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TitleEskers as mineral exploration tools: how to sample eskers and interpret data
AuthorCummings, D I; Broscoe, D; Kjarsgaard, B A; Lesemann, J; Russell, H A J; Sharpe, D R
Source39th Annual Yellowknife Geoscience Forum, abstracts of talks and posters; by Fischer, B J; Watson, D M; Northwest Territories Geoscience Office, Yellowknife Geoscience Forum Abstracts Volume vol. 2011, 2011 p. 95-96
Alt SeriesEarth Sciences Sector, Contribution Series 20110222
Meeting2011 Yellowknife Geoscience Forum; Yelloknife; CA; November 15-17, 2011
File formatpdf
Subjectseconomic geology; surficial geology/geomorphology; drift prospecting; drift deposits; indicator elements; glacial landforms; eskers; glacial deposits; kimberlites; diamond; indicator minerals; Cenozoic; Quaternary
ProgramDiamonds, GEM: Geo-mapping for Energy and Minerals
LinksOnline - En ligne
AbstractEskers on the Canadian Shield are commonly sampled during mineral exploration campaigns. This practice has led to the discovery of mineral deposits, including the Lac de Gras kimberlite field, NWT. Despite this, few non-proprietary studies have been conducted to help understand how to best sample eskers for indicator minerals and how to interpret esker data. To gain insight into this problem, we have reviewed over 100 years of esker-related literature. The review reveals that (1) companies commonly apply stream sampling guidelines to eskers, in that they target gravelly facies, the idea being that these facies are more likely to contain more heavy minerals per unit volume than sandy facies; and (2) indicator mineral dispersal trains in eskers are of similar length to those in the underlying till from which they were sourced, but are displaced downflow by less than one to several tens of kilometers.
Knowledge gaps identified during the review are being addressed by research at the Geological Survey of Canada under the Geomapping for Energy and Minerals (GEM) program. Our research group postulates that a better scientific understanding of how eskers form is the key to better exploration success using eskers. An integrated approach has been adopted in which esker dispersal trains are examined at all scales, from tree-shaped esker networks that are hundreds of kilometers long to microscopic abrasion features on individual sediment grains. At the largest scale, a semi-automated technique for mapping eskers has been developed using DEM and spectral remote sensed data (Broscoe et al., 2010) that will help quantify esker dimensions (e.g., volumes) over large expanses of terrain and thus provide insight into how eskers form and, among other things, the amount of esker-related aggregate in northern Canada. At a regional scale, a new dataset of roughly 500 till and esker samples from East Arm, NWT, has been collected that shows the abundance of indicator minerals in eskers and the underlying till to decrease downflow in a nearly parallel fashion. These trends are similar to those identified previously in eskers, and reinforce the idea that indicator mineral dispersal trains in eskers generally do not extend far past those in the underlying till. At a local scale, new data from an esker in Northern Ontario indicate that heavy minerals occur in greater abundance in the sandy facies as opposed to the gravelly facies, which brings into question the current practice of targeting gravelly esker facies when sampling for indicator minerals. At the smallest scale, tumbling mill experiments have been carried out that show kimberlite clasts will abrade (lose mass) 3 to 3500 times faster than typical Shield lithologies as they are transported across the landscape, which may explain the anomalously high concentrations of indicator minerals at the heads of some kimberlite dispersal trains. In concert, these research initiatives are helping provide companies with knowledge needed to increase exploration success while searching for mineral resources in Canada.