Kimberlite Indicator Mineral Results from Reconnaissance Till Sampling in the East Peace River Region (NTS 84C/East), Alberta
R.C. Paulen1,
B. Waight1 & I.M. Kjarsgaard2
1 Alberta Energy and Utilities Board/Alberta Geological Survey, 4th Floor, Twin Atria Building, 4999 – 98 Ave., Edmonton, Alberta, T6B 2X3
2 Consulting Mineralogist, 15 Scotia Place, Ottawa, Ontario, K1S 0W2
During
the summer of 2002, the Alberta Geological Survey completed the surficial
mapping of the Peace River map area (NTS 84C) as part of a multi-year program
initiative under the Alberta Mineral Strategy. During the course of surficial
mapping, reconnaissance till samples were collected to document the regional
kimberlite indicator mineral (KIM) content of the surface tills and to
potentially stimulate exploration in areas not proximal to known kimberlite
occurrences. Surficial mapping and ice flow reconstruction studies in the Peace
River region provide crucial information that have direct implications for kimberlite
exploration using drift prospecting.
Of the 19 samples collected and processed, 14 contain KIMs including pyrope, eclogitic garnet, Cr-diopside, ilmenite, chromite and olivine. KIMs were detected in samples that are located in excess of 90 km away from known kimberlitic sources. It is possible that some of these KIMs were derived from secondary or tertiary sediment sources or have been glacially transported from known sources (i.e. long distance dispersion); but some of the KIMs are suspected to be from undiscovered sources. At one site in particular, a number of KIMs were recovered from a till that has drastic textural, mineralogical and geochemical differences from the ubiquitous regional surface till. This likely reflects a different source provenance of the KIMs than those contained within the overlying younger till.
It is important to understand the complex ice flow history that affected this region before attempting to utilize drift prospecting methods to explore for the sources of the KIMs. A reconstruction of late Wisconsin ice flow is presented for the southern Buffalo Head Hills. The interpretation of erosional ice-flow indicators and clast orientation studies demonstrates that there were variable flow directions that could have influenced kimberlite dispersal trains. The lower till was deposited by ice flowing in a southwesterly direction, indicating a source to the northeast. The upper till was initially deposited by Late Wisconsin Laurentide ice flowing generally in a southwesterly direction during glacial maximum. Sometime after glacial maximum, southwardly flowing ice in the northern Peace River valley advanced out of the Peace River valley from the northwest and flowed over the southwestern flank of the Buffalo Head Hills. This southeasterly surge was deflected by a large mass of surging ice that was flowing south-southwest down the Loon River Valley. These deflections likely occurred prior to ice stagnation. However, the main erosion and dispersion of kimberlitic debris likely still occurred during glacial maximum (southwestward dispersal), but palimpsest (offset) dispersal trains are suspected in this region from the late southeasterly glacial flow.