What is stillwater complex?

The Stillwater Complex is a large layered intrusion located in south-central Montana, USA. It is one of several complexes in the region that contains platinum group elements (PGE). The Stillwater Complex is considered a type example of layered intrusions, which are large-scale igneous bodies that form through a process of fractional crystallization. The complex was emplaced into the Archean crust about 2.7 billion years ago and covers an area of approximately 4,250 km².

The complex is composed of a series of layered rocks that are rich in sulfide minerals, including pentlandite and chalcopyrite. These sulfide minerals contain significant amounts of PGEs, including platinum, palladium, and rhodium. The Stillwater Complex is one of the largest sources of PGEs in the world, accounting for about 3% of global production.

The complex has undergone significant exploration and mining activities since the early 20th century. The Stillwater Mining Company, founded in 1992, has become the largest producer of PGEs from the complex, mining both the J-M Reef and Lower Banded Series. The company operates two mines on the complex, the Stillwater Mine and the East Boulder Mine.

Despite its economic importance, the Stillwater Complex is also of great scientific interest. Its unique geology provides insights into the processes of magmatic differentiation and sulfide mineralization, and it has been the focus of numerous research studies and geological investigations.