Natural basalt columns in Racos Traditional Cache
Natural basalt columns in Racos
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The Racos Basalts-geological preserve placed in the western part of the Persani Mountains, near Rupea, (on the national road DN Brasov-Sighisoara), with spectacular volcanic basalt structures.
The basalt products are the result of the intraplate magmatic activity in the Transylvanian - Pannonian block from Romania and Hungary, following alpine consolidations. Volcanic break out centres generated along a NE-SW alignment that marks fractures of the lithosphere belonging to the
most recent geological periods, continuing south of the Danube. Racos zone from Persani Mountains is the best known and spectacular zone with typical features and a lot of varieties of basaltic rocks.
The volcanic activity in these regions took place from the Badenian to the end of the Pleistocene.
Moments of paroxysm alternated calm phases. Tectono - enetic interpretation of the geology of the Eastern Carpathians is linked to the presence of continental lithosphere below a the Neogene volcanic arch. The presence of this represents an advanced stage in the evolution of the compression - subduction activity that took place at the boundary of two large tectonic plates, demonstrated to have been existed on the territory of Romania at the end of the Pliocene and the beginning of the Quaternary periods.
The lavas emitted during such an activity had basaltic affinity, but it were, mostly, quite viscous and accompanied by large quantities of gases, which determine the explosive and permanent character of the activity. The activity consisted in rhythmic and continuous explosions, of lava rich in gases and vapor. This resulted in fragmentation of the lava and the formation of bombs and scorias.
The presence of olivine and quartz in basalts of Persani is an argument for classifying these rocks into the "olivine basalts” the basanite - tephrite field. According to the scientific classification chart of igneous rocks (Quartz, Sodic feldspar, Plagioclase, Feldspatoidite) the studied sampled are classified into the basanite tephrite field) .
The petrography and mineralogical characteristics, rendered from geological research and microscopic studied are sand, common for all basalts types. They structure a megascopic appearance of black or brownish or reddish color for corias, with massive, vacuolar or scoria textures. The chemistry of all studied basaltic lavas confirmed their alkaline character, similar to that of many types of basalt in the world.
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