Resumo

MAHDAVI, Mansoureh; DABIRI, Rahim  e  HOSSEINI, Elham Shah. Magmatic Evolution and Compositional Characteristics of Tertiary Volcanic Rocks Associated with the Venarch Manganese Mineralization, Sw Qom, Central Iran. Earth Sci. Res. J. [online]. 2015, vol.19, n.2, pp.141-145. ISSN 1794-6190.  https://doi.org/10.15446/esrj.v19n2.49372.

The manganese (Mn) deposits of Iran date from late Proterozoic to Pliocene but the major high-grade Mn ore deposits are associated with tertiary basic to intermediate volcanic rocks. The Venarch Mn deposit is located in the SW Qom city and considered as one of the largest in Iran. The Mn mineralization is mostly hosted by Eocene high-k volcanic and pyroclastic rocks of Urmia-Dokhtar Magmatic Arc (UDMA). The study area mainly consists of basalt, trachybasalt, andesite, and basaltic-andesite that are intruded by Eocene-Oligocene monzodiorite, monzonite, and granodiorite intrusions. The Venarch Mn ore bodies are mostly hosted by shale beds and wrapped by altered mega-porphyritic andesites and spilitic lavas both in the foot and hanging walls. Petrographic studies show that the principal ore minerals are pyrolusite, psilomelane, and other Mn-oxides, and quartz and calcite were determined as the gang minerals. Integration of field geology, petrography, and geochemical results suggest a hydrothermal origin for the Venarch Mn deposit. Our geochemical data furthermore suggest the volcanic host rocks to be comparable to high-K series of subduction zones.

Palavras-chave : Geochemistry; Mn mineralization; Petrogenesis; Venarch; Central Iran.

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