What are Lamprophyres? — History, Definitions, Classification

Abstract

To an uncomfortably large number of geologists, the term ‘lamprophyre’ conjures up predominantly negative images: of rotten dykes forming miniscule, impersistent outcrops; of legion obscure rock-types named after equally obscure European villages. To many, indeed, the term connotes little more than ‘horribly altered’, or ‘impossible to classify’. This is all a pity, for it has severely delayed the recognition until recently that lamprophyres have an importance out of all proportion to their absolute abundance among igneous rocks: as windows into the deep mantle and mantle processes, as possible indicators for precious mineral deposits (notably diamond and gold), as parental magmas to an extraordinarily wide range of other igneous rock-types, and, in their own right, as sources of innumerable exotic mineral varieties and geochemical compositions. The reasons for this delayed appreciation of lamprophyres are salutory, and deserve a brief historical exposition.