Abstract

Instrumental neutron activation and atomic absorption analyses for 31 elements in marine biogenic pyrite from carbonate concretions in the Upper Lias (Lower Jurassic) of Yorkshire, England, are reported. Mo, As, and, to a lesser extent, Cu are concentrated in pyrite relative to the host sediment and occur together with low concentrations (<30 ppm) of Ni and Zn and trace amounts (<5 ppm) of Mn and Co. The concentrations of all the remaining elements determined in the sulfide are at or below the detection limit of the method used and are relatively enriched in the host sediment. The difference in the levels of trace element in pyrite and host sediments means that a small amount of contamination of sulfide separates by host sediment introduces large errors in the determination of trace elements by analysis of host sediments. Statistical procedures to correct for contamination are described. The results of this preliminary study suggest various approaches by which corrected trace element data may enable biogenic sedimentary pyrite to be distinguished from other types of pyrite.The two textural forms of pyrite (framboidal and euhedral) are related to the availability of iron within the sediment, which may indirectly control trace element composition. Early framboidal pyrite formed by the redistribution of iron locally within the sediment. Once local sources are exhausted, growth of euhedral pyrite requires transportation of iron into the sediment from an external source. Trace element abundances in sedimentary pyrite can be related to the sources of iron used in pyritization.

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