Robert M. Creed

St. Catherines
Ontario

Deceased: August 07, 2000, Calgary

OBITUARY

A belt two miles wide on the east side of Lake Ainslie between Scotsville and Trout Brook was investigated. The outcrops and mine sites within the belt were visited, and several hundred feet of drill core were examined. Thin sections of the veins and enclosing rocks were studied, and qualitative analyses and X-ray diffraction were used when needed.

Resting upon a basement of metamorphic and granitic rocks are volcanic and sedimentary rocks of Carboniferous age. The basal Mississippian Fisset Brook Formation is represented by sedimentary rocks, andesite and welded rhyolitic tuff of which the latter has been previously called rhyolite flows and felsite dikes at Lake Ainslie (East Side). The Fisset Brook and older rocks appear as inliers in the Horton sedimentary cover near Scotsville and Lake Ainslie (East Side); these inliers are on the axis of a north-trending anticline. The deformation is probably of Late Paleozoic age and was accompanied by the development of faults which are the sites of barite-fluorite-calcite mineralization.

The main barite-fluorite mineralization is found in faults in the Fisset Brook and George River rocks, but barite stringers in the Horton and Windsor rocks indicate that the age is post-Early Windsor. The mineralization occurred during the later periods of the Late Paleozoic or Hercynian orogeny after the intense folding, but while fault and fracture systems were still active.

Varying proportions of barite, fluorite and calcite within the veins give rise to bands which are parallel to the original fissures. Calcite and numerous cavities, which appear to be the result of the dissolution of calcite, are concentrated near the edges of the veins, and the calcite content increases with depth in the veins. Trace amounts of sulphides (pyrite and chalcopyrite) occur in the barite veins, but are not of economic importance. Similarly, sphalerite and galena are found in the overlying Horton and Windsor rocks and are associated with the barite mineralization. The wallrock appears to have been inert to the mineralization process. The absence of igneous activity adjacent to these deposits, and several others in the province, suggests an amagmatic genesis; the spatial relationship of barite occurrences in Nova Scotia to the Windsor basins perhaps indicates a connection. A brief review of the aqueous barite-fluorite-calcite system showed that brine solutions, such as some modern oilfield brines, are capable of transporting and depositing these minerals. The solubilities of the components is dependent on both temperature and ionic strength, but precipitation appears to be controlled predominantly by temperature. The observed features in the veins are thus explained by brine solutions or by brine solutions derived from connate waters.

Future exploration for barite and fluorite might be directed toward rocks which would be capable of maintaining fissures which were produced by the Late Paleozoic deformation; this would perhaps be in the crestal portions of anticlines, as now found. Such a program should perhaps be restricted to areas marginal to or within the Windsor sedimentary basins.

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Pages: 185
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