Linking metamorphism and plate boundaries over the past 2 billion years

Author:

Liu Yebo1,Mitchell Ross N.2,Brown Michael3,Johnson Tim E.1,Pisarevsky Sergei14

Affiliation:

1. Earth Dynamics Research Group, The Institute for Geoscience Research (TIGeR), Department of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia

2. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

3. Laboratory for Crustal Petrology, Department of Geology, University of Maryland, College Park, Maryland 20742, USA

4. Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033, Russia

Abstract

Abstract Since the Jurassic, there has been a clear spatiotemporal correlation between different types of metamorphism and active convergent plate margins. However, the extent to which this relationship extends into the past is poorly understood. We compared paleogeographic reconstructions and inferred plate kinematics with the age and thermobaric ratio (temperature/pressure [T/P]) of metamorphism over the past 2 b.y. The null hypothesis—that there is no spatiotemporal link between inferred plate margins and metamorphism—can be rejected. Low-T/P metamorphism is almost exclusively located near plate margins, whereas intermediate- and high-T/P metamorphism skews toward increasingly greater distances from these margins, consistent with three different tectonic settings: the subduction zone, the mountain belt, and the orogenic hinterland, respectively. However, paleogeographic reconstructions suggest that so-called “paired metamorphic belts” are rare and that high- and low-T/P localities more commonly occur along strike from each other. The observation that bimodal metamorphism is largely a function of distance from the trench and that end-member T/P types rarely occur in the same place can be explained if the style of orogenesis has evolved from hotter to colder, consistent with the abrupt emergence of low-T/P metamorphism in the Cryogenian. The widespread development of high-T/P rocks in orogenic hinterlands in the Proterozoic was followed by the production and efficient exhumation of low-T/P rocks in subduction channels in the Phanerozoic.

Publisher

Geological Society of America

Subject

Geology

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