Tectono-Magmatic Setting of Cretaceous Pillow Basalts in the North Part of The Alborz Mountains in East of Guilan Province (North of Iran): A Part of Ophiolite Sequence or Intra-Continental rift?

The pillow basalts, Cretaceous in age, outcrop in the northern part of Alborz in the East of Guilan province (north of Iran). The pillow lavas are mainly olivine basalts. From geochemical point of view, these rocks are transitional or mildly alkalic series and negative anomaly of Nb-Ta, Zr, Ba; positive anomaly of Kand Pb; low ratios of Ce/Pb, Nb/U and high ratios of Th/Nb and Ba/Zr are geochemical evidences of crustal contamination. In tectonic setting diagrams, the pillow lavas plots in intra continental rift Basalts terrain and is comparable with the Transitional Ethiopian Rift Basalts. The geochemical studies show that the pillow basalts are derived from the spinel-lherzolite mantle source and originated from less than 60km depth with less than %15 partial melting.