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The Role of Recycled Oceanic Crust in the Generation of Alkaline A‐Type Granites
Author(s) -
Yang WuBin,
Niu HeCai,
Hollings Pete,
Zurevinski Shan E.,
Li NingBo
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2017jb014921
Subject(s) - geology , subduction , oceanic crust , crust , geochemistry , mantle (geology) , intraplate earthquake , adakite , protolith , zircon , craton , lithosphere , partial melting , paleontology , tectonics
Melting and dehydration of subducted oceanic slabs dominate element recycling within the subduction factory, but the role of recycled oceanic crust in the source of intraplate magmas is poorly understood. In situ zircon O‐Hf isotope data from two Early Cretaceous alkaline A‐type granites that are genetically related to large‐scale extension of eastern China in the Late Mesozoic (circa 125 Ma) yield low δ 18 O (1.8 ± 0.3‰ to 5.1 ± 0.3‰, 2 σ ) and positive εHf( t ) (1.5 ± 1.2 to 17 ± 1.2, 2 σ ). This suggests the contribution of altered oceanic crust and an enriched mantle component in the source region. Elevated initial 87 Sr/ 86 Sr and 206 Pb/ 204 Pb ratios, and εHf( t ) whole rock values with relatively constant εNd( t ) values beyond the normal mantle array, require a component that underwent seawater interaction in the source of protolith. The geochemical data require a complex source region for the alkaline A‐type granites in NE China involving more than 40% recycled oceanic crust. This altered oceanic crust beneath the Late Mesozoic lithospheric mantle likely represents remnants of multiple subduction and collision events between microblocks from the Late Paleozoic to Early Mesozoic in northeastern China. Recycling of subducted oceanic crust represents a novel exotic source for the origin of alkaline A‐type granites in intraplate extensional settings.