Physical Sciences and Mathematics Commons^™

Potassium Metasomatism At The Polymetallic Nico Deposit, Northwest Territories, Canada, Gregory B. Robinson

Electronic Thesis and Dissertation Repository

High temperature K-metasomatism pervasively replaced Paleoproterozoic volcanic and metasedimentary rocks at Lou Lake NWT. This replacement developed primarily at the structural interface juxtaposing non-metamorphosed Lou Lake volcanic rocks over Treasure Lake Group metasedimentary rocks. This crustal-scale fault developed coeval with the emplacement of anorogenic magmatism within a post-collision extensional setting. Emplacement of porphyry dykes into the fault breccia coincided with K-metasomatism at peak upper-greenschist to amphibolite-facies thermal conditions.

The K-metasomatism resulted from co-mingling of descending crustal fluids and ascending potassic magmatic fluids along the decollement surface. Pervasive K-metasomatism resulted in complete replacement of precursor rocks by potassium feldspar. The pronounced …