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ABSTRACT: Problems in Exploration and Genesis of Young (0.5-3 MA) Hydrothermal Gold-Silver Deposits in the Asian Pacific Rim Region

Laurence P. James

Published and unpublished studies show some recently identified epithermal gold-silver ore systems in Japan-East Asia are very young. Some occurrences have cooled completely, and genetic models are not yet backed by 3-D geology. Attempts to use standard geological, geochemical, and geophysical exploration techniques in this environment reveal special problems. Rules and models developed for older, more lithified rock units do not always strictly apply.

Problems in very young volcanic areas include: (1) post-ore ash fall and welded tuff sheets, (2) extreme porosity and permeability of poorly consolidated volcanic host rocks, and (3) local complexity of volcanic units.

The upper parts of some young ore systems show surprising variability in contained metals (e.g., Au/Ag, Te, Bi, Cu, As, Sb, Zn) in different deposits associated with nearly the same rock types and general geological environment. We must await deeper exposures to determine whether the character of underlying magma systems and wall rock alteration relate to these variations.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990