Scientific publications

The southern part of the Kostomuksha greenstone structure with well-developed ultramafic rock fields seems to have a soapstone potential. The main factor, responsible for the occurrence of soapstone deposits, is petrographic. The deposits are located in the peridotitic komatiite field. A structuraltectonic factor is responsible for the position of the talc-bearing field. Granitoid intrusions depend on NE- and near-E-Wtrending fault zones that also control soapstone fields. The main talc-carbonate rock bodies are restricted to the axial zone and the south-eastern slope of the syncline. Near contacts between ultramafics and granitoids and gabbroid intrusions, in quartz vein zones etc. the soapstone differs considerably in composition from Finnish soapstone. Occurring here are talcchloritic, talc-chloritic-amphibole, talc-serpentine-tremolitic and other soapstone varieties. The leading role in the formation of talc-carbonate rocks after serpentinites under corresponding P-T conditions was played by carbonic acid. The addition of hydrotherms with silica and alumina gave rise to talc-chloritic rocks and other intermediate soapstone varieties.