جستجوی مقالات مرتبط با کلیدواژه "شمال غربی ایران" در نشریات گروه "زمین شناسی"

Plio-Quaternary volcanic units are located in different regions of Azerbaijan in the north-west of Iran. Field observations show the placement of volcanic materials in connection with linear geo-structural structures such as fractures and main faults and the axis of young folds. The studied rocks include basalt, basaltic andesite, trachyandesite, trachyte, dacite, rhyodacite and rhyolite, which are from the calc-alkaline and alkaline magma series with high potassium. Young basaltic lavas are composed of basalt, olivine-basalt, tephrite, which belong to the alkaline magma series. The studied samples show enrichment in K, Ba, Rb, Th, U, Cs. Investigating the chemical behavior of chromium, nickel, cobalt, Ti, V and MgO against SiO2 indicates the pollution process. LREE enrichment and HREE depletion indicate that the magma of these rocks originated from the asthenosphere mantle with a garnet source and a low relative melting degree. The positive anomalies of Cs, U, Ba, Rb, and K and the low negative anomalies of Ta, Nb, and Eu in the basaltic samples can be interpreted as crustal contamination. Examining the effects of AFC shows that the contamination process played an important role in the formation of magmas. Medium acidic volcanic units are cut by lamprophyre dykes in some areas.  Examining the tectonic structures of the samples indicates volcanic arcs after the collision.

Mazraeh deposit is located at 20 Km north of Ahar, Eastern Azerbaijan, North-West of Iran. The area is situated in the Western Alborz – Azerbaijan geotectonic zone. Intrusion of the Oligocene – Miocene Sheyvardaagh batholith in to the older carbonate and volcanoclastic rocks is responsible for contact metamorphism, contact metasomatic mineralization, and formation of schist, hornfels, marble and epidote - garnet Skarn. This batholith is a subduction-related calc to sub alkaline, peralominous and S-type granitoids. Due to the extensive Tertiary magmatism, skarnization and extensive alterations, this zone is one of the remarkable Fe, Au, Cu-mineralization in Iran. Therefore, a lots of research and investigations have been done by the Geological Survey of Iran and different government and private companies. The following paper is results of our research about Cu -Fe- Au skran mineralization in the Mazreh area, NW of Iran.

This research was conducted in two parts, field and laboratory analysises. In the field section, after carrying out geological surveys and detailed examination of 6800 meters of drilling cores from 61 boreholes, a total of 60 samples were chosen from 21 selected typical boreholes of different sizes. About 36 samples from intrusive rocks choosed to preparing thin sections for petrographic studies and major chemical analysis by XRF. Also, 24 samples from mineralized zones were selected for preparation of polished sections, mineralographical study and geochemical analysis by ICP-OES.

Major alterations are chloritic, propilitic and sericitic which have close genetic relationship to mineralization zone. The main mineralization stage occurs as exoskarn in garnet-epidote skarn type. The major rock forming minerals in the skarn are garnet (adradite and grossularite), epidote, actinolite, chlorite, biotite, sericite and amphibole. Mineralogical paragenesis consists of magnetite, pyrite and copper sulfides such as chalcopyrite, bornite and covellite, hematite (especularite), goethite and malachite. The mineralization is vein, veinlet and disseminated type. The main mineralization stage occurs in retrograde skarn. Average value of Cu is 16284 ppm, FeOt 35.05 percent, Au 3380 ppb and Ag 9.94 ppm. There is no correlation between the values of Au and Cu as well as Ag and Au with S. It seems that Au mineralization is not simultaneous with Cu skarn mineralization but Ag mineralization is simultaneous with skarn phase. The geological, mineralogical and geochemical data show that the granitoid batholith of Mazraeh area is a fertile pluton with Cu – Fe-Au skarn mineralization.

The mineralogical and geochemical data show that Sheyvardaagh batholith intrusive rocks are S-type and inlmenite series. Tectonomagmatic setting of these granitoid batholith lies within subduction-related calc to sub alkaline, peralominous and S-type granitoids. A/NK and A/CNK diagram shows these granitoids are close to fertile Fe-Cu-Au granitoid batholith and related skarn. The geological, mineralogical and geochemical data show that the granitoid batholith of Mazraeh area is a fertile pluton with Cu – Fe-Au skarn mineralization.

We would like to express our gratitude to the management and respected staff of research and development affairs of the National Copper Industries of Iran (Sarchshme) for supporting of this research and to the staff of the National Copper Company located in Ahar and Warzghan cities for their cooperation in the field visit and sampling.