Origin of alkaline volcanic rocks occuring on the volcanic front of the Izu-Mariana arc, northwest Pacific.

1994 ◽  
Vol 89 (6) ◽  
pp. 233-244 ◽  
Author(s):  
Yasuo IKEDA ◽  
Makoto YUASA
Keyword(s):  
Volcanic Rocks ◽  
Northwest Pacific ◽  
Volcanic Front ◽  
Mariana Arc

Discerning asthenospheric, lithospheric, and crustal influences on the geochemistry of Quaternary basalts from the Iskut–Unuk rivers area, northwestern British Columbia

1995 ◽  
Vol 32 (9) ◽  
pp. 1451-1461 ◽  
Author(s):  
Brian L. Cousens ◽  
Mary Lou Bevier
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Volcanic Field ◽  
Northwest Pacific ◽  
Small Range ◽  
Geochemical Composition ◽  
Basaltic Rocks ◽  
Depleted Mantle ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Pleistocene- to Holocene-age basaltic rocks of the Iskut–Unuk rivers volcanic field, at the southern terminus of the Stikine Volcanic Belt in the northern Canadian Cordillera, provide information on the geochemical composition of the underlying mantle and processes that have modified parental magmas. Basaltic rocks from four of the six eruptive centres are moderately evolved (MgO = 5.7–6.8%) alkaline basalts with chondrite-normalized La/Sm = 1.6–1.8, 87Sr/86Sr = 0.70336–0.70361, εNd = +4.4 to +5.9, and 206Pb/204Pb = 19.07–19.22. The small range of isotopic compositions and incompatible element ratios imply a common "depleted" mantle source for the basalts, similar to the sources of enriched mid-ocean ridge basalts from northwest Pacific spreading centres or alkali olivine basalts from the western Yukon. Positive Ba and negative Nb anomalies that increase in size with increasing SiO2 and 87Sr/86Sr indicate that the basalts are contaminated by Mesozoic-age, arc-related, Stikine Terrane crust or lithospheric mantle through which the magmas passed. Lavas from a fifth volcanic centre, Cinder Mountain, have undergone greater amounts of fractional crystallization and are relatively enriched in incompatible elements, but are isotopically identical to least-contaminated Iskut–Unuk rivers basalts. Iskut–Unuk rivers lavas share many of the geochemical characteristics of volcanic rocks from other Stikine Belt and Anahim Belt centres, as well as alkali olivine basalts from the Fort Selkirk volcanic centres of the western Yukon.

scholarly journals Molybdenum isotopes unmask slab dehydration and melting beneath the Mariana arc

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hong-Yan Li ◽  
Rui-Peng Zhao ◽  
Jie Li ◽  
Yoshihiko Tamura ◽  
Christopher Spencer ◽  
...  
Keyword(s):  
Radiogenic Isotopes ◽  
Volcanic Front ◽  
Mud Volcanoes ◽  
Subduction Channel ◽  
Elemental Ratios ◽  
Arc Magmas ◽  
Molybdenum Isotopes ◽  
Mariana Arc ◽  
Slab Dehydration ◽  
Forearc Mantle

AbstractHow serpentinites in the forearc mantle and subducted lithosphere become involved in enriching the subarc mantle source of arc magmas is controversial. Here we report molybdenum isotopes for primitive submarine lavas and serpentinites from active volcanoes and serpentinite mud volcanoes in the Mariana arc. These data, in combination with radiogenic isotopes and elemental ratios, allow development of a model whereby shallow, partially serpentinized and subducted forearc mantle transfers fluid and melt from the subducted slab into the subarc mantle. These entrained forearc mantle fragments are further metasomatized by slab fluids/melts derived from the dehydration of serpentinites in the subducted lithospheric slab. Multistage breakdown of serpentinites in the subduction channel ultimately releases fluids/melts that trigger Mariana volcanic front volcanism. Serpentinites dragged down from the forearc mantle are likely exhausted at >200 km depth, after which slab-derived serpentinites are responsible for generating slab melts.

scholarly journals Geochemical Evolution of Arc and Slab Following Subduction Initiation: a Record from the Bonin Islands, Japan

2020 ◽  
Vol 61 (5) ◽  
Author(s):  
Osamu Ishizuka ◽  
Rex N Taylor ◽  
Susumu Umino ◽  
Kyoko Kanayama
Keyword(s):  
Volcanic Rocks ◽  
Leading Edge ◽  
Geochemical Evolution ◽  
Pelagic Sediment ◽  
Bonin Islands ◽  
Stratigraphic Framework ◽  
Pacific Margin ◽  
Volcaniclastic Rocks ◽  
Mariana Arc ◽  
Ocean Ridge

Abstract Volcanism following the initiation of subduction is vital to our understanding of this specific magma-generation environment. This setting is represented by the first development of the Izu–Bonin–Mariana arc system as subduction commenced along the Western Pacific margin in the Eocene. A new collection of volcanic rocks recovered from the islands and exposed crustal sections of the Bonin Ridge spans the first 10 Myr of arc evolution. An elemental and radiogenic isotope dataset from this material is presented in conjuction with new 40Ar/39Ar ages and a stratigraphic framework developed by a detailed mapping campaign through the volcanic sections of the Bonin Islands. The dating results reveal that both the locus and type of magmatism systematically changed with time in response to the progressive sinking of the slab until the establishment of steady-state subduction at around 7–8 Ma. Following initial mid-ocean ridge basalt (MORB)-like spreading-related basalt magmatism, volcanic centres migrated away from the trench and changed from high-Si boninite to low-Si boninite or high-Mg andesite, then finally tholeiitic or calcalkaline arc magma. Subducting pelagic sediment combined with Pacific-type igneous ocean crust dominates the slab input to the shallow source of high-Si boninites at 49 Ma, but high-precision Pb isotope data show that this sediment varies in composition along the subducting plate. At around 45 Ma, volcanism switched to low-Si boninite and the pelagic sediment signature was almost entirely replaced by volcanic or volcaniclastic material originating from a HIMU ocean island source. These low-Si boninites are isotopically consistent with a slab component comprising variable proportions of HIMU volcaniclastic rocks and Pacific MORB. In turn, this signature was replaced by a Pacific MORB-dominated flux in the post 45 Ma tholeiite and calcalkaline volcanic rocks. Notably, each change in slab-derived flux coincided with a change in the magma type. Fluctuations in the slab-derived geochemical signature were superimposed on a change in the mantle wedge source from highly depleted harzburgite to a depleted MORB-type mantle-type source. In turn, this may correspond to the increasing depth of the leading edge of the slab through this 5 Myr period.

scholarly journals Element transport from slab to volcanic front at the Mariana arc

1997 ◽  
Vol 102 (B7) ◽  
pp. 14991-15019 ◽  
Author(s):  
Tim Elliott ◽  
Terry Plank ◽  
Alan Zindler ◽  
William White ◽  
Bernard Bourdon
Keyword(s):  
Volcanic Front ◽  
Element Transport ◽  
Mariana Arc

Migration of a volcanic front inferred from K-Ar ages of late Miocene to Pliocene volcanic rocks in central Japan

Island Arc ◽  
2014 ◽  
Vol 23 (3) ◽  
pp. 236-250 ◽  
Author(s):  
Hitomi Nakamura ◽  
Teruki Oikawa ◽  
Nobuo Geshi ◽  
Akikazu Matsumoto
Keyword(s):  
Late Miocene ◽  
Volcanic Rocks ◽  
Volcanic Front ◽  
Central Japan

Evolution of the tertiary volcanic rocks in the Izu-Mariana arc

1978 ◽  
Vol 41 (4) ◽  
pp. 548-562 ◽  
Author(s):  
K. Shiraki ◽  
N. Kuroda ◽  
S. Maruyama ◽  
H. Urano
Keyword(s):  
Volcanic Rocks ◽  
Mariana Arc
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