Lece volcanic complex, Medveđa, Jablanica District, Central Serbia, Serbiai

Regional Level Types
Lece volcanic complex	Volcanic Field
Medveđa	Municipality
Jablanica District	District
Central Serbia	Province
Serbia	Country

Lece volcanic complex which is situated in the southern part of Serbia and covers an area of over 700 km2. The five agate localities are Rasovača, Ždraljevići, Sokolov Vis, Mehane, and Vlasovo.

The Lece Volcanic Complex is located in southern Serbia at the border between two large geotectonic units—the Serbian–Macedonian Massif and the Vardar Zone. The formation of this volcanic massif is heavily influenced by two regional fault structures. The first is the Tupale dislocation, extending over the eastern part of the Lece volcanic massif and continuing through the Tupale andesitic mass and further over the Bujanovac massif. The second regional fault structure is the Merdare dislocation, running along the western edge of the massif in the direction of Strezovce–Dražnja–Kravari–Kuršumlija.
The Lece Volcanic Complex comprises two main groups of andesitic rocks: amphibole and pyroxene andesites. Apart from andesites and their pyroclastics, andesite basalts, dacites, and latites are also present to a much lesser extent. Andesites are predominantly found in the central parts of the Lece Volcanic Complex, while pyroclastics are more frequent in its peripheral parts. Amphibole andesites include hornblende andesites, hornblende-biotite andesites, hornblende-pyroxene andesites, hornblende-pyroxene andesites with biotite, and transitional types to dacites. The pyroxene andesites of the Lece Volcanic Complex include augite andesites, augite-hypersthene andesites, transition types to dacites, and andesite-basalts.
Pyroclastic rocks constitute approximately 40% of the volcanic complex and delineate the boundary between the volcanic rocks and the adjacent geological formations.
Pyroclastic rocks of the Lece Volcanic Complex manifest as volcanic breccias, volcanic agglomerates, and tuffs. Volcanic agglomerates are less abundant than volcanic breccias and tuffs. The pyroclastic series attains a thickness of 100 m, with volcanic clasts ranging from one millimeter to over one meter. Hornblende andesite predominates in the composition of pyroclastic rocks, i.e., volcanic breccias and agglomerates.
Significant amounts of agate have also been found in the secondary placer occurrences. Particularly interesting are alluvial placers of three rivers that run through the Lece Volcanic Complex: Velika Kosanica, Kosanica, and Lecka River

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References