How Do Secondary Minerals in Granite Help Distinguish Paleo- from Present-Day Permeable Fracture Zones? Joint Interpretation of SWIR Spectroscopy and Geophysical Logs in the Geothermal Wells of Northern Alsace

<div>Examples of mineralogical assemblages of the granitic basement observed in cores (middle) and in cuttings (right); these assemblages define the different hydrothermal alteration grades (left). GRAN: unaltered granite; HLOW: low hydrothermal alteration; HMOD: moderate hydrothermal alteration; HHIG: high hydrothermal alteration; HEXT: extreme hydrothermal alteration; VEIN: secondary drusy quartz vein; Anh: anhydrite; Bt: biotite; Cal: calcite; Chl: chlorite; Hem: hematite; Ilt: illite; Kfs: potassic feldspars; Pl: plagioclase; Qz: quartz.</div>

Geofluids

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Figure 3: How Do Secondary Minerals in Granite Help Distinguish Paleo- from Present-Day Permeable Fracture Zones? Joint Interpretation of SWIR Spectroscopy and Geophysical Logs in the Geothermal Wells of Northern Alsace 

Figure 3 | How Do Secondary Minerals in Granite Help Distinguish Paleo- from Present-Day Permeable Fracture Zones? Joint Interpretation of SWIR Spectroscopy and Geophysical Logs in the Geothermal Wells of Northern Alsace 