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 are man tle. Cold ores have osmium isotope compositions similar to those of the und erlying subduction-modified mantle peridotite source region, indicating tha t the primary origin of the metals was the mantle. Because the mantle is re latively depleted in gold, copper, and palladium, tectonic processes that e nhance the advective transport and concentration of these fluid soluble met als may be a prerequisite for generating porphyry-epithermal copper-gold de posits.