AMPHIBOLE IN ULTRA-DEPLETED PERIDOTITES FROM THE HOROKANAI OPHIOLITE, HOKKAIDO, JAPAN: BONINITE MELT TRAPPED IN THE MANTLE WEDGE
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AMPHIBOLE IN ULTRA-DEPLETED PERIDOTITES FROM THE HOROKANAI OPHIOLITE, HOKKAIDO, JAPAN : BONINITE MELT TRAPPED IN THE MANTLE WEDGE. / Tamura, Akihiro; Nishio, Ikuya; Iwata, Yuya; Arai, Shoji; Morishita, Tomoaki.
In: Ofioliti, Vol. 49, No. 1, 2024, p. 37-54.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - AMPHIBOLE IN ULTRA-DEPLETED PERIDOTITES FROM THE HOROKANAI OPHIOLITE, HOKKAIDO, JAPAN
T2 - BONINITE MELT TRAPPED IN THE MANTLE WEDGE
AU - Tamura, Akihiro
AU - Nishio, Ikuya
AU - Iwata, Yuya
AU - Arai, Shoji
AU - Morishita, Tomoaki
N1 - Publisher Copyright: © 2024, Edizioni ETS. All rights reserved.
PY - 2024
Y1 - 2024
N2 - Ultra-depleted peridotites have been reported from the mantle sections of a number of ophiolitic complexes (e.g., Papua New Guinea and New Caledo-nia). Such rocks are residues derived from boninitic melts in supra-subduction zones, particularly in forearcs. In the mantle wedge, slab-derived fluid-melt containing H2O increases the degree of melting and metasomatizes the peridotites. However, the relationship between high-degree melting under hydrous conditions and metasomatism is not well understood. In this paper, we report petrological features of amphibole-bearing ultra-depleted peridotites from the Horokanai ophiolite, Hokkaido, Japan. The peridotite complex in the Horokanai ophiolite consists of clinopyroxene-free harzburgite, orthopyroxene-poor harzburgite, and dunite. The harzburgites contain high-Cr# spinel (0.70-0.85) and orthopyroxene with very low abundances of incompatible elements (e.g., Y < 0.01 µg/g; Ti ~ 2 µg/g). Pargasitic-edenitic amphibole occurs as spinel-hosted inclusions and as an interstitial phase to olivine and orthopyroxene. The harzburgite is a residue formed by the high-degree melting caused by fluid flux. The hydrous conditions cause incongruent melting of orthopyroxene, producing a depleted Si-rich melt (i.e., a boninitic melt). Because such Si-rich melt can coexist with Cr-rich spinel under these conditions, amphibole is ultimately crystallized in the harzburgite. Such amphibole formation is important in producing secondary sodic amphibole during alteration of ultra-depleted peridotites.
AB - Ultra-depleted peridotites have been reported from the mantle sections of a number of ophiolitic complexes (e.g., Papua New Guinea and New Caledo-nia). Such rocks are residues derived from boninitic melts in supra-subduction zones, particularly in forearcs. In the mantle wedge, slab-derived fluid-melt containing H2O increases the degree of melting and metasomatizes the peridotites. However, the relationship between high-degree melting under hydrous conditions and metasomatism is not well understood. In this paper, we report petrological features of amphibole-bearing ultra-depleted peridotites from the Horokanai ophiolite, Hokkaido, Japan. The peridotite complex in the Horokanai ophiolite consists of clinopyroxene-free harzburgite, orthopyroxene-poor harzburgite, and dunite. The harzburgites contain high-Cr# spinel (0.70-0.85) and orthopyroxene with very low abundances of incompatible elements (e.g., Y < 0.01 µg/g; Ti ~ 2 µg/g). Pargasitic-edenitic amphibole occurs as spinel-hosted inclusions and as an interstitial phase to olivine and orthopyroxene. The harzburgite is a residue formed by the high-degree melting caused by fluid flux. The hydrous conditions cause incongruent melting of orthopyroxene, producing a depleted Si-rich melt (i.e., a boninitic melt). Because such Si-rich melt can coexist with Cr-rich spinel under these conditions, amphibole is ultimately crystallized in the harzburgite. Such amphibole formation is important in producing secondary sodic amphibole during alteration of ultra-depleted peridotites.
KW - boninite
KW - harzburgite
KW - hydrous melting
KW - mantle wedge
KW - pargasite
U2 - 10.4454/ofioliti.v49i1.568
DO - 10.4454/ofioliti.v49i1.568
M3 - Journal article
AN - SCOPUS:85184389324
VL - 49
SP - 37
EP - 54
JO - Ofioliti
JF - Ofioliti
SN - 0391-2612
IS - 1
ER -
ID: 384955732