Time- and Strata-Bound Ore Deposits

The problem of time-and strata-bound formation of ore deposits has during the past decade become one of the most debated topics in cur­ rent international discussion. Due to the amazing results of modern mineral exploration and world-wide geophysical research, the mutual relationship between the complex geological history pf a crustal seg­ ment and the development of distinct metallogenic provinces (ore belts) has received much interest. Reviewing the earth''s history in this light one can now recognize metallogenic epochs even of global range which document the existence of world-wide time-bound ore enrich­ ments. The knowledge of these metallogenetic processes has been growing step by step for several decades. It began with simple observations and sceptic interpretations, which at first threw heretical spot lights on to the edifices of the prevailing theories on granitic differentiation as the favoured source of ore deposits. It was obvious that the new ideas at first referred to ore enrichments in sedimentary sequences, nowadays summarized under the term strata-bound, and mainly interpreted as stratiform or sedimentary ore deposits. Moreover, the modern term "strata-bound" also includes ore mineralizations which are bound to distinct units of layered (intrusive or extrusive) igneous complexes as a general descriptive term without genetical restriction! Albert Maucher is one of the representatives of the initial era who discussed these genetical questions critically in the decade before the 2nd World War.