Evolution of Stress Fields in the Porya Guba Dike Field
(Kandalaksha Gulf, White Sea)

T. I. Vasil’eva and E. S. Przhiyalgovskii

Geological Institute (GIN), Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia

e-mail: tania@ilran.ru

Received March 18, 2004

Abstract—The tectonic evolution of the Por’ya Guba segment of the White Sea Rift System began in the late
Paleoproterozoic, i.e., soon after completion of the Svecofennian collision. The fracture system that controlled
localization of the lamproite dike complex was formed under conditions of horizontal compression combined
with shear. Subsequently, this system predetermined the location of a rift-graben segment that formed as a result
of simple shear. The reactivation of the rift system in the Middle Paleozoic proceeded in two stages. The first
stage, when strike-slip movements along previously formed faults predominated, resulted in formation of
quartz–carbonate veins bearing base-metal mineralization. The veins that filled the shear fractures opened
owing to local reorientation of the stress field. The second stage fitted the transtension conditions, and the Late
Devonian alkaline ultramafic dikes of this stage intruded into the already existing fracture system, which was
oriented at a roughly right angle to the predominant stress orientation.

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