Larimar is an ornamental and semiprecious stone known worldwide as being iconic of the Dominican Republic. This rock is composed mainly of pectolite, usually seen associated with natrolite and calcite, as well as carbonaceous material, chalcocite and hematites. Sometimes, disseminations such as native copper, also occur amongst several other minerals. The rock crops out in a very small area (< 0.3 km2 , Los Checheses-Los Chupaderos mine or simply the Larimar mine) as a result of the transpressional movement of the Arroyo Seco fault which exposed the basement. The host rock is composed mainly of olivine basaltic lava flows (15 - 18% olivine, 6 - 8% pyroxene, 5 - 10% plagioclase and < 1% opaque minerals in a 64 to 72% groundmass), as well as related basaltic breccias. These volcanic rocks are strongly altered (by hydrothermal, tectonic and weathering processes) at different scales. Olivine phenocrysts were highly serpentinized and altered to iddingsite; pyroxene phenocrysts have some degrees of argillization and sericite; and carbonate has formed minerals from plagioclase crystals. Clays and quartz veinlets are also present as secondary minerals. Pectolite and natrolite minerals fill open spaces in the volcanic rock (vesicules, fractures, cavities, crustification and comb structure vugs) and substitute organic pieces (wood) by an epygenic process as a result of temperatures of 200°- 340°C, during a phyllic epithermal transition to mesothermal (quarz-sericitic) alteration. Larimar is not just a unique gemstone but it is also a very rare petrification process. Therefore we propose the term xilolarimar. The formation environment is suggested to be an oceanic island construction prior to the Eocene time, probably Late Cretaceous. Further studies are necessary to understand the blue pectolite (a colour mainly linked to Mn, V and Cu), its formation mode and its petrogenic environment.
The SciBar Cosmic Ray Telescope (SciCRT) is aimed to help elucidate the acceleration mechanism of high-energy ions that may produce neutrons at the Sun. It is a fully active scintillator tracker which consists of 14,848 plastic scintillator bars, originally constructed for accelerator neutrino oscillation experiments. The SciCRT; it has a huge detector volume compared with conventional Solar Neutron Telescopes (SNTs), e.g. 15 times larger than Mexico SNT. Furthermore, the SciCRT can measure the energy deposition of each particle as neutron ADC data which have not been registered before. Neutron ADC data provide us with a precise measurement of energies deposited at the detector. The SciCRT was deployed at the summit of Mt. Sierra Negra (4,600 m) and began to acquire data in September 2013. Then we partially upgraded the DAQ system developed originally for an accelerator experiment, as the readout rate of the DAQ system was significantly limited for our experiment. This paper highlights sensitivity numerical studies of solar neutrons that the SciCRT is able to register. At first, we focus in the accuracy to determine the spectrum power-law index, assuming an instantaneous emission of solar neutrons. This is required to determine the power-law index within an error of ±1.0 in order to discuss the efficiency of the acceleration. Then in the case of the fixed power-law index, we discuss the capability of discriminating three different lengths of emission times: 0 min, 5 min, and 8 min. Finally we evaluate whether it is possible to discriminate a different combination of these two parameters simultaneously. Thus, we show that data from the SciCRT will unlock the degeneracy problem amid the emission time and the energy spectrum of solar neutrons.35th International Cosmic Ray Conference
Un Telescopio de Neutrones Solares (TNS) fue instalado en la cima del volcán Sierra Negra, Pue., México (19.0º N , 97.3º W, 4580 m sobre el nivel del mar); el cual se encuentra en operación desde el 2004. En este trabajo, utilizamos los valores de la presión barométrica, de la presión dinámica, de la temperatura ambiental y de la humedad relativa obtenidos por una estación meteorológica cercana al TNS, para calcular los coeficientes de corrección atmosféricos para el flujo registrado de rayos cósmicos. Cuando los datos de rayos cósmicos están libres de las variaciones de origen atmosférico, analizamos los perfiles de tiempo observados por el TNS durante seis decrecimientos tipo Forbush seleccionados para el período 2011-2013. Los resultados obtenidos por varios canales de depósito de energía (30,60,90 MeV) son discutidos para establecer la confiabilidad del TNS para este tipo de eventos.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.