The study of geochemical nature of Tertiary volcanics and younger basaltic rocks in northeast region of Birjand

In northeast region of Birjand، two distinct groups of volcanic rocks are exposed. Paleogene andesitic، dacitic and rhyolitic rocks as the major formation and younger mogearites، andesitic basalts and basalts that have erupted in the paleogene intermediate to acidic extrusive rocks background with the main trend of northwest – southeast. Investigations show that these two lithological complexes are the results of two different petrogenetical phenomenas and they have different genetic and geochemical characteristics. Intermediate to acidic volcanic rocks belong to active continental margin calcoalkaline rocks and they have formed from differentiation of a primary andesitic magma that are affected from crustal contamination at least in its rhyolitic and dacitic terms. The major nature of basaltic volcanic rocks is alkaline and they belong to intraplate basalts with mantle magmatic source that has erupted to the surface through extensional systems as the right lateral fault zones revenue.