64 research outputs found
Strontium Isotope Characteristics (ÎŽ88/86Sr, 87Sr/86Sr) of ArimaâType Brines Originated From SlabâFluids
Abstract In the southwest Japan forearc, slabâfluids produced from subducted materials migrate to crustal levels and appear as deepâseated brine. We have analyzed for the firstâtime stable strontium isotopes in nonâvolcanic spring water with high salinity, referred to as Arimaâtype saline water that likely originate from slabâfluid that upwelled along major faults. The stable strontium isotope compositions of the saline water are isotopically light (ÎŽ88/86Sr = 0.122â0.157â°) and different from those of local bedrock and nearâsurface water. The light strontiumâenriched and radiogenic signature of the saline water reflects the primary characteristic of slabâfluids without an isotopic overprint in the crust. The Arimaâtype brines show signatures of slabâfluids at forearc depth, which is different from the slabâfluids at subarc depth estimated from arc lavas. The characteristic features of the Arimaâtype brines are explained by a larger contribution of subducted sediments and strontium isotope fractionation during fluids generation at shallower depth
Magmatic He distribution around Unzen volcano inferred from intensive investigation of helium isotopes in groundwater
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