Rare-earth mineral deposits in Kalgoorlie, Western Australia (left) and carbon dioxide - rich fluid inclusions (right).
Researchers in Beijing, China are using cutting-edge technology to advance our understanding of the composition of fluid inclusions trapped in minerals. In this work, researchers probe the ongoing challenge of how to observe phase changes of these materials as a function of temperature with IR spectroscopy, whilst also accounting for temperature deviations due to the IR itself.
Hong-Rui Fan’s group from the Institute of Geology and Geophysics at the Chinese Academy of Sciences are looking at the size and composition of various inclusions and minerals, including CO₂-rich and salt/water inclusions in quartz, stibnite, wolframite and pyrite. Using a Linkam THMSG600, they were able to identify how much the temperature deviated during microthermometric measurements due to “warming” from IR light.
They have discovered that transparent and translucent minerals absorb more IR energy, and thus a greater effect on phase transition temperatures was seen. They propose using the lowest energy IR light in conjunction with the smallest field diaphragm possible to minimise the IR heating. A temperature cycling method was also used (cycling heating/cooling with IR) in order to mitigate these heating effects. Linkam’s THMSG600 with LINK control software can precisely control and monitor temperature while imaging and measuring the evolution in size and shape of fluid inclusions, and is compatible with many FTIR spectrometers.
References
Peng, H., Fan, H., Santosh, M. et al. “Infrared microthermometry of fluid inclusions in transparent to opaque minerals: challenges and new insights.” (2020) Miner Deposita DOI: 10.1007/s00126-019-00950-z
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