| Popis: |
Magmatic sulfide deposits are divisible into two major groups, those that are valued primarily for their Ni and Cu and that are mostly sulfide rich (>10% sulfide), and those that are valued primarily for their PGE and tend to be sulfide poor (3.0 Ga) komatiites but appear at around 2.7Ga in continental (Kambalda, Western Australia) or island-arc (Perseverance-Mount Keith, Western Australia) environments, possibly because it was these environments that offered the opportunity for interaction with felsic rocks. It is suggested that the development of these environments in the Archean was an additional control on the age distribution of these deposits. It is postulated that the restricted secular distribution of PGE-enhanced intrusions is also due to the need for a hot mantle to give rise to U-type magmas. |
