The sulphur and oxygen isotopic composition of anhydrite from the Upper Pechora basin (Russia): new data in the context of the evolution of the sulphur isotopic record of Permian evaporites

Abstract

1 Na tional Acad emy of Sci ences of Ukraine, In sti tute of Ge ol ogy and Geo chem is try of Com bus ti ble Min er als, Naukova, 3a, 79060 Lviv, Ukraine 18 O of anhydrite from ha lite fa cies var ies from +12.6 to +15.0‰ and +7.5 to +10.9‰ re spec tively. The quan ti ta tive ra tio of py rite con tent from the wa ter-in sol u ble res i due (silty-sand frac tion) is char ac ter ized by ex tremely low (<<1%) to high (4-5%) steep gra da tion val ues. The in creased pres ence of py rite in di cates the in flu ence of bac te rial sul phate re duc tion. The sul phate re duc tion pro cess was more in tense, es pe cially when evaporites were formed in mud. The nar row fluc tu a tion range of sul phur and ox y gen iso topes val ues of the mea sured anhydrite in dicates low lev els of frac tion ation. It was es tab lished that dur ing the Perm ian, evo lu tion ary changes in the con tent of sul phate ions in sea wa ter cor re late with the sul phur iso to pic com po si tion of ma rine evaporites.