Journal
CHEMICAL GEOLOGY
Volume 569, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.chemgeo.2021.120124
Keywords
Iron isotopes; The South China Sea; IODP Expedition 349; Pyroxenite; Plate subduction
Categories
Funding
- Strategic Priority Research Program (A) of the Chinese Academy of Sciences [XDA22050103]
- National Key Resource & Development Program of China [2016YFC0600408]
- Taishan Scholar Program of Shandong [ts201712075]
- AoShan Talents Cultivation Program - Qingdao National Laboratory for Marine Science and Technology [2017ASTCP-OS07]
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The study reveals that basalts from the South China Sea exhibit MORB-like Fe isotopic signatures, suggesting the presence of pyroxenitic components in the peridotitic mantle, possibly derived from subducted materials. This indicates that the origin of backarc basin basalts with MORB-like Fe isotopic signatures can be influenced by the presence of multiple factors, particularly in cases of a heterogeneous mantle source.
Clarifying the genesis of backarc basin basalts (BABBs) is of great significance for understanding the cycling of subducted materials. Here we show MORB-like Fe isotopic signatures (delta Fe-56) of basalts recovered from the South China Sea (SCS), a well-developed backarc basin, as an indicator to investigate the influence of subduction on the BABBs. Whole-rock chemical compositions and olivine chemistry indicate the presence of pyroxenitic components in the peridotitic mantle. Melting of a pyroxenite-bearing peridotite indicates an addition of similar to 10-40% of pyroxenitic melts to the peridotitic mantle in the SCS, which should result in higher delta Fe-56 values than that of global MORBs. It is inconsistent with the MORB-like delta Fe-56 values we observed in the SCS basalts. Therefore, a component with low delta Fe-56 signatures may exist in the source of the SCS basalts, which is most likely derived from subducted materials. Such a scenario can be well corroborated by mixing depleted MORB mantle with subducted fluids and pyroxenitic melts. This study emphasizes that the MORB-like Fe isotopic signatures in backarc basin basalts can be caused by multi-factors, especially in the case of heterogeneous mantle source.
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