Composite minor intrusions as windows into subvolcanic magma reservoir processes; mineralogical and geochemical evidence for complex magmatic plumbing systems in the British Tertiary igneous province

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doi: 10.1144/jgs.158.1.47
Authors:Preston, R. J.
Author Affiliations:Primary:
University of Aberdeen, Department of Geology and Petroleum Geology, Aberdeen, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, Vol.158(Part 1), p.47-58. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:2001
Note:In English. 45 refs.; illus., incl. 2 tables, geol. sketch map
Summary:The Rudh' a Chromain sill is a composite minor intrusion emplaced into Jurassic sandstones on the south coast of the Ross of Mull, NW Scotland, and is part of a suite of basic-silicic sheets associated with the early development of the 58-56 Ma Mull Central Igneous Complex. New whole-rock major and trace element data combined with Sr-Nd-Pb isotope data indicate that two distinct magma end members were involved in the formation of the sill: a tholeiitic basaltic andesite magma generated by contamination and fractional crystallization of regionally available olivine tholeiite basaltic magma, and a rhyolitic magma produced predominantly through crustal melting of basement metasediments. Intermediate compositions at the gradational boundaries between the basic margins and silicic interior of the sill formed by high temperature diffusive hybridization within a compositionally-zoned magma reservoir prior to sheet emplacement. The basic portions of the sheet are replete with a large variety of crustal xenoliths, as well as numerous gabbroic and noritic cumulate fragments. The Rudh' a Chromain sill therefore preserves evidence for the complex interplay between a number of magmatic processes which, when combined with data from the remainder of the suite, suggests that the magmatic plumbing system which fed the sill complex was not simply one large, long-lived magma chamber, but rather a plexus of variably connected sheet-like magma reservoirs.
Subsections:Igneous petrology
Subjects:Cenozoic; Chemical composition; Chemical reactions; Igneous rocks; Intrusions; Isotope ratios; Magma chambers; Magmas; Major elements; Metamorphism; Mineral composition; Mixing; Petrography; Tertiary; Trace elements; Volcanic rocks; Whole rock; Argyllshire Scotland; Europe; Great Britain; Hebrides; Inner Hebrides; Mull Island; Scotland; United Kingdom; Western Europe; Northwestern Scotland; Rudh'a Chromain; Strathclyde region Scotland
Coordinates:N561500 N564000 W0054000 W0063000
Abstract Numbers:01M/2143
Record ID:2001012702
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
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