Skip to Main Content
Book Chapter

The sanukitoid series: magmatism at the Archaean–Proterozoic transition

By
Hervé Martin
Hervé Martin
Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, BP 10448, F-63000 Clermont-Ferrand, FranceCNRS, UMR 6524, LMV, F-63038 Clermont-Ferrand, France IRD, R 163, LMV, F-63038 Clermont-Ferrand, France, Email: h.martin@opgc.univ-bpclermont.fr
Search for other works by this author on:
Jean-François Moyen
Jean-François Moyen
Department of Geology, University of Stellenbosch, Private Bag X 01, 7602 Matieland, South Africa
Search for other works by this author on:
Robert Rapp
Robert Rapp
Research School of Earth Sciences, The Australian National University, Canberra, ACT, 0200 Australia
Search for other works by this author on:
Published:
October 01, 2010

A specific type of granitoid, referred to as sanukitoid (Shirey & Hanson 1984), was emplaced mainly across the Archaean–Proterozoic transition. The major and trace element composition of sanukitoids is intermediate between typical Archaean TTG and modern arc granitoids. However, among sanukitoids, two groups can be distinguished on the basis of the Ti content of the less differentiated rocks of the suite: high- and low-Ti sanukitoids. Melting experiments and petrogenetic modelling show that they may have formed by either (1) melting of mantle peridotite previously metasomatised by felsic melts of TTG composition, or (2) by reaction between TTG melts and mantle peridotite (assimilation). Rocks of the sanukitoid suite were emplaced at the Archaean–Proterozoic boundary, possibly marking the time when TTG-dominated granitoid magmatism changed to a more modern-style, arc-dominated magmatism. Consequently, the intermediate character of sanukitoids is not only compositional but chronological. The succession of granitoid magmatism with time is integrated in a plate tectonic model where it is linked to the thermal evolution of subduction zones, reflecting the progressive cooling of Earth: (1) the Archaean Earth’s heat production was high enough to allow the production of large amounts of TTG granitoids formed by partial melting of recycled basaltic crust (‘slab melting’); (2) at the end of the Archaean, due to the progressive cooling of the Earth, the extent of slab melting was reduced, resulting in lower melt:rock ratios. In such conditions the slab melts can be strongly contaminated by assimilation of mantle peridotite, thus giving rise to low-Ti sanukitoids. It is also possible that the slab melts were totally consumed in reactions with mantle peridotite, subsequent melting of this ‘melt-metasomatised mantle’ producing the high-Ti sanukitoid magmas; (3) after 2·5 Ga, Earth heat production was too low to allow slab melting, except in relatively rare geodynamic circumstances, and most modern arc magmas are produced by melting of the mantle wedge peridotite metasomatised by fluids from dehydration of the subducted slab. Of course, such changes did not take place exactly at the same time all over the world. The Archaean mechanisms coexisted with new processes over a relatively long time period, even if they were subordinate to the more modern processes.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

Sixth Hutton Symposium on The Origin of Granites and Related Rocks: Proceedings of a Symposium held in Stellenbosch, South Africa, 2- 6 July 2007

John D. Clemens
John D. Clemens
Department of Earth Sciences, University of Stellenbosch, South Africa
Search for other works by this author on:
Colin Donaldson
Colin Donaldson
EESTRSE Editor:
Search for other works by this author on:
Carol D. Frost
Carol D. Frost
Guest Editors:
Search for other works by this author on:
Alexander F.M. Kisters
Alexander F.M. Kisters
Guest Editors:
Search for other works by this author on:
Jean-François Moyen
Jean-François Moyen
Guest Editors:
Search for other works by this author on:
Tracy Rushmer
Tracy Rushmer
Guest Editors:
Search for other works by this author on:
Gary Stevens
Gary Stevens
Guest Editors:
Search for other works by this author on:
Geological Society of America
Volume
472
ISBN print:
9780813724720
Publication date:
October 01, 2010

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal