In
the past decade several significant intrusion-related gold deposits have been
discovered in terranes historically exploited for tin-tungsten mineralization
(eg Tintina Gold
Province, Yukon and Alaska, Tasman Fold Belt, Australia and the Altaid orogenic collage in
central Eurasia). This paper presents new data
on the geological and geochemical characteristics of these deposits that links
them to magmatic-hydrothermal processes and highlights their implications for
exploration. New data from several intrusion-related gold provinces suggest that
these deposits are found in areas that contain granodiorite to granite, but with
a locally significant mafic component, have Rb/Sr ratios ranging between 0.1 and
1.0, and are moderately reduced (Fe2O3/FeO ~ 0.1 to 0.6)
ilmenite series, metaluminous, I-types. The intrusions are distinct from
porphyry copper intrusions and tin granites, but are more akin to tungsten
granites. Hydrothermal fluid types vary with depth of emplacement in
intrusion-related gold deposits and new proton induced X-ray emission (PIXE)
data from syn-ore fluid inclusions in shallow and deep deposits provide
fascinating insight into the variation in metal content between the different
settings consistent with observed deposit metal associations. Exploration for
intrusion-related gold deposits in tintungsten terranes should focus on regions
that contain both mafic and felsic intrusion that are moderately reduced,
metaluminous, I-type granites rather than terranes with dominantly highly
fractionated, strongly reduced, peraluminous S-types. Intrusion-related gold
systems occur in variety of deposit styles (in part controlled by host rock,
proximity to granite, and depth of emplacement) and exploration geologists need
to be aware of the variety of target types in and around the intrusive
environment, and be able to recognise whether they are exploring a shallow or
deep intrusion-related gold setting.