Peperite, Pumice and Perlite in Submarine Volcanic Successions: Implications for VHMS Mineralisation

摘要

The volcanic successions that host massive suphide deposits are diverse in composition, facies types and facies relationships. They also show a variety of spatial and temporal relationships to mineralisation. In many examples, such as the Koongie Park Formaiton in Western Australia, the host succession includes more or less conformable syn-volcanic sills with peperitic contacts. Such sills can be an important source of heat for fluid circulation, influencing patterns of hydrothermal alteration and the location of co-eval and later mineralisation. The impact of syn-volcanic sills on the host succession depends in part on the initial porosity and permeability of the enclosing facies. The special properties of glassy pumice-being highly porous, permeable, and reactive-allow pumice-rich facies to preferentially focus hydrothermal fluid flow.