Petrography And Uplift History Of The Quaternary Takidani Granodiorite- Could It Have Hosted A Supercritical (Hdr) Geothermal Reservoir?
Journal Article: Petrography And Uplift History Of The Quaternary Takidani Granodiorite- Could It Have Hosted A Supercritical (Hdr) Geothermal Reservoir?
AbstractThe Quaternary Takidani Granodiorite (Japan Alps) is analogous to the type of deep-seated (3-5 km deep) intrusive-hosted fracture network system that might support (supercritical) hot dry/wet rock (HDR/HWR) energy extraction. The I-type Takidani Granodiorite comprises: porphyritic granodiorite, porphyritic granite, biotite-hornblende granodiorite, hornblende-biotite granodiorite, biotite-hornblende granite and biotite granite facies; the intrusion has a reverse chemical zonation, characterized by >70 wt% SiO2 at its inferred margin and <67 wt% SiO2 at the core. Fluid inclusion evidence indicates that fractured Takidani Granodiorite at one time hosted a liquid-dominated, convective hydrothermal system, with <380°C, low-salinity reservoir fluids at hydrostatic (mesothermal) pressure conditions. 'Healed' microfractures also trapped >600°C, hypersaline (~35 wt% NaCleq) fluids of magmatic origin, with inferred minimum pressures of formation being ~600-750 bar, which corresponds to fluid entrapment at ~2.4-3.0 km depth. Al-in-hornblende geobarometry indicates that hornblende crystallization occurred at about 1.45 Ma (7.7-9.4 km depth) in the (marginal) eastern Takidani Granodiorite, but later (at ~1.25 Ma) and shallower (~6.5-7.0 km) near the core of the intrusion. The average rate of uplift across the Takidani Granodiorite from the time of hornblende crystallization has been 5.1-5.9 mm/yr (although uplift was about 7.5 mm/yr prior to ~1.2 Ma), which is faster than average uplift rates in the Japan Alps (~3 mm/yr during the last 2 million years). A temperature-depth-time window, when the Takidani Granodiorite had potential to host an HDR system, would have been when the internal temperature of the intrusive was cooling from 500°C to ~400°C. Taking into account the initial (7.5 mm/yr) rate of uplift and effects of erosion, an optimal temperature-time-depth window is proposed: for 500°C at 1.54-1.57 Ma and ~5.2±0.9 km (drilling) depth; and 400°C at 1.36-1.38 Ma and ~3.3±0.8 km (drilling) depth, which is within the capabilities of modern drilling technologies, and similar to measured temperature-depth profiles in other active hydrothermal systems (e.g. at Kakkonda, Japan).
- Masatoshi Bando, Greg Bignall, Kotaro Sekine and Noriyoshi Tsuchiya
- Published Journal
- Journal of Volcanology and Geothermal Research, 2003
- Not Provided
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Masatoshi Bando,Greg Bignall,Kotaro Sekine,Noriyoshi Tsuchiya. 2003. Petrography And Uplift History Of The Quaternary Takidani Granodiorite- Could It Have Hosted A Supercritical (Hdr) Geothermal Reservoir?. Journal of Volcanology and Geothermal Research. (!) .