ماهيت ژئوشيميايي ولكانيسم ائوسن در شمال منطقه انارك (شمال شرق استان اصفهان)

Geology Department, the University of Isfahan

Eocene volcanic rocks with andesite, andesibasalt to dacite composition in north of the Anarak area are exposed as small and scattered masses. Exposures of these rocks mainly follow the faults direction. Geothermometry studies of even equilibrated amphibole-plagioclase phenocrysts indicate that crystallization temperature of these phenocrysts ranges between 835°C to 925°C. Results of amphiboles barometry on the base of A1 content shows that amphibole phenocrysts in these volcanic rocks had been crystallized in pressure of about 6.19-8.62 Kbar. On the basis of calculated pressure, magma chamber of these rocks have occured about 30km in depth. The geochemistry trends in the Harker and spider diagrams for rare earth elements, Eocene volcanism in north of Anarak area is specified with two distinctive magmatic series. In terms of magmatic series segregation diagrams, these two series have transitional characteristics and tend to be shoshonitic type. Enrichment and depletion in some elements such as Ta, Th, Ce and K is related to the contamination and magma mixing in Eocene volcanism in the north of Anarak area.