TRACE ELEMENT DISTRIBUTION WITHIN MELNIKOVITE PYRITE, HILLTOP AU DEPOSIT, NEVADA

The goals of this project were to determine the relative concentrations and distribution of Sb, As, Co and Ni in melnikovite (banded) pyrite, which represents the fifth of six mineralizing events within the Hilltop gold deposit, Lander County, Nevada. The deposition of melnikovite pyrite post-dates gold deposition within the Hilltop system.

The melnikovite pyrite occurs as vein and fracture-fill material and breccia matrix within Ordovician Valmy Formation host rocks (chert, quartzite, argillite, and siltstone) and consists of “massive” pyrite or fibrous pyrite/marcasite bands; individual melnikovite pyrite bands are ≤0.75cm wide.

Element maps illustrating the relative abundance and distribution of Sb, As, Co and Ni were created via electron microprobe using melnikovite pyrite bands within the same core sample. Cobalt was evenly distributed throughout all bands; As and Sb are most abundant in the fibrous bands. Melnikovite pyrite studied here contained no Ni, whereas previously-published studies (Kelson and Crowe, 2005) of melnikovite pyrite from the Hilltop deposit noted various concentrations of Ni within the pyrite bands.