Podiform chromitite in the arc mantle: chromitite xenoliths from the Takashima alkali basalt, Southwest Japan arc

1994 ◽  
Vol 29 (5) ◽  
pp. 434-438 ◽  
Author(s):  
S. Arai ◽  
N. Abe
Keyword(s):  
Alkali Basalt ◽  
Southwest Japan ◽  
Podiform Chromitite

scholarly journals Abyssal Peridotite as a Component of Forearc Mantle: Inference from a New Mantle Xenolith Suite of Bankawa in the Southwest Japan Arc

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 540 ◽  
Author(s):  
Shoji Arai ◽  
Akihiro Tamura ◽  
Makoto Miura ◽  
Kazuma Seike
Keyword(s):  
Alkali Basalt ◽  
Mantle Peridotite ◽  
Chromian Spinel ◽  
Abyssal Peridotite ◽  
Southwest Japan ◽  
Limited Sampling ◽  
Basalt Dike ◽  
Light Rare Earth Elements ◽  
Arc Magma ◽  
Forearc Mantle

Lithology and petrologic nature of the forearc mantle have been left unclear due to the very limited sampling to date. Here, we present petrological data on a forearc peridotite suite obtained as xenoliths in an alkali basalt dike (7.5 Ma) from the Bankawa area in the Southwest Japan arc for our better understanding of the forearc mantle. The host alkali basalt is of asthenosphere origin, and passed through a slab window with slight chemical modification by the slab-derived component. The Bankawa peridotite suite is comprised of lherzolites, which contain various amounts of secondary phlogopite and were metasomatized to various degrees. The least metasomatized lherzolite exhibits Fo91 of olivine, Cr/(Cr + Al) = 0.3 of chromian spinel, and depletion of middle to light rare-earth elements in clinopyroxene, and is overall similar to an abyssal lherzolite. It had originally formed at the proto-Pacific Ocean and then was trapped at a eastern margin of Eurasian continent by initiation of subduction. The forearc mantle peridotite formed as a residue of proto-arc magma formation is depleted harzburgite as represented by the peridotites obtained from the forearc seafloor, but can be less depleted abyssal peridotite if being devoid of partial melting or reaction with magmas after entrapment.

A new type of orthopyroxenite xenolith from Takashima, Southwest Japan: silica enrichment of the mantle by evolved alkali basalt

2006 ◽  
Vol 152 (3) ◽  
pp. 387-398 ◽  
Author(s):  
Shoji Arai ◽  
Yohei Shimizu ◽  
Tomoaki Morishita ◽  
Yoshito Ishida
Keyword(s):  
Alkali Basalt ◽  
Southwest Japan ◽  
New Type

scholarly journals A reply to the comments on "Garnet-bearing spinel harzburgite xenolith from Arato-yama alkali basalt, southwest Japan by Yamamoto et al.".

2001 ◽  
Vol 30 (4) ◽  
pp. 194-197
Author(s):  
Masatsugu YAMAMOTO ◽  
Shiho ABE ◽  
Hiromi ABE ◽  
Mitsuhiro YASUI ◽  
Tsutomu KISHI
Keyword(s):  
Alkali Basalt ◽  
Southwest Japan

scholarly journals Garnet-bearing spinel harzburgite xenolith from Arato-yama alkali basalt, southwest Japan.

1999 ◽  
Vol 94 (2) ◽  
pp. 46-56 ◽  
Author(s):  
Masatsugu YAMAMOTO ◽  
Shiho ABE ◽  
Hiromi ABE ◽  
Mitsuhiro YASUI ◽  
Tsutomu KISHI
Keyword(s):  
Alkali Basalt ◽  
Southwest Japan

Characterization of groundwater based on δ2H, δ18O and Cl− concentration beneath the Osaka Plain, Southwest Japan

2019 ◽  
Vol 53 (4) ◽  
pp. 235-247
Author(s):  
Tsuyoshi Shintani ◽  
Harue Masuda ◽  
Kaori Okazaki ◽  
Emilie Even ◽  
Masahiko Ono ◽  
...  
Keyword(s):  
Southwest Japan

40Ar–39Ar dating of alkali basaltic dykes along the southwest coast of Greenland: Cretaceous and Tertiary igneous activity along the eastern margin of the Labrador Sea

1999 ◽  
pp. 19-29 ◽  
Author(s):  
Lotte Melchior Larsen ◽  
David C. Rex ◽  
W. Stuart Watt ◽  
Philip G. Guise
Keyword(s):  
Alkali Basalt ◽  
Dyke Swarm ◽  
Labrador Sea ◽  
Precambrian Basement ◽  
Stress Regime ◽  
Southwest Coast ◽  
Eastern Margin ◽  
Step Heating ◽  
Igneous Activity ◽  
Break Up

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Melchior Larsen, L., Rex, D. C., Watt, W. S., & Guise, P. G. (1999). 40Ar–39Ar dating of alkali basaltic dykes along the southwest coast of Greenland: Cretaceous and Tertiary igneous activity along the eastern margin of the Labrador Sea. Geology of Greenland Survey Bulletin, 184, 19-29. https://doi.org/10.34194/ggub.v184.5227 _______________ A 380 km long coast-parallel alkali basalt dyke swarm cutting the Precambrian basement in south-western Greenland has generally been regarded as one of the earliest manifestations of rifting during continental stretching prior to break-up in the Labrador Sea. Therefore, the age of this swarm has been used in models for the evolution of the Labrador Sea, although it has been uncertain due to earlier discrepant K–Ar dates. Two dykes from this swarm situated 200 km apart have now been dated by the 40Ar–39Ar step-heating method. Separated biotites yield plateau ages of 133.3 ± 0.7 Ma and 138.6 ± 0.7 Ma, respectively. One of the dykes has excess argon. Plagioclase separates confirm the biotite ages but yield less precise results. The age 133– 138 Ma is earliest Cretaceous, Berriasian to Valanginian, and the dyke swarm is near-coeval with the oldest igneous rocks (the Alexis Formation) on the Labrador shelf. A small swarm of alkali basalt dykes in the Sukkertoppen (Maniitsoq) region of southern West Greenland was also dated. Two separated kaersutites from one sample yield an average plateau age of 55.2 ± 1.2 Ma. This is the Paleocene–Eocene boundary. The swarm represents the only known rocks of that age within several hundred kilometres and may be related to changes in the stress regime during reorganisation of plate movements at 55 Ma when break-up between Greenland and Europe took place.

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