Faulting processes controlled by the nonuniform thermal structure of the crust and uppermost mantle beneath the northeastern Japanese island arc

2008 ◽  
Vol 113 (B8) ◽  
Author(s):  
Bunichiro Shibazaki ◽  
Kazuteru Garatani ◽  
Takaya Iwasaki ◽  
Akiko Tanaka ◽  
Yoshihisa Iio
Keyword(s):  
Thermal Structure ◽  
Island Arc ◽  
Japanese Island ◽  
Uppermost Mantle

Anorthite megacrysts from island arc basalts

1995 ◽  
Vol 59 (394) ◽  
pp. 1-14 ◽  
Author(s):  
Mitsuyoshi Kimata ◽  
Norimasa Nishida ◽  
Masahiro Shimizu ◽  
Shizuo Saito ◽  
Tomoaki Matsui ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Isotope Ratio ◽  
Island Arc ◽  
Japanese Island ◽  
Sr Isotope ◽  
Native Copper ◽  
Chemical Zoning ◽  
Basaltic Magmas ◽  
End Members ◽  
Lateral Variations

AbstractAnorthite megacrysts are common in basalts from the Japanese Island Arc, and signally rare in other global fields. These anorthites are 1 to 3 cm in size and often contain several corroded Mg-olivine inclusions. The megacrysts generally range from An94Ab4Ot2 to An89Ab6Ot5 (Ot: other minor end-members, including CaFeSi3O8, CaMgSi3O8, AlAl3SiO8, □Si4O8) and show no chemical zoning. They often show parting. Redclouded megacrysts contain microcrystals of native copper with a distribution reminiscent of the shape of a planetary nebula. Hydrocarbons are also present, both in the anorthite megacrysts and in the olivines included within them. Implications of lateral variations in the Fe/Mg ratio of the included olivines, in Sr-content and in Sr-isotope ratio of the anorthite megacrysts with respect to the Japanese island arc, relate to mixing of crustal components and subducted slab-sediments into the basaltic magmas.

scholarly journals Petroleum resources in the Japanese island-arc setting

Episodes ◽  
1991 ◽  
Vol 14 (3) ◽  
pp. 236-241 ◽  
Author(s):  
Yoshiro Kikuchi ◽  
Satoshi Tono ◽  
Masaaki Funayama
Keyword(s):  
Island Arc ◽  
Japanese Island ◽  
Petroleum Resources ◽  
Arc Setting

scholarly journals Light hydrocarbons in volcanic gases from the Japanese island arc.

1995 ◽  
Vol 29 (4) ◽  
pp. 231-242 ◽  
Author(s):  
Yasuhiro Kiyosu ◽  
Noriko Asada
Keyword(s):  
Island Arc ◽  
Volcanic Gases ◽  
Japanese Island ◽  
Light Hydrocarbons

scholarly journals Deep-focus earthquakes: spatial patterns, possible causes and geodynamic consequences

2018 ◽  
Vol 9 (3) ◽  
pp. 947-965
Author(s):  
A. N. Didenko ◽  
M. I. Kuzmin
Keyword(s):  
Lower Mantle ◽  
Chemical Elements ◽  
Island Arc ◽  
Japanese Island ◽  
Mantle Boundary ◽  
Geological Processes ◽  
Wide Range ◽  
Significant Difference ◽  
Lithospheric Plates ◽  
Deep Focus

The spatial analysis was conducted to analyze the positions of earthquakes hypocenters in the transit zone of the upper mantle and the focal mechanisms of the strongest earthquakes in the subduction slabs of theOkhotskSeasegment of the Kuril-Kamchatka island arc and theJapanSeasegment of the Japanese island arc. It revealed a significant difference in the morphology of these slabs, as well as in the positions of the earthquake hypocenters relative to the active and stagnating parts of the slabs and the forces that caused the earthquakes. Based on the seismic data presented in the article, it is confirmed that there are two types of subduction of the oceanic lithospheric plates in the mantle. The article discusses relationships between the subduction and various geological processes at the upper–lower mantle boundary. It considers possible causes (including those related to phase transitions) of deep-focus earthquakes, in case of which splitting of the oceanic lithospheric plates takes place at depths near the upper–lower mantle boundary. Subduction of the oceanic lithospheric plates and their splitting predetermine a possibility for the crustal elements to penetrate into the lower mantle and deeper into the D″ layer, wherein new plumes arise and transport the deep magma together with the recycled substance into the crust. Deep-focus earthquakes are a necessary link in the mechanism providing for the recycling of chemical elements in the crust – mantle – D″ layer system and thus leading to the formation of a wide range of mineral deposits.

Earthquake locations and seismic wave propagation in the upper 250 km of the Tonga island arc

1969 ◽  
Vol 59 (3) ◽  
pp. 1115-1135
Author(s):  
Walter Mitronovas ◽  
Bryan Isacks ◽  
Leonardo Seeber
Keyword(s):  
Seismic Waves ◽  
Seismic Wave Propagation ◽  
Island Arc ◽  
Seismic Zone ◽  
Magma Chambers ◽  
Uppermost Mantle ◽  
Short Term ◽  
High Attenuation ◽  
Upper Limit ◽  
Anomalous Propagation

abstract This paper reports results of a series of short-term seismic observations made on nearly all the major island groups of the Tonga island arc. These data extend the mapping of anomalous propagation of seismic waves from earthquakes beneath the island arc reported by Oliver and Isacks (1967), and significantly increase the number of accurately located earthquakes beneath the Tonga Islands. The data of this paper, combined with those of Sykes et al (1969), indicate that the inclined seismic zone of the Tonga island arc is very thin even at shallow depths. Most of the hypocenters are confined to a slab of about 25 km thickness. This thickness probably still reflects the precision of locations and may only be a measure of the upper limit of the thickness of the seismic zone. The inclined seismic zone, which has a dip of about 45° at intermediate depths in the mantle, appears to decrease in dip or bend over at depths less than about 50 km and appears to intersect the surface at or near the axis of the trench. The wedge-shaped region above the inclined seismic zone appears to be relatively aseismic, although some minor seismic activity has been located at shallow depths beneath the line of active volcanoes. P and S phases with anomalously large amplitudes and frequencies from deep earthquakes (> 400 km) were observed at all sites occupied in Tonga, including sites on two volcanoes. These observations and observations from shallower events include ray paths that emerge nearly vertically beneath the volcanoes. Thus, any region of high attenuation (low Q) below the volcanoes, such as magma chambers, must be limited in extent. These data, in conjunction with regional observations of Sn, indicate that a broad zone of low Q material in the uppermost mantle exists west of the volcanoes on the concave side of the arc. However, the P and S phases recorded on the volcanic ridge exhibit an emergent and drawn-out character that contrasts with the sharp and impulsive character of phases recorded on the non-volcanic ridge. These observations are interpreted to indicate considerable heterogeneity beneath the volcanoes.

Non-transparent uppermost mantle in the island-arc region of Japan

2006 ◽  
Vol 420 (1-2) ◽  
pp. 189-204 ◽  
Author(s):  
Takashi Iidaka ◽  
Takaya Iwasaki ◽  
Kazuo Yoshimoto
Keyword(s):  
Island Arc ◽  
Uppermost Mantle

scholarly journals First report on two ostracod genera Loxoconcha Sars, 1866 (Loxoconchidae) and Xestoleberis Sars, 1866 (Xestoleberididae) along the coast of Vietam

2019 ◽  
Vol 41 (4) ◽  
Author(s):  
Le Doan Dung ◽  
Akira Tsukagoshi
Keyword(s):  
Protected Area ◽  
Marine Protected Area ◽  
The Philippines ◽  
Island Arc ◽  
Japanese Island ◽  
Phylogenetic Groups ◽  
Nha Trang Bay ◽  
Group A ◽  
Long Bay ◽  
Group B

One survey was done with SCUBA diving in Ha Long Bay and Cat Ba Island, Northern Vietnam (December 2013) and another one at Nha Trang Bay Marine Protected Area, Nha Trang city, Central Vietnam and Phu Quoc Marine Protected Area, Kien Giang Province, Southern Vietnam (November 2014). Sixteen species of the genus Loxoconcha and fourteen species of the genus Xestoleberis were found and identified. Eight species of the genus Loxoconcha were identified in group A, three species in group B, two in group C and three unidentified. Meanwhile, twelve species of the genus Xestoleberis were classified in group A and two in group B according to phylogenetic groups. From geographical distribution of the pore groups of the species in two genera Loxoconcha and Xestoleberis showed that the fauna of these genera in Vietnam is close to those of southern part of Japanese Island Arc, i.e., from Amami Island to the Philippines and Australia rather than Japanese Island Arc faunas.  

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