Genetic types and identification characteristics of colloform pyrite

Colloform pyrite is widely distributed in various geological bodies and the genetic information can be obtained by in-depth study of its classification type.By comparing and analyzing the morphology, the internal structure and geochemical features, the hydrothermal and sedimentary colloform pyrite can be effectively distinguished.In combination with the mapping method of Fe-S, Co-Ni, S-Se, Se-Te and sulfur isotope mapping proposed in this paper, the trace characteristics of colloform pyrite of various genetic types were compared.The colloform pyrite of sedimentary origin is mostly spherical, ellipsoidal and agglomerated, with Co/Ni < l, S/Se > 2.5×10⁴, Se/Te < 0.45, and a wide-ranging δ³⁴S ratio(-13‰~+13‰).Under the microscope, mineral isomorphism of clay are often observed.The colloform pyrite of hydrothermal origin mostly occurs as irregular veins and has a certain orientation, with 1 < Co/Ni < 5, lower S/Se ratio(< 2.5×10⁴), and the Se/Te ratio more than 0.45, as well as a narrow range of ³⁴S ratio(0~ 5‰).Among them, the colloform pyrite Co/Ni, S/Se and Se/Te of magmatic hydrothermal origin are all higher than the metamorphic hydrothermal origin.The nucleated and growing process of sedimentary colloform pyrite origin is under the anaerobic condition.In the bacterial sulfate reduction zone with the H₂S, metal elements such as Cu, Zn and Mo are enriched in the crystalline nano-sized pyrite particles in the form of sulfide melt.The colloform pyrite of hydrothermal origin can be used as a mineral carrier.Au, As and other elements occur in the zone of colloform pyrite as a consequence of heteroepitaxial Stranski-Krastanov growth.The mineralogical phase can be changed into pyrrhotite under the lower temperature, which promotes the precipitation of copper.