Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)

This paper focuses on constraining the erosion rate in the area of the Allchar Sb-As-Tl-Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long-term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L-8 CD, L1b/R, L1c/R, and L-4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo-depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo-depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo-depth values allow estimating the relative contributions of 205Pb derived from pp-neutrino and fast cosmic-ray muons, respectively, which is an important prerequisite for the LOREX experiment

Determination of erosion rate at Allchar region with cosmogenic Nuclides

Allchar is a Sb-As-Tl-Au deposit located at the north - western margin of the Kozuf Mountains in Macedonia, close to the Greek border. The mine contains the world’s largest known concentration of thallium-bearing minerals, especially lorandite (TlAsS2). LOREX, the acronym for LORandite EXperiment, is the only geochemical solar neutrino experiment still actively pursued. It addresses the determination of the long-term average of the solar neutrino flux, based on the neutrino-capture reaction 205 Tl + νe → 205 Pb + e - occurring in the lorandite of the Allchar mine. The final step of LOREX will be the extraction of the lorandite and the quantitative determination of the 205Pb / 205Tl ratio, thus providing the product of solar neutrino flux and neutrino-capture cross section, integrated over the lorandite age of 4.31 · 106 yr. Based on the present-day solar luminosity, it is expected that about 23 atoms of 205Pb of solar neutrino origin will be found per gram of lorandite. In contrast with the production of 205 Pb by solar neutrinos, which is independent of depth, cosmogenic 205Pb produced from fast muons of cosmic ray origin is strongly depth-dependent and very sensitive to the longterm erosion history of the field area. For erosion rate determination, we have so far applied three independent series of measurements of cosmogenic 26Al, 10Be and 53Mn. Firstly, the 26Al concentration in quartz was determined using the AMS system at VERA (Vienna Environmental Research Accelerator). Secondly, a series of measurements of the 10Be and 26Al contents was performed at the AMS of PRIME Lab, Purdue University, and finally AMS measurements at the Tandem facility of the TU Munich provided the concentration of 53 Mn in pyrite (FeS2). For the two ore bodies containing lorandite, we derived lower limits of the erosion rate of ~33 m/Myr at Crven Dol (NW part of Allchar deposit) and 67 m/Myr in the central part (SE part of Allchar deposit), in fair agreement with quantitative geomorphologic studies

O JEDNOJ ANALOGIJI IZMEĐU SLOŽENIH HEMIJSKIH REAKCIJA I ELEKTRIČNIH KOLA

U ovom radu, kao za karakterističan primer iz hemijske kinetike, za reakciju prvog reda, sistem složenih hemijskih jednačina matematičkim transformacijama sveden je na sistem homogenih i nehomogenih diferencijalnih jednačina prvog i drugog reda, koje su pogodne za predstavljanje preko električne analogije. Nakon toga, posmatrana su električna kola sa rednom i paralelnom vezom u kojima su prisutne sve tri karakteristične otpornosti i to sa i bez strujnog izvora. Primenom Kirhofovih zakona, izvedene su pogodne diferencijalne jednačine u zavisnosti od naelektrisanja, napona i jačine struje, a koje predstavljaju opšti model za uspostavljanje analogije sa ranije izvedenim sličnim hemijskim jednačinama za određivanje koncentracije jedinjenja, u kojima su uključene i konstante brzine reakcije. Na kraju, na primeru jedne od karakterističnih izvedenih električnih relacija u diferencijalnom obliku, dat je tabelarni prikaz analogije između električnih i veličina koje figurišu u hemijskim jednačinama, kao i neke mogućnosti primene prikazanih analogija

Geochemical Detection of the pp-Neutrino flux with 205Tl LOREX collaboration

An indispensable goal of this proposal still remains the determination of the neutrino capture probability by 205Tl. The ratio 205Pb/205Tl in lorandite provides only the product of solar neutrino flux and neutrino capture probability into the different nuclear states of 205Pb

Lorandite from Allchar, a long-term double detector for pp-neutrinos and fast myons

The Sb-As-Tl-Au deposit at Allchar, providing one of the world-wide largest concentrations of thallium and also numerous other Tl-bearing minerals, may open an outstanding scientific perspective. Allchar belongs to the Serbian – Macedonian metallogenic province located near the border between Macedonia and Greece. By a long-lasting international research it has been shown that Lorandite from Allchar can serve, together with cogenetic monitor minerals, as a geochemical detector for both, the flux of solar pp-neutrinos, averaged over the geological age of Lorandite, and for the average flux of fast cosmic myons within the same period of time

Geochemical Determination of the pp-Neutrino Flux with 205Tl-LOREX: A Progress Report

Intensive research from the 1970's to 1990's towards geochemical detection of solar neutrinos using 205 Tl, 98 Mo and 81 Br has left 205 Tl the only viable candidate. LOREX (LORandite EXperiment ) is based on determining the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205 Tl+v e → 205 Pb+e - , the lowest threshold (52 keV) for neutrino capture. The ratio of 205 Pb/ 205 Tl in lorandite (TlAsS 2 ) depends also on contributions from fast muon cosmic radiation. The latter is a function of paleo - depth, including the eroded layer over 4.3 Ma, determined using cosmogenic nuclides ( 26 Al, 36 Cl, 3 He and 21 Ne) in the ore body Crven Dol (Tl - As - Sb - S) in Allchar (Macedonia). The results give a l ower limit of paleo - depth of 490mwe and an upper limit of 2300mwe. From this the ratios 205 Pb ve / 205 Pb tot are estimated as 2:8 and 6:4, respectively. Identification of the 205 Pb nuclei in the lead sample extracted from the lorandite mineral requires 10 - 10 to 10 - 11 overall detection sensitivity for 205 Pb/Pb and comparable suppression of the 205 Tl isobar. This is proposed by full stripping of 205 Pb at high energy (345MeV/u) at the RIKEN - RIBF ion - beam facility. 205 Tl isobar separation is already largely achiev ed by chemical Pb - Tl separation by the overall sample preparation. Samples with a higher concentration ( 205 Tl/natPb=1%) are necessary for a guide - beam and initial accelerator tuning. A sample with a considerably lower level of about 10 - 8 is needed for cont rol of the beam analysis system with 205 Tl ions, in the presence ultimately of a lighter guide beam, to limit the in - beam production of 205 Pb by the (p,n) reaction on 205 Tl in the energy - loss and ion - stripping steps in the accelerator and the subsequent Bi gRIPS/Mass - Ring experimental apparatus. The relative cross sections between full stripping of 205 Pb and (p,n) on 205 Tl is estimated as 10 5 . Test experiments to verify the various aspects of the proposed approach at the RIBF are under preparation

Geochemical Determination of the Solar pp-Neutrino Flux with LOREX: A Progress Report

LOREX (LORandite EXperiment) is a geochemical experiment addressing the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205Tl + ve → 205Pb + e- with an unprecedentedly low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is getting the precise, background-corrected ratio of 205Pb/205Tl in lorandite (TlAsS2). This report presents the status of major challenges being addressed, in particular the determination of the paleo-depth of lorandite, including the eroded layer over 4.3 Ma, as well as the choice of appropriate techniques for extraction, separation and quantitative determination of the ultra-low 205Pb concentration in the extracted lorandite samples