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The Weaklaw Vent, SE Scotland : metasomatism of eruptive products by carbo-hydro-fluids of probable mantle origin

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dc.abstract.en<p>The Weaklaw vent in SE Scotland (East Lothian coast), inferred to be Namurian, produced lava spatter and volcanic bombs. The latter commonly contained ultramafic xenoliths. All were metasomatised by carbonic fluids rich in incompatible elements. The lavas and xenoliths are inferred to have been basanites and lherzolites prior to metasomatism. The abundance and size of (carbonated) peridotite xenoliths at Weaklaw denotes unusual rapidity of magma ascent and high-energy eruption making Weaklaw exceptional in the British Isles. The lavas and xenoliths were altered subsequently by low-temperature (&lt;200°C) carbo-hydrous fluids to carbonate, clay and quartz assemblages. A small irregular tuffisite ‘dyke’ that transects the ejecta is also composed dominantly of carbonates and clays. The peridotitic xenoliths are typically foliated, interpreted as originating as pre-entrainment mantle shear-planes.</p> <p>Analyses of the relic spinels shows them to be compositionally similar to spinels in local unaltered lherzolites from near-by basanitic occurrences. Chromium showed neither significant loss nor gain but was concentrated in a di-octahedral smectite allied to volkonskoite. It is in the complex association of smectite with other clays, chlorite and possibly fuchsite that the diverse incompatible elements are concentrated.</p> <p>We conclude that late Palaeozoic trans-tensional fault movement caused mantle shearing. Rapid ascent of basanite magma entrained large quantities of sheared lithospheric mantle. This was followed by ascent of an aggressive carbonate-/ hydroxyl-rich fluid causing pervasive metasomatism. The vent is unique in several ways: in its remarkable clay mineralogy and in displaying such high Cr-clays in a continental intra-plate setting; in being more productive in terms of its ‘cargo’ of peridotite xenoliths; in presenting an essentially un-eroded sequence of Namurian extrusives; and, not least, for giving evidence for post-eruptive, surface release of small-melt, deep-source fluids.</p>
dc.affiliationUniwersytet Warszawski
dc.contributor.authorUpton, Brian G.J.
dc.contributor.authorOdling, Nic
dc.contributor.authorKirstein, Linda A.
dc.contributor.authorUnderhill, John R.
dc.contributor.authorPuziewicz, Jacek
dc.contributor.authorNtaflos, Theodoros
dc.contributor.authorBagiński, Bogusław
dc.contributor.authorHillier, Steve
dc.contributor.authorAndersen, Jens C.
dc.contributor.authorRollinson, Gavin K.
dc.contributor.authorPerrillat, Jean-Philippe
dc.date.accessioned2024-01-26T10:51:48Z
dc.date.available2024-01-26T10:51:48Z
dc.date.issued2019
dc.description.financeNie dotyczy
dc.description.number6
dc.description.volume83
dc.identifier.doi10.1180/MGM.2019.67
dc.identifier.issn0026-461X
dc.identifier.urihttps://repozytorium.uw.edu.pl//handle/item/123320
dc.identifier.weblinkhttp://dx.doi.org/10.1180/mgm.2019.67
dc.languageeng
dc.pbn.affiliationearth and related environmental sciences
dc.relation.ispartofMineralogical Magazine
dc.relation.pages855-867
dc.rightsClosedAccess
dc.sciencecloudnosend
dc.subject.enfaulting
dc.subject.enbasanite
dc.subject.enspinel lherzolite xenolith
dc.subject.enmetasomatism
dc.subject.enchrome-rich smectite
dc.subject.entuffisite
dc.subject.enrare-element transport
dc.subject.enmantle degassing
dc.titleThe Weaklaw Vent, SE Scotland : metasomatism of eruptive products by carbo-hydro-fluids of probable mantle origin
dc.typeJournalArticle
dspace.entity.typePublication