The building blocks of continental crust: Evidence for a major change in the tectonic setting of continental growth at the end of the Archean
TL;DR: This paper showed that post-Archean continental crust does not begin life in oceanic arcs, and that continental crust was not formed by seafloor plate tectonics in the late Archean.
About: This article is published in Gondwana Research.The article was published on 2013-03-01. It has received 272 citations till now. The article focuses on the topics: Continental crust & Continental margin.
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TL;DR: In this article, the authors argue that the production of mantle-derived or juvenile continental crust during the accretionary history of the Central Asian Orogenic Belt (CAOB) has been grossly overestimated.
699 citations
Cites background from "The building blocks of continental ..."
...Therefore, continental arcs may have been more common in the CAOB than so far envisaged, in line with a suggestion of Condie and Kröner (2013) that such arcs played a major role in continental evolution through geologic time....
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TL;DR: In this paper, detrital zircons have been used to estimate that at least 60% to 70% of the present volume of the continental crust had been generated by 3 Ga, which may have been linked to the onset of signifi cant crustal recycling through subduction at convergent plate margins.
Abstract: Continental crust is the archive of Earth history. The spatial and temporal distribution of Earth’s record of rock units and events is heterogeneous; for example, ages of igneous crystallization, metamorphism, continental margins, mineralization, and sea water and atmospheric proxies are distributed about a series of peaks and troughs. This distribution refl ects the different preservation potential of rocks generated in different tectonic settings, rather than fundamental pulses of activity, and the peaks of ages are linked to the timing of supercontinent assembly. The physiochemical resilience of zircons and their derivation largely from felsic igneous rocks means that they are important indicators of the crustal record. Furthermore, detrital zircons, which sample a range of source rocks, provide a more representative record than direct analysis of grains in igneous rocks. Analysis of detrital zircons suggests that at least ~60%–70% of the present volume of the continental crust had been generated by 3 Ga. Such estimates seek to take account of the extent to which the old crustal material is underrepresented in the sedimentary record , and they imply that there were greater volumes of continental crust in the Archean than might be inferred from the compositions of detrital zircons and sediments. The growth of continental crust was a continuous rather than an episodic process, but there was a marked decrease in the rate of crustal growth at ca. 3 Ga, which may have been linked to the onset of signifi cant crustal recycling, probably through subduction at convergent plate margins. The Hadean and Early Archean continental record is poorly preserved and characterized by a bimodal TTG (tonalites, trondhjemites, and granodiorites) and greenstone association that differs from the younger record that can be more directly related to a plate-tectonic regime. The paucity of this early record has led to competing and equivocal models invoking plate-tectonic– and mantle-plume–dominated processes. The 60%–70% of the present volume of the continental crust estimated to have been present at 3 Ga contrasts markedly with the <10% of crust of that age apparently still preserved and requires on going destruction (recycling) of crust and subconti nental mantle lithosphere back into the mantle through processes such as subduction and delamination.
502 citations
Cites background from "The building blocks of continental ..."
...Also the preservation potential of intra-oceanic arcs, which are largely submarine, is poor (Condie and Kröner, 2012)....
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TL;DR: In this article, the authors proposed a "arc-like signature" model for the origin of the continental crust (CC), which is based on the "island arc" model.
237 citations
Cites background from "The building blocks of continental ..."
...Recently, Condie and Kroner (2013) suggested a major change in the tectonic setting of continental growth at the end of the Archean from “oceanic plateau settings” in the Archean to continental arc settings thereafter....
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TL;DR: In this article, the authors proposed that the North China Craton (NCC) can be divided into six micro-blocks with >∼3.0-3.8-Ga old continental nuclei.
Abstract: The North China Craton (NCC) has a complicated evolutionary history with multi-stage crustal growth, recording nearly all important geological events in the early geotectonic history of the Earth. Our studies propose that the NCC can be divided into six micro-blocks with >∼3.0–3.8 Ga old continental nuclei that are surrounded by Neoarchean greenstone belts (GRB). The micro-blocks are also termed as high-grade regions (HGR) and are mainly composed of orthogneisses with minor gabbros and BIF-bearing supracrustal beds or lenses, all of which underwent strong deformation and metamorphism of granulite- to high-grade amphibolite-facies. The micro-blocks are, in turn, from east to west, the Jiaoliao (JL), Qianhuai (QH), Ordos (ODS), Ji'ning (JN) and Alashan (ALS) blocks, and Xuchang (XCH) in the south. Recent studies led to a consensus that the basement of the NCC was composed of different blocks/terranes that were finally amalgamated to form a coherent craton at the end of Neoarchean. Zircon U-Pb data show that TTG gneisses in the HGRs have two prominent age peaks at ca. 2.9–2.7 and 2.6–2.5 Ga which may correspond to the earliest events of major crustal growth in the NCC. Hafnium isotopic model ages range from ca. 3.8 to 2.5 Ga and mostly are in the range of 3.0–2.6 Ga with a peak at 2.82 Ga. Recent studies revealed a much larger volume of TTG gneisses in the NCC than previously considered, with a dominant ca. 2.7 Ga magmatic zircon ages. Most of the ca. 2.7 Ga TTG gneisses underwent metamorphism in 2.6–2.5 Ga as indicated by ubiquitous metamorphic rims around the cores of magmatic zircon in these rocks. Abundant ca. 2.6–2.5 Ga orthogneisses have Hf-in-zircon and Nd whole-rock model ages mostly around 2.9–2.7 Ga and some around 2.6–2.5 Ga, indicating the timing of protolith formation or extraction of the protolith magma was from the mantle. Therefore, it is suggested that the 2.6–2.5 Ga TTGs probably represent a coherent event of continental accretion and major reworking (crustal melting). As a distinct characteristic, nearly all GRBs in the NCC underwent amphibolite-facies metamorphism. Zircon U-Pb ages of metamorphosed GRB mafic rocks mainly show two peak ranges at ∼2.6–2.5 and 2.8–2.7 Ga. The mafic rocks are commonly believed to be derived from metabasalts, it is therefore possible that the ages represent the time of metamorphism. The tectonic settings of the GRBs are still a problem. Their geochemical characteristics are, respectively, similar to back-arc basins, rifts, island arcs or suggest imprints of mantle plumes. BIFs occur in all GRBs but also in the HGRs. This metallogenic specificity is quite different from all Phanerozoic geotectonic settings. The ∼2.5 Ga metamorphic-magmatic event is stronger than in most other cratons in the world. How to understand the geological significance of the 2.5 Ga event? The following points are emphasized: (1) nearly all old rocks >2.5 Ga underwent metamorphism at ∼2.52–2.5 Ga; (2) Archean basement rocks in the NCC experienced strong partial melting and migmatization; (3) granitoid rocks derived from partial melting include potassium granites, TTG granites and monzonites. These granitoids rocks intruded both the Archean greenstone belts and micro-blocks; (4) ∼2.5 Ga mafic dikes (amphibolites), granitic dikes (veins) and syenitic-ultramafic dykes are also developed. Therefore, we suggest an assembly model that all micro-blocks in the NCC were welded together by late Archean greenstone belts at the end of the late Neoarchean. We also propose that the various micro-blocks were surrounded by small ocean basins, and the old continental crust and the oceanic crust were hotter than today. Subduction and collision were on much smaller scales as compared to the Phanerozoic plate tectonic regime, although the tectonic style and mechanisms were more or less similar. The formation of crustal melt granites is one of the processes of cratonization, inducing generation of stable upper and lower crustal layers. This process also generated an upper crust of more felsic composition and a lower crust of more mafic composition, due to molten residual materials and some underplated gabbros.
230 citations
Additional excerpts
...The recent studies show that the oldest continental rocks in the Earth are tonalitic gneiss and the oldest zircons are detrital zircons in sedimentary rocks which were sourced from TTG protoliths (e.g., Wilde et al., 2001; Iizuka et al., 2006; Nemchin et al., 2006; Harrison, 2009; Herzberg et al., 2010; Condie and Kröner, 2013; Nance et al., 2013)....
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TL;DR: In this paper, a series of experiments were run using a 2-D petrological-thermomechanical numerical model in which the collision of spontaneously moving continental plates was simulated for values of ambient upper-mantle temperature and radiogenic heat production increasing from those appropriate to the present-day.
217 citations
References
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01 Jan 1989
TL;DR: In this article, trace-element data for mid-ocean ridge basalts and ocean island basalts are used to formulate chemical systematics for oceanic basalts, interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone.
Abstract: Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.
19,221 citations
Additional excerpts
...mantle (PM), Sun and McDonough (1989)....
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TL;DR: In this paper, the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories are discussed.
Abstract: This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories. We review the composition of the upper, middle, and lower continental crust. We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes. Finally, we compare the Earth's crust with those of the other terrestrial planets in our solar system and speculate about what unique processes on Earth have given rise to this unusual crustal distribution.
7,831 citations
TL;DR: A new tectonic model, postulating the growth of giant subduction-accretion complexes along a single magmatic arc now found contorted between Siberia and Baltica, shows that Asia grew by 5.3 million square kilometres during the Palaeozoic era as mentioned in this paper.
Abstract: A new tectonic model, postulating the growth of giant subduction-accretion complexes along a single magmatic arc now found contorted between Siberia and Baltica, shows that Asia grew by 5.3 million square kilometres during the Palaeozoic era. Half of this growth may have occurred by the addition of juvenile crust newly extracted from the mantle, supporting models of considerable continental growth continuing throughout the Phanerozoic eon.
3,180 citations
Book•
01 Jan 2014
TL;DR: This extensively updated new edition of the widely acclaimed Treatise on Geochemistry has increased its coverage beyond the wide range of geochemical subject areas in the first edition, with five new volumes which include: the history of the atmosphere, geochemistry of mineral deposits, archaeology and anthropology, organic geochemistry and analytical geochemistry as discussed by the authors.
Abstract: This extensively updated new edition of the widely acclaimed Treatise on Geochemistry has increased its coverage beyond the wide range of geochemical subject areas in the first edition, with five new volumes which include: the history of the atmosphere, geochemistry of mineral deposits, archaeology and anthropology, organic geochemistry and analytical geochemistry. In addition, the original Volume 1 on "Meteorites, Comets, and Planets" was expanded into two separate volumes dealing with meteorites and planets, respectively. These additions increased the number of volumes in the Treatise from 9 to 15 with the index/appendices volume remaining as the last volume (Volume 16). Each of the original volumes was scrutinized by the appropriate volume editors, with respect to necessary revisions as well as additions and deletions. As a result, 27 per cent were republished without major changes, 66per cent were revised and 126 new chapters were added. In a many-faceted field such as Geochemistry, explaining and understanding how one sub-field relates to another is key. Instructors will find the complete overviews with extensive cross-referencing useful additions to their course packs and students will benefit from the contextual organization of the subject matter. Six new volumes added and 66per cent updated from 1st edition. The Editors of this work have taken every measure to include the many suggestions received from readers and ensure comprehensiveness of coverage and added value in this 2nd edition. The esteemed Board of Volume Editors and Editors-in-Chief worked cohesively to ensure a uniform and consistent approach to the content, which is an amazing accomplishment for a 15-volume work (16 volumes including index volume)!
2,880 citations