Abstract

The Flin Flon – Snow Lake greenstone belt is of Archean or Aphebian age and has been metamorphosed to greenschist or low amphibolite facies during the Hudsonian orogeny. It contains four rock units — the Amisk Group, the Missi Group, metadiorite and metagabbro bodies, and the Boundary Intrusions. The rocks contain two main magnetizations, an early B magnetization and a later A magnetization. Both magnetizations contain reversals. The A magnetization (43 sites, direction 168°, +73°, k = 17, α95 = 5°, pole 24°N, 095°W) is found in all rock units. It can be divided into three parts (1, 2 and 3) which have the same general direction, but which are significantly different from one another. It is suggested that A1 is a viscous partial thermoremanence (vptrm), and A2 possibly a chemical remanence (crm). Both are considered to have been acquired during uplift (1600–1700 m.y.) following the Hudsonian orogeny. A3 is possibly a crm acquired during late fault movements and appears to be carried by hematite developed during retrograde metamorphism. A3 is considered to be about 1600 m.y. old. The B magnetization (7 sites, 129°, +04°, k = 12, α95 = 18°, pole 20°S, 046°W) occurs in all rock units except the Missi. It is particularly well developed in the Boundary Intrusions where it is considered to be a primary thermoremanent magnetization (trm). In other rock units B is considered to be a vptrm acquired during heating at the time of emplacement of the Boundary Intrusions. The B magnetization is considered to be about 1800 m.y. old. Some enigmatic magnetizations with very high blocking temperatures above 700 °C were observed. Formulas for calculating the coercivities in rocks with more than one magnetization are given.

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