『Abstract
Ages of giant gold systems (＞500 t gold) cluster within well-defined
periods of lithospheric growth at continental margins, and it
is the orogen-scale processes during these mainly Late Archaean,
Palaeoproterozoic and Phanerozoic times that ultimately determine
gold endowment of a province in an orogen. A critical factor for
giant orogenic gold provinces appears to be thickness of the subcontinental
lithospheric mantle (SCLM) beneath a province at the time of gold
mineralisation, as giant gold deposits are much more likely to
develop in orogens with subducted oceanic or thin continental
lithosphere. A proxy for the latter is a short pre-mineralisation
crustal history such that thick SCLM was not developed before
gold deposition. In contrast, orogens with protracted pre-mineralisation
crustal histories are more likely to be characterised by a thick
SCLM that is difficult to delaminate, and hence, such provinces
will normally be poorly endowed. The nature of the lithosphere
also influences the intrinsic gold concentrations of potential
source rocks, with back-arc basalts, transitional basalts and
basanites enriched in gold relative to other rock sequences. Thus,
segments of orogens with thin lithosphere may enjoy the conjunction
of giant-scale fluid flux through gold-enriched sequences. Although
the nature of the lithosphere plays the crustal role in dictating
which orogenic gold provinces will contain one or more giant deposits,
the precise siting of those giants depends on the critical conjunction
of a number of province-scale factors. Such features control plumbing
systems, traps and seals in tectonically and lithospherically
suitable terranes within orogens.
Keywords: Orogenic gold; Giant gold deposits; Metallogeny; Tectonics;
Lithosphere; Endowment』
Introduction
Characteristics of giant orogenic gold systems
The importance of orogen- to lithosphere-scale processes
Tectonic and lithospheric constraints on terranes hosting giant
orogenic gold systems
Archaean examples
Palaeoproterozoic examples
Phanerozoic examples
Tectonic setting and gold-enriched source rocks
Siting of giants within giant-bearing provinces
Summary and conclusions
Acknowledgements
References