Determination of pressure from measured Raman frequency shifts of anhydrite and its application in fluid inclusions and HDAC experiments

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• 作者：Xueyin Yuan^a ; ^b ; Robert A. Mayanovic^c ; Haifei Zheng^a ; ^{hfzheng@pku.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Anhydrite ; Raman spectroscopy ; Geobarometry ; HDAC ; Fluid inclusions
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2016
• 出版时间：1 December 2016
• 年：2016
• 卷：194
• 期：Complete
• 页码：253-265
• 全文大小：2199 K

文摘

A new geobarometry was derived from the quantified relationships among Raman vibrational frequencies of anhydrite, pressure and temperature, as determined from in-situ micro-Raman spectroscopy of natural anhydrite crystals measured at p–T conditions up to 560 °C and 1400 MPa by using a hydrothermal diamond anvil cell (HDAC). With this geobarometry, the pressure in HDAC experiments and in anhydrite-bearing fluid inclusions can be determined directly from the ν_{1, 1016}, ν_{3, 1128} and ν_{3, 1160} Raman frequency shifts of anhydrite at high p–T conditions relative to their values measured at ambient conditions. The pressure can be determined to an accuracy of better than 30 MPa based on the attainable accuracy of ±0.1 cm⁻¹ for the fitted ν₁ Raman peak positions, provided the measured spectra are calibrated using the emission peak of an external fluorescent light source. The feasibility and reliability of this geobarometry were verified by rebuilding the p–T history of two fluid inclusions from the ν₁ frequency shifts of anhydrite daughter minerals from room to high temperatures, and by measuring the phase-transition pressures of calcite–CaCO₃(II)–CaCO₃(III) sequence at ambient temperature in a HDAC experiment using anhydrite as a Raman pressure sensor.