Pectolite in the Carolina kimberlitic intrusion, Espigão D'Oeste – Rondônia, Brazil. (June 2020) - Weska, R.K.
Abstract: In this study, we characterize pectolite that occurs in a Carolina kimberlitic intrusion from the Pimenta Bueno Kimberlite Field (PBKF). The PBKF is the only kimberlite field of Permo-Carboniferous age in Brazil and is found on the southern Amazonian Craton. Pectolite, an Na–Ca-silicate usually identified in alkaline rocks as a primary mineral, is not common in the mineral paragenesis of kimberlites and is described here for the first time in Brazil. The genesis of pectolite in kimberlite has been well-studied and can be interpreted as a primary or secondary mineral resulting from the infiltration of an Na-rich fluid into metasomatic reactions. In the rocks from the PBKF, pectolite mainly occurs as fibrous and radial aggregates enriched in K2O that grow between olivine partially altered to serpentine and phlogopite. The results of field and petrographic observations suggest that the PBKF pectolite is of secondary origin, having formed during the hydrothermal alteration of the Carolina kimberlitic intrusion. Highlights: Pectolite is uncommon in the mineral paragenesis of kimberlites. Pectolite is described for the first time in a kimberlite intrusion in Brazil. Pectolite formed a result of groundmass alteration and phlogopite leaching.