Crust-Mantle Interactions and Granitoid Diversification – Insights from Archaean Cratons
Based upon contemporary (2011-2015) research from the UNESCO-IGCP project ‘The Changing Early Earth’, this GSL Special Publication documents the evidence for fundamental change in the tectonics and magmatism on the Archaean Earth. Initial mafic magmas (erupted as oceanic crust, island arcs or plateaus) evolved through to the calc-alkaline Tonalite – Trondhjemite – Granodiorite (TTG) rock suites of accreting microcontinents, to the diversity of late Archaean granitoids generated at thick convergent continental margins.
An overview paper introduces the research context, including an essential background section on the specific terminology associated with the geochemical (compositional) nomenclature and classification, characteristic features, age relations and temporal – spatial patterns of Archaean granitoids. The volume contains three main regionally-based thematic sections of seven papers: Mesoarchaean Volcanic Supracrustals from Greenland, Mantle-derived Alkaline Rocks from Western Karelia (Fenno-Scandian Shield) and Mantle to Crustal Melting in the Indian Shield. A final section of three papers presents current insights derived from associated studies in metamorphic petrology.
The contributions chronicle the development of crust-forming magmatism from minor early Archaean (Eoarchaean) crust-mantle interactions to the appearance of extensive multisource granitoids, exhibiting crustal recycling (via mantle and intra-crustal reworking) at the end of the Archaean. These insights significantly expand the debate on the origin of Archaean igneous rocks and their role in deciphering Archaean crustal evolution and tectonics, providing new evidence for increasing crust-mantle interactions, granitoid diversification and the changing plate tectonic ‘style’ operating towards the end of the Archaean. The overall conclusion is the pre-eminence of convergent tectonic regimes over plume tectonics as the main crustal growth mechanism since the Eoarchaean.
The volume provides an excellent overview of the recent interdisciplinary geoscientific developments within this important and evolving field. The contributions are well-written and edited, complemented with appropriate figures, photographs and data-tables, features that one has come to expect from the GSL Special Publication series. A minor presentational criticism is that a couple of field photographs appear to have colour ‘bled’ in the print copy obtained by this reviewer, unfortunately distracting from the feature details described.
In summary, the editors and contributors are to be congratulated. An informative and recommended read.
Reviewed by Mark Griffin
CRUST-MANTLE INTERACTIONS AND GRANITOID DIVERSIFICATION – INSIGHTS FROM ARCHAEAN CRATONS by HALLA, J, WHITEHOUSE, M J, AHMAD T AND BAGAI, Z (editors). Geological Society of London Special Publication No 449. 2017. Geological Society of London. ISBN 978-1-78620-280-2. Hbk. 256pp. ISSN 0305-8719. List Price: £110.00, Fellows’ Price £55.00. W: www.geolsoc.org.uk/SP449.