Plume-subduction interaction forms large auriferous provinces

Santiago Tassara,José M González-Jiménez,William L Griffin,Fernando Barra,Diego Morata,Graham Begg,Martin Reich,Michel Grégoire,Manuel E Schilling,Suzanne Y O’Reilly,Edward Saunders,Alexandre Corgne

doi:10.1038/s41467-017-00821-z

Abstract

Gold enrichment at the crustal or mantle source has been proposed as a key ingredient in the production of giant gold deposits and districts. However, the lithospheric-scale processes controlling gold endowment in a given metallogenic province remain unclear. Here we provide the first direct evidence of native gold in the mantle beneath the Deseado Massif in Patagonia that links an enriched mantle source to the occurrence of a large auriferous province in the overlying crust. A precursor stage of mantle refertilisation by plume-derived melts generated a gold-rich mantle source during the Early Jurassic. The interplay of this enriched mantle domain and subduction-related fluids released during the Middle-Late Jurassic resulted in optimal conditions to produce the ore-forming magmas that generated the gold deposits. Our study highlights that refertilisation of the subcontinental lithospheric mantle is a key factor in forming large metallogenic provinces in the Earth’s crust, thus providing an alternative view to current crust-related enrichment models.

Highlights

Gold enrichment at the crustal or mantle source has been proposed as a key ingredient in the production of giant gold deposits and districts
The Deseado Massif is an underexplored auriferous province of ~60,000 km[2] located in the southernmost part of Argentina in South America[9]. It hosts several Au–Ag epithermal deposits including low sulfidation, intermediate sulfidation and polymetallic epithermal deposits associated with calc-alkaline rhyolites, basaltic andesites and basalts from the late magmatic stages of the Chon Aike silicic large igneous province (CA-SLIP)[11, 12] (Fig. 1)
The CA-SLIP is represented by the extensive volcanism that was active from 187 to 144 Ma contemporaneously with the initial break-up of Gondwana[13], and includes two main stages of petrogenesis

Summary

Introduction

Gold enrichment at the crustal or mantle source has been proposed as a key ingredient in the production of giant gold deposits and districts. Discontinuities between buoyant and rigid domains in the SCLM provide the channelways for the uprising of Au-rich fluids or melts from the convecting underlying mantle, and when connected to the overlying crust by trans-lithospheric faults, a large Au deposit or well-endowed auriferous province can be formed[7]. The giant Ladolam Au deposit in Papua New Guinea gives a good single-deposit case example of this mechanism since deep trans-lithospheric faults connect the crustal Au deposit directly with the mantle source, and similar Os isotopic compositions are exhibited by Au ores and metal-enriched peridotite of the underlying mantle[1] Despite these evidences, the genetic relation between a pre-enriched mantle source and the occurrence of gold provinces in the upper crust remains controversial since limited evidence is available at a broader regional scale. Our observations of ultramafic xenoliths sampled from monogenetic volcanoes from the Deseado Massif, southern Patagonia, provide unprecedented evidence that an enriched SCLM might be the primary source for the generation of this auriferous province

Methods

Results

Conclusion