Compositional, structural and vibrational spectroscopic characteristics of feldspar megacrysts in alkali basalts from southern Slovakia

Journal of Geosciences

Monika Huraiová^1¹  Vratislav Hurai^4²  Rainer Abart^3³  Christian Lengauer^2⁴ 

[1]Comenius University, Department of Mineralogy and Petrology, Ilkovičova 6, 842 15 Bratislava, Slovakia^1

[2]Slovak Academy of Sciences, Institute of Earth Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovakia^4

[3]University of Vienna, Department of Lithospheric Research, Althanstrasse 14 (UZA II), 1090 Vienna, Austria^3

[4]University of Vienna, Institute for Mineralogy and Crystallography, Althanstrasse 14 (UZA II), 1090 Vienna, Austria^2

关键词: Slovakia;    feldspar;    Western Carpathians;    megacryst;    alkali basalt;    Pannonian Basin;   

DOI  :  10.3190/jgeosci.266

学科分类：自动化工程

来源: Ceska Geologicka Spolecnost / Czech Geological Society

【 摘 要 】

Feldspar megacrysts in Late Miocene-Pliocene maars, diatremes and basaltic lava flows in the northern part of the Pannonian Basin span the compositional range from Na-sanidine, through anorthoclase to oligoclase and andesine. Newly formed An₈₂ plagioclase (bytownite) crystallized within composite melt inclusions hosted by the oligoclase. Powder X-ray diffraction data indicate strong structural disorder diagnostic of the high albite-high sanidine series typical of magmatic feldspars. The magmatic origin is also corroborated by chemical compositions, which plot along the 700 ± 50 °C solvus, with the exception of the most sodic Ab₇₉ plagioclase megacryst projecting along the 600 °C isotherm. Vibrational spectroscopic records document that the basic groups of magmatic feldspars can be identified by the specific pattern of the group I and IV bands in the 350-600 cm^-1 range. The IVa band at 560-570 cm^-1 is diagnostic for triclinic feldspars. The anorthite and orthoclase contents can be inferred from the 506-515 cm^-1 (Ia) and 473-486 cm^-1 (Ib) peak separation values combined with the Ia bandwidth.

【 授权许可】

CC BY