Regional Prospecting in Labrador Using Lake Geochemical DataData f rom the Nat iona l Geochemica l Reconnaissance (NGR) program of the Government of Canada provide numerous indicators of the possible presence of rare-earth mineralization. Although these data led directly to the discovery of the Strange Lake rare-earth / rare-metal deposit, a number of other anomalies have not been fully investigated. Study of assessment files reveals that some of these anomalies are associated with distinctive geophysical patterns, characteristic of known rare-earth occurrences elsewhere but unrecognized as such, at the time the data were collected.

The map to the right shows the distribution of fluoride ion in waters collected as part of the NGR work. The colour codes assigned to different value ranges are based on natural subdivisions in the data set. Samples associated with the uppermost

-class(> 68 ppb F ) are associated with rare-earth occurrences at Strange Lake, Flowers River, Misery Lake (dispersion train) and Letitia Lake, and there are a number of other well-defined, hitherto-unexplained anomalies.

GEOCHEMICAL EXPLORATIONFOR RARE-EARTH METALS

The map to the left shows the distribution of Furthermore, Misery Lake is associated with a molybdenum in lake sediment on both sides of the distinctive circular magnetic anomaly, and a similar Labrador-Québec border, north of the Smallwood feature, known as the Michikamats Anomaly, is Reservoir, superimposed on newly-released present on the Labrador side. Michikamats is also residual total magnetic field data. Because samples characterized by elevated molybdenum, and from Labrador and Québec were analyzed by anomalous levels of several rare-earth metals, in different methods, the two geochemical data sets lake sediment, as well as a strong fluoride anomaly have been scaled separately to compensate for a in lake water. There are several other lake slight background shift. geochemical anomalies, associated with

geophysically-defined features, on this map.The Misery Lake rare earth deposit in Québec is characterized by a strong lake-sediment Fluoride data are not available for Misery Lake itself molybdenum anomaly; molybdenum enrichment is but waters from lakes down-ice of Misery Lake on also characteristic of some rare-earth deposits of the Labrador side of the border are strongly the Khibina Massif of northwestern Russia. anomalous (see map above).

Integrating Geophysical and Geochemical Data

Large filled circles indicate lake-sediment samples returning analytical values that exceed the 97.5-percentile for the regional data set (19 ppm Mo in Labrador, 21.9 ppm Mo in Québec). Partially-filled circles indicate values between the 90- and 97.5-percentile (8-19 ppm Mo in Labrador, 9.5-21.9 ppm Mo in Québec). Small circles indicate values less than the 90-percentiles.

Beryllium dispersion in till down-ice from the Strange Lake Deposit.

Nevertheless, wherever bedrock is covered by surficial deposits, and when geochemical and geophysical surveys. In areas of permafrost, mudboils accompanied by adequate knowledge of the glacial history of an area, the offer a source of till that is easy of access and lends itself to rapid sampling. sampling of till is an essential and helpful follow-up tool for regional

Follow-up Sampling: Strange LakeThe Strange Lake deposit has a distinctive ribbon-like glacial dispersion train that is defined by many rare-earth and other elements, extends for more than 40 kilometres and is rather untypical of glacial dispersion from mineral deposits in the Canadian Shield.

0 200100

km

Labrador Lake WaterFluoride Ion (ppb)

< 10–

11 - 32

33 - 67

68 - 980