Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies
Determining the influence of subduction input on back-arc basin magmatism is important for understanding material transfer and circulation in subduction zones. Although the mantle source of Okinawa Trough (OT) magmas is widely accepted to be modified by subducted components, the role of slab-derived...
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MDPI AG
2021-12-01
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| author | Zhigang Zeng Xiaohui Li Yuxiang Zhang Haiyan Qi |
| author_facet | Zhigang Zeng Xiaohui Li Yuxiang Zhang Haiyan Qi |
| author_sort | Zhigang Zeng |
| collection | DOAJ |
| description | Determining the influence of subduction input on back-arc basin magmatism is important for understanding material transfer and circulation in subduction zones. Although the mantle source of Okinawa Trough (OT) magmas is widely accepted to be modified by subducted components, the role of slab-derived fluids is poorly defined. Here, major element, trace element, and Li, O and Mg isotopic compositions of volcanic lavas from the middle OT (MOT) and southern OT (SOT) were analyzed. Compared with the MOT volcanic lavas, the T9-1 basaltic andesite from the SOT exhibited positive Pb anomalies, significantly lower Nd/Pb and Ce/Pb ratios, and higher Ba/La ratios, indicating that subducted sedimentary components affected SOT magma compositions. The δ<sup>7</sup>Li, δ<sup>18</sup>O, and δ<sup>26</sup>Mg values of the SOT basaltic andesite (−5.05‰ to 4.98‰, 4.83‰ to 5.80‰ and −0.16‰ to −0.09‰, respectively) differed from those of MOT volcanic lavas. Hence, the effect of the Philippine Sea Plate subduction component, (low δ<sup>7</sup>Li and δ<sup>18</sup>O and high δ<sup>26</sup>Mg) on magmas in the SOT was clearer than that in the MOT. This contrast likely appears because the amounts of fluids and/or melts derived from altered oceanic crust (AOC, lower δ<sup>18</sup>O) and/or subducted sediment (lower δ<sup>7</sup>Li, higher δ<sup>18</sup>O and δ<sup>26</sup>Mg) injected into magmas in the SOT are larger than those in the MOT and because the injection ratio between subducted AOC and sediment is always >1 in the OT. The distance between the subducting slab and overlying magma may play a significant role in controlling the differences in subduction components injected into magmas between the MOT and SOT. |
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| language | English |
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| spelling | doaj.art-f2cffa1199d34ff9a4897e6f5a3ed91b2023-11-23T14:16:01ZengMDPI AGJournal of Marine Science and Engineering2077-13122021-12-011014010.3390/jmse10010040Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction StudiesZhigang Zeng0Xiaohui Li1Yuxiang Zhang2Haiyan Qi3Seafloor Hydrothermal Activity Laboratory, CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, ChinaSeafloor Hydrothermal Activity Laboratory, CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, ChinaSeafloor Hydrothermal Activity Laboratory, CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, ChinaSeafloor Hydrothermal Activity Laboratory, CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, ChinaDetermining the influence of subduction input on back-arc basin magmatism is important for understanding material transfer and circulation in subduction zones. Although the mantle source of Okinawa Trough (OT) magmas is widely accepted to be modified by subducted components, the role of slab-derived fluids is poorly defined. Here, major element, trace element, and Li, O and Mg isotopic compositions of volcanic lavas from the middle OT (MOT) and southern OT (SOT) were analyzed. Compared with the MOT volcanic lavas, the T9-1 basaltic andesite from the SOT exhibited positive Pb anomalies, significantly lower Nd/Pb and Ce/Pb ratios, and higher Ba/La ratios, indicating that subducted sedimentary components affected SOT magma compositions. The δ<sup>7</sup>Li, δ<sup>18</sup>O, and δ<sup>26</sup>Mg values of the SOT basaltic andesite (−5.05‰ to 4.98‰, 4.83‰ to 5.80‰ and −0.16‰ to −0.09‰, respectively) differed from those of MOT volcanic lavas. Hence, the effect of the Philippine Sea Plate subduction component, (low δ<sup>7</sup>Li and δ<sup>18</sup>O and high δ<sup>26</sup>Mg) on magmas in the SOT was clearer than that in the MOT. This contrast likely appears because the amounts of fluids and/or melts derived from altered oceanic crust (AOC, lower δ<sup>18</sup>O) and/or subducted sediment (lower δ<sup>7</sup>Li, higher δ<sup>18</sup>O and δ<sup>26</sup>Mg) injected into magmas in the SOT are larger than those in the MOT and because the injection ratio between subducted AOC and sediment is always >1 in the OT. The distance between the subducting slab and overlying magma may play a significant role in controlling the differences in subduction components injected into magmas between the MOT and SOT.https://www.mdpi.com/2077-1312/10/1/40Li-O-Mg isotopesmagmaplate subductionOkinawa Troughwestern Pacific |
| spellingShingle | Zhigang Zeng Xiaohui Li Yuxiang Zhang Haiyan Qi Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies Journal of Marine Science and Engineering Li-O-Mg isotopes magma plate subduction Okinawa Trough western Pacific |
| title | Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies |
| title_full | Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies |
| title_fullStr | Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies |
| title_full_unstemmed | Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies |
| title_short | Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies |
| title_sort | lithium oxygen and magnesium isotope systematics of volcanic rocks in the okinawa trough implications for plate subduction studies |
| topic | Li-O-Mg isotopes magma plate subduction Okinawa Trough western Pacific |
| url | https://www.mdpi.com/2077-1312/10/1/40 |
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