The role and conditions of second-stage mantle melting in the generation of low-Ti tholeiites and boninites: the case of the Manihiki Plateau and the Troodos ophiolite.

Golowin, Roman, Portnyagin, Maxim, Hoernle, Kaj , Sobolev, Alexander, Kuzmin, Dimitry and Werner, Reinhard (2017) The role and conditions of second-stage mantle melting in the generation of low-Ti tholeiites and boninites: the case of the Manihiki Plateau and the Troodos ophiolite. Contributions to Mineralogy and Petrology, 172 (11-12, Article Nr. 104). DOI 10.1007/s00410-017-1424-3.

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Abstract

High-Mg, low-Ti volcanic rocks from the Manihiki Plateau in the Western Pacific share many geochemical characteristics with subduction-related boninites such as high-Ca boninites from the Troodos ophiolite on Cyprus, which are believed to originate by hydrous re-melting of previously depleted mantle. In this paper we compare the Manihiki rocks and Troodos boninites using a new dataset on the major and trace element composition of whole rocks and glasses from these locations, and new high-precision, electron microprobe analyses of olivine and Cr-spinel in these rocks. Our results show that both low-Ti Manihiki rocks and Troodos boninites could originate by re-melting of a previously depleted lherzolite mantle source (20–25% of total melting with 8–10% melting during the first stage), as indicated by strong depletion of magmas in more to less incompatible elements (Sm/Yb < 0.8, Zr/Y < 2, Ti/V < 12) and high-Cr-spinel compositions (Cr# > 0.5). In comparison with Troodos boninites, the low-Ti Manihiki magmas had distinctively lower H2O contents (< 0.2 vs. > 2 wt% in boninites), ~ 100 °C higher liquidus temperatures at a given olivine Fo-number, lower fO2 (ΔQFM < + 0.2 vs. ΔQFM > + 0.2) and originated from deeper and hotter mantle (1.4–1.7 GPa, ~ 1440 °C vs. 0.8–1.0 GPa, ~ 1300 °C for Troodos boninites). The data provide new evidence that re-melting of residual upper mantle is not only restricted to subduction zones, where it occurs under hydrous conditions, but can also take place due to interaction of previously depleted upper mantle with mantle plumes from the deep and hotter Earth interior.

Document Type: Article
Keywords: Manihiki Plateau, High-Ca boninite, Mantle plume, Second-stage melting, Refractory lherzolite, Troodos ophiolite
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1007/s00410-017-1424-3
ISSN: 0010-7999
Projects: MANIHIKI II
Expeditions/Models/Experiments:
Date Deposited: 22 Nov 2017 09:05
Last Modified: 11 Jan 2019 15:55
URI: http://oceanrep.geomar.de/id/eprint/40177

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