Magmatic Evolution and Compositional Characteristics of Tertiary Volcanic Rocks Associated with the Venarch Manganese Mineralization, Sw Qom, Central Iran

Abstract

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 Mnoxides, 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.Los yacimientos de manganeso (Mn) en Irán datan del Proterozoico tardío hasta el Plioceno, pero el mayor grado de los depósitos de la mena de manganeso se asocian a rocas volcánicas básicas a intermedias de edad Terciaria. El yacimiento de manganeso en la mina de Venarch se localiza al suroeste de la ciudad de Qom y está considerado como uno de los más grandes de Irán. La mineralización de manganeso se presenta en su mayoría en las rocas piroclásticas y volcánicas de alto contenido de K del Eoceno en el Arco Magmático Urmia-Dokhtar (UDMA, en inglés). El área de estudio presenta basaltos, traquibasaltos, andesitas y andesitas basálticas que están intruidas por monzodioritas, monzonitas y granodioritas del Eoceno-Oligoceno. Los cuerpos de mineral de manganeso en Venarch en su mayoría están dentro de capas de pizarra y envueltos por lavas espiliticas y andesitas megaporfiroides tanto en las paredes del piso como en las colgantes. Los estudios petrográficos muestran que los minerales son pirolusitas, silomelanas y otros óxidos de manganeso, mientras que los cuarzos y las calcitas constituyen los minerales de ganga. La integración de los trabajos de geología de campo, petrográficos y geoquímicos sugieren un origen hidrotérmal del yacimiento de manganeso de Venarch. Los datos geoquímicos de este estudio también sugieren que la roca volcánica anfitriona es comparable con las series ricas en K de las zonas de subducción. ABSTRACT RESUMEN

Radon concentration and effective dose in drinking groundwater and its relationship with soil type

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Discrete Fracture Network (Dfn) Modelling of Fractured Reservoir Based on Geomechanical Restoration, a Case Study in the South of Iran

“…Moreover, the basis of the method involves calculating the stress distribution at the time of fracture generation using all structural data including: faults, fractures and folds, rock characteristics, and tectonic events. Also, secondary activities, such as mineralization and rock inclusions are essential, especially for mining exploration (Mahdavi et al, 2015). The main components of the forward geomechanical restoration model are: (1) the initial condition of paleo-geometry, (2) the constitutive laws of sedimentary units, and (3) boundary constraints.…”