Devonian ore clastic turbidites of the Molodezhnoe massive copper sulfide deposit, Southern Urals

Abstract

We present data on the composition of Devonian ore clastic sediments accumulated at the boundaries of the orebodies of the Molodezhnoe massive copper sulfide deposit, Southern Urals. They are interpreted to be accumulated during the synsedimentary and postsedimentary stages. The synsedimentary stage was marked by gravity transport and accumulation of products of the destruction of high-temperature black smoker chimneys. During the postsedimentary stage, the deposits underwent two types of mineralogical and geochemical transformation: (1) infiltration-metasomatic effects of ore-bearing solutions and infiltration effects of seawater causing redistribution of copper and carbonates in the sediments and formation of authigenic minerals (chalcopyrite, siderite, secondary calcite, and apatite and replacement of aluminosilicates by chlorite) and (2) dehydration accompanied by the replacement of iron hydroxides by hematite and amorphous silica by quartz. Temperatures of the postsedimentary alteration were estimated from a fluid inclusion study and thermodynamic computer modeling as 150–250°C and correspond to the metagenesis stage (burial metamorphism). The organic matter composition was characterized by TOC, hydrogen and oxygen indices (HI and OI), and δ13C values.