Publication Date:
2020-07-30
Description:
Elevated concentrations of certain large ion lithophile elements (LILE; e.g., Ba, K, Rb,
Cs, Ca, Sr), U, and Pb in arc magmas relative to high field strength elements (HFSE; e.g.,
Ti, Th, Hf, Nb, Zr) are considered key indicators of fluid addition to arc magma source
regions worldwide, but the fluid sources and processes of mass transfer are controversial.
Dehydration of downgoing slabs releases fluids that can flow through and react with metamorphosed
ultramafic-mafic rock packages in me´lange zones near slab-mantle interfaces.
New geochemical data from Syros, Greece, reveal that these fluids preferentially leach
LILEs, U, and Pb when they infiltrate and react with subducted metasedimentary rocks.
Transfer of these LILE-, U-, and Pb-enriched fluids to the mantle wedge at subarc depths
could directly trigger partial melting and generate magmas with elevated Ba/Th, Sr/Th,
Pb/Th, and U/Th, as well as radiogenic Sr. Alternatively, if fluid transfer occurs at shallower
depths (e.g., Syros), the metasomatized mantle could be carried deeper by wedge
corner flow to ultimately undergo partial melting in subarc regions.
Type:
Article
,
PeerReviewed
Format:
text
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