Petrology, geochemistry and chemical nature of the Goft and Mohammadabad manganese ore host rocks, in the Late Cretaceous volcanic-sedimentary sequence southwest of Sabzevar

The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern edge of the southern anticline in the unit 4 of regional stratigraphic column and Goft manganese deposit is occurred in the southeastern edge of the northern anticline in the first unit of the regional stratigraphic column. The host rocks of Goft and Mohammadabad deposits include red tuff and Marly tuff and limy tuff, respectively. According to geochemical studies, tectonic environment of manganese deposits in the southwest of Sabzevar is a rifting environment that has been formed in the Sabzevar back-arc basin. The rocks of the region have a wide range of basalt, rhyolite, dacite, olivine-basalt, andesite-basalt and trachy-andesite, which formed aligned with pyroclastic sediment and Late Cretaceous sedimentary units. Dacite rocks are the thickest felsic rock unit in the area. The values of major oxides, the pattern of rare earth elements (REE), and the changes in trace elements in spider diagrams indicate the bimodal and tholeiitic nature of the volcanic rocks of the region, which are deposited in extension environment with a mixed range from basalt to rhyolite.