Cerro Prieto Geothermal Field (Baja California, Mexico) – A fossil system? Insights from a noble gas study

Mantle Degassing Through Continental Crust Triggered by Active Faults: The Case of the Baja California Peninsula, Mexico

“…The distinction between colored and gray symbols is as in Figure caption. The reported literature data are as follows: SSGF from Mazzini et al (); CPGF from Welhan et al (), Polyak et al (), Birkle et al (), and Pinti et al (); LTVGF from Birkle et al (); LV from Schmitt et al (); PB, SC, and UR from Vidal et al (); UR, AC, SC, SV, VG, SA, and ECH from Polyak et al (); and BC from Forrest et al (). (b) Binary plot of the CH 4 /CO 2 ratio versus 3 He/ 4 He corrected for air contamination (Rc/Ra).…”

“…The variability of the 3 He/ 4 He ratios in Cerro Prieto Geothermal field indicates variable crustal contamination by radiogenic 4 He produced at a local scale from U‐Th‐rich country rocks (Mazor & Truesdell, ; Welhan et al, ). A recent and detailed study carried out by Pinti et al () points to limited modern freshwater recharge and thus to the presence of a nearly fossil geothermal system. In detail, the authors suggest that connate waters dominate the central portion of the field and mix with the magmatic fluid containing mantle He that enter laterally into the reservoir, through the main lateral strike‐slip faults (i.e., the Cerro Prieto and Imperial faults).…”

“…The distinction between colored and gray symbols is as in Figure caption. The reported literature data are as follows: SSGF from Mazzini et al (); CPGF from Birkle et al (), Pinti et al () and Richard et al (); and LTVGF from Birkle et al () and Richard et al (). VPDB = Vienna Pee Dee Belemnite.…”

“…This group also includes other gas emissions (Salton Sea and Cerro Prieto geothermal fields; Figures and a) in the northeastern BCP. Gases from Salton Sea have 3 He/ 4 He ratios of 6.1–6.6 Ra (Mazzini et al, ), while those from Cerro Prieto are in the range 3.3–7.3 Ra (Pinti et al, ; Polyak et al, ; Welhan et al, ). This magmatic signature is associated with volcanic activity that occurred less than 25 ka ago (Schmitt et al, , ).…”

“…The Las Tres Vírgenes geothermal field, Agua Agria, and Fumarole have an asterisk because they belong to the Las Tres Vírgenes Volcanic Zone (LTVVZ). The uncolored symbols are gas emissions and volcanic rocks that were previously investigated by the following authors: SSGF from Welhan (1981) and Mazzini et al (2011); CPGF from Truesdell et al (1978), Welhan et al (1978), Polyak et al (1982), Mazor and Truesdell (1984), Des Marais et al (1988), Birkle et al (2016), Pinti et al (2018), and Richard et al (2019); LTVGZ from Birkle et al (2016) and Richard et al (2019); LV from Schmitt et al (2010); GB from Lupton (1979), Galimov and Simoneit (1982), and Welhan and Lupton (1987); PBn and AB from Spelz et al (2015); AL from Castillo et al (2002); PB, SC, and UR from Vidal et al (1981), Vidal et al (1982), and Polyak et al (1991); UR, AC, SC, SV, VG, SA, and ECH from Polyak et al (1991); SJ and PU from Negrete-Aranda et al (2015); and BC from Forrest et al (2005). In the map, CA, California; AZ, Arizona; NM, New Mexico; SON, Sonora; SIN, Sinaloa.…”