TY - JOUR

T1 - The role and conditions of second-stage mantle melting in the generation of low-Ti tholeiites and boninites

T2 - the case of the Manihiki Plateau and the Troodos ophiolite

AU - Golowin, Roman

AU - Portnyagin, Maxim

AU - Hoernle, Kaj

AU - Sobolev, Alexander

AU - Kuzmin, Dimitry

AU - Werner, Reinhard

PY - 2017/12/1

Y1 - 2017/12/1

N2 - 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.

AB - 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.

KW - High-Ca boninite

KW - Manihiki Plateau

KW - Mantle plume

KW - Refractory lherzolite

KW - Second-stage melting

KW - Troodos ophiolite

KW - TRACE-ELEMENT COMPOSITION

KW - SUBDUCTION INITIATION

KW - MIDOCEAN RIDGES

KW - DEPLETED MANTLE

KW - EXPERIMENTAL CALIBRATION

KW - VOLCANIC GLASS

KW - MACQUARIE ISLAND

KW - ONTONG JAVA PLATEAU

KW - OCEANIC-CRUST

KW - SOLOMON-ISLANDS

UR - http://www.scopus.com/inward/record.url?scp=85035117530&partnerID=8YFLogxK

U2 - 10.1007/s00410-017-1424-3

DO - 10.1007/s00410-017-1424-3

M3 - Article

AN - SCOPUS:85035117530

VL - 172

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

SN - 0010-7999

IS - 11-12

M1 - 104

ER -