High ³ He/ ⁴ He in central Panama reveals a distal connection to the Galápagos plume

Abstract

It is well established that mantle plumes are the main conduits for upwelling geochemically enriched material from Earth's deep interior. The fashion and extent to which lateral flow processes at shallow depths may disperse enriched mantle material far (>1,000 km) from vertical plume conduits, however, remain poorly constrained. Here, we report He and C isotope data from 65 hydrothermal fluids from the southern Central America Margin (CAM) which reveal strikingly high 3He/4He (up to 8.9RA) in low-temperature (≤50 °C) geothermal springs of central Panama that are not associated with active volcanism. Following radiogenic correction, these data imply a mantle source 3He/4He >10.3RA (and potentially up to 26RA, similar to Galápagos hotspot lavas) markedly greater than the upper mantle range (8 ± 1RA). Lava geochemistry (Pb isotopes, Nb/U, and Ce/Pb) and geophysical constraints show that high 3He/4He values in central Panama are likely derived from the infiltration of a Galápagos plume–like mantle through a slab window that opened ∼8 Mya. Two potential transport mechanisms can explain the connection between the Galápagos plume and the slab window: 1) sublithospheric transport of Galápagos plume material channeled by lithosphere thinning along the Panama Fracture Zone or 2) active upwelling of Galápagos plume material blown by a “mantle wind” toward the CAM. We present a model of global mantle flow that supports the second mechanism, whereby most of the eastward transport of Galápagos plume material occurs in the shallow asthenosphere. These findings underscore the potential for lateral mantle flow to transport mantle geochemical heterogeneities thousands of kilometers away from plume conduits.

Magmatic Carbon and Helium in Springs Reveals the Vitality of a Dormant Volcano, Taranaki, New Zealand

“…At high-temperature TVZ geothermal sites, 3 He/ 4 He approaches MORB (maximum 8.2 R C /R A at Wairakei, Giggenbach et al, 1993;Torgersen et al, 1982;Hulston & Lupton, 1996). The Taranaki signature is typical of dormant volcanoes, such as Mount Shasta in the United States ( 3 He/ 4 He = 5.9 R A , Symonds et al, 2003) that last erupted in AD1250, and fits within the global mean of 5.4 ± 1.9 R A (Bekaert et al, 2021;Hilton et al, 2002).…”

Deciphering complex groundwater age distributions and recharge processes in a tropical and fractured volcanic multi‐aquifer system

“…Mantle-derived contributions of helium have been widely reported across Costa Rica and Panama (Barry et al, 2019;Bekaert et al, 2021;Gazel et al, 2009Gazel et al, , 2011Lee et al, 2017;Melián et al, 2019) Based on the current land use (Figure 7), these recharge eleva- water resources management plans in this tropical volcanic multiaquifer system, since better territorial guidelines or regulations may be undertaken to preserve critical recharge zones.…”

“…12.32 yr) (Clarke et al, 1976;Lucas & Unterweger, 2000;Schlosser et al, 1989) to tritiogenic helium isotope ( 3 He trit ). The difficulty involved in this method corresponds to the existence of different sources of helium in the subsurface, for example, the potential contributions from crust and/or mantle sources (Barry et al, 2019;Bekaert et al, 2021;Schlosser et al, 1989;Solomon & Cook, 2000).…”

“…Commonly, R/R a ≈ 1 means that groundwater is in equilibrium with the atmosphere, whereas R/R a > 1 refers to elevated 3 He contributions from degassing of upper mantle sources (up to R/R a $ 8), and R/ R a < 1 is attributed to helium accumulation from the crust (R/ R a $ 0.05) (Bekaert et al, 2021;Di Piazza et al, 2015;Ezaki et al, 2019;Heilweil et al, 2009;Hershey et al, 2007;Hiett et al, 2021;Lee et al, 2017;Rizzo et al, 2016;Solomon & Cook, 2000).…”

Episodic intraplate magmatism fed by a long-lived melt channel of distal plume origin

“…This apparent paradox can be explained if the same pulse of plume material responsible for the melt channel’s formation was also responsible for the demise of the Farallon Plate and the birth of a new spreading center (i.e., the GSC). Assuming a mantle flow speed of 8 cm/year ( 45 ), the plume material would take longer than 5 Ma to reach the location of the sampled sill intrusions (Fig. 5 and fig.…”