Marc H. Charest

The New Ross area, Lunenburg County, is situated in the centre of the South Mountain batholith and is part of the New Ross-Vaughan Complex which diapirically intruded biotite granodiorite. Eighteen samples were analysed for all major elements, fifty-one specimens were investigated for Li, Sn, Mo, Cu, Nb, Rb, Sr, Ba, Zr, K, and Ti, and seventeen were analysed for W. These data, along with field mapping and petrography, show that the area is underlain mainly by two-mica adamellite and porphyry, which grade texturally and chemically into one another. These are intruded by mica aplite dykes. Small diapirs of leucoadamellite were then introduced. Finally, late aplites, pegmatites, and quartz veins, often greisenized and sometimes mineralized, intruded the leucoadamellites and the contacts of the New Ross-Vaughan Complex. Radiometric dating indicates that emplacement and/or cooling of all the rocks of the New Ross area at least occurred over a period of 15-20 m.y.

Metallization resulted principally in the precipitation of copper sulphides, molybdenite, cassiterite and wolframite, along with Li, Be, P, F, As, Zn, Mn, Nb-Ta and reported Li minerals. It is restricted to late stage aplites, pegmatites, veins, but most importantly greisens. Regionally, there is a strong correlation between the location of known mineral occurrences and the large negative gravity anomaly in the South Mountain batholith. This suggests that sufficient degrees of chemical evolution, to produce high concentrations of certain elements, occurred only in the thickest part of the batholith where cooling was slowest and fractional crystallization was most efficient. The implication is that other areas, remote from New Ross, have rather low potential for mineralization.

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Supervisors: D. . Clarke