Carlin and Sediment Hosted Vein Deposits-An Intriguing Case of Common Characteristics

Sediment-Hosted-Vein deposits (SHV) constitute a family of gold-bearing vein
deposits that occur worldwide, but are found primarily in Asia. This family of
deposits includes some of the world’s largest gold deposits such as Muruntau, Sukhoy
Log, Baleyskoe, Maysky, and Kumtor in Asia, as well as Bendigo and Ballarat and
many smaller gold vein deposits in Victoria, Australia. Other smaller deposit examples
occur in Nova Scotia (Canada), Nome (Alaska) and in pre-Cordillera rocks of South
America. These deposits are united by common characteristics which include Late
Proterozoic to early Paleozoic passive-margin shale-siltstone host rocks; extended
crust as basement to the host rocks; multiple episodes of deformation of which foldthrust
tectonism is the most significant; Au±As, Sb, W metal suite; neutral, low to
moderate salinity hydrothermal fluid chemistry; minimal to moderate grade metamorphism;
active plutonic magmatism at or near the time of mineralization; and
occurrence within a field of multiple deposits commonly in association with large
placer fields.
Remarkably, this list of characteristics is virtually identical to the major characteristics
that define Carlin type deposits. However, there are a few significant differences
that set Carlin type deposits apart. These include the absolute and relative
timing of mineralization, carbonate content of host rocks, and the role of decalcification.
If these distinctions are considered to be local variations on a grander theme,
Carlin and SHV type deposits share some important characteristics that may have
contributed to their genesis. Namely, the passive margin sedimentary sequence and its
underlying extended crust appear to be most important. Under compressional tectonism,
faults in extended basement are reactivated and contribute to the fold-fault patterns
created in the overlying sedimentary rocks and also likely provide significant
pathways for deep-sourced hydrothermal fluids and magma.
Understanding the importance of these regional to local scale characteristics and
the fact that they are common to some of the greatest gold deposits in the world provides
a unique set of exploration criteria. The application of these criteria in the
search for both types of deposits may be important.