South Danesfahan Basalts and their Metasomatised MantleSource

Category Petrology
Group GSI.IR
Location 21th symposium on geosciences
Holding Date 21 May 2008

Abstract:
      Trace element geochemistry of south Danesfahan Tertiary basalt is a key to unraveling their source mantle region. Basalt is calc-alkaline in character and show typical island arc trace element patterns. This indicates magmatism from a mantle wedge to which mobile elements (Sr, K, Rb and Ba) had been added by a subduction zone fluid. The fluids derived from the subducting Neotethyan oceanic slab and metasomatized mantle. Trace element ratios Rb/Sr, Ba/Rb and Th/U in the basalt are particularly characteristic in identifying the nature of metasomatic minerals developed in the mantle wedge. The basalt containing lower Ba/Rb and higher Rb/Sr and Th/U ratios represents magma in equilibrium with the phlogopite bearing metasomatized mantle. The other basalt with lower relative amount of Rb and higher relative amounts of K and Sr represents magma in equilibrium with the amphibole bearing metasomatized mantle.

General:
     Trace element geochemistry of south Danesfahan Tertiary basalt is a key to unraveling their source mantle region. Basalt is calc-alkaline in character and show typical island are trace element patterns. This indicates magmatism from a mantle wedge to which mobile elements (Sr, K, Rb and Ba) had been added by a subduction zone fluid. The fluids derved from the subducting Neotethyan oceanic slab and metasomatized mantle. Trace element ratios Rb/Sr, Ba/Rb and Th/U in the basalt are particularly characteristic in identifying the nature of metasomatic minerals developed in the mantle wedge. The basalt containing lower Ba/Rb and higher Rb/Sr and Th/U ratios represents magma in equilibrium with the phlogopite bearing metasomatized mantle. The other basalt with lower relative amount of Rb and higher relative amounts of K and Sr represents magma in equilibrium with the amphibole bearing metasomatized mantle.

tags: ISFAHAN