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Book ChapterDOI

Crustal and mantle evolution

01 Jan 2005-pp 144-180
TL;DR: The evolution of the Earth's crust is tied closely to that of the mantle and a review of the evolution of this dynamic system with the cooling of Earth over the last 4.6 Ga is given in this paper.
Abstract: This chapter shows the way the evolution of the crust is tied closely to that of the mantle and reviews the evolution of this dynamic system with the cooling of the Earth over the last 4.6 Ga. A number of investigators agree that the history of the Earth's crust and mantle are closely related and that many of the features found in the crust are controlled by processes in the mantle. Theories for the origin of the Earth's crust fall into three broad categories: heterogeneous accretion of the Earth, impact models, and terrestrial models. The oldest preserved fragments of continental crust from 4.0 to 3.8 Ga are chiefly of tonalitic (tonalite–trondhjemite–granodiorite, or TTG) gneisses containing fragments of komatiite and basalt (amphibolite), some of which may be remnants of the early oceanic crust. Model lead ages of the Earth and isotopic ages from meteorites suggest that the earliest terrestrial crust may have formed just after or during the late stages of planetary accretion, about 4.5 Ga. Although the original extent of early Archean continental fragments is not known, they comprise less than 10% of the preserved Archean crust.
Citations
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Journal ArticleDOI
TL;DR: In the early 1970s, deep-sea hydrothermal systems have been considered as likely candidates for the origin and early evolution of life on Earth as discussed by the authors, however, while subsequent investigations have revealed a great diversity of modern deepsea Hydrothermal ecosystems, they have done little to shed light on the issues of the origin of life, metabolism, cells, or communities.
Abstract: Since their discovery in the late 1970s, deep-sea hydrothermal systems have been considered as likely candidates for the origin and early evolution of life on Earth. However, while subsequent investigations have revealed a great diversity of modern deep-sea hydrothermal ecosystems, they have done little to shed light on the issues of the origin and early evolution of life, metabolism, cells, or communities. Phylogenetic, biochemical and geochemical clues all seem to point to the early evolution of hydrogenotrophic chemolithoautotrophy such as methanogenesis and sulfurreduction, thus pinpointing the availability of hydrogen as one of the key elements needed for the early evolution of earthly life. Hydrogen-driven, photosynthesis-independent communities are very rare on the contemporary Earth, however, being unambiguously found only in subsurface environments of H2-dominated hydrothermal systems. Such systems have been termed hyperthermophilic subsurface lithoautotrophic microbial ecosystems (Hyper...

71 citations


Cites background from "Crustal and mantle evolution"

  • ...Komatiite is a distinctive volcanic rock of the Archean and is common in Archean greenstone successions, whereas it is unusual in the Proterozoic and quite rare in the Phanerozoic (Condie, 1997)....

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Journal ArticleDOI
TL;DR: It is proposed that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth and should be considered prime sites in the search for evidence of past life on Mars.
Abstract: The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal-sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond.

61 citations


Cites background from "Crustal and mantle evolution"

  • ...On Earth, plate tectonics is the main process responsible for crustal recycling and for transporting deep crustal and mantle materials to the surface or near subsurface (Condie, 2016)....

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Journal ArticleDOI
TL;DR: In this paper, the authors present abundant observations of hydrogen produced at natural hydrothermal settings as well as in laboratory experiments and present the key mineral reactions responsible for the bulk of this hydrogen production.
Abstract: Heat produced in the mantle and core of the Earth by the decay of radioactive elements and mineral fusion results in large-scale mantle convection. The outer shell of the Earth that floats on the convective mantle is divided into rigid lithospheric plates. Subduction of dense cold plates into the mantle leads to plate tectonics. At divergent plate margins, heat is dissipated through hydrothermal convection cells. As ocean water is entrained into hydrothermal cells it interacts with fresh magmatic rocks and liberates ferrous iron. This iron reduces the ocean water to such an extent that it decomposes and forms hydrogen. Molecular hydrogen, as the most reduced component in the system, forms a basal component to a deep dark biosphere powered by metastable redox gradients. In this paper we review the driving force behind a hydrogen-driven deep biosphere. We present abundant observations of hydrogen produced at natural hydrothermal settings as well as in laboratory experiments. The key mineral reactions responsible for the bulk of this hydrogen production are then presented. A division of the reaction progression into an oxidized state and a reduced state is suggested. The amount of hydrogen produced is insignificant in the oxidized state whereas it becomes proportional to the amount of ferrous iron oxidized in the reduced state. The bulk of basalt-hosted aquifers are expected to reside in the oxidized state because of the low content of ferrous minerals, whereas abundant olivine in ultramafic-hosted systems is responsible for large-scale hydrogen production. Today the majority of the seafloor is basaltic. The Archean seafloor on the other hand consisted of fewer ultramafic exposures, but was dominated by ultramafic magnesium-rich lavas with a higher potential for hydrogen production than the present seafloor.

22 citations

Journal ArticleDOI
01 May 2019-Geology
TL;DR: Barham et al. as discussed by the authors used the Kolmogorov-Smirnov (KS) test for disparity analysis of detrital zircon data and found that the k-means test is sensitive to the last 2 Ga of global continental break-up and assembly (50% of the timeframe).
Abstract: We thank Mitchell (2019) for his interest in our paper concerning temporally-framed detrital zircon disparity analysis, and its example application to understanding crustal evolution. Our colleague presents two main, but ultimately flawed, comments taking issue with our use of (i) geographic grouping, and (ii) Kolmogorov-Smirnov (KS) tests. While disparity-through-time analysis is established in some areas of geoscience (e.g., paleontology; Guillerme and Cooper, 2018), its use with detrital zircon data is novel. Mitchell inaccurately conflates the approach with classic source-to-sink detrital zircon provenance studies. Although the temporal-disparity approach we present could be applied at the basin scale, we evaluate global-scale homogeneity/heterogeneity of zircon populations. The justifications for, and limitations of, the geographic grouping of detrital zircon data were discussed at length by us (Barham et al., 2019). It is abundantly clear that we recognize that the aggregated mosaics of crustal fragments constituting the current continental arrangements do not necessarily reflect geologically coherent entities throughout Earth history. Geographic grouping is used only as a spatially unitized reference frame for the purposes of disparity analysis through time. Mitchell claims geographic grouping renders a “majority of each data set essentially arbitrary”. However, this statement is demonstrably incorrect. Statistical tests of disparity versus the supercontinent cycle presented by us prove that this grouping remains sensitive to at least the last 2 Ga of global continental break-up and assembly (50% of the timeframe). Mitchell’s error appears, in part, to be assuming we are only looking for local similarities within and between geographically restricted terranes, rather than attempting to capture global disparity using geographic binning as a reference frame. Further support for our interpretation is evident when a completely different geographic grouping is used. Tracking detrital zircon disparity through the same 4 Ga of Earth history (200 Ma intervals) using a hemispheric division (North vs. South), reveals a statistically correlated pattern tracing the supercontinent cycle (Table 1). Although more muted, this simplistic geographic grouping still demonstrates increasing “global” detrital zircon similarity during supercontinent intervals, and decreasing similarity during continent dispersion.

15 citations

References
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01 Jan 1985
TL;DR: In this paper, the authors describe the composition of the present upper crust and deal with possible compositions for the total crust and the inferred composition of lower crust, and the question of the uniformity of crustal composition throughout geological time is discussed.
Abstract: This book describes the composition of the present upper crust, and deals with possible compositions for the total crust and the inferred composition of the lower crust. The question of the uniformity of crustal composition throughout geological time is discussed. It describes the Archean crust and models for crustal evolution in Archean and Post-Archean time. The rate of growth of the crust through time is assessed, and the effects of the extraction of the crust on mantle compositions. The question of early pre-geological crusts on the Earth is discussed and comparisons are given with crusts on the Moon, Mercury, Mars, Venus and the Galilean Satellites.

12,457 citations

Journal ArticleDOI
TL;DR: In this article, a three-layer crust consisting of upper, middle, and lower crust is divided into type sections associated with different tectonic provinces, in which P wave velocities increase progressively with depth and there is a large variation in average P wave velocity of the lower crust between different type sections.
Abstract: Geophysical, petrological, and geochemical data provide important clues about the composition of the deep continental crust. On the basis of seismic refraction data, we divide the crust into type sections associated with different tectonic provinces. Each shows a three-layer crust consisting of upper, middle, and lower crust, in which P wave velocities increase progressively with depth. There is large variation in average P wave velocity of the lower crust between different type sections, but in general, lower crustal velocities are high (>6.9 km s−1) and average middle crustal velocities range between 6.3 and 6.7 km s−1. Heat-producing elements decrease with depth in the crust owing to their depletion in felsic rocks caused by granulite facies metamorphism and an increase in the proportion of mafic rocks with depth. Studies of crustal cross sections show that in Archean regions, 50–85% of the heat flowing from the surface of the Earth is generated within the crust. Granulite terrains that experienced isobaric cooling are representative of middle or lower crust and have higher proportions of mafic rocks than do granulite terrains that experienced isothermal decompression. The latter are probably not representative of the deep crust but are merely upper crustal rocks that have been through an orogenic cycle. Granulite xenoliths provide some of the deepest samples of the continental crust and are composed largely of mafic rock types. Ultrasonic velocity measurements for a wide variety of deep crustal rocks provide a link between crustal velocity and lithology. Meta-igneous felsic, intermediate and mafic granulite, and amphibolite facies rocks are distinguishable on the basis of P and S wave velocities, but metamorphosed shales (metapelites) have velocities that overlap the complete velocity range displayed by the meta-igneous lithologies. The high heat production of metapelites, coupled with their generally limited volumetric extent in granulite terrains and xenoliths, suggests they constitute only a small proportion of the lower crust. Using average P wave velocities derived from the crustal type sections, the estimated areal extent of each type of crust, and the average compositions of different types of granulites, we estimate the average lower and middle crust composition. The lower crust is composed of rocks in the granulite facies and is lithologically heterogeneous. Its average composition is mafic, approaching that of a primitive mantle-derived basalt, but it may range to intermediate bulk compositions in some regions. The middle crust is composed of rocks in the amphibolite facies and is intermediate in bulk composition, containing significant K, Th, and U contents. Average continental crust is intermediate in composition and contains a significant proportion of the bulk silicate Earth's incompatible trace element budget (35–55% of Rb, Ba, K, Pb, Th, and U).

2,909 citations

Journal ArticleDOI
16 Jan 1997-Nature
TL;DR: Basaltic volcanism'samples' the Earth's mantle to great depths, because solid-state convection transports deep material into the (shallow) melting region as mentioned in this paper.
Abstract: Basaltic volcanism 'samples' the Earth's mantle to great depths, because solid-state convection transports deep material into the (shallow) melting region. The isotopic and trace-element chemistry of these basalts shows that the mantle contains several isotopically and chemically distinct components, which reflect its global evolution. This evolution is characterized by upper-mantle depletion of many trace elements, possible replenishment from the deeper, less depleted mantle, and the recycling of oceanic crust and lithosphere, but of only small amounts of continental material.

2,397 citations