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| Titel |
Heterogeneous source components of intraplate basalts from NE China induced by the ongoing Pacific slab subduction |
| VerfasserIn |
Huan Chen, Qun-Ke Xia, Jannick Ingrin, Etienne Deloule |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127382
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| Publikation (Nr.) |
 EGU/EGU2016-7252.pdf |
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| Zusammenfassung |
| In recent few years, the recycled oceanic slab has been increasingly suggested to be the
enriched component in the mantle source of widespread intra-plate small-volume basaltic
magmatism in eastern China. The recycled oceanic slab is a mixture of sediment, upper
oceanic crust and lower gabbro oceanic crust, and will undergo alteration and dehydration
during the recycling progress. The influence of these different components on the mantle
source needs to be further constrained.
The Chaihe-aershan volcanic field in Northeast China is located close to the surface
position of the front edge of the subducted Pacific slab and includes more than 35
small-volume Quaternary basaltic volcanoes, which provides an opportunity to
study the evolution of mantle source in detail and the small-scale geochemical
heterogeneity of the mantle source. We measured the oxygen isotopes and water content of
clinopyroxene (cpx) phenocrysts by secondary ion mass spectrometry (SIMS) and
Fourier transform infrared spectrometry (FTIR), respectively. The water content
of magma was then estimated based on the partition coefficient of H2O between
cpx and basaltic melt. The measured δ18O of cpx phenocrysts (4.27 to 8.57 ) and
the calculated H2O content of magmas (0.23-2.70 wt.%) show large variations,
reflecting the compositional heterogeneity of the mantle source. The δ18O values
within individual samples also display a considerable variation, from 1.28 to 2.31‰
suggesting mixing of magmas or the sustained injection of magmas with different
δ18O values during the crystallization. The relationship between the averaged δ18O
values of cpx phenocrysts and the H2O/Ce, Ba/Th, Nb/La ratios and Eu anomaly of
whole-rocks demonstrates the contribution to three components in the mantle source
(hydrothermally altered upper oceanic crust or marine sediments, altered lower gabbroic
oceanic crust, ambient mantle). The proportions of these three components varied
strongly within a limited period (∼1.27 Ma to ∼0.25 Ma). As only the Pacific slab is
constantly subducted to the eastern Asia during that time, we suggested that its
ongoing subduction is the only reasonable candidate to result in the compositional
heterogeneity and rapid variation of enriched components in such a limited and
recent time. Combines with previous studies on other basalt localities of eastern
China, these new results confirm that the Pacific slab subduction play a key role in
the triggering of the wide spread Cenozoic basaltic volcanism in eastern China. |
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