Osmium isotope constraints on ore metal recycling in subduction zones
Veined peridotite xenoliths from the mantle beneath the giant Ladolam gold deposit on Lihir Island, Papua New Guinea, are 2 to 800 times more enriched in copper, gold, platinum, and palladium than surrounding depleted arc mantle. Gold ores have osmium isotope compositions similar to those of the underlying subduction-modified mantle peridotite source region, indicating that the primary origin of the metals was the mantle. Because the mantle is relatively depleted in gold, copper, and palladium, tectonic processes that enhance the advective transport and concentration of these fluid soluble metals may be a prerequisite for generating porphyry-epithermal copper-gold deposits.
McInnes
BI
Commonwealth Scientific and Industrial Research Organization Exploration and Mining, Post Office Box 136, North Ryde, New South Wales 1670, Australia; Department of Earth Sciences, Monash University, Clayton, Victoria 3168, Australia;
McBride
JS
Evans
NJ
Lambert
DD
Andrew
AS