Jakob Johannes Sederholm

Sederholm, Jakob Johannes 

Born July 20, 1863, in Helsinki; died there June 26, 1934. Finnish geologist.

Sederholm joined the staff of the Geological Commission of Finland in 1888 and was director of the commission from 1893 to 1933. His principal works deal with the geology and petrography of the Precambrian rocks of Finland, particularly gneisses and rapakivi granites. Sederholm introduced the term “migmatite” into petrography in 1907. Between 1923 and 1934 he developed a theory of migmatites. He associated the formation of migmatites with a large intrusion of granitic magma, which finely penetrated the gneisses owing to a mobile fluid that he termed ichor. These concepts were subsequently developed by a group of Soviet geologists, including D. S. Korzhinskii, into the modern concepts of transmagmatic solutions and granitization. A mineral from the pyrrhotite group, sederholmite(β-NiSe), has been named for Sederholm.

WORKS

On Migmatites and Associated Pre-Cambrian Rocks of Southwestern Finland, parts 1–3. Helsinki, 1923–34. (Bulletin de la Commission geologique de Finland, nos. 58, 77, and 107.)
On the Geology of Fennoscandia. Helsinki, 1932. (Bulletin de la Commission géologique de Finland, no. 98.)
“The Upper Ienissei Drainage Area (Territory of Uriankhai).” Acta geographica, 1927, no. 1. Helsinki, 1925. (Coauthor.)