Silurian undersea basalts in VMS mineralization in the North-East of Shahrood

Abstract

The Soltan-Meydan basaltic suite contains a range of undersea mafic volcanic rocks whose stratigraphy position indicates lower Paleozoic (Silurian). In geology of Iran it has been named Soltan-Meydan Formation. However, Tectono-magmatic aspects of this suite and their relationship with copper mineralization have not been studied yet. The aim of this study is to clarify these relationships. Out of three traverses of this suite more than 150 rock samples were collected and their thin sections were studied. 14 relatively fresh samples were selected for the purpose of geochemical analysis of major and trace plus REE elements. Thin section studies indicate a wide range of hydrothermal alterations, in which Chloritization is the most altered mineral. The Soltan-Meydan volcanic suite represents within-plate magmatism which seems to have erupted in the extensional regime. Some samples with more than 1% copper concentration contain copper sulfide mineralization. In addition, samples with high concentration of Zn and Pb are common figures in most whole rock analyses. Copper sulfides, hydrated copper carbonates, iron oxides and jasper are accompanied by two types of associations of hydrothermal alteration: a) high temperature associations and b) low temperature associations. Consequently, they may have generated volcanic massive sulfide (VMS) deposits in the mentioned suite.