The ability to distinguish ancient lamprophyres from other mafic and ultramafic intrusive rock types has become increasingly important. Lamprophyres have been used as marker horizons in the mapping of several Precambrian terranes, they have been recognized for decades as possible indicators of gold mineralization, and their presence has implications for the tectonic interpretation of ancient greenstone belts. Whilst fresh, undeformed lamprophyres are readily recognized, metamorphosed, altered and/or deformed examples are more problematical. The intrusive ages of Kambalda lamprophyres are constrained by available field and geochronological evidence, including direct dating of one kersantite, to the period 2684-2660 Ma. These rocks therefore belong to the world's oldest group of alkaline rocks and lamprophyres so far recognized, which also includes contemporaneous examples from Canada, Zimbabwe and, probably, Tanzania. Despite their extreme age and low- to medium-grade regional metamorphic history, these rocks still preserve characteristic lamprophyric textures, chemistry and mineralogy. Only where metamorphism has been overprinted by gold-related alteration and deformation do the lamprophyres cease to be recognizable petrographically. However, their unique chemistry persists and, despite losses of the most mobile elements from presumed magmatic compositions, altered and deformed specimens still retain far higher contents of Sr, K, Ba, Th, Nb, P, Zr and Ce than basalts of the local greenstone succession. Even lamprophyres which have been converted to biotite-plagioclase-carbonate-pyrite schists retain this distinctive chemical signature. During both alteration and metamorphism, ‘mobile’ elements (K, Rb, Sr, Ba) display far larger changes than archetypal ‘immobile’ elements (Ce, Nb, Zr, P, Ti), clearly sanctioning traditional preference for the latter in assessing altered rocks. However, the surprising loss of Nb during biotitization of hornblende indicates that negative Nb anomalies, conventionally regarded as indicators of subduction-related magmatism, can also be induced purely by alteration processes.

Book Reviews Existentialism and Religious Belief. By David E. Roberts Edited by Roger Hazelton. (New York : O.U.P. London : O.U.P. 1957. Pp. viii + 344. Price 30s). Ronald W. Hepburn Ronald W. Hepburn Search for other works by this author on: Oxford Academic Google Scholar The Philosophical Quarterly, Volume 9, Issue 37, October 1959, Pages 383–384, https://doi.org/10.2307/2216378 Published: 01 October 1959

Previous articleNext article No AccessCritical ReviewsConflict in Christology. John Stewart Lawton David E. RobertsDavid E. Roberts Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Religion Volume 28, Number 1Jan., 1948 Article DOIhttps://doi.org/10.1086/483657 Views: 2Total views on this site PDF download Crossref reports no articles citing this article.

Previous articleNext article No AccessCritical ReviewsHow to Think of Christ. William Adams Brown David E. RobertsDavid E. Roberts Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Religion Volume 26, Number 1Jan., 1946 Article DOIhttps://doi.org/10.1086/483413 Views: 4Total views on this site PDF download Crossref reports no articles citing this article.