A volcanic chronosequence as a time-resolved paleo-detector array to study the cosmic-ray flux in the Late Pleistocene and Holocene

TL;DR

This paper proposes using olivine xenoliths from the Chaîne des Puys as a time-resolved paleo-detector array to reconstruct the cosmic-ray muon flux over roughly the last 40,000 years. It introduces a three-stage modeling pipeline combining MCEq/crflux for the historical muon flux, Geant4 for muon-induced recoils in olivine, and SRIM for track-length calculations, along with background estimates from radiogenic neutrons and uranium fission. By exploiting a chronosequence of eruptions that expose mantle material at different times, the method enables time-differential measurements of the flux and sensitivity to events such as the Laschamp geomagnetic excursion and a nearby SN, using the Antlia remnant as a benchmark. The work demonstrates feasibility and motivates experimental efforts under the PRImuS project to recover and analyze olivine tracks for long-timescale high-energy astrophysics.

Abstract

We present a phenomenological study demonstrating the feasibility of using olivine xenoliths from the Chaîne des Puys as a time-resolved paleo-detector array to probe the cosmic-ray flux over the last 40,000 years. This volcanic region provides a unique chronosequence of samples brought to the surface by well-dated eruptions. By modeling the expected density of nuclear recoil tracks induced by cosmic-ray muons in olivine, we show that the signal is detectable and above backgrounds from natural radioactivity. We demonstrate that by analyzing samples with different exposure ages, it is possible to construct a time-differential measurement of the cosmic-ray flux. This method shows sensitivity to historical variations, such as the enhanced flux expected during the Laschamp geomagnetic excursion ($\sim$41~kyr) and the potential contribution from nearby supernovae, for which we use the Antlia supernova remnant precursor as a benchmark. This work establishes a new application of the paleo-detector technique for long-scale time-domain high-energy astrophysics and provides the direct scientific motivation for experimental efforts to measure these track records.

Figures (5)

• Figure 1: A map of the main part of the Chaîne des Puys volcanic field, west of Clermont-Ferrand.
• Figure 2: Differential track production rate in olivine. Left: Contributions to the track rate spectrum from elastic recoils on the original nuclides composing the mineral in brown for negative and grey for positive muons; tracks from isotopes produced by negative muon spallation and low energy capture in pink, tracks from isotopes produced by positive muon spallation in olive green. Right: The expected rate from cosmic-ray muons (negative and positive) for the "normal" scenario is in the blue line, for the "SN250" scenario in the orange line. The two main backgrounds are also shown in purple and green for radiogenic neutrons and fission fragments.
• Figure 3: Predicted number of tracks per gram of olivine for each volcanic sample, in the normal flux scenario. The muon-induced track spectra are shown for all eruptions, scaling with their respective exposure times, while the background from fission and neutrons is shown in dashed lines.
• Figure 4: Total number of muon-induced tracks expected from a collection of 0.2-gram samples, one from each volcanic eruption. The cumulative signal is shown for both the normal cosmic-ray flux scenario (blue) and the SN250 (orange), with bands representing a Poissonian uncertainty. The dashed lines indicate the contribution from each individual eruption in the normal case. The green line represents the expected summed counts of all the fission tracks.
• Figure 5: Time evolution of the total integrated number of muon-induced tracks as a function of sample exposure time. The points represent the expected signal for each of the volcanic scenarios in the normal (blue) and SN250 (orange) flux scenarios, with Poissonian, Poissonian + 10% counting error, and Poissonian + 30% counting error bands. For each flux, an enhancement due to the lower Earth's magnetic field during the Laschamp event is shown as a dashed line deviating from each flux scenario in the time interval between 30 and 40 kya. The inset shows a zoom in the 7 to 14 kyr range, an interval of time in which eruptions were particularly frequent. Time uncertainties in the eruption dating are represented by the grey vertical bands.