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Geochemical regularities and genetic significance of ophiolitic basalts

Geochemical regularities and genetic significance of ophiolitic basalts
Geochemical regularities and genetic significance of ophiolitic basalts
Al2O3/TiO2 and CaO/TiO2 ratios of primitive mid-ocean ridge basalts increase along with degree of partial melting (TiO2 content decreases) until ratios seen in chondrites (about 20 and 17, respectively) are reached at ?0.8% TiO2. Low-Ti (<0.6%) basalts from ophiolitic complexes (for example, Troodos and Betts Cove), island arcs, and interarc basins are characterized by much higher Al2O3/TiO2 and CaO/TiO2 ratios (up to 60). Such low-Ti ophiolitic basalts could be formed by remelting of a severely depleted source that had experienced a previous episode of magma extraction of the type in mid-ocean ridges. We suggest that these low-Ti basalts are not formed at mid-ocean ridges but are products of a spreading center close to a subduction zone, for example, in an interarc basin or incipient island-arc site. In this model, remelting of the refractory source is induced by the introduction of water from subducted oceanic crust. Geochemical data on high-Mg volcanic rocks from Papua and the Mariana Trench are presented, and an analogy with low-Ti ophiolitic basalts is suggested. “Basaltic komatiites” from ophiolitic complexes are discussed, and it is suggested that there are critical geochemical differences between these and Archean komatiites.
0091-7613
689-693
Sun, Shen-Su
d5b232c6-4b9b-419c-833c-b7e05d97ec1e
Nesbitt, Robert W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Sun, Shen-Su
d5b232c6-4b9b-419c-833c-b7e05d97ec1e
Nesbitt, Robert W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4

Sun, Shen-Su and Nesbitt, Robert W. (1978) Geochemical regularities and genetic significance of ophiolitic basalts. Geology, 6 (11), 689-693. (doi:10.1130/0091-7613(1978)?6<689:GRAGSO>?2.0.CO;2).

Record type: Article

Abstract

Al2O3/TiO2 and CaO/TiO2 ratios of primitive mid-ocean ridge basalts increase along with degree of partial melting (TiO2 content decreases) until ratios seen in chondrites (about 20 and 17, respectively) are reached at ?0.8% TiO2. Low-Ti (<0.6%) basalts from ophiolitic complexes (for example, Troodos and Betts Cove), island arcs, and interarc basins are characterized by much higher Al2O3/TiO2 and CaO/TiO2 ratios (up to 60). Such low-Ti ophiolitic basalts could be formed by remelting of a severely depleted source that had experienced a previous episode of magma extraction of the type in mid-ocean ridges. We suggest that these low-Ti basalts are not formed at mid-ocean ridges but are products of a spreading center close to a subduction zone, for example, in an interarc basin or incipient island-arc site. In this model, remelting of the refractory source is induced by the introduction of water from subducted oceanic crust. Geochemical data on high-Mg volcanic rocks from Papua and the Mariana Trench are presented, and an analogy with low-Ti ophiolitic basalts is suggested. “Basaltic komatiites” from ophiolitic complexes are discussed, and it is suggested that there are critical geochemical differences between these and Archean komatiites.

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Published date: 1978
Organisations: Geochemistry

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Local EPrints ID: 361801
URI: https://eprints.soton.ac.uk/id/eprint/361801
ISSN: 0091-7613
PURE UUID: 13894bfe-6587-4951-b63e-33c21d529229

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Date deposited: 03 Feb 2014 13:44
Last modified: 18 Jul 2017 02:58

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