Reconnaissance-scale till survey in the New Liskeard-Temagami region, Ontario: kimberlite indicator minerals and geochemistry

Abstract

This report describes results of a reconnaissance-scale kimberlite indicator mineral (KIM) till survey in the area south of the known Lake Timiskaming kimberlite field, between New Liskeard and Marten River. The survey provides information on the regional background content of KIM in till, the nature of KIM signatures in till just down-ice of known kimberlites, and, the distribution of KIM anomalies that warrant further investigation. Three phases of flow are associated with erosion, transportation and deposition of till in the region. The main carriers of glacial debris, however, were the two oldest ice flows to the southwest and south. A large dispersal train of Paleozoic limestone derived from upper Lake Timiskaming trends south-southwest across the area, but has been truncated in its proximal part (Latchford area) by the last southeast ice flow indicating that in this area, southeast ice flow was a major carrier of debris. These situations have to be taken into consideration in the interpretation of dispersal trains formed by the three major ice flows. Mg-ilmenite is the most abundant and widespread KIM in the till in the study area. Chromite occurs in approximately the same till samples that contain Mgilmenite, but is generally present in lower abundances. Pyrope in till is approximately half as abundant as Mg-ilmenite. Cr-diopside is similar in abundance to pyrope and is present in almost every sample. Elevated Crdiopside abundances that are not accompanied by other KIMs likely are not from kimberlite. Anomalous concentrations of kimberlite indicator minerals in till occur: on the Red Squirrel Road; near Temagami; along Highway 11 in the central part of the study area; on the east side of Lake Timiskaming; and on the Rabbit Lake forest access road. Some of these anomalies coincide with anomalies identified by the OGS in their recent stream sediment survey (Allan, 2001). Additional till sampling combined with geophysics should be conducted to determine the extent of the KIM anomalies and trace them to their bedrock source, with a sample spacing that is much smaller ( <500 m) than used in this reconnaissance survey.