Ammonium illite at the Jerritt Canyon district and Goldstrike property, Nevada: its spatial distribution and significance in the exploration of carlin-type deposits

Ammoniated hydrothermal fluids interact with potassium-bearing minerals in
wall rock material to create an ammonium illite footprint that is a vector for the exploration
of Carlin-type deposits. Ammonium illite from theWaterpipe Canyon area in
the Jerritt Canyon district and the North Screamer deposit on the Goldstrike property
is characterized using short-wave infrared reflective spectroscopy and 3-D modeling.
Four types of illite (sericitic, phengitic, potassic, and intermediate) are identified
and classified based on the wavelength position of the main AlOH absorption feature
near 2200 nm. Ammonium is measured primarily in sericitic illite and phengitic illite.
On surface, ammonium illite forms an alteration footprint that mimics hematite alteration
in proximity to structure. These footprints are associated with anomalous gold
on surface thus providing evidence that ammoniated fluids migrated along the same
fluid conduits that deposited gold. 3-D modeling establishes that ammonium illite deposited
laterally and vertically outboard of gold mineralization. The pathways in
which fluids migrated are mapped from the deposit towards the paleosurface by modeling
ammonium in the wall rock. The ease at which ammonium illite is identified with
a reflectance spectrometer makes this a quick and effective tool for locating fluid conduits
emanating from buried gold deposits.