Near-infrared spectroscopic determination of salinity and internal pressure of fluid inclusions in minerals

Hiroyuki Kagi, Akiko Kiyasu, Tasuku Akagi, Masayuki Nara, Takayuki Sawaki

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A near-infrared (NIR) spectroscopic method is proposed to achieve the simultaneous determination of salinity and internal pressure of fluid inclusions in natural minerals. A combination band between the antisymmetric stretching and bending vibrations of molecular water at approximately 5180 cm-1 was observed for standard salt solutions and natural minerals containing fluid inclusions with known salinities. A curve-fitting procedure was used to analyze the change in the band shape of the combination. Justification of the calibration was confirmed by observation of fluid inclusions in natural minerals whose salinities had already been determined using microthermometry. The detection limit of the present method is 1 NaCl-eq wt. %. The minimum size of fluid inclusions that produced well-resolved spectra was approximately 30 μm. This method was applied to assess micro fluid inclusions in a natural diamond with cubic growth habit (cuboid). The salinity and residual pressure of those fluid inclusions were estimated respectively as 4.4 wt. % NaCl-eq and 0.6-0.8 GPa. The present method is complementary to Raman microscopy and microthermometry for the determination of salinity in fluid inclusions of geological samples.

Original languageEnglish
Pages (from-to)430-436
Number of pages7
JournalApplied Spectroscopy
Issue number4
Publication statusPublished - Apr 1 2006
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Instrumentation
  • Spectroscopy

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