- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
Graphite was deposited in and around a diabase intruded along post-Borrowdale Volcanic, pre-Bala faults about 4,000 feet above the Skiddaw Slate-Borrowdale Volcanic boundary. Associated copper-lead-zinc mineralization follows faults of the same trend, and is isotopically dated at 470 million years (mid-Ordovician). The breakdown of carbon monoxide in the magmatic gases was promoted by substances (notably pyrite, iron oxides, iron silicates, and quartz) which catalysed the Boudouard reaction 2CO <--> CO 2 + C. The PT conditions of deposition of the graphite and associated minerals are estimated at P approximately 1,000 bars, T approximately 120 degrees to 600 degrees C. Possible occurrences of natural interlamellar compounds of graphite are discussed.