ژیوشیمی سنگ های دگرگونی ناحیه ای سبزوار، شمال بلوک های خرد قاره

Hp/lt metabasite rocks can preserve some evidences of tectonic and geochemical processes of a subduction zone. sabzevar ophiolite and metabasites which are located at the north of central iranian microcontinent block (cim) have preserved such evidences. the metabasites are fossil oceanic crust of neotethys-related basin. metabasites are composed of glaucophane schist, amphibolite and greenschist. major and trace element contents of the rocks indicate that blueschist and amphibolite protoliths were morb basalts. rare earth elements show presence of two morb types, n- and e-morb. ?ree is 132-246 (ppm) and 617-744 (ppm) for the n- morb and e-morb basalts, respectively. la/yb ratio is ranging from 0.43-0.79 for n-morb and 8.7 and 1.1 for e-morb. the mg# ranges are between 0.24-0.27, 0.23-0.24, 0.42 and 0.38 for glaucophane schist, garnet amphibolite, amphibolite and chlorite schist, respectively, which indicates a weak fractional crystallization in the original magma. high pressure rocks were formed due to northward subduction of neotethys-branch of sabzevar basin between cim and eurasia since upper cretaceous to eocene.