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Cretaceous kaolin and silica sand in Nova Scotia

Early Cretaceous deposits of unconsolidated quartz (silica) sand and kaolin clay are found within the Carboniferous and Triassic basins of Nova Scotia and New Brunswick (Figs. 1,2). These deposits are presently mined for brick clay, aggregate and silica sand. Several Nova Scotia-based companies have staked much of the area underlain by Cretaceous strata with the goal of assessing the economic potential of these deposits. Previous work by government and industry has left a rich legacy of geological data including ~700 drill holes, and ~50 km of high resolution reflection seismic data (Fig. 3).

The Cretaceous sediments in the Maritimes are collectively termed the Chaswood Formation and include quartz sand and gravel intercalated with kaolinitic mud units, occurring in fault-bounded sedimentary basins buried by glacial drift. The largest of these basins are termed the Shubenacadie Outlier (~13 km2) and the Elmsvale Basin (~44 km2) located in central mainland Nova Scotia. A small outlier (West Indian Road) is presently the site of a major silica sand quarry operated by Shaw Resources (Fig.2). The maximum thickness of the Chaswood Formation is ~150m in the Elmsvale Basin, but averages ~40 m in thickness (Fig.7). The sand and clay strata form pods and lenses of various scales and sizes but overall the sand/clay ratio is ~1:1. Beds of sand contain 1-20% mud and clay samples contain 5-30% sand. Kaolinitic muds in the Chaswood Formation are composed of quartz, mica and kaolinite with alumina (Al2O3) content of ~23-25%, and >30% in clay separates (Fig.6A) . Silica sand deposits are generally >95-99% SiO2 upgradeable by washing, seiving, and magnetic separations (Fig.6B). Heavy minerals in silica sands of the Chaswood Formation are dominated by ilmenite, rutile, and magnetite.

Kaolin clay and silica sand tonnages within the Shubenacadie and Elmsvale basins together are estimated at 1.7 billion tons and 980 million tons respectively. One key to realizing the potential of these resources is the development of high end kaolin products already identified in the various basins including high duty refractory clays for ceramics, and paper grade kaolins. Another use for Nova Scotia kaolin, not yet evaluated, is as a strengthening mix for concrete. Recently, Orbite Aluminae Inc. from Quebec has developed an acid leach technique to extract aluminum and other valuable metal cations from clays and shales. Orbite has shown interest in developing high alumina Nova Scotia clays in the western Elmsvale Basin.
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