Petrology
Habib Biabangard; Farzad Molazadebravate
Abstract
Kuh-Som, KuhzaBozorg and KuhzaKochak volcanic cones are located in the southeastern of Bam and northwest of Bazman cites. From the perspective geology these cones are belong to the Iranian central zone and south-eastern edge of Lut block. These cones are composed of extrusive igneous rocks such as basalt, ...
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Kuh-Som, KuhzaBozorg and KuhzaKochak volcanic cones are located in the southeastern of Bam and northwest of Bazman cites. From the perspective geology these cones are belong to the Iranian central zone and south-eastern edge of Lut block. These cones are composed of extrusive igneous rocks such as basalt, olivine basalt, andesite and basaltic andesite, and are predominant trachytic texture. Plagioclase, pyroxene and olivine are main minerals. Pyroclastic deposits, lapilli, tuff, ash and volcanic bombs, along with lava flows are main construction volcanic cones. These volcanoes are monogenitic and limited eruption. Based on type material that construction cone of the volcanoes, it seems they are among between Hawaii to Strambolian volcanoes. These rocks shows enrichment to LILE relative to HREE (Ce / Yb= 33-45) , high ratio Zr / Y (33.4), enrichment to LILE and negative anomaly from Ni, Cr and nearly Eu that reveals these rocks related to Calc-alkaline magmatism. In spider diagrams of trace elements and rare earth elements that normalized to Chondrites and primitive mantle show light rare earth elements enriched more than high rare earth elements and show pattern similar to affiliate subduction zones. Geochemical characteristics such as ratio of La / Yb 8/6 to 7/13, low Rb content with the tectonic setting discrimination diagrams indicate that they are related to subduction environments and low tendency to intapalate zone. Source of magma that formed these volcanoes resulted from melting of a garnet Lherzolite at depth of 100 to 110 Km. Tectonomagmatic diagrams shows these rocks dependence on of continental subduction environments to show slightly into the intraplate zone, so that it seems the volcanic cones of them related to the Makran and Oman subduction and related to Makran- Chaghy magmatic arc.
K Shiaian; J Ghalamghash; M Vosoughi Abediny; F Masoudi
Abstract
The Bazman volcano is located in the Makran Magmatic Arc. The pyroclastic rocks and lava with rhyodacitic to basaltic composition and calc-alkaline affinities erupted from the central and lateral craters of this volcano during the Quaternary period. The primitive mantle normalized Multi-elements diagrams ...
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The Bazman volcano is located in the Makran Magmatic Arc. The pyroclastic rocks and lava with rhyodacitic to basaltic composition and calc-alkaline affinities erupted from the central and lateral craters of this volcano during the Quaternary period. The primitive mantle normalized Multi-elements diagrams show a relatively high abundance of LIL relative to HFS incompatible elements with negative anomalies of Nb and Ti. Their chondrite–normalized REE patterns are slightly enriched in LREE relative to HREE with negative Eu anomalies. These geochemical features suggest that the volcanic rocks of bazman formed in a subduction setting by partial melting of metasomatized mantle. On the base of La/Yb vs Dy/Yb and La/Sm vs Sm/Yb diagrams the sources of the magmas is phlogopite-spinel-lherzolite or/and phlogopite-garnet- lherzolite.
M.R Omidvar Eshkalak; A.A Mokhtari
Abstract
The studied area is located in the southeastern end of the Sahand- Bazman Magmatic Belt in the north of Bazman volcano. This area composed of Miocene volcanic rocks including andesitic to dacitic lavas along with tuffaceous sandstone, ignimbrite, agglomerate, tuff and siltstone that underwent propyilitic, ...
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The studied area is located in the southeastern end of the Sahand- Bazman Magmatic Belt in the north of Bazman volcano. This area composed of Miocene volcanic rocks including andesitic to dacitic lavas along with tuffaceous sandstone, ignimbrite, agglomerate, tuff and siltstone that underwent propyilitic, argillic, sericitic, carbonatic and silicified alterations. Predominant form of the mineralization is silica veins and hydrothermal breccia, which crop out within the alteration zones. The textures within the silica veins include coliform, vuggy, stratiform, banded and hydrothermal breccias. The results of sample analysis demonstrate that hydrothermal breccias have the highest grades of Au (up to 27.6 ppm), and the silica veins with banded texture and fine grained sulfide bearing silica veins are other important Au- bearing mineralization in the next orders. The geochemical investigations demonstrate good positive correlation between Au and Ag, Sb, As, Pb, Zn, Mo, Bi and Hg in the Au- bearing silica veins. The fluid inclusion studies on silica veins with banded texture indicate that the salinity of fluids is 1.22-7.77 W% NaCl, and homogenization temperature is 190-296◦C. Based on the field evidences along with mineralogy, textures and structures of silica veins, geochemical and fluid inclusion investigations, the Au mineralization in the north of Bazman can be classified as low sulfidation epithermal gold deposits.
