『Abstract
Mineral deposit types commonly have a distinctive temporal distribution
with peaks at specific periods of Earth history. Deposits of less
redox-sensitive metals, such as gold, show long-term temporal
patterns that relate to first-order changes in an evolving Earth,
as a result of progressively declining heat production and attendant
changes in global tectonic processes. despite abundant evidence
for plate tectonics in the early Precambrian, it is evident that
plume events were more abundant in a hotter Earth.
Episodic growth of juvenile continental crust appears to have
been related to short-lived (<100 m.y.) catastrophic mantle-plume
events and formation of supercontinents, whereas shielding mantle-plume
events correlated with their breakup. different mineral deposit
types are associated with this cycle of supercontinent formation
and breakup. Broadly synchronous with juvenile continental crust
formation was the development of subcontinental lithospheric mantle,
which evolved due to progressively declining heat flow and decreasing
plume activity. Archean subcontinental lithospheric mantle has
a distinct mineralogical composition and is buoyant, whereas later
lithosphere was progressively more dense. Changes in the buoyancy
of both oceanic lithosphere and subcontinental lithospheric mantle
led to evolution of tectonic scenarios in which buoyant, roughly
equidimensional, early Precambrian craton were rimmed by Proterozoic
or Phanerozoic linear elongate belts of neutral to negative buoyancy.
Orogenic gold deposits, which formed over at least 3.4 b.y.,
had the highest preservation potential of any gold deposit type.
The pattern of formation and preservation, from episodic to more
cyclic, broadly mirrors that of crustal growth. Early Precambrian
(mostly ca. 2.7 and 2.0-1.8 Ga) deposits, protected from uplift
and erosion in the centers of buoyant cratons, are rare between
ca. 1.7 Ga and 600 Ma due to the change to more modern-style plate
tectonic processes, with nonpreservation of deposits of this age
due to uplift and erosion of more vulnerable orogenic belts. Volcanic-hosted
massive sulfide (VHMS) deposits were accreted into the convergent
margin terranes in which orogenic gold deposits were forming.
Their temporal distribution, from strongly episodic to more cyclic
peaks, also supports a model of selective preservation.
The first appearance of iron-oxide copper-gold (IOCG) deposits
at 〜2.55 Ga closely follows development of early Precambrian subcontinental
lithosphere mantle. Their genesis involved melting of metasomatized
subcontinental lithosphere mantle, so they could not form until
such metasomatized mantle evolved below cratons with buoyant lithosphere.
Giant Precambrian paleoplacer gold deposits probably formed by
effective fluvial sorting under extreme climatic conditions but
were largely preserved due to early buoyant subcontinental lithospheric
mantle below hosting foreland basins. Unequivocal intrusion-related
gold deposits are related to complex felsic intrusions with a
mixed mantle-crustal signature, which intruded deformed shelf
sedimentary sequences close to but outside craton margins. Given
that post-Paleoproterozoic uplift and erosion is likely in vulnerable
orogenic belts with negatively buoyant lithosphere, this deposit
type is likely to be rare in Paleozoic and older terranes.
Gold-bearing deposit types thus display distinctive temporal
distributions related to change from a more buoyant plate tectonic
style in the early hotter Earth to a modern plate tectonic style
typical of the Phanerozoic. Later Archean formation of buoyant
subcontinental lithospheric mantle was particularly important
in the anomalous preservation of some earlier formed deposit types
located inboard of craton margins and in providing critical conditions
for the formation of others. Development of negatively buoyant
subcontinental lithospheric mantle can explain the lack of preservation
of some deposit types that formed in the later Proterozoic. A
single fundamental concept of coupled episodic crustal growth
and preservation in the Archean and Paleoproterozoic, evolving
to decoupled episodes of growth and preservation from the Mesoproterozoic
onward, can thus explain the temporal distribution of a number
of gold-bearing mineral deposit types.』
Introduction
Juvenile continental crust and the supercontinent cycle
Mantle-plume events and the supercontinent cycle
The transition from Archean to modern-style plate tectonics
Evolution of the subcontinental lithospheric mantle
Tectonic evolution and secular change in metallogeny: Useful markers
Tectonic evolution and secular change in metallogeny: Messages
from orogenic gold deposits
Examples of tectonically induced selective preservation
Volcanic-hosted massive sulfide deposits
Placer and paleoplacer gold
Examples of tectonically induced selective formation and preservation
Iron-oxide copper-gold (IOCG) deposits
Intrusion-related gold deposits
Synthesis
Future research and exploration significance
Acknowledgments
References