Diversity and Distribution of Culturable Thermus Species in Terrestrial Hot Springs of Southwestern Yunnan Province in China

The Yunnan geothermal area has many neutral and alkalescent thermal springs. Members of the genus Thermus have been found in thermal environments. In this study, we attempted to cultivate numerically abundant Thermus species using a variety of different strategies. A total of 223 strains of Thermus-like bacteria were isolated from seventeen hot spring samples of four geothermal regions (Baoshan, Dali, Lincang and Dehong). These strains were classified into two genera, Thermus and Meiothermus, based on 16S rDNA. The optimal isolation temperature of the Thermus genus was 63–70 °C. The highest Thermus diversity was found at 63 °C. Thermus brockianus was a universal culturable bacterium in the four geothermal regions. The principal component analysis (PCA) showed that T. oshimai preferred to inhabit the hot springs of the Baoshan (Bs) geothermal region, and T. amyloliquefaciens dominated the Dali (Dl) geothermal region, whereas T. tengchongensis accumulated in the Lincang (Lc) and Dehong (Dh) geothermal regions. The results suggested that Thermus species had habitat-preferable characteristics among the four geothermal regions. The findings may help identify the niche from which Thermus strains can likely be isolated.

Appraising Mahallat Geothermal Region using thermal surveying data accompanied by the geological, geochemical and gravity analyses

Mahallat Geothermal Region, located in the central part of Iran, is known as one of the largest low-temperature geothermal fields. In this study, Mahallat geothermal resource has been evaluated based on integrated geological, geochemical and geophysical analyses. Gravity data revealed three major negative anomaly zones. Based on the geochemical analyses, quartz geothermometers are more reliable than others and confirmed that the reservoir is about 90 °C. Lithological properties of Jurassic layers and high sulphate content observed in geochemical data showed traces of the coal-rich layers on the hot fluids. Measured temperatures in 7 boreholes with the depths ranging from 50 to 100 m, have proposed that expected geothermal gradient will be about 81.5 °C/km. Among all drilled boreholes, the data coming from only one resulted in this almost reliable gradient. Other boreholes are clearly too shallow or affected by upflow or downflow of water along existing faults. Geological, geochemical, gravity and measurements of drilled boreholes suggested the existence of a shallow reservoir with an approximate temperature of 90 °C. Regarding gravity and observed faults, geothermal reservoir is elongated parallel to one of the main faults of the region with NE-SW strike.

DELINEATION OF SUBSIDENCE IN THE ALTERATION ZONE IN ULUBELU GEOTHERMAL FIELD BASED ON INTERFEROMETRY SYNTHETIC APERTURE RADAR TIME SERIES

Ulubelu is a geothermal region managed by Pertamina Geothermal Energy (PGE) located in Mount Kukusan, Sula, Kabawok, Kuripan and Rindingan. The learning of subsidence is required for disaster mitigation. This research use 33 SAR data of Sentinel1-A which bundled for generate an APS and then using multi temporal analysis to generate InSAR time series from 2018 September to 2017 April. InSAR time series can detect indication of subsidence practically and quickly. Decrease velocity of subsidence in the Ulubelu geothermal region is an average of 3,3 mm/yr (X=453.558, Y=9.412.437, 48 S zone. This subsidence is domination by altered rocks compaction. In the other hand, the geological structure (faults) and lithology also surface loading affected the subsidence. Pekon Gn. Tiga, Karang Rejo, Muara Dua and Pagar Alam are the worst of subsidence area. Mitigation must to be clear early for areas that have the worst subsidence in Ulubelu geothermal field.