Assessment of Chaves Low-Temperature CO₂-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach

Table 6

Isotopic composition of whole rocks and mineral separates from Vilarelho da Raia AC2 drill cores. After [37].

Sample	Type of alteration	Depth (m)	Whole-rock		Muscovite		Chlorite
			δ^18O	δ^2H	δ^18O	δ^2H	δ^18O	δ^2H
AM3	Pervasive (low)	(Surface)	+11.41	−75.0
AM80	Pervasive (low)	(Surface)	+11.47	−66.1	+9.7	−70
VR23	Pervasive	81.15			+8.5	−44
VR27a	Vein	89.70	+10.10	−42.0	+9.1
VR27b	Pervasive	89.70	+10.18	−69.0	+11.6		+6.3	−53.0
VR32a	Pervasive	100.55	+11.25	−66.4	+8.6
VR32b	Vein	100.55	+10.91	−44.5	+9.1	−42
VR39	Vein	129.70	+10.80	−65.0	+10.2	−70	+5.2	−75.0
VR41	Pervasive	140.50			+9.8	−64
VR70a	Vein	195.30	+10.82	−56.0	+9.4	−45
VR70b	Pervasive	195.30	+10.91	−44.5	+9.3

Note: The term “low” means a rock sample displaying low pervasive alteration characteristics (almost an unaltered rock sample).