Lithogeochemical studies in the vicinity of the Buchans Massive sulphide deposits, central Newfoundland

Thurlow, J. Geoffrey (1973) Lithogeochemical studies in the vicinity of the Buchans Massive sulphide deposits, central Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Buchans orebodies are stratiform massive volcanogenic sulphide deposits associated with calc-alkaline volcanism of probable Silurian age. Since 1928, approximately 16 million tons of ore have been mined with an average grade of 14.97% Zn, 7.73% Pb, 1.37% Cu, 3.73 oz. Ag and .046 oz. Au. The ore is intimately associated with volcaniclastic siltstones and laharic breccias within rhyolitic ash flows. It was deposited in chemically favourable depressions by precipitation of base metals from (sea?)water which was enriched in these components by submarine fumarolic activity during quiescent phases in volcanism. Most of the massive sulphide deposits are underlain by less important stringer and stockwork mineralization which is distinct in both time and space from the major orebodies. -- Two hundred and ninety three chemical analyses of diamond drill core samples for eleven major and fourteen trace elements were performed in order to obtain reconnaissance lithogeochemical data on the volcanic rocks and in an attempt to develop a new exploration technique based on rock geochemistry. The area of study was restricted to a single cross section two miles long by one mile deep containing a representative portion of most lithologic units and three major orebodies. Studies of elemental distributions in the vicinity of the orebodies indicate that dispersion of ore metals is generally restricted to within one hundred feet of the orebodies. Study of lateral elemental variations within lithologic units indicates a broad increase of base metals in most units from northwest to southeast over a distance of about two miles. -- The abundances of Ba, Pb and Zn are distinctly higher in volcanic rocks and sediments related to ore compared to those unrelated to ore. These differences are consistent throughout the entire cross section and are statistically significant at a high level of confidence. Cu, Ag and Hg in some instances are likewise higher in units associated with mineralization. The enrichment of these elements is attributed to a metal-rich volatile phase which accompanied volcanism which produced lithologic units related to mineralization. An expanded geological-lithogeochemical exploration program appears justified on the basis of these results.

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