Skip navigation
Skip navigation

U-Th-Pb SHRIMP ages and oxygen isotope composition of zircon from two contrasting late Variscan granitoids, Nisa-Albuquerque batholith, SW Iberian Massif: Petrologic and regional implications

Sola, A. Rita; Williams, Ian; Neiva, A.M.R.; Ribeiro, M.L.

Description

The late Variscan Nisa-Albuquerque batholith in the SW Iberian Massif, consists of a dominant very coarse-grained porphyritic S-type monzogranite to syenogranite (Nisa monzogranite) surrounding a discontinuous central core that includes contrasting very fine-grained I-type tonalite-granodiorite (Aldeia da Mata tonalite). The batholith is located at the boundary between the Central Iberian and Ossa-Morena Zones, a complex segment of crust that was subject to both Cadomian and Variscan tectonism....[Show more]

dc.contributor.authorSola, A. Rita
dc.contributor.authorWilliams, Ian
dc.contributor.authorNeiva, A.M.R.
dc.contributor.authorRibeiro, M.L.
dc.date.accessioned2015-12-10T22:14:14Z
dc.identifier.issn0024-4937
dc.identifier.urihttp://hdl.handle.net/1885/50193
dc.description.abstractThe late Variscan Nisa-Albuquerque batholith in the SW Iberian Massif, consists of a dominant very coarse-grained porphyritic S-type monzogranite to syenogranite (Nisa monzogranite) surrounding a discontinuous central core that includes contrasting very fine-grained I-type tonalite-granodiorite (Aldeia da Mata tonalite). The batholith is located at the boundary between the Central Iberian and Ossa-Morena Zones, a complex segment of crust that was subject to both Cadomian and Variscan tectonism. Variscan zircons in the Nisa monzogranite can be broadly classified into three texturally and chemically distinct types with mutually indistinguishable SHRIMP 206Pb/238U ages: 1) high-U, low-Th/U (<0.1) outermost overgrowths (307.4±4.0 Ma); 2) moderate U and Th/U zircon with concentric zoning occurring both as inner overgrowths and whole grains (305.4±6.2 Ma)";; and 3) texturally discordant cores (309.0±4.6 Ma). Many other cores have ages in the ranges 2.56-1.85 and 0.66-0.51 Ga. The overgrowths and Variscan cores with low Th/U have uniformly high δ18O (9.5±0.2‰). Variscan cores with moderate Th/U have a wide range of δ18O (6.7-10.9‰). Cores older than 500 Ma have an even wider range of composition (4.4-10.0‰). Zircon from the central Aldeia da Mata tonalite, in contrast, contains no inherited cores, has moderate to high Th/U (0.5-1.8), and is uniform in 206Pb/238U age (306.2±3.0 Ma) and δ18O (7.4±0.3‰). The zircon in the Nisa monzogranite records a history of magma genesis involving mixing between 1) a metaluminous magma progressively contaminated by a small sedimentary component, and 2) a more voluminous peraluminous magma originating from a largely metasedimentary source. The inherited zircon age pattern closely matches the age pattern of detrital zircon in early Paleozoic sediments from North Africa. The zircon in the Aldeia da Mata tonalite records nothing of the age of the magma's source rocks, but the moderately high δ18O does preclude derivation of the magma directly from the mantle. Both the chemical and isotopic compositions of the tonalite zircon make it highly unlikely that the tonalite magma was a component in the monzogranite magma mixture.
dc.publisherElsevier
dc.sourceLithos
dc.subjectKeywords: batholith; granite; granitoid; Hercynian orogeny; oxygen isotope; petrology; SHRIMP dating; source rock; thorium isotope; uranium-lead dating; zircon; Iberian Massif Granite magma genesis; Iberian Massif; Oxygen isotopes; SHRIMP; Variscan; Zircon
dc.titleU-Th-Pb SHRIMP ages and oxygen isotope composition of zircon from two contrasting late Variscan granitoids, Nisa-Albuquerque batholith, SW Iberian Massif: Petrologic and regional implications
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume111
dc.date.issued2009
local.identifier.absfor040313 - Tectonics
local.identifier.absfor040303 - Geochronology
local.identifier.absfor040203 - Isotope Geochemistry
local.identifier.ariespublicationu4047674xPUB199
local.type.statusPublished Version
local.contributor.affiliationSola, A. Rita, INETI - National Institute of Engineering and Industrial Technology
local.contributor.affiliationWilliams, Ian, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationNeiva, A.M.R., University of Coimbra
local.contributor.affiliationRibeiro, M.L., INETI - National Institute of Engineering and Industrial Technology
local.description.embargo2037-12-31
local.bibliographicCitation.startpage156
local.bibliographicCitation.lastpage167
local.identifier.doi10.1016/j.lithos.2009.03.045
dc.date.updated2016-02-24T10:32:03Z
local.identifier.scopusID2-s2.0-74849086994
local.identifier.thomsonID000268835900005
CollectionsANU Research Publications

Download

File Description SizeFormat Image
01_Sola_U-Th-Pb_SHRIMP_ages_and_oxygen_2009.pdf1.41 MBAdobe PDFThumbnail


Items in Open Research are protected by copyright, with all rights reserved, unless otherwise indicated.

Updated:  19 May 2020/ Responsible Officer:  University Librarian/ Page Contact:  Library Systems & Web Coordinator