Hydrothermal breccia pipe structures: general features and genetic criteria - II Phreatic breccia

Abstract

ABSTRACT. Phreatic and phreatomagmatic breccias are the two end-member styles of hydromagmatic breccias. A previous contribution deals with phreatomagmatic breccias with an emphasis on their general features and those genetic criteria that allow an accurate and rapid recognition.Phreatic breccias are presented here. Their general features, i.e. environment/ depth of formation, general form/geometry, dimensions, contacts with the host rocks, fragments, matrix, alteration, mineralization, surface connection, fluidization and facies changes were examined. Furthermore, genetic criteria, very useful in phreatic breccia recognition are summarized.