Alteration pathways in Cenozoic volcanic suites of the Styrian Basin: an integrated petrographic–geochemical approach

We present a study that investigates the post-eruptive geochemical evolution of six sites from Miocene and Pliocene volcanic suites from Styria (SE Austria). The sites are Weitendorf, Gleichenberg, Klöch, Hochstraden, Steinberg and Fürstenfeld. We focus on a stratigraphic sequence that transitions from lavas to porous, laminated ash tuffs and pyroclastic rocks. An integrated approach was performed combining petrography, whole rock geochemistry, and isocon–τ relative mass balance modeling to decipher fluid–rock interaction and element mobility. 

Detailed petrography (based on microscopy work with thin sections) show that the six sites exhibit different alteration stages ranging from weak alteration over mafic phenocryst alteration (reducing versus oxidizing) to palagonite and zeolite formation. Mass balance modeling allows us to establish alteration pathways where Miocene units follow a path of pronounced alkali leaching and Mn depletion, whereas Pliocene high‑alkaline units display more variable pathways. 

The site‑specific fingerprints delineate contrasting nutrient and redox landscapes that provide a geochemical baseline for further studies on soil development and vegetation.