Origin of Tremadoc kerogen-bearing siltstones and argillites of North Estonia

Kerogen-bearing siltstones and argillites (dictyonema shale) are of sedimentary origin. They are characterized Ьу а high content of sapropelic organic matter, К and S as well as bу an extremely heterogeneous distribution of rare and radioactive elements. 19 determinations of isotope composition of sulfur showed а relatively wide range of 34 S (+2.9 ... -16.1 %0). However, the distribution of this indicator seems to bе of а discrete character. About 58 %, of the samples have isotope composition similar to meteoric standard (б34 S +2.9 ... -3.8 %0). On the basis of а generally accepted standpoint about the participation of biogenic sedimentary sulfide sulfur and the sulfur of restored marine sulfates in ore formation, we do not exclude the potential significant flux of abyssal sulfur bу postvolcanic solutions. The abyssal solutions serve as the main source of heavy metals influx into the sedimentary basin.