The Nickeliferous Iveland-Evje amphibolite and its relation.

Abstract

The pre-Cambrian nickelferous meta-norite at Iveland-Evje represents an amphibolite body entirely surrounded by gneissous granite and augen genisses. More than 90% of the amphibolite body is made up with schistose or gneissic rocks in most of which alternating dark and light layers have developed through the combined effect of recrystallization and internal differential movements. So thorough has been the re-working of the material that the determination of the nature of the original rock is utterly impossible. The conclusion that at least part of this rock was norite is based entirely on circumstancial evidences, such as the association with nickel ore, and the petrographical analogy of certain facies of the Evje rock with nickelferous norite elsewhere. The individual dark and light bands, although sharply separated, are composed of exactly the same kinds of mineral: Plagioclase has the same chemical composition, and hornblende and biotite exhibit the same optical constants in both bands; only the relative proportions of the minerals differ radically. In some places banding is not well developed, but light and dark constituents have separated in concretionary patches.