Geology Seminar Series - Dr. Santiago Tassara - From mantle plumes to epithermal deposits: the journey of gold to form an auriferous province

There is consensus that magmatic-hydrothermal gold deposits form after the efficient transfer of metals from magmas to fluids and the onset of long-lived hydrothermal systems. A longstanding question, however, is whether the magmas parental to gold deposits are derived from distinct deep sources that are particularly enriched with gold. A widely proposed view posits that melting of such source regions (e.g., lithospheric mantle domains) would produce magmas with increased metallogenic fertility, thus controlling the formation of auriferous crustal domains. This talk will test this hypothesis by focusing on the Deseado Massif auriferous province in the Argentinian Patagonia. The Deseado Masif, hosting over 50 low sulfidation gold-silver epithermal deposits (~28.2 Moz Au equivalent), is the world’s southernmost metallogenic province. First, we will dive deep into the lithospheric mantle beneath this region by using peridotite xenoliths to gain insights into the inner workings of the Earth’s mantle during metallogenesis. Then, this deep viewpoint will be contrasted against the Re-Os isotope composition of the mineralizations in the overlying crust, which allows to directly trace the source of gold in the epithermal deposits. By the end of this talk, I will have provided a “bottom-up” perspective into the role of the lithospheric mantle in the formation of the Desaedo Massif gold province.