scholarly journals Geological interpretation of volcanism and segmentation of the Mariana back-arc spreading center between 12.7°N and 18.3°N

2017 ◽  
Vol 18 (6) ◽  
pp. 2240-2274 ◽  
Author(s):  
Melissa O. Anderson ◽  
William W. Chadwick ◽  
Mark D. Hannington ◽  
Susan G. Merle ◽  
Joseph A. Resing ◽  
...  
Keyword(s):  
Spreading Center ◽  
Geological Interpretation ◽  
Back Arc

scholarly journals Origins of chemical diversity of back-arc basin basalts: A segment-scale study of the Eastern Lau Spreading Center

2009 ◽  
Vol 114 (B6) ◽  
Author(s):  
Antoine Bézos ◽  
Stéphane Escrig ◽  
Charles H. Langmuir ◽  
Peter J. Michael ◽  
Paul D. Asimow
Keyword(s):  
Chemical Diversity ◽  
Spreading Center ◽  
Back Arc

scholarly journals Submarine back-arc lava with arc signature: Fonualei Spreading Center, northeast Lau Basin, Tonga

2008 ◽  
Vol 113 (B8) ◽  
Author(s):  
Nicole S. Keller ◽  
Richard J. Arculus ◽  
Jörg Hermann ◽  
Simon Richards
Keyword(s):  
Spreading Center ◽  
Lau Basin ◽  
Back Arc

scholarly journals Crustal structure and evolution of the Niuafo'ou Microplate in the northeastern Lau Basin, Southwestern Pacific

2020 ◽  
Author(s):  
Florian Schmid ◽  
Heidrun Kopp ◽  
Michael Schnabel ◽  
Anke Dannowski ◽  
Ingo Heyde ◽  
...  
Keyword(s):  
Gravity Data ◽  
Seafloor Spreading ◽  
P Wave ◽  
Spreading Center ◽  
Plate Boundaries ◽  
Volcanic Arc ◽  
Lau Basin ◽  
Refraction Seismic ◽  
Wave Tomography ◽  
Back Arc

<p>The northeastern Lau Basin is one of the fastest opening and magmatically most active back-arc regions on Earth. Although the current pattern of plate boundaries and motions in this complex mosaic of microplates is fairly well understood, the structure and evolution of the back-arc crust are not. We present refraction seismic, multichannel seismic and gravity data from a 300 km long east-west oriented transect crossing the Niuafo’ou Microplate (back-arc), the Fonualei Rift and Spreading Centre (FRSC) and the Tofua Volcanic Arc at 17°20’S. Our P wave tomography model shows strong lateral variations in the thickness and velocity-depth distribution of the crust. The thinnest crust is present in the Fonualei Rift and Spreading Center, suggesting active seafloor spreading there. In the much thicker crust of the volcanic arc we identify a region of anomalously low velocities, indicative of partial melts. Surprisingly, the melt reservoir is located at ~17 km distance to the volcanic front, supporting the hypothesis that melts are deviated from the volcanic arc towards the FRSC in sub-crustal domains. We identify two distinct regions in the back-arc crust, representing different opening phases of the northeastern Lau Basin. During initial extension, likely dominated by rifting, crust of generally lower upper-crustal velocities formed. During an advanced opening phase, likely dominated by seafloor spreading, crust of higher upper-crustal velocities formed and is now up to 11 km thick. This thickening is the result of magmatic underplating, which is supported by elevated upper mantle temperatures in this region.</p>

scholarly journals The tectonic and volcanic evolution of the Mangatolu Triple Junction

2020 ◽  
Author(s):  
Rebecca Mensing ◽  
Margaret Stewart ◽  
Mark Hannington ◽  
Alan Baxter ◽  
Dorothee Mertmann
Keyword(s):  
Triple Junction ◽  
Hydrothermal Systems ◽  
Spreading Center ◽  
Valuable Insight ◽  
Triple Junctions ◽  
Lau Basin ◽  
The North ◽  
Spreading Centers ◽  
Spreading Rates ◽  
Back Arc

<p>The Mangatolu Triple Junction (MTJ) is an intraoceanic back-arc spreading center that is host to at least 3 distinct hydrothermal systems. It is located in the NE Lau Basin, which opened due to rollback of the Pacific plate along the Tonga-Kermadec trench. At the MTJ, three spreading centers meet in a ridge-ridge-ridge (RRR)-type triple junction separating the Tonga plate in the east, the Niuafo’ou microplate in the southwest, and an unnamed microplate in the north. The MTJ is directly linked to the formation and evolution of the Northeast Lau microplate mosaic, as plate fragmentation inevitably results in the formation of triple junctions, but it remains unclear whether the spreading centers are the drivers of plate fragmentation or a consequence of stress relocation related to microplate rotation. Detailed investigation of the geology and structural setting of the MTJ therefore provides valuable insight into the development in the northeast Lau Basin. Here we present the first comprehensive 1:200,000 geological map of the MTJ, based on a compilation of marine geophysical data (hydroacoustics, magnetics, and gravity) derived from 7 research cruises that have investigated the region between 2004 and 2018. Analysis of the mapped geological formations at the MTJ shows the importance of relict arc crust originating from the Tofua Arc in the architecture of the triple junction, which includes three stages of back-arc crust development and extensive off-axis volcanism. The spreading centers along each arm of the MTJ exploit pre-existing crustal weaknesses, interpreted to have formed during initial Lau Basin opening. A reconstruction of the basin opening, based on the mapped features and published spreading rates, revealed that initiation of the MTJ commenced approximately 180,000 years ago, consistent with the very recent and ongoing dynamic evolution of the NE Lau Basin and emerging microplate mosaic. Intersecting fabrics indicate sequential evolution of the 3 arms of the triple junction, with extension along the northeast arm dominant in the early history and more recent extension along the southern and western arms. The results of this study contribute to our growing understanding of the tectonic framework of the northeast Lau Basin and the role of triple junctions in microplate formation.</p>

scholarly journals Geochemical characteristics of back-arc basin lower crust and upper mantle at final spreading stage of Shikoku Basin: an example of Mado Megamullion

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Norikatsu Akizawa ◽  
Yasuhiko Ohara ◽  
Kyoko Okino ◽  
Osamu Ishizuka ◽  
Hiroyuki Yamashita ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Spreading Center ◽  
Chemical Compositions ◽  
Olivine Gabbro ◽  
Pb Isotope ◽  
Shikoku Basin ◽  
Source Mantle ◽  
Evolutional Process ◽  
Back Arc

AbstractThis paper explores the evolutional process of back-arc basin (BAB) magma system at final spreading stage of extinct BAB, Shikoku Basin (Philippine Sea) and assesses its tectonic evolution using a newly discovered oceanic core complex, the Mado Megamullion. Bulk and in-situ chemical compositions together with in-situ Pb isotope composition of dolerite, oxide gabbro, gabbro, olivine gabbro, dunite, and peridotite are presented. Compositional ranges and trends of the igneous and peridotitic rocks from the Mado Megamullion are similar to those from the slow- to ultraslow-spreading mid-ocean ridges (MOR). Since the timing of the Mado Megamullion exhumation corresponds to the very end of the Shikoku Basin opening, the magma supply was subdued and highly episodic, leading to extreme magma differentiation to form ferrobasaltic, hydrous magmas. In-situ Pb isotope composition of magmatic brown amphibole in the oxide gabbro is identical to that of depleted source mantle for mid-ocean ridge basalt (MORB). In the context of hydrous BAB magma genesis, the magmatic water was derived solely from the MORB source mantle. The distance from the back-arc spreading center to the arc front increased away through maturing of the Shikoku Basin to cause MORB-like magmatism. After the exhumation of Mado Megamullion along detachment faults, dolerite dikes intruded as a post-spreading magmatism. The final magmatism along with post-spreading Kinan Seamount Chain volcanism were introduced around the extinct back-arc spreading center after the opening of Shikoku Basin by residual mantle upwelling.

scholarly journals Basalt from the Extinct Spreading Center in the West Philippine Basin: New Geochemical Results and Their Petrologic and Tectonic Implications

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1277
Author(s):  
Zhengxin Yin ◽  
Weiping Wang ◽  
Liang Chen ◽  
Zhengyuan Li ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Mantle Source ◽  
Spreading Center ◽  
Isotopic Data ◽  
The West ◽  
Mafic Rocks ◽  
West Philippine Basin ◽  
Mantle Reservoir ◽  
Back Arc ◽  
Parental Melts ◽  
Ocean Ridge

We present geological, bulk-rock geochemical and Sr–Nd–Hf isotopic data for mafic rocks from the West Philippine Basin (WPB). These mafic rocks comprise pillow basalts characterized by a vesicular structure. The mid-ocean ridge basalt (MORB)-normalized trace element patterns of basalts from the study area display depletions in Nb. In addition, the chondrite-normalized lanthanide patterns of basalts from the WPB are characterized by significant depletions in the light lanthanides and nearly flat Eu to Lu segments. The investigated rocks have initial 87Sr/86Sr ratios (87Sr/86Sr(i)) of 0.703339–0.703455 and high εNd(t) values (8.0 to 8.7). Furthermore, basalts from the WPB have 176Hf/177Hf ratios that range from 0.28318 to 0.28321 and high εHf(t) from 15.2 to 16.3. Semi-quantitative modeling demonstrates that the parental melts of basalts from the study area were derived by ~20% adiabatic decompression melting of a rising spinel-bearing peridotite source. The Sr–Nd–Hf isotopic compositions of basalts from the WPB indicate that their parental magmas were derived from an upper mantle reservoir possessing the so-called Indian-type isotopic anomaly. Interpretation of the isotopic data suggests that the inferred mantle source was most likely influenced by minor inputs of a sediment melt derived from a downgoing lithospheric slab. Collectively, the petrographic and geochemical characteristics of basalts from the study area are analogous to those of mafic rocks with a back-arc basin (BAB)-like affinity. As such, the petrogenesis of basalts from the WPB can be linked to upwelling of an Indian-type mantle source due to lithospheric slab subduction that was followed by back-arc spreading.

A new species of alvinocaridid shrimp Rimicaris Williams & Rona, 1986 (Decapoda: Caridea) from hydrothermal vents on the Mariana Back Arc Spreading Center, northwestern Pacific

2019 ◽  
Vol 39 (5) ◽  
pp. 640-650 ◽  
Author(s):  
Tomoyuki Komai ◽  
Thomas Giguère
Keyword(s):  
New Species ◽  
Hydrothermal Vents ◽  
Coi Gene ◽  
Spreading Center ◽  
Northwestern Pacific ◽  
Distal Margin ◽  
Mitochondrial Coi ◽  
Mitochondrial Coi Gene ◽  
Back Arc ◽  
A New Species

AbstractA new species of the alvinocaridid shrimp genus RimicarisWilliams & Rona, 1986, R. falkoraen. sp., is described and illustrated based on material from deep-sea hydrothermal vents (3,630–3,912 m deep) on the Mariana Back Arc Spreading Centre, northwestern Pacific, representing the tenth described species of the genus. The new species is morphologically most similar to R. paulexa (Martin & Shank, 2005), but the presence of numerous short setae scattered on the carapace surface, the relatively long antennular stylocerite usually reaching the distal margin of article 2 of the antennular peduncle and the spiniform posteromesial projection of the uropodal protopod distinguish the new species from all congeners. Genetic analysis using the barcoding region of the mitochondrial COI gene supports the recognition of the species as new.

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