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Western Northern Luzon Isotopic Evidence of Transition From Proto‐South China Sea to South China Sea Fossil Ridge Subduction
Author(s) -
Liu HaiQuan,
Yumul Graciano P.,
Dimalanta Carla B.,
Queaño Karlo,
Xia XiaoPing,
Peng TouPing,
Lan JiangBo,
Xu YiGang,
Yan Yi,
Guotana Juan Miguel R.,
Olfindo Valerie Shayne
Publication year - 2020
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2019tc005639
Subject(s) - geology , magmatism , subduction , geochemistry , basalt , mantle (geology) , mantle wedge , paleontology , tectonics
Temporal geochemical comparisons are conducted for representative magmatism from western Northern Luzon to reconstruct the Cenozoic tectonics. Oligo‐Pleistocene magmas from western Northern Luzon display elemental and Sr‐Nd‐Hf‐Pb‐O isotope geochemistry similar to intraoceanic arc magmatism, consistent with derivation from the mantle wedge, coupled with fractional crystallization. Specifically, the Oligo‐Miocene (~26.8–15.6 Ma) Central Cordillera diorite complex samples exhibit a negative correlation between Sr‐Nd isotopes, consistent with mantle metasomatism by fluids/melts released from pelagic sediments. The Mio‐Pleistocene samples (<~9 Ma) exhibit consistent 87 Sr/ 86 Sr ratios with variable ε Nd and partially overlap with those of Scarborough seamount basalts, consistent with mantle metasomatism by fluids/melts released from the Scarborough seamount basalts, which are being subducted beneath Northern Luzon with the South China Sea fossil ridge. Temporal changes in Sr‐Nd‐Hf‐Pb isotopes are also observed for the Taiwan‐Luzon arc magmatism. The Oligo‐Miocene (>~9 Ma) magmatism exhibit intraoceanic arc isotopic signatures, suggestive of a chemical imprint from subducted pelagic sediments. The Mio‐Pleistocene (<~9 Ma) lavas display enriched mantle‐type isotope compositions, consistent with an input of terrigenous sediment in the mantle. The temporal variations in Sr‐Nd‐Hf‐Pb isotopes for the Taiwan‐Luzon magmatism, combined with paleomagnetic evidence, mirror a transition from the Proto‐South China Sea to the South China Sea fossil ridge subduction beneath western Northern Luzon at ~9 Ma. In addition, this study also highlights the importance of relatively enriched components in the lower plate in the maturation of overriding juvenile oceanic crust in an arc‐continent collision system.