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Journal ArticleDOI

The enigmatic sources of I-type granites: The peritectic connexion

01 Oct 2011-Lithos (Elsevier)-Vol. 126, Iss: 3, pp 174-181
About: This article is published in Lithos.The article was published on 2011-10-01. It has received 287 citations till now. The article focuses on the topics: Felsic & Igneous differentiation.
Citations
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Journal ArticleDOI
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 enigmatic sources of I-type gra..."

  • ...Hf isotopic heterogeneity is also observed in magmatic zircons of I-type granitoids generated in arc environments, thus confirming field and petrological evidence that most granitoid protoliths are not chemically homogeneous (e.g., Clemens et al., 2011; Miller et al., 2011)....

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Journal ArticleDOI
01 Sep 2012-Lithos
TL;DR: A review of the ideas, concepts and arguments brought forward in these 40 years, and try to address some open questions is given in this paper, where the authors focus on the identification and description of this suite, and the recognition that it is a typical Archaean lithology.

631 citations


Cites background from "The enigmatic sources of I-type gra..."

  • ...erals (garnet or clinopyroxene) as proposed by Clemens et al. (2011). Three selected...

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  • ..., 1998) as well as metaluminous “I-type” granites (Clemens et al., 2011) show a negative correlation between A/CNK and Fe+Mg....

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Journal ArticleDOI
TL;DR: In this paper, phase diagrams for pelite are used to illustrate the mineralogical controls on melt production and the consequences of different clockwise pressure-temperature (P - T ) paths on melt composition.
Abstract: At low temperatures (<750 °C at moderate to high crustal pressures), the production of sufficient melt to reach the melt connectivity transition (∼7 vol%), enabling melt drainage, requires an influx of aqueous fluid along structurally controlled pathways or recycling of fluid via migration of melt and exsolution during crystallization. At higher temperatures, melting occurs by fluid-absent reactions, particularly hydrate-breakdown reactions involving micas and/or amphibole in the presence of quartz and feldspar. These reactions produce 20–70 vol%, melt according to protolith composition, at temperatures up to 1000 °C. Calculated phase diagrams for pelite are used to illustrate the mineralogical controls on melt production and the consequences of different clockwise pressure-temperature ( P - T ) paths on melt composition. Preservation of peritectic minerals in residual granulites requires that most of the melt produced was extracted, implying a flux of melt through the suprasolidus crust, although some may be trapped during transport, as recorded by composite migmatite-granite complexes. Peritectic minerals may be entrained during melt drainage, consistent with observations from leucosomes in migmatites, and dissolution of these minerals during ascent may be important in the evolution of some crustal magmas. Since siliceous melt wets grains, suprasolidus crust may become porous at only a few volume % melt, as evidenced by microstructures in residual migmatites in which quartz or feldspar pseudomorphs form after melt films and pockets. With increasing melt volume and decreasing effective pressure, assuming the residue is able to deform and compact, the source becomes permeable at the melt connectivity transition. At this threshold, a change from distributed shear-enhanced compaction to localized dilatant shear failure enables melt segregation. The result is a highly permeable vein network that allows transfer of melt to ascent conduits at the initiation of a melt-extraction event. Melt is drained from the anatectic zone via several extraction events, consistent with evidence for incremental construction of plutons from multiple batches of magma. Buoyancy-driven magma ascent occurs via dikes in fractures or via high-permeability zones controlled by tectonic fabrics; the way in which these features relate to compaction and the generation of porosity waves is discussed. Emplacement of laccoliths (horizontal tabular intrusions) and wedge-shaped plutons occurs around the ductile-to-brittle transition zone, whereas steep tabular sheeted and blobby plutons represent back freezing of melt in the ascent conduit or lateral expansion localized by instabilities in the magma–wall-rock system, respectively.

422 citations


Cites background from "The enigmatic sources of I-type gra..."

  • ...Recently, the restite-unmixing hypothesis has been refi ned into the “peritectic assemblage entrainment” hypothesis of Clemens et al. (2011) and Clemens and Stevens (2012)....

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  • ...One explanation for this discrepancy is that natural melts selectively entrain peritectic minerals from the source (Stevens et al., 2007; Clemens et al., 2011; Clemens and Stevens, 2012), and that these entrained mineral grains are dissolved or achieve equilibrium during ascent through a process of…...

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  • ...—Bowen (1947) Today, the difference of opinion has transferred to the fi eld of isotope geochemistry, where it refers to the proportion of mantle versus crustal source material in granites (e.g., Kemp et al., 2009; Clemens et al., 2011; Clemens and Stevens, 2012)....

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  • ...In contrast, Clemens et al. (2011) maintain that I-type granites are of purely crustal origin, but they are derived from arc volcanic and sedimentary rocks of intermediate composition that pass on the isotope signature of a mixed mantle and crustal source....

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  • ...I typology refl ects the nature of the entrained material in both cases, and granites remain linked to their sources in this revised restite model (Clemens et al., 2011; Clemens and Stevens, 2012), even though they may not image their respective sources as earlier implied (Chappell et al., 1987;…...

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Journal ArticleDOI
01 Mar 2012-Lithos

412 citations

Journal ArticleDOI
15 Nov 2012-Lithos
TL;DR: In this article, it was shown that the I-type granites in the Lachlan Fold Belt formed at lower temperatures and almost half of those rocks for which bulk chemical compositions are available are peraluminous.

335 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the thermodynamic properties of 154 mineral endmembers, 13 silicate liquid end-members and 22 aqueous fluid species are presented in a revised and updated data set.
Abstract: The thermodynamic properties of 154 mineral end-members, 13 silicate liquid end-members and 22 aqueous fluid species are presented in a revised and updated data set. The use of a temperature-dependent thermal expansion and bulk modulus, and the use of high-pressure equations of state for solids and fluids, allows calculation of mineral–fluid equilibria to 100 kbar pressure or higher. A pressure-dependent Landau model for order–disorder permits extension of disordering transitions to high pressures, and, in particular, allows the alpha–beta quartz transition to be handled more satisfactorily. Several melt end-members have been included to enable calculation of simple phase equilibria and as a first stage in developing melt mixing models in NCKFMASH. The simple aqueous species density model has been extended to enable speciation calculations and mineral solubility determination involving minerals and aqueous species at high temperatures and pressures. The data set has also been improved by incorporation of many new phase equilibrium constraints, calorimetric studies and new measurements of molar volume, thermal expansion and compressibility. This has led to a significant improvement in the level of agreement with the available experimental phase equilibria, and to greater flexibility in calculation of complex mineral equilibria. It is also shown that there is very good agreement between the data set and the most recent available calorimetric data.

4,482 citations

Journal ArticleDOI
01 Jan 2005-Lithos
TL;DR: In this article, an analysis of an extensive adakite geochemical database identifies two distinct compositional groups: high-SiO2 adakites (HSA) which represent subducted basaltic slab-melts that have reacted with peridotite during ascent through mantle wedge and low-Si O 2 adakitic mantle wedge.

2,125 citations

Journal ArticleDOI
TL;DR: In this article, an algorithm for the construction of phase diagram sections is formulated that is well suited for geodynamic problems in which it is necessary to assess the influence of phase transitions on rock properties or the evolution and migration of fluids.

1,780 citations