Variation of magma source in the Oman ophiolite inferred from distribution of magmatic dykes in the mantle

Research Article| April 01, 2015 Melts of sediments in the mantle wedge of the Oman ophiolite Karsten M. Haase; Karsten M. Haase 1GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossgarten 5, 91054 Erlangen, Germany Search for other works by this author on: GSW Google Scholar Sarah Freund; Sarah Freund 1GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossgarten 5, 91054 Erlangen, Germany Search for other works by this author on: GSW Google Scholar Jürgen Koepke; Jürgen Koepke 2Institute for Mineralogy, Leibniz Universität Hannover, Callinstrasse 3, 30167 Hannover, Germany Search for other works by this author on: GSW Google Scholar Folkmar Hauff; Folkmar Hauff 3GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany Search for other works by this author on: GSW Google Scholar Martin Erdmann Martin Erdmann 2Institute for Mineralogy, Leibniz Universität Hannover, Callinstrasse 3, 30167 Hannover, Germany Search for other works by this author on: GSW Google Scholar Geology (2015) 43 (4): 275–278. https://doi.org/10.1130/G36451.1 Article history received: 14 Nov 2014 rev-recd: 09 Jan 2015 accepted: 22 Jan 2015 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Karsten M. Haase, Sarah Freund, Jürgen Koepke, Folkmar Hauff, Martin Erdmann; Melts of sediments in the mantle wedge of the Oman ophiolite. Geology 2015;; 43 (4): 275–278. doi: https://doi.org/10.1130/G36451.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The rocks in the crustal section of the Oman ophiolite show an increasing input of a subduction component with time, most likely reflecting the generation of the ophiolite above a subducting slab. Field relations, new geochemical data, and Nd-Hf isotope data for felsic to mafic intrusive rocks in the mantle harzburgite from the Haylayn block in the Oman ophiolite suggest late magmatic events in a mantle wedge shortly before obduction of the ophiolite. Incompatible element contents and low εNd and εHf of the felsic rocks exclude differentiation from mafic magmas, but are consistent with an origin by partial melting of pelagic sediments similar to leucogranites in continental collision zones. These melts apparently mixed with mafic magmas resembling enriched late-stage lavas from the ophiolite. The leucogranitic intrusions into the mantle wedge confirm the transfer of melts of sediments from the subducted plate into the mantle at subduction zones. We suggest that the enrichment of Rb, K, and Pb observed in the Oman boninites is caused by addition of melts of sediments similar to those from the Haylayn block to the boninite source in the mantle wedge. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

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10.1130/g36451.1

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Geologic and isotopic investigations of the early Cretaceous Sierra Nevada Batholith, Tulare Co., CA, and the Ivrea Zone, NW Italian Alps: examples of interaction between mantle-derived magma and continental crust

Diane Clemens Knott

Two igneous suites containing layered ultramafic-mafic cumulates were investigated with the intent to characterize the parental magma and to identify processes significant to the petrogenesis of these rocks. In both study areas, the early Cretaceous Sierra Nevada batholith and the Ivrea Zone, isotopic systematics of the cumulates were found to preserve the characteristics of the mantle-derived parental magma and to record the effects of fractional crystallization and assimilation. Modeling the relative importance of these processes and characterization of the material derived from the mantle are necessary to understanding the growth of the continental crust. Geologic mapping of 110 mi2 of the 125 to 110 Ma Stokes Mountain region reveals the presence of layered cumulate megaxenoliths and two coeval ring dike complexes. Petrographic analysis and geochemical modeling of 125 dominantly mafic and intermediate samples demonstrate the comagmatic nature of this suite. Combined oxygen, strontium and neodymium analysis of 22 samples indicates, however, that each ring complex was fed by an isotopically distinct parental magma (eNd(115) = +6.1, Sri = 0.70338, δ18O = 6.6‰ ; (eNd(115) = +5.7, Sri = 0.70372, δ18O = 6.7‰) both of which were derived from a variably contaminated, depleted mantle source. Minor assimilation of continentally-derived metasediments and mafic-ultramafic material of the Kings-Kaweah ophiolite further affected the isotopic evolution of the two subsuites. Hydrothermal alteration in the subvolcanic environment is recorded only by rare stoped xenoliths of 120 Ma hypabyssal intrusives. Late Hercynian (≈300 - 270 Ma) magmatism produced the 10 km thick Mafic Complex lying at the base of the Ivrea-Strona-Ceneri crustal cross section. δ18O analysis of 237 whole rock samples and 26 mineral separates reveals that presumably early intrusions into the cool crust preserve the depleted mantle signature of the modeled parental magma (eNd(115) = +7, Sri = 0.703, δ18O = 6.5‰) while later intrusions assimilated significant amounts of the 10 - 12‰ metapelite. Subsequent intrusion of voluminous basaltic magma fonned a large, convecting magma chamber in which assimilation was concentrated within boundary layers. Such lower crustal production of high-18O (δ18O = 8 - 10‰) mafic magmas is suggested as contributing to the petrogenesis of upper crustal Permian granites.

Batholith

Underplating

Fractional crystallization (geology)

Ultramafic rock

10.7907/aa6n-ey25.

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Citations (15)

New models for the genesis of plagiogranites in the Oman ophiolite

Lithos (2009)

Hugh Rollinson

Fractional crystallization (geology)

Magma chamber