The middle Jurassic–Early Cretaceous pillow and massive lava flows associated with pelagic sediments in the Ghaleh-Rigi area, southern east of Iran: age and geochemistry

The Ghaleh-Rigi complex is located in northern margin of the Sanandaj–Sirjan Zone (western Iran) and the southern part of the Central Iran Micro-continent block. The study area is covered by pillow and massive lava flows associated with micro gabbro and pelagic sediments including mudstone and radiolarian ribbon chert. Geochemical analysis indicates similar mantle source for magmatic rocks. These rocks show tholeiitic affinity with depletion in high-field strength elements (HFSEs) and light rare-earth elements (LREEs). They also show enrichment in large-ion lithophile elements (LILEs) in primitive mantle normalized multi-element diagrams. All samples show variable depletion in Th followed by depletion of HFSE and trace element concentrations and negative Nb anomaly (Th/Nb=0.23-035), which is a typical characteristic from magmas related to subduction zone. In addition, ratio of Y/Nb against Zr/Nb and Ce/Y against Zr/Nb and also REE flat patterns are similar to N-MORB-like source. These features suggest generation of magma in the back-arc basin. According to geochemical and petrogenesis studies, these rocks shows around 10% partial melting of a mixed spinel–garnet-bearing source composed of 50% PM and 50% MORB source. Based on bio-chronological investigation, the radiolarian cherts associated with volcanic rocks show Early Bajocian to Berriasian; Callovian- Valanginian; and Oxfordian- Valanginian ages.