Tertiary metallogeny of the western Alborz - Azerbaijan (Mianeh- Syahrud) with region-specific approach (Hashtjin)
The studied area in this thesis is a regional of 1150 square kilometers on the part of sheet Hashtjin (1:100000). This region is located in the western Alborz - Azerbaijan Geological zone and in the borders of three provinces of Azarbaijan-e Sharqi, Ardabil and Zanjan.
The oldest and most extensive rock units related to the study area include Tuffite and lavas of the Eocene Karaj Formation. Lavas in this area involve trachy-andesite, basalt, and sometimes dacite. During the Cimmerian and Laramid orogenies, the region entirely exposed from water or to have been shallow sea. Eocene volcanism occurred in marine environment or in a dry environment. With the Oligocene plutonism, the region experienced volcanism of trachyte, dacite, rhyolite and ignimbrite. There is an obvious unconformity between the lava and tuffite of Karaj Formation. Youngest sediments deposited in the region are alluvial detritic deposit of Hashtjin basin. Last volcanic activity is Neogene or Quaternary in age with the composition of trachy-basalt.
Intrusive massifs in the region include quartz monzonite, monzonite, monzogranite, granodiorite, granite, Quartz diorite, quartz syenite and diorite, but the dominant rock is quartz monzonite. Petrographic evidence indicates crystallization depth is low. Sub volcanic masses composition mainly is quartz monzonite porphyry and diorite. Most specimens belong to the masses with Shoshonitic series that are rich in potassium. They are I- type and peraluminous. Based on measurements of biotite thermometer, the crystallization temperature ranges between 730 and 880, oxygen fugacity between 13 and 17 and between 700 and 800 based on the normative chart.
Based on the chemical composition of amphibole, the emplacement depth ranges between 1.4 to 3 km. Amount of water vapor pressure in the environment governing crystallization of these rocks, based on the chart, ranges between 2 to 10 Kb. Diagrams represent different masses intruded in the subduction regime and active continental margins or volcanic arc. Behavior of rare earth element spider diagrams state a volcanic arc regime at the same time or after the collision stage.
Fluid inclusion studies carried out on minerals extracted from a vein show that the thermal range of lead and zinc mineralization in the region is between 220 to 240 degrees and for the copper mineralization between 280 to 320 degrees.