Daczko, NR and Piazolo, S orcid.org/0000-0001-7723-8170 (2022) Recognition of melferite – A rock formed in syn-deformational high-strain melt-transfer zones through sub-solidus rocks: A review and synthesis of microstructural criteria. Lithos, 430-431. 106850. p. 1. ISSN 0024-4937
Abstract
Melt transfer and migration occurs through both supra- and sub-solidus rocks. Mechanisms of melt transfer include dyking, mobile hydrofracturing and diffuse porous melt flow where melt flow may or may not be channelized via instabilities or into high-strain zones of active deformation. Here, we highlight the microstructural- and outcrop-scale signatures of syn-deformational melt-migration pathways through high-strain zones that cut sub-solidus rocks. High-strain zones with high proportions (>10%) of macroscopic, internally undeformed, felsic or leucocratic material are readily interpreted as important melt-migration pathways and are most common in supra-solidus host rocks. However, it is challenging to recognise high-strain melt-migration pathways through sub-solidus rocks; these pathways may lack noticeable felsic or leucocratic components at the outcrop scale and share many macroscopic features in common with ‘classic' sub-solidus mylonite, such that the two are generally conflated. We contrast field and microstructural characteristics of ‘classic' mylonite originating from solid-state deformation with those of high-strain zones that also cut sub-solidus rocks yet have microstructural indicators of the former presence of melt. We compile several features allowing one to distinguish solid-state from melt-present deformation in high-strain zones that cut sub-solidus rocks. Our aim is to encourage geologists to assess such high-strain zones on a case-by-case basis, in view of sub-solidus (i.e., mylonitic) versus melt-present deformation. Such assessment is crucial as (1) rocks deformed in the presence of melt, even small percentages of melt, are orders of magnitude weaker than their solid-state equivalents, (2) melt-rock interaction in such zones may result in metasomatism, and (3) such zones may sustain long-lived melt migration and ascent enabling chemical differentiation at a crustal scale. With this contribution we aim to increase the ease of recognising this important subset of melt-migration pathways by assisting in clarity of description and interpretation of high-strain rocks.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 Elsevier B.V. This is an author produced version of a paper published in Lithos. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | High-strain zone; Mylonite; Melt-present deformation; Shear zone; Microstructures; Melt migration and ascent |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 26 Sep 2022 09:26 |
Last Modified: | 03 Sep 2023 00:13 |
Status: | Published |
Publisher: | Elsevier BV |
Identification Number: | 10.1016/j.lithos.2022.106850 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:190743 |