U-series isotope data on Lau basin glasses: the role of subduction-related fluids during melt generation in back-arc basins
- Peate, David W.
- Kokfelt, Thomas F.
- Hawkesworth, Chris J.
- Van Calsteren, Peter W.
- Hergt, Janet M.
- Pearce, Julian A.
DOIAbstract
New thermal ionization mass spectrometry U-series disequilibrium data are presented for 24 basaltic to dacitic glasses from active spreading centres in the back-arc Lau Basin (SW Pacific), together with additional inductively coupled plasma mass spectrometry trace element analyses and Sr–Nd–Pb isotope data. Valu Fa Ridge samples, adjacent to the arc front, have high U/Th and (230Th/238U) <1, implying a recent (≪350 ka) addition of a U-rich slab-derived fluid. The Valu Fa data can be combined with existing 230Th–238U data for the Central Tonga arc to infer a fluid addition event at ∼50 ka. The similar sources and time scales for fluid transfer beneath the Valu Fa Ridge and beneath the arc itself suggest that the Valu Fa Ridge is propagating ...
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