Минералогия (Sep 2018)
CHEMICAL COMPOSITION AND TRACE ELEMENT PATTERN OF A PYRRHOTITE-PYRITE NODULE FROM THE DERGAMYCH CO-BEARING MASSIVE SULFIDE DEPOSIT, SOUTH URALS
Abstract
Distribution of trace elements of pyrrhotite-pyrite nodule from sulfide-serpentinite «gravelites» of the Dergamysh Co-bearing massive sulfide deposit is studied using LA ICP MS method. The nodule is zonal with a central porous core composed of pyrrhotite and a pyrite rim, which were probably formed during diagenesis (pyrite) and anadiagenesis (pyrrhotite). Each zone is characterized by its own geochemical features. Cobalt, Ni, and As are main trace elements of the pyrite rim. The LA ICP MS mapping showed that the distribution of Co and Ni in radial intergrowths of pyrite crystals is zonal and sectorial. The central parts of the crystals are enriched in Co and Ni relative to the fine outer rim. Arsenic is characterized by higher contents in the central parts of the pyrite crystals. Its lower contents are typical of a zone, which adjoins the porous pyrrhotite core, as well as of a fine rim zone. Antimony and Se are concentrated in pyrite. Their higher contents are typical of the marginal parts of crystals. The higher (but discontinuous) Tl contents are determined in a narrow marginal part of the pyrite crystals. Silver in pyrite is distributed relatively homogeneous. Pyrrhotite from a nodule core is characterized by the higher contents of most trace elements. The higher Mo, Ti, and U contents form a discontinuous rim around the nodule at the contact with silicates. Vanadium, Ga, Mn, and Cr are associated with each other and are present mostly in silicates. Different behavior of some trace elements is identified during diagenesis and anadiagenesis of the sulfide-serpentinite «gravelites».
