Economic Geology
Mitra Eftekhari; Mohammad reza Hosseinzadeh; Mohsen Moayyed
Abstract
The Studied area is located in vicinity of the Sherbit village, about 28 km to the northwest of Ahar (in Eastern Azerbaijan province. Quartz monzonite intrusion is the host rock of hydrothermal tourmaline in this area. On the basis of their textural features, the tourmalines can be divided into four ...
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The Studied area is located in vicinity of the Sherbit village, about 28 km to the northwest of Ahar (in Eastern Azerbaijan province. Quartz monzonite intrusion is the host rock of hydrothermal tourmaline in this area. On the basis of their textural features, the tourmalines can be divided into four groups: 1) tourmaline veins, 2) tourmaline-breccias, 3) massive tourmaline and 4) pore space filling tourmaline. Based on the petrography and electron microprobe analysis studies, tourmalines of Sherbit area are correspond to intermediate schorl-dravite with more tendencies toward dravite composition and have been formed in hydrothermal conditions. According to reasons such as more Mg values compared to Fe, low Al amounts, fine scale zoning, content of fluorine, tendency toward outer side of alkali- and proton-deficient vectors and lack of negative correlation between Fe and Mg. Separated tourmaline from the quartz– tourmaline vein shows a very similar pattern to the quartz monzonite samples, which are characterised by a pattern with depletion in HREEs relative to LREEs. It can be concluded that REE concentrations and patterns of tourmaline from the different studied tourmaline rocks are controlled by the host rock and not by the hydrothermal fluid causing boron metasomatism.
B Hajalilou; Z Karimzadeh; M Advai
Abstract
The properties and situation of copper mineralization in the Haj Alibay Kandi area determined by quartz vein fluid inclusion and geophysical explorations in this study. The most important rock units include Oligocene intrusive rocks with monzonite and quartzmonzonite compositions. These rocks belong ...
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The properties and situation of copper mineralization in the Haj Alibay Kandi area determined by quartz vein fluid inclusion and geophysical explorations in this study. The most important rock units include Oligocene intrusive rocks with monzonite and quartzmonzonite compositions. These rocks belong to calc-alkaline series and post orogenic and post collision regimes. The mineralization in this area was controlled by faults with NE-SW direction. These mineralizations are related to the Sheivar-Dagh and younger intrusives. Chalcopyrite, pyrite, chalcocite, digenite, covelite, malachite, bornite and iron oxides were determined by mineralographical studies. On the basis of geophysical explorations, the chargebility anomaly at the depth of 40 to 50 meters is related to the concentration of sulphide minerals. This anomaly is conforms with faulting system in the area. The salinity of ore bearing fluid is from 5 to 50 wt% of NaCl and the homogenization temperature is 200 to 2400c and higher, on the basis of fluid inclusions studies. Fluid inclusions data are conformable with porphyry and epithermal copper deposits. This study shows that the boiling of ore fluids occurred at the mineralization stage. The shape of copper mineralization is vein and veinlets in this area and similar to cordilleran vein type deposit which can be observed at the top of porphyry copper deposits . Therefore, the formation of porphyry copper deposit at the deep levels of this area is expected.
A Alizadeh; R Safari
Abstract
Seismic values are the main parameters in evaluating the neotectonic activity of a region. In August 11, 2011, two Mb=6.4 and Mb=6.3 earthquakes occurred in Ahar-Varzaghan region within 11 minutes. Seismotectonic investigations imply that the faults generating the events are the young faults of the regions. ...
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Seismic values are the main parameters in evaluating the neotectonic activity of a region. In August 11, 2011, two Mb=6.4 and Mb=6.3 earthquakes occurred in Ahar-Varzaghan region within 11 minutes. Seismotectonic investigations imply that the faults generating the events are the young faults of the regions. Also, distribution of the epicenters represent a pattern consistent with the fault trends in the area. Temporal and spatial distribution of the earthquakes (fractal analysis) as earthquake pre-indicators together with a-b values were used toassessthe neotectonic activity and explore the seismic model of the Ahar area. Results showa sharp decrease in b-value,indicating that the main shock was associated with a zone of high strain rate. The seismic model presented for the Ahar area illustrates three periods after the main shock including: 1) an early quiescence Q1, 2) an aftershock period B, and 3) a late quiescence Q2. The rather increase in b-value during the Q2period is interpreted to indicate stress decrease in the region.
R Dabiri; M.H Emami; H Mollaei; M Ghaffari; M Vosougi Abedini; N Rashidnejad Omran
Abstract
Quaternary volcanic rocks are widely developed in NW of Ahar, NW Iran. Based on geochemical data, these rocks mainly consist of alkali basalts, trachybasalts, basaltic trachyandesites and trachyandesites. The major- and trace-element chemistry indicates that the lavas are dominantly alkaline in character. ...
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Quaternary volcanic rocks are widely developed in NW of Ahar, NW Iran. Based on geochemical data, these rocks mainly consist of alkali basalts, trachybasalts, basaltic trachyandesites and trachyandesites. The major- and trace-element chemistry indicates that the lavas are dominantly alkaline in character. The studied rocks display microlithic porphyritic texture with phenocrysts of olivine, clinopyroxene, and plagioclase ± amphibole ± biotite. Major and trace element abundances vary along continuous trends of increasing SiO2, Al2O3, K2O, Na2O, Ba and Rb decreasing CaO, Fe2O3* and Cr with decreasing MgO.The volcanic rocks in this area are characterized by the LILE and LREE enrichments and negative HFSE anomalies. The Sr and Nd isotopic ratios vary from 0.704463 to 0.704921and from 0.512649 to 0.512774, respectively.CaO/Al2O3 ratios versus MgO, La/Sm ratios versus Rb and Ba and Zr versus Th suggest that that fractional crystallization was a major process during the evolution of magmas. AFC modeling and isotopic data as well as microscopic evidence, clearly indicate that crustal contamination accompanied by the fractional crystallization played an important role in petrogenesis of the trachyandesites. Also, geochemical and isotopic compositions indicate that magma mixing was not essential process in the evolution of Ahar magmas. Alkali basaltswith high 143Nd/144Nd ratio, low 87Sr/86Sr ratio and high MgO, Ni and Cr contents indicate that they crystallized from relatively primitive magmas. REE modelling and Trace element ratios indicate that the alkali baslats were derived by small degrees (~1-3%) of partial melting from the spinel lherzolite.
