Two-cells phase separation in shallow submarine hydrothermal system at Milos Island, Greece: Boron isotopic evidence

Shein Fu Wu, Chen-Feng You, Bo Shian Wang, Eugenia Valsami-Jones, Emmanuel Baltatzis

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Three types of hydrothermal vent fluids, herein referred to as cave, submarine-brine and seawater-like, were recovered from a shallow submerged system at Milos in the Aegean Sea, Greece, for detailed chemical and isotopic analyses. The cave fluids discharge through rock fissures near sea-level and have low pH, chlorinity, and B concentrations relative to seawater. The submarine-brine fluids are characterized by high Cl and contain >10 times seawater B concentrations. A scenario involving a two-cells circulation is proposed; one occurs at 1-2 km and another at shallower depth. The deeper saline reservoir has experienced subcritical phase separation, partitioning 0.42 mM B in vapor and 6.8 mM in brine with no detectable isotopic fractionation. The reaction temperature in the saline reservoir is 313C calculated from the Na-K-Ca geothermometry. The vapors rise directly to form the cave vents, whereas the saline fluids transport in different pathways and are influenced by seawater mixing to form the variable submarine-brine fluids. The seawater-like fluids circulate at shallower depths, where calculated temperature is 248C and show slightly diluted B (0.36-0.41 mM) and seawater δ11B. These fluids probably resulted from heating of down-flow seawater and may have experienced groundwater discharge and partial Mg removal. This study represents the first two-cells circulation occurring at Milos and emphasizes the important role of phase separation in shallow submarine hydrothermal system.

Original languageEnglish
Article numberL08613
JournalGeophysical Research Letters
Volume38
Issue number8
DOIs
Publication statusPublished - 2011 Apr 28

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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