The Smrekovec mountains are characterised by a widespread occurrence of volcanic rocks of the Upper Oligocene age. Their development is closely related to volcanic activity which resulted in the formation of a submarine stratovolcano complex, emplaced onto pre-Tertiary carbonate basement and locally, on Upper Oligocene marine marls and silts. Magma composition varied with time during volcanic activity. The original tholeiitic magmas very likely underwent a differen tiation due to low pressure crystal fractionation, resulting in the development of andesitic and finally rhyodacitic magmas. The early stage of volcanic activity was dominantly non-explosive; the main style of fragmentation was autoclastic, relat ed to chill and quench processes that affected lavas and high-level intrusive bod ies. During the late-stage of volcanic activity, explosive volcanism was also pre sent, being most probably related to magmatic and combined magmatic-hydrovolcanic activity. Explosions also seem to have generated or triggered volcaniclastic debris flows and turbidity ash flows. Shallow intrusive bodies (syn-volcanic sills and feeder dykes) were a local source of heat that generated hydrothermal/geothermal conditions in the enclos ing, water-saturated volcaniclastic sediments. Consequently laumontite, analcime, clinoptilolite, heulandite, thomsonite, yugawaralite, prehnite, pumpellyite, albite, apophyllite, epidote, sphene, chlorite and mixed-layered clay minerals developed as replacements of the primary constituents, interstitial fillings and vein minerals. Kratka vsebina Smrekovško podgorje grade vulkanske kamnine zgornjeoligocenske starosti. Njihov nastanek je vezan na razvoj vulkanskega masiva, sestavljenega iz enega ali več stratovulkanov, ki so delovali v morskem okolju. Podlaga sestoji iz mezozojskih karbonatnih kamnin, ponekod tudi iz zgornjeoligocenskih laporjev in meljevcev. Sestava magme se je med vulkanskim delovanjem spreminjala. Prvotna sesta
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