Petrology, Geochemistry and Thermobarometery of Abraq-Harmak Volcanic rocks, west of Lut block, Central Iran

Abraq-Harmak area is located 40 Km northwest of Bam (southeast of Kerman province). Based on structural geology of Iran, this area is placed in the central Iranian zone, Urmieh-Dokhtar volcanic and Dehaj – Sarduyeh magmatic belt. The major units of the area are basaltic to dacitic lava flows with their pyroclastic rocks. Previous studies have done on these rocks by Dimeterich et al., 1973, Hosseini et al., 1993, Girou and Conrad, 1976, Zahedi, 2005, Alidadi Soleimani, 1394 and Mirali, 1392. In this paper, we are attempted to identify petrography, mineral chemistry, and the conditions of formation rocks in the Abraq-Harmak area. We have taken 150 samples rocks from of Abraq-Harmak area, and then prepared 110 thin sections. Petrographic studies were done and 9 samples select for analyzes. These samples are sending to Iranian Mineral Processing Center (IMIDRO) and determine amounts of major, minor and trace elements by XRF and ICPMS methods, respectively. The chemical analysis of pyroxene and plagioclase minerals was done on 35 points by EPMA-SX100 type electron micro probe with 15 Kv accelerator voltage, 15 nA current intensity and 5-micron beam size. Data was processed and interpreted using the usual geological software and related graphs. Calc-alkaline basaltic flow that belonging to active continental subduction region show usually "zigzag", pattern of accessory and rare earth elemental and they are more enrichment in light rare earth elements than heavy earth elements (Gil, 2010, Wilson, 1980). The whole rocks and mineral geochemical studies on the Abraq-Harmak lavas shows that they are belong to the calc-alkaline basalts of the subduction areas. Also, accessory and rare elements normalized to Chondrite (Boynton, 1984) show similar patterns and similar to the basalts of the subduction regions. Pb, Ta and Cs elements have positive anomalies and Ti and P elements have negative anomalies, which are usually due to crustal contamination and magmatic differentiation (Reichew et al., 2004; Kurkcuoglu et al., 2008). Calc-alkaline basaltic lava is usually formed in the high oxygen fugacity (Gil, 2010). Thermo-barometry of plagioclase and pyroxene minerals in the Abraq-Harmak lavas indicate that the magma forming this lava are stopping at the sub surface and crystallization of them within magma chamber (less than 23 Km) and High oxygen fugacity. Whole rock chemistry, minor and rare earth elements spider diagrams and other tectonomagmatic diagrams indicate Abraq-Harmak volcanic rocks are belonging to subduction zones. The chemistry of clinopyroxene mineral shows that Abraq-Harmak volcanic rocks are Calc-alkaline and related to subduction environments. Aluminum distribution of these minerals structure of indicates that they are crystallize from a hydrous magma with a 10 percent vapor pressure and with high oxygen fugacity. Temperature of clinopyroxenes formation (range from 950 to 1200 C) and pressure (2 to 5 Kb) indicate their crystallization happen during ascent magma and in shallow magmatic chamber. It seems that the magma formed these rocks, is formed from subduction of Arabian plate under the Iranian plate in the Urumieh-Dokhtar area