『Abstract
Ophiolite, and discussions on their origin and significance in
Eareth's history, have been instrumental in the formulation, testing,
and establishment of hypotheses and theories in earth sciences.
The definition, tectonic origin, and emplacement mechanisms of
ophiolites have been the subject of a dynamic and continually
evolving concept since the nineteenth century. Here, we present
a review of these ideas as well as a new classification of ophiolites,
incorporating the diversity in their structural architecture and
geochemical signatures that results from variations in petrological,
geochemical, and tectonic processes during formation in different
geodynamic settings. We define ophiolites as suites of temporally
and spatially associated ultramafic to felsic rocks related to
separate melting episodes and processes of magmatic differentiation
in particular tectonic environments. Their geochemical characteristics,
internal structure, and thickness vary with spreading rate, proximity
to plumes or trenches, mantle temperature, mantle fertility, and
the availability of fluids. Subduction-related ophiolites include
suprasubduction-zone and volcanic-arc types, the evolution of
which is governed by slab dehydration and accompanying metasomatism
of the mantle, melting of the subducting sediments, and repeated
episodes of partial melting of metasomatized peridotites. Subduction-unrelated
ophiolites include continental-margin, mid-ocean-ridge (plume-proximal,
plume-distal, and trench-distal), and plume-type (plume-proximal
ridge and oceanic plateau) ophiolites that generally have mid-ocean-ridge
basalt (MORB) compositions. Subduction-related lithosphere and
ophiolites develop during the closure of ocean basins, whereas
subduction-unrelated types evolve during rift drift and seafloor
spreading. The peak times of ophiolite genesis and emplacement
in Earth history coincided with collisional events leading to
the construction of supercontinents continental breakup, and plume-related
supermagmatic events. Geochemical and tectonic fingerprinting
of Phanerozoic ophiolites within the framework of this new ophiolite
classification is an effective tool for identification of the
geodynamic settings of oceanic crust formation in Earth history,
and it can be extended into Precambrian greenstone belts in order
to investigate the ways in which oceanic crust formed in the Archean.』
Introduction
Historical background and new definition of ophiolites
Early ideas and evolving ophiolite concept
New definition of ophiolites
Ophiolite pulses and global tectonics
A new classification of ophiolites
Tectonic settings of ophiolite types
Geochemical fingerprinting of ophiolite types
Petrogenesis of ophiolite types in different tectonic setting
Application to Precambrian greenstone belts
Isua supracrustal belt
Wawa greenstone belts
Jormua Complex
Summary
Conclusions
Acknowledgments
References cited