Sulfur in the Earth's Crust, its Origin and Natural Cycle

Abstract

Abstract The outer volume of the earth (mantle and crust) contains distinctly less sulfur than primary cosmic matter represented by carbonaceous and common chondritic meteorites (5.9 % and 2.1 % S). Sediments (4250 ppm S) have accumulated a large proportion of the total sulfur of the earth's crust (43 %). Metamorphic and magmatic rocks as the other typical crustal materials contain distinctly less sulfur (~600 ppm S). They originate to a large extent from former sediments. At higher pT conditions the precursor sediments have lost more than three quarters of their original sulfur concentration. Pyrite (FeS 2 ) is the common sulfur mineral of sediments. It forms from bacterially reduced sea water sulfate and sedimentary iron oxides. This abundant process in the interstitial volume of sediments produces isotopically light sulfur. Sea water (1.4 × 10 15 t S) preferentially accumulates the isotopically heavy sulfur from residual solutions of the bacterial reduction etc. The storage of sulfur in crustal sinks (sediments, ocean crust), which partly remove materials from the crust to the mantle by subduction, is compensated by degassing of volcanic rocks (10 5 to 10 6 t S per year).