Resolution of the effects of crustal assimilation, sediment subduction, and fluid transport in island arc magmas; Pb-Sr-Nd-O isotope geochemistry of Grenada, Lesser Antilles

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doi: 10.1016/S0016-7037(96)00272-4
Authors:Thirlwall, M. F.; Graham, A. M.; Arculus, R. J.; Harmon, R. S.; Macpherson, C. G.
Author Affiliations:Primary:
University of London, Royal Holloway, Department of Geology, Egham, United Kingdom
Other:
BP Exploration Operation Company, United Kingdom
Australian National University, Australia
U. S. Army Research Office, United States
Volume Title:Geochimica et Cosmochimica Acta
Source:Geochimica et Cosmochimica Acta, 60(23), p.4785-4810. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037
Publication Date:1996
Note:In English. 58 refs.; illus., incl. 6 tables, sketch map
Summary:Analyses are presented of major, trace elements, and Sr, Nd, Pb and O isotopes of suites of lavas (low La/Yb picrites, high La/Yb picrites, low-CaO andesite differentiation series (M-series), low Mg, high Ca-series basalts (C-series), evolved M-series, M-C transitional series and high-SiO2 andesites. The lavas are genetically related but the groups span different volcanic centres. The magmas were derived by fractional crystallization from picrites with ∼ 15% MgO. Variations in primary melt composition resulted from: 1) variations in the amount of hydrous fluid, increasing from most M-series picrites through the transitional M-C lavas, to the least-fractionated Ca-rich basalts of the C-series, the latter forming through ∼ 16% olivine fractionation from high Sr/Nd picrites; 2) from variations in the amount of subducted sediment in the mantle source and 3) from variations in the melt fraction extracted from subduction-modified mantle source. Most magma groups have undergone some high-level assimilation in the arc crust due to assimilation-fractional crystallization processes. Isotopic evidenc for this is discussed. [R.K.H.]
Subjects:Alkaline earth metals; Basalts; Fluid dynamics; Fractional crystallization; Igneous rocks; Isotope ratios; Isotopes; Lead; Magmas; Metals; Mid-ocean ridge basalts; Nd-144/Nd-143; Neodymium; O-18/O-16; Oxygen; Pb-206/Pb-204; Picrite; Plate tectonics; Radioactive isotopes; Rare earths; Sr-87/Sr-86; Stable isotopes; Strontium; Subduction; Ultramafic composition; Volcanic rocks; Antilles; Caribbean region; Grenada; Lesser Antilles; West Indies
Abstract Numbers:97M/2753
Record ID:1997012518
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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