Natural Resources

Open File LAB/1585 - A High-Density Lake Sediment and Water Survey in Two Areas of Central and Western Labrador (NTS Map Areas 13E/1, 2 and 8 and Labrador Portions of 23I/12 (North Half), 23I/13, 23J/9, 15 and 16 and 23O/1, 2 and 7)

J.W. McConnell and M.J. Ricketts

St. John's, Newfoundland, October, 2011

Abstract

A detailed lake sediment and water survey was conducted over two areas in central and western Labrador in 2006. Samples were collected from NTS map areas 13E/1, 2 and 8 in the Winokapau Lake area. In the Schefferville area, samples were collected from the Labrador portions of NTS map areas 23I/12 (north half), 23I/13, 23J/9, 15 and 16 and 23O/1, 2 and 7.

The Winokapau Lake area is underlain by a mid- to late-Precambrian mixed gneiss, granitoid and gabbroid crystalline terrane, which is part of the northern Grenville Province. There is one known occurrence of pyrite and four of copper in the area. The Schefferville survey area is part of the southeastern Churchill Province and is underlain predominantly by mid-Paleoproterozoic sedimentary and volcanic rocks of the Labrador Trough. There are numerous occurrences of mineralization including 36 pyrite, 29 copper and 2 zinc.

A nominal sample density of one per four square kilometres was used, although the presence of some areas without suitable lakes reduced the effective sample density. Samples of organic lake sediment were collected from 1004 sites and water samples were obtained from 1036 sites. Of these, 531 sediment samples and 541 water samples were collected in the Winokapau Lake area and 473 sediment samples and 495 water samples were collected in the Schefferville area. In addition, one site in twenty was sampled, in duplicate, for quality control. Sampling was conducted by float-equipped helicopter using a weighted tubular steel gravity sampler for sediment collection. Lake sediment was analyzed using four methods for 48 unique elements plus loss-on-ignition. In addition, 12 of these elements were analyzed by two methods for a total of 60 separate determinations. Lake water was analyzed for conductivity, pH, SO4 and 25 elements. In addition, water samples from the Winokapau Lake area were analyzed for uranium in water.

The report provides summary statistics of the geochemical data, correlation analyses of selected sediment and water data, histograms, cumulative frequency plots, sample location maps and symbol maps showing the distribution of most elements and variables in sediment and water. The symbols are overlain on maps showing geology derived from 1:100 000-scale mapping in the Winokapau Lake area and 1:1 000 000-scale mapping in the Schefferville area. Drainage features are shown at 1:250 000 scale. The sample location maps show more detailed 1:50 000-scale drainage features.

There are many areas demarcated by samples having anomalous contents of various ore elements. Of particular interest are uranium and copper in the Winokapau Lake area and the base metals copper, nickel and zinc as well as gold in the Schefferville area.

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