this is probably a maximum due to contamination by Precambrian biotite. Palaeomagnetic pole determinations gave results identical to those of Oka (Lower Cretaceous).

BOLTON, T.E. and LIBERTY, B.A. 1972. 24th International Geological Congress, Canada. Field Excursion Guidebook, B-23 to B-27: 20-2.
TUTTLE, O.F. and GITTINS, J. 1966. Carbonatites. John Wiley, New York. 591pp.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith