Mechanics of Magma Chamber with the Implication of the Effect of CO2 Fluxing

The rheological contrast between the viscous magma in the magmatic chambers and the surrounding rocks, having an elastic behavior, has allowed for a disturbance of the stress field, which, at a magmatic pressure unequal to the lithostatic one, can give rise to various modes of rock failure, leading to an eruption. In this context, one of the most important problems is represented by the mechanical stability of both large and extra-large magmatic chambers, such as the Yellowstone magmatic chamber. Due to its large volume, the critical overpressure necessary to start the volcanic eruption requires large added volumes of magma and fluids. The viscous relaxation of deviatoric stresses in the thermal areole of large chambers on a time scale of more than few years increases the critical volumetric flow rate of magma to 0.1–1 km3/yr. In this chapter, we have demonstrated that the deep CO2 flux related with the underplating of basaltic magma has significantly enhanced the expansion of the magmatic chamber. In Yellowstone, the CO2 fluxing can be the driver of its cyclic uplift and subsidence having a period of several decades. The extraction of water from the silicic melt by CO2 increases the volume of the fluid up to 4 times, thus multiplying the pumping effect of the fluid. In a long term, simple estimates have also indicated that the CO2 flux can significantly contribute to the heat balance, which can be up to the half one with respect to the value associated with the basaltic magma. The integrated stability index of a magma chamber has been tested during the beginning of the interglacial periods, when the rate of generation of the basaltic magma in a plume setting is of an order of magnitude higher than the normal one. The spikes of rhyolitic magmatism in some periods of the last Quaternary interglacials have been weakened for the Yellowstone case history. The last Pleistocene glaciation activated only strong hydrothermal eruptions, which may imply that at present, the level of CO2 and basalt supply rate is not high enough to cause a major eruption in Yellowstone in the near future

Optical Properties and Structure of Most Stable Subnanometer (ZnAs2)n Clusters

ZnAs2 nanoclusters were fabricated by incorporation into pores of zeolite Na-X and by laser ablation. Absorption and photoluminescence spectra of ZnAs2 nanoclusters in zeolite were measured at the temperatures of 4.2, 77 and 293 K. Both absorption and PL spectra consist of two bands which demonstrate the blue shift from the line of free exciton in bulk crystal. We performed the calculations aimed to find the most stable clusters in the size region up to size of the zeolite Na-X supercage. The most stable clusters are (ZnAs2)6 and (ZnAs2)8 with binding energies of 7.181 eV and 8.012 eV per (ZnAs2)1 formula unit respectively. Therefore, we attributed two bands observed in absorption and PL spectra to these stable clusters. The measured Raman spectrum of ZnAs2 clusters in zeolite was explained to be originated from (ZnAs2)6 and (ZnAs2)8 clusters as well. The PL spectrum of ZnAs2 clusters produced by laser ablation consists of a single band which has been attributed to emission of (ZnAs2)8 cluster.Comment: Article accepted for publication in Physica B: Physics of Condensed Matte