Subduction, mantle metasomatism, and gold: A dynamic and genetic conjunction

Abstract

Global gold deposit classes are enigmatic in relation to first-order tectonic scale, leading to controversial genetic models and exploration strategies. Traditionally, hydrothermal gold deposits that formed through transport and deposition from auriferous ore fluids are grouped into specific deposit types such as porphyry, skarn, high- and low-sulfidation–type epithermal, gold-rich volcanogenic massive sulfide (VMS), Carlin-type, orogenic, and iron-oxide copper-gold (IOCG), and intrusion-related gold deposits (IRGDs). District-scale mineral system approaches propose interrelated groups such as porphyry Cu-Au, skarn Cu-Au-Ag, and high-sulfidation Au-Ag. In this study, the temporal evolution of subduction-related processes in convergent margins was evaluated to propose a continuum of genetic models that unify the various types of gold deposits. At the tectonic scale of mineral systems, all hydrothermal gold deposits are interrelated in that they formed progressively during the evolution of direct or indirect subduction-related processes along convergent margins. Porphyry-related systems formed initially from magmatic-hydrothermal fluids related to melting of fertile mantle to initiate calc-alkaline to high-K felsic magmatism in volcanic arcs directly related to subduction. Formation of gold-rich VMS systems was related to hydrothermal circulation driven by magmatic activity during rifting of oceanic arcs. Orogenic gold deposits formed largely through fluids derived from devolatilization of the downgoing slab and overlying sediment wedge during late transpression in the orogenic cycle. Carlin-type deposits, IRGDs, and some continental-arc porphyry systems formed during the early stages of orogenic collapse via fluids directly or indirectly related to hybrid magmatism from melting of lithosphere that was metasomatized and gold-fertilized by earlier fluid release from subduction zones near margins of continental blocks. The IOCGs were formed during postorogenic asthenosphere upwelling beneath such subduction-related metasomatized and fertilized lithospheric blocks via fluid release and explosive emplacement of volatile-rich melts. Thus, importantly, subduction is clearly recognized as the key unifying dynamic factor in gold metallogenesis, with subduction-related fluids or melts providing the critical ore components for a wide variety of gold-rich deposit types.

The distribution, characteristics and fluid sources of lode gold deposits: An overview

“…Different from the model of subducting slab-derived fluids, the model of mantle-derived melts/fluids has two stages of exsolving ore-forming fluids. The SCLM was firstly metasomatized during subduction, and then mantlederived fluids were generated by devolatilization of the lithosphere mantle, or mantle-derived melts migrated upward into the crust (Groves et al, 2020). However, some researchers argued that mantle-derived melts/fluids and oreforming fluids may just share the same deep transcrustal fault during ascent and may not be have a genetic link (Goldfarb and Groves, 2015).…”

“…Ore-forming fluids of lode gold deposits associated with the destruction of the NCC may have been derived directly from devolatilization of subducted slabs and overlying sediments (Goldfarb and Santosh, 2014). However, many researchers emphasized the role of the metasomatized SCLM beneath the NCC in gold mineralization (Li et al, 2012a;Zhu et al, 2015;Groves et al, 2020;Wang Z C et al, 2020). It is still enigmatic that ore-forming fluids were sourced from mantle-derived melts/fluids (Tan et al, 2012), or exsolved from felsic magmas that experienced mixing of the crust and mantle-derived magmas (Li et al, 2012b).…”

Auriferous Quartz Veining Due to CO2 Content Variations and Decompressional Cooling, Revealed by Quartz Solubility, SEM-CL and Fluid Inclusion Analyses (The Linglong Goldfield, Jiaodong)

“…The Jiaodong gold province (JGP) has been the subject of many detailed studies for many decades [28][29][30][31], and its geology and metallogeny have been synthesized and updated by many past and recent researchers [32][33][34][35][36][37][38][39][40][41][42][43][44]. Therefore, only a brief introduction closely relevant to this study is provided.…”

Formation of Gold Alloys during Crustal Differentiation of Convergent Zone Magmas: Constraints from an AU-Rich Websterite in the Stanovoy Suture Zone (Russian Far East)

“…Gold is an important commercial metal in various types (porphyry, epithermal, volcanogenic massive sulfide, Carlin-type, intrusion-related, etc.) of ore deposits at convergent plate margins [1][2][3][4][5][6][7][8][9][10][11][12]. Because of their high solubility in a wide range of silicate melts and hydrothermal fluids, gold and associated base and precious metals (Ag, Cu, Mo, Pt, Pd) are transported into the upper crust by metal-rich, basaltic to dacitic magmas and deposited in epithermal and porphyry environments in subduction and collision zones [3][4][5][6]11,[13][14][15][16][17][18][19][20].…”