Natural Resources

Open File NFLD/3134 - Till Geochemistry of the Gander Lake and Gambo Map Areas (NTS 2D/16 and 2C/13)

D. Brushett

St. John's, Newfoundland, October, 2011

Abstract

This report provides the results from the first year of a multi-year (commenced in 2009) till geochemistry and surficial mapping program in northeast Newfoundland, which focused on areas north and east of Gander Lake (NTS map areas 2D/16 and 2C/13). Regional till sampling was conducted at a spacing of 1 sample per 1 km2 in areas of good access, and 1 sample per 4 km2 where helicopter support was required; a total of 496 till samples were collected. Geochemical data of 53 elements, from BC- or C-horizon till samples, is presented and includes the results of analyses by ICP-ES for aluminum, arsenic, barium, beryllium, cadmium, calcium, cerium, chromium, cobalt, copper, dysprosium, iron, lanthanum, lead, lithium, magnesium, manganese, molybdenum, nickel, niobium, phosphorus, potassium, scandium, sodium, strontium, titanium, vanadium, yttrium, zinc and zirconium; by INAA for antimony, arsenic, barium, bromine, calcium, cerium, cesium, chromium, cobalt, europium, gold, iron, hafnium, iridium, lanthanum, lutetium, mercury, molybdenum, nickel, neodymium, rubidium, scandium, samarium, selenium, silver, sodium, strontium, tantalum, tin, terbium, thorium, tungsten, uranium, ytterbium, zinc and zirconium. A complete data listing, field duplicate data, and individual element distribution maps, on a bedrock geology base map, are also provided.

The study area is dominated by till, of varying thicknesses, and organic deposits. Inland, the till cover is extensive and it conceals much of the bedrock, creating a gently undulating topography. Toward the coast, the topography is rugged and till cover is generally thin (or absent) and exposed bedrock prominent. Sediment in the Butts Pond area include glaciofluvial and hummocky deposits, esker-like ridges, and a raised marine delta that formed during deglaciation, as the ice was retreating toward Gander Lake.

The data from ice-flow mapping showed two regionally extensive events. The earliest ice flow was eastward throughout the field area, likely from a source north of Red Indian Lake. The most recent regional flow was north-northeastward and was only observed in the western part of the study area, the remainder being covered by stagnant ice.

Anomalous concentrations of gold, arsenic, chromium, copper, lead and zinc are present throughout the study area, particularly in tills overlying the metasedimentary rocks of Jonathans Pond Formation.

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