Petrogenesis of Miocene subvolcanic rocks in the Western Outer Carpathians (southeastern Moravia, Czech Republic)

Journal of Geosciences

article

David Burianek¹  Kamil Kropac³ 

[1] Czech Geological Survey;Department of Geological Sciences, Faculty of Science, Masaryk University;Department of Geology, Faculty of Science, Palacký University Olomouc

关键词: Neogene subvolcanic rocks;    geochemistry;    mineral chemistry;    P–T–X conditions;    Western Outer Carpathians;   

DOI  :  10.3190/jgeosci.286

学科分类：自动化工程

来源: Ceska Geologicka Spolecnost / Czech Geological Society

【 摘 要 】

Neogene subvolcanic rocks in southeastern Moravia form numerous dykes and laccoliths, ranging from clinopyroxene–amphibole and amphibole trachybasalt, through trachyandesite, to biotite–amphibole trachydacite. Leucocratic andmelanocratic cumulate gabbro and basalt enclaves up to 70 cm in diameter are rarely present, respectively, within thetrachydacite and trachyandesite.The parental magmas rose along tensional fissures spatially related to the Nezdenice Fault but probably never reachedthe surface. The range of major (e.g., SiO2 44–62 wt. %, mg# 20–65) and trace-element compositions can be explainedthrough magma mixing and mingling and subsequent fractional crystallization.Mineral chemistry shows limited compositional variation of mafic minerals. Diopside phenocrysts indicate narrow rangesof XMg (0.65–0.84) and usually display normal zoning with small Mg-rich cores and Fe-rich rims. Phlogopites from thetrachydacite and gabbro enclaves show a mutually similar composition (XFe 0.36–0.43 and IVAl 2.44–2.59). Amphibolesfrom individual samples of basalt, trachybasalt and trachyandesite are likewise chemically relatively homogeneous (XMg0.51–0.86, Si 5.78–6.55). Chemical compositions of amphibole phenocrysts from the trachybasalts and trachyandesitesindicate multi-stage crystallization at depth of 32 to 21 km for this magmatic system. Systematic changes in Si, Ti, VIAl,XMg contents in amphiboles from trachydacites and gabbro enclaves can be explained by fractional crystallization in ashallower magma reservoir (~20–10 km).

【 授权许可】

CC BY