Alkaline Rocks and Carbonatites of the World

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Deloro Stock

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Occurrence number: 
031-00-100
Country: 
Canada
Region: 
Ontario
Location: 
Longitude: -77.58, Latitude: 44.53

The Deloro Stock intrudes sediments and volcanics of the Grenville and Hastings Groups within the Grenville Structural Province near its southern boundary with overlying Palaeozoic sediments, which partly cover it. The stock is principally composed of a massive, red peralkaline granite grading to syenite and followed by a small intrusion of leucocratic granophyric granite. The massive granite consists principally of quartz, perthite, some albite, riebeckite-crossite, biotite, magnetite and accessories. This is the hypersolvus granite illustrated by Tuttle and Bowen (1958, Plate 2) as the Madoc granite. A zone of aenigmatite-bearing granite 100-200 m wide lies along the western margin. A peralkaline granite is shown at Moira Lake east-southeast of the Deloro Stock by Davidson et al. (1979, Fig. 1_19.4) but no details are given.

Economic: 
Mineralization associated with the stock includes deposits of magnetite, gold-bearing arsenopyrite in quartz veins, and a central zone of Cu sulphides, pyrite and magnetite. The second and third types of deposit were formerly mined (Wilson, 1965).
Age: 
A Rb-Sr isochron age, based on six samples, of 1059+-46 Ma is given by Stockwell (1972) and 1096+-48 Ma by Davidson et al. (1979, Table 19.2). K-Ar on riebeckite gave 875 Ma (Wanless et al., 1965, p. 85) and another determination on riebeckite 989 Ma (MacIntyre et al., 1967, Table 2).
References: 
DAVIDSON, A., BRITTON, J.M., BELL, K. and BLENKINSOP, J. 1979. Regional synthesis of the Grenville Province of Ontario and western Quebec. Paper, Geological Survey of Canada, 79-1B: 153-72. MACINTYRE, R.M., YORK, D. and MOORHOUSE, W.W. 1967. Potassium-argon age determinations in the Madoc-Bancroft area in the Grenville Province of the Canadian Shield. Canadian Journal of Earth Sciences, 4: 815-28. STOCKWELL, C.H. 1972. Geological setting and interpretation. Paper, Geological Survey of Canada, 72-23: 49-52. TUTTLE, O.F. and BOWEN, N.L. 1958. Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O. Memoir, Geological Society of America, 74: 1-153. WANLESS, R.K., STEVENS, R.D., LACHANCE, G.R. and RIMSAITE, R.Y.H., 1965. Age determinations and geological studies. Paper, Geological Survey of Canada, 64-17(Part 1): 1-126
Fig. 57 Deloro Stock (after Stockwell, 1972, Fig 20)
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