When and Where? — Global Distribution, Igneous Associations

Abstract

Because they are partly characterized by peculiar textural features and by high contents of mobile elements (Chapters 1,3,5), lamprophyres are among the least likely of igneous rocks to be recognizable after even low-grade metamorphism. The older and/or more foliated they are, the more easily they may be confused with other metabasites: for example, foliated Caledonian microdiorites in northern Scotland were long called “foliated lamprophyres” and “lamproschists” in the mistaken belief that they were metamorphosed equivalents of younger Caledonian lamprophyres (D.Smith 1979). In the converse sense, “amphibolites” long known to be useful marker bands in the Limpopo Belt of Zimbabwe turned out on closer examination to be metalamprophyres (Watkeys & Armstrong 1985). This intrinsic confusion was exacerbated by the former tendency of some geologists to call any peculiar or altered igneous rock a “lamprophyre” (Chapter 1).