Abstract
Earth’s internal heat drives its dynamic engine, causing mantle
convection, plate tectonics, and the geodynamo. These renewing and
protective processes, which make Earth habitable, are fueled by a
primordial (kinetic) and radiogenic heat. For the past two decades,
particle physicists have measured the flux of geoneutrinos, electron
antineutrinos emitted during β − decay. These ghost-like particles
provide a direct measure of the amount of heat producing elements (HPE:
Th & U) in the Earth and in turn define the planet’s absolute
concentration of the refractory elements. The geoneutrino flux has
contributions from the lithosphere and mantle. Detector sensitivity
follows a 1/r 2 (source detector separation distance) dependence.
Accordingly, an accurate geologic model of the Near-Field Lithosphere
(NFL, closest 500 km) surrounding each experiment is required to define
the mantle’s contribution. Because of its proximity to the detector and
enrichment in HPEs, the local lithosphere contributes ∼50% of the
signal and has the greatest effect on interpreting the mantle’s signal.
We re-analyzed the upper crustal compositional model used by Agostini et
al. (2020) for the Borexino experiment. We documented the geology of the
western Near-Field region as rich in potassic volcanism, including some
centers within 50 km of the detector. In contrast, the Agostini study
did not include these lithologies and used only a HPE-poor,
carbonate-rich, model for upper crustal rocks in the surrounding ∼150 km
of the Borexino experiment. Consequently, we report 3× higher U content
for the local upper crust, which produces a 200% decrease in Earth’s
radiogenic heat budget, when compared to their study. Results from the
KamLAND and Borexino geoneutrino experiments are at odds with one
another and predict mantle compositional heterogeneity that is
untenable. Combined analyses of the KamLAND and Borexino experiments
using our revised local models strongly favor an Earth with ∼20 TW
present-day total radiogenic power. The next generation of geoneutrino
detectors (SNO+, counting; and JUNO, under construction) will better
constrain the HPE budget of the Earth.