Density, Viscosity and Velocity (Ascent Rate) of Alkaline Magmas

摘要: Three distinct alkaline magmas, represented by shonkinite, lamprophyre and alkali basalt dykes, characterize a significant magmatic expression of rift-related mantle-derived igneous activity in the Mesoproterozoic Prakasam Alkaline Province, SE India. In present study we have estimated emplacement velocities (ascent rates) for these three varied magmas compared with other silicate to explore composition control on ascent rates. The dykes variable widths lengths none wider than 1 m. shonkinites are fine- medium-grained rocks clinopyroxene, phologopite, amphibole, K-feldspar perthite nepheline as essential minerals. They exhibit equigranular hypidiomorphic foliated textures. Lamprophyres basalts characteristically show porphyritic Olivine, amphibole biotite phenocrysts lamprophyres whereas olivine, clinopyroxene plagioclase form phenocrystic mineralogy basalts. calculated densities [2.54–2.71 g/cc shonkinite; 2.61–2.78 lamprophyre; 2.66–2.74 basalt] viscosities [3.11–3.39 Pa s 3.01–3.28 2.72–3.09 utilized compute magmas. Since crystal-laden, also effective infer crystal velocities. Twenty percent crystals magma increase viscosity 2.7 times consequently decrease rate crystal-free computed rates range from 0.11–2.13 m/sec, 0.23–2.77 m/sec 1.16–2.89 respectively. Ascent width density difference, proportion crystals. If constant m is assumed magma-filled dyke propagation model, then sequence decreasing order (4.68–15.31 m/sec) > ultramafic-mafic (3.81–4.30 intermediate-felsic (1.76–2.56 m/sec). We propose that SiO2 content terrestrial can be modeled semi-quantitative “geospeedometer”