Crustal structure of the southern Okinawa Trough: Symmetrical rifting, submarine volcano, and potential mantle accretion in the continental back‐arc basin

2017 ◽  
Vol 122 (1) ◽  
pp. 622-641 ◽  
Author(s):  
Ryuta Arai ◽  
Shuichi Kodaira ◽  
Kaiho Yuka ◽  
Tsutomu Takahashi ◽  
Seiichi Miura ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Okinawa Trough ◽  
Submarine Volcano ◽  
Southern Okinawa Trough ◽  
Back Arc

scholarly journals Spatial and temporal distribution of low frequency volcanic earthquakes in the southern Okinawa Trough back-arc basin

2019 ◽  
Vol 30 (5) ◽  
pp. 621-631
Author(s):  
Jing-Yi Lin ◽  
Wen-Nan Wu ◽  
Chih-Chieh Su ◽  
Ching-Hui Tsai ◽  
Hsu-Hsiao Sun ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Low Frequency ◽  
Temporal Distribution ◽  
Spatial And Temporal Distribution ◽  
Volcanic Earthquakes ◽  
Southern Okinawa Trough ◽  
Back Arc

3D Seismic Imaging and Geophysical Characteristics of an Embryo Hydrothermal Field in the Southern Okinawa Trough

2020 ◽  
Author(s):  
Ho-Han Hsu ◽  
Liang-Fu Lin ◽  
Tzu-Ting Chen ◽  
Char-Shine Liu ◽  
Jih-Hsin Chang ◽  
...  
Keyword(s):  
Hydrothermal Fluid ◽  
Okinawa Trough ◽  
Hydrothermal Field ◽  
3D Seismic ◽  
Side Scan Sonar ◽  
Massive Sulfides ◽  
Single Beam ◽  
Southern Okinawa Trough ◽  
Fault Structures ◽  
Back Arc

<p>    Multi-scale geophysical survey including pseudo-3D seismic, sub-bottom profiling, side-scan sonar, multi-beam and single-beam bathymetry, heat flow investigations as well as bottom-water, core and dredge sampling works have been conducted in a newly discovered hydrothermal field named as Geolin Mounds at about 1,510 depth in the Okinawa Trough. Ship-mounted bathymetric data cannot detect specific morphological features on the seafloor in this field; however, “rock grove” morphological characteristics are observed by using deep-towed side-scan sonar. Moreover, vigorous flare features in water column are detected by multi-beam and single-beam echo sounder, and widely distributed high heat flow anomalies (> 10,000 mW/m<sup>2</sup>) also exist in the survey area. Due to strong Kuroshio Current during our multi-channel seismic survey, 5-40°streamer feathering effect occurred. To take advantage of swath distributed seismic reflection points caused by streamer feathering, we developed a pseudo-3D technique and produced a 3D seismic cube from this uneven seismic dataset. The 3D seismic imaging and sub-bottom profiling results indicate widely-distributed anomalies such as blanking zone and high-amplitude reflectors around the Geolin Mounds hydrothermal field and could link the specific features above seafloor. The 3D seismic cube also provides better estimation of the areas of blanking zone on selected time slice and better characterizes fault structures in the hydrothermal field. The geochemical analysis results present high Ag, Au, As, Bi, Cd, Cu, Fe, Pb, Sb, and Zn concentrations have been found in our coring and dredging samples. Relatively high concentration of methane, rare earth elements and <sup>3</sup>He/<sup>4</sup>He ratio in near bottom seawater samples are also shown. Based on the geophysical and geochemical works, we propose that the Geolin Mounds hydrothermal field is without underlying submarine volcanos and hydrothermal fluid migration could be related to fault development. This hydrothermal field is in its embryo stage of evolution and constantly supported by active hydrothermal circulation. As a consequence, seafloor massive sulfides deposits and related geomorphological features can keep developing with hydrothermal fluid circulation along migration conduits. The fault structures and volcanic activities due to back-arc spreading process in the Southern Okinawa Trough should dominated creatures of those fluid migrating conduits.  We suggest that the Geolin Mounds hydrothermal field could sustainably grow and have high potential of massive sulfides resources in the Southern Okinawa Trough. Furthermore, this hydrothermal field can serve as a good observatory for get better understanding of seafloor edifice development and ore mineralization associated with hydrothermal circulation activities in a back-arc spreading tectonics.</p>

scholarly journals Characteristics of seismicity in the southern Okinawa Trough and their relation to back-arc rifting processes

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Ryuta Arai
Keyword(s):  
Seismic Reflection ◽  
Okinawa Trough ◽  
Statistical Characteristics ◽  
Ryukyu Islands ◽  
Seismic Reflection Data ◽  
Seismicity Rate ◽  
Southern Okinawa Trough ◽  
The Ryukyu Islands ◽  
Stress Changes ◽  
Back Arc

AbstractThe southern part of the Okinawa Trough forms a narrow back-arc rift basin where evidence for submarine volcanoes and active hydrothermal venting is observed. The region is also known to cause large crustal earthquakes frequently which often accompany a rapid increase in seismicity rate. Although such swarm-like activities are common in active volcanic regions and are considered to be primarily induced by crustal fluid flows, potential interactions between tectonic, magmatic and hydrologic processes have been poorly examined in the southern Okinawa Trough despite these processes happening in the proximity. Here, I report the spatial and statistical characteristics of seismic activity in the southern Okinawa Trough and discuss their relation to other rifting-related phenomena. Most of the earthquakes with magnitude greater than 5 are localized around the rift axes (the Yaeyama Rift and the Yonaguni Rift) where seismic reflection data indicated the presence of solidified magmatic intrusions into the shallow sedimentary layers. I found the areas around the rift axes show low b values of < 0.8 and suggest that stress changes directly induced by dike intrusions beneath the rift axes control the occurrence of swarm activities. On the contrary, regions with high b values (> 1.2) are found around the Ishigaki Knoll and the Hatoma Knoll. These two areas are located between the rift axes and the Ryukyu Islands and correspond to potential submarine volcanoes proposed by seafloor bathymetry and seismic reflection images. This result may constrain the location of the volcanic front in the region.

Active tectonics and volcanism in the southernmost Okinawa Trough back-arc basin derived from deep-towed sonar surveys

2021 ◽  
pp. 229047
Author(s):  
Ching-Hui Tsai ◽  
Shu-Kun Hsu ◽  
Song-Chuen Chen ◽  
Shiou-Ya Wang ◽  
Lien-Kai Lin ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Active Tectonics ◽  
Back Arc

Late Holocene paleoenvironmental changes in the southern Okinawa Trough inferred from a diatom record

2011 ◽  
Vol 56 (11) ◽  
pp. 1131-1138 ◽  
Author(s):  
DongLing Li ◽  
Hui Jiang ◽  
TieGang Li ◽  
MeiXun Zhao
Keyword(s):  
Late Holocene ◽  
Okinawa Trough ◽  
Paleoenvironmental Changes ◽  
Southern Okinawa Trough

scholarly journals Metallic mineralization associated with pillow basalts in the Yaeyama Central Graben, Southern Okinawa Trough, Japan

2006 ◽  
Vol 3 (0) ◽  
pp. 1-8 ◽  
Author(s):  
Makoto Watanabe ◽  
Kenichi Hoshino ◽  
Ryota Shiokawa ◽  
Yuki Takaoka ◽  
Hideo Fukumoto ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Southern Okinawa Trough

scholarly journals Rare earth element geochemistry of sediments from the southern Okinawa Trough since 3 ka: Implications for river-sea processes and sediment source

2019 ◽  
Vol 11 (1) ◽  
pp. 929-947
Author(s):  
Siyi Hu ◽  
Zhigang Zeng ◽  
Xue Fang ◽  
Bowen Zhu ◽  
Xiaohui Li ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Okinawa Trough ◽  
Sediment Source ◽  
Sediment Sources ◽  
Terrigenous Sediments ◽  
Southern Okinawa Trough ◽  
Ree Fractionation ◽  
Siliciclastic Sediments

Abstract The sediment sources in the southern Okinawa trough (SOT) are still controversial and few studies have focused on the effects of transport processes on the elemental composition of initial terrigenous materials. Here we present rare earth element (REE) and trace element data on siliciclastic sediments from 14C age-dated Core S3, which was collected from the SOT, to provide reliable evidence for illustrating the modified effects of marine environments on terrigenous sediments deposited at different stages and exposing changes in sediment source over the past 3 ka. Compared with bulk sediments, the siliciclastic sediments in S3 have more variable REE fractionation parameters and lower middle REE (MREE) contents. Our REE data indicate that during river-sea processes, MREE-enriched fractions such as Fe–Mn oxides and carbonate were added to the original terrigenous sediments before deposition, weakening the degree of REE fractionation in the initial sediments; thus, care should be taken when using REE data from bulk samples to decipher source changes. The temporal changes in sediment source in S3 can be broadly identified based on the REE fractionation parameters of the residual fractions, and the results are largely consistent with the findings obtained by heavy mineral examinations. Units 1 and 3 are dominated by reworked shelf sediments of Changjiang origin,while the proportion of Taiwan-derived sediment is notably higher in Units 2 and 4. The sediment flux of Taiwan origin in the SOT was much smaller than previously thought. Huanghe-derived sediments and volcanic materials did not contribute significantly to the late Holocene sedimentation in the SOT. The large variations in sediment sources in S3 were possibly caused by changes in transport patterns driven by time-dependent changes in oceanic currents.

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