The lithospheric setting of Carlin-type deposits: An important clue to their genetic associations and deposit associates

Carlin-type deposits have traditionally been regarded as a deposit class for which
world-class examples are largely restricted to northern Nevada, although some global
analogs have been suggested. Economic geology research, which has been largely
based on the deposits themselves, has not delivered an unequivocal genetic model,
although a late Eocene (ca 42–36 Ma) timing of mineralization, coeval with intrusive
magmatism in the broader district, is well established.
At the continental or lithospheric scale, the “unique” Carlin-type deposits occupy
a similar, but anomalous tectonic niche to the zoned Bingham Canyon porphyry system
and the intrusion-related gold deposits (IRGDs) of the Tombstone-Tungsten belt,
Yukon. Unlike most epigenetic gold deposits in metamorphic belts, all of these metallogenic
districts are hosted in previously thrusted and folded, miogeosynclinal, calcareous
Paleozoic to Mesozoic sedimentary sequences above Precambrian subcontinental
lithospheric mantle (SCLM). In addition, the districts share a similar relative tectonic
timing, with mineralizing events taking place at the onset of regional extension, immediately
following the cessation of protracted compression. Both the zoned Bingham
district and zoned Tombstone-Tungsten belt owe their metal endowment to the intrusion
of anomalous magmas, involving a component of basic alkaline melt from metasomatically-
enriched domains within the SCLM. Avariety of evidence suggests this is
also a permissive model for Carlin-type deposits due to their broad spatial and temporal
relationship to magmatism in the same terrane, if not in the immediate ore environment.
It is also consistent with the lack of any other geologically reasonable
thermal engine to drive the hydrothermal systems given deposit control by compressional
structural geometries related to earlier orogeny, insignificant to no coeval volcanism,
and minimal extension in Carlin-type districts relative to surrounding areas
of the Basin and Range Province.