『Abstract
Compilation and analysis of the paleomagnetically constrained
plate tectonic reconstructions for the last 2.5 Ga of Earth's
history reveal that continental and oceanic hemispheres are principal
and stable first order divisions on the Earth, with cyclical breakup
and reassembly of the continental crust into supercontinents.
Although the breakup of the supercontinent Rodinia at 0.75 Ga
marked important reorganization of the plate tectonic pattern,
the movements of large continental masses, both before and after
the breakup of Rodinia, show remarkable synchronism, albeit in
significantly rearranged combinations.
The patterns with disassembled continents coincided with periods
when substantially more than 50% of the continental masses, occurred
either in the northern (during Palaeoproterozoic and Cenozoic
times) or southern (during Neoproterozoic to middle Palaeozoic
times) hemispheres, whereas the reassembled supercontinents were
always symmetrically centred near the Equator. It is proposed
that such regularity might be governed by a convection-driven
move of the continental fragments towards a pole after the breakup
of the supercontinent, followed by gyroscopic rebalancing (or
shift) of all earth's solid shells (e.g., entire mantle + lithosphere)
towards the Equator relative to the more stable-oriented magnetic
currents in the liquid core. this process is somewhat similar
to the true polar wander concept, but it takes into account the
spinning forces of the Earth. Mantle convection is considered
as an important force, constantly driving the plates in the oceanic
hemisphere and keeping the continental hemisphere intact.
The periods of gyroscopic rebalancing correspond to the reassembly
of the supercontinents at 2.7〜2.5 Ga (Kenorland), 2.0〜0.75 Ga
(Columbia and its modification into Rodinia), and 0.32〜0.18 Ga
(Pangaea). The main reassembly mechanism, in addition to rifting,
spreading and collision, is large-scale strike-slip translation
of not only relatively small lithotectonic terranes, but also
of major cratons. These cycles govern changes from the dominantly
extension- to collision- and plume-related mineral deposit types
in the internal orogens in the continental hemisphere, whereas
subduction-related to collision-related mineral deposit types
remain persistent through the metallogenic cycles at the oceanic/continental
hemisphere transion zone, just migrating oceanward in time.
Keywords: Gyroscopic Earth; Global tectonics; Global metallogeny』
1. Introduction
2. Continental masses after breakup of Rodinia
2.1. Post-Rodinian supercontinental cycle and its metallogeny
2.2. Post-Pangaea supercontinental cycle and its metallogeny
2.3. Summary I
3. Pre-Rodinian history
3.1. Pre-Rodinian reconstructions and metallogeny
3.2. Summary II
4. The gyroscopic Earth
4.1. Apparent and true polar wander
4.2. Supercontinent cycles
5. Conclusions
Acknowledgements
References