Lorandite from Allchar as geochemical detector for pp-solar neutrinos

Abstract LOREX (LORandite EXperiment) is a geochemical project addressing the solar proton–proton neutrino flux for the period of 4.31(2) Ma from the reaction  205 Tl +  ν e → 205 Pb + e − with a very low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is to obtain the precise, background-corrected ratio of  205 Pb/ 205 Tl in the mineral lorandite (TlAsS 2 ) as geochemical detector occurring in the ore deposit of Allchar in Macedonia. This study presents a report on the excavation of lorandite bearing ore from adit P-21 of the ore body Crven Dol as well as on the separation of pure lorandite from the raw ore. A detailed mineralogical and chemical investigation of the separated lorandite is performed with special regard to the question of its use as detector for solar pp-neutrinos.