Textural immaturity of cumulates as an indicator of magma chamber processes; infiltration and crystal accumulation in the Rum Eastern Layered Intrusion

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doi: 10.1144/0016-76492006-021
Authors:Holness, M. B.
Author Affiliations:Primary:
University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 164(3), p.529-539. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:2007
Note:In English. 53 refs.; illus., incl. 1 table, geol. sketch map
Summary:Textural maturity describes the extent to which rocks have approached textural equilibrium. For igneous rocks, this is a function of the time-integrated thermal history in the sub-solidus which, for cumulate rocks, generally translates to the cooling history via the rate of solidification of the accumulating crystal mush. The most straightforward way to quantify the textural maturity of orthocumulates (sensu lato) is to measure the angle subtended at the corners of interstitial grains. Texturally mature cumulates have angle populations with median values of c. 120°, whereas texturally immature cumulates have lower medians, inherited by the interstitial phase, which infills either an impingement texture in the accumulating mush or a texturally equilibrated pore topology. Textural observations of allivalites from the Rum Layered Suite demonstrate that stratigraphically localized excursions towards textural immaturity are the result of either transient, relatively rapid, solidification rates (perhaps a result of the arrival of cold crystal-laden bodies of fluid on the chamber floor) or late-stage infiltration of fully solidified cumulates by evolved liquids expelled upwards by compaction of underlying horizons. These two processes have distinct textural and compositional signatures.
Sections:Petrology
Subsections:Igneous rocks
Subjects:Compaction; Crystals; Cumulates; Gabbros; Grain boundaries; Igneous rocks; Intrusions; Layered intrusions; Magma chambers; Magmas; Nesosilicates; Olivine; Olivine group; Orthosilicates; Peridotites; Petrography; Plutonic rocks; Settling; Silicates; Textures; Thermal history; Troctolite; Ultramafics; Europe; Great Britain; Hebrides; Highland region Scotland; Inner Hebrides; Inverness-shire Scotland; Rhum; Scotland; United Kingdom; Western Europe; Allivalite; Crystal mush; Eastern Layered Intrusion; Textural maturity
Coordinates:N565500 N570500 W0061500 W0063000
Abstract Numbers:07M/1659
Record ID:2007062054
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States, Reference includes data from The Geological Society, London
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