9.07 - Mechanism of Continental Crustal Growth

https://doi.org/10.1016/B978-0-444-53802-4.00159-7Get rights and content

Abstract

The continental crust comprising the outmost 20–80 km of the solid surface of the Earth and covering ~ 41% of the Earth’s surface area is of great antiquity and contains the record of most of the geological (physical and chemical) evolution of the Earth. The oldest surviving rocks date from more than four billion years ago, a few hundred million years after the formation of the Earth. A major research theme in Earth Sciences is the understanding of the mechanism of continental crust growth. Different models suggested early creation and subsequent recycling of continental crust material or continuous or episodic crustal growth (the “Anderson-Moorbath debate”). This debate is entwined with discussions on the geodynamic-magmatic environment of crustal growth and the role that arcs and/or mantle plumes play in juvenile crustal growth (the “Reymer and Schubert dilemma”). We discuss mantle overturn and accretion models that invoke episodic activity of large mantle plumes and accretion of juvenile mantle material (such as the oceanic plateaus) to the continents (the “MOMO model”), alternative arc-tectonic models, or recent suggestions for continents preservation models. New insights on the earliest history of continental crust and the relation to mantle evolution come from the exciting studies on radiogenic isotopes of Hf in zircons and radiogenic Nd isotopes (e.g. 143Nd and 142Nd, the decay products of 147Sm and the extinct 146Sm) in magmatic rocks.

It appears that throughout the past ~ 2.7 Ga major segments of continental crust over the globe were evolved through similar evolution and petrogenetic histories: early formation of thick sequences of basalts in oceanic environment that resemble those of plume-related oceanic plateaus (e.g. the Cretaceous Ontong Java plateau in the Pacific), this phase is followed by a long phase (~250–300 Ma) of arc subducation-related calc-alkaline magmatism (such as the western Pacific arc) that comprise major juvenile addition to the continental crust. After cessation of subduction process, the existing crust and lithospheric mantle evolve through metamorphism and melting that produce calc-alkaline and alkaline granitic magmas that comprise most of the uppermost continental crust. Production of granitic magmas requires water in their sources (e.g. amphibolites). The role of water in shaping the unique structure, composition, and landscape of the outermost Earth is emphasized in the Campbell and Taylor concept of: no water, no granites, no oceans, no continents.

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Cited by (3)

  • Three stages to form a large batholith after terrane accretion – An example from the Svecofennian orogen

    2016, Precambrian Research
    Citation Excerpt :

    Different geochemical series are formed if the accreting terranes have different compositions. If oceanic crust is involved (i.e. oceanic arc or plateau) the magmas form tholeiitic series and if continental crust is involved (i.e. island arc or old continental block) the magmas form calc-alkaline series (Defant and Drummond, 1990; Defant and Nielsen, 1990; Marsh, 2015; Stein and Ben-Avraham, 2015). In post-accretion events, the partial melts of the mafic crust or the fractionation of the differentiated mantle-derived mafic magmas may form alkaline series (Collins et al., 1982; Turner et al., 1992; Frost et al., 2001; Moyen and Martin, 2012).

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