Description

From fossil hydrothermal systems, we know that indicator minerals can be used as vector to the central fluid pathways. These indicator minerals have been studied in fossil systems at the surface as well from logging in drill cores. Imaging spectroscopy of rocks and drill cores is increasingly becoming a mainstream method to measure and analyze these indicator minerals in big datasets, e.g. In mining operations, but also increasingly in the geothermal sector.
Through the GEOCAP project, the KenGen project and the link with GNS, we have collaborations with geothermal companies and research organizations in Indonesia, Kenya and New Zealand. Previous MSc and PhD work within our department has shown interesting results and your work will further build upon it.
From the work of PhD student Kartika Savitri, for example, we have seen that some unexpected differences exist between the official mineral descriptions by the geothermal company and our SWIR result. Particularly remarkable is that earlier studies found epidote (an extremely important temperature indicator mineral in the geothermal industry) at different depths in the well, while our imaging spectroscopy results are clearly whoing that it is NOT epidote, but we are not clear yet what it then is and where this discrepancy is coming from.

Objectives and Methodology

The objective of this study would be to investigate what the green minerals in the drill cuttings really are and possibly how to best prevent future misinterpretations as epidot. To help solve this question the drill cuttings can be measured with imaging spectrometry at different scales and wavelength ranges (VIS SWIR and LWIR). You may want to use other analytical methods like XRD, ICP-OES and possibly Imaging µ-XRF or EMPA.
Knowing the answer to this question will give an extra puzzle piece in the understanding of this particular geothermal system in Indonesia, but will also directly help the industry to avoid misinterpretations of the important geothermal indicator mineral “epidote”.

Further reading

Savitri et al. (under review) Infrared spectroscopy for geothermal exploration: Current status and future direction, Geothermics