Advantages of Using Modern Thermodynamic Software in Geothermobarometry Modeling of Geological Processes Compared to the Conventional Methods, Thermocalc as example. Application on Geothermobarometry Modeling for Southern Syria Volcanism (Tal Al-Ashaer).

This paper discusses a geothermobarometry modeling computer software called Thermocalc through an applied example from the southern Syria volcanism, specifically from Tal Al-Ashaer volcano, is given. A graphical P-T diagram for a given chemical bulk composition of some spinel-bearing peridotite rocks (from Tal Al-Ashaer) is created. The results and their interpretation, in addition to limitations and constraints are discussed. Based on the mineralogical analysis linked to the studied mineral assemblage modes, the bulk-rock chemical composition is calculated and a geothermobarometry model using Thermocalc is made. The created model shows that the general conditions at which the rock-forming minerals (coexisting in equilibrium) define a field of stability with a range of temperature goes from 700 to 1100 C° corresponding a range of pressure between 8 and 15 Kbar. Using one of Thermocalc tools (composition isopleths) the most precise P-T conditions at which the rock was formed are estimated; T = 892 C° and P = 10.5 Kbar. The corresponding depth at which the studied samples were formed is about 36 Km. Accordingly, the crust-upper mantle boundary in the studied region is placed at that depth.