Talk
Mountains graphic with white diamonds on itGeoscience and Exploration

Linkages between Paleoproterozoic magmatism and Fe-Oxide mineralization in the Nonacho Basin, NWT

Online pre-recorded
(Student abstract)

Author(s)

A.R-G. Roy-Garand (Presenting)
Saint Mary's University
K.L. Landry
Saint Mary's University
E.A. Adlakha
Saint Mary's University
A.T. Terekhova
Saint Mary's University
J.H. Hanley
Saint Mary's University
H.F. Falck
Government of the Northwest Territories
E.M. Martel
Northwest Territories Geological Survey

The Nonacho Basin is a fault-bound Paleoproterozoic Basin located southeast of Great Slave Lake along the western margin of the Rae Craton of the Western Churchill Province. The basin hosts numerous hydrothermal polymetallic (Cu-Pb-Zn-Ag-U-Th-Mo) occurrences spatially associated with Fe-oxide mineralization (magnetite, hematite) and extensive alkali-calcic alteration (i.e. albitization and potassic alteration). Field investigations by the Northwest Territories Geological Survey (NTGS) recognized that Fe-oxide mineralization is widespread throughout the entire basin, occurring in: (i) the gneisses and granitoids of the Archean-Paleoproterozoic basement, (ii) Paleoproterozoic basinal sedimentary rocks and (iii) Paleoproterozoic alkaline intrusive rocks (e.g., Sparrow and Red dykes, Thekulthili Stock) that crosscut the basin. All aforementioned lithologies are variably replaced by hydrothermal alkali-calcic alteration which appears to be focused along regional structures.

The style and paragenesis of overprinting alteration assemblages have been evaluated using a combination of field observations and µ-XRF (micro-beam X-Ray Fluorescence) elemental distribution maps. The types of alteration identified include early high temperature (HT) sodic alteration (albite), which is overprinted by HT iron-calcic alteration (type-ii magnetite and amphibole), HT potassic-iron alteration (type-iii magnetite and k-feldspar) and low temperature potassic-iron alteration (hematite and sericite).

The Paleoproterozoic alkaline magmatism (i.e. Thekulthili Stock, Red Dykes and Sparrow Dykes) is one of the youngest events and contain primary igneous magnetite (type-I magnetite). The magmatic influx may be a heat engine and possible fluid source for the hydrothermal polymetallic mineralization and alteration of the Nonacho Basin. The association of Fe-oxides with i) widespread alkali-calcic alteration and polymetallic mineral occurrences along regional structures, and ii) alkaline magmatism, is similar to mineralization styles of world class Iron Oxide Copper Gold (IOCG) and affiliated hydrothermal ore deposits. Future work will assess the potential for IOCG style mineralization in the Nonacho Basin by examining the mineral assemblages and trace elements of different Fe-oxides by LA-ICP-MS.