Porphyritic pyroxene-bearing granitoids - a strongly weathered rock group in central Finland

Auteur :
LAHTI, S. I.

Description :
Preglacial weathering. Two stages have been recognized in the weathering process. The first stage is characterized by granular disintegration followed by the subsequent alteration of biotite into vermiculite, and leaching of K, Na and Mg. During the second weathering stage plagioclase is altered into kaolinite, and the breakdown of dark minerals promotes leaching of Ca, Na, Fe and Mg. The residue has been slightly enriched in K-feldspar, quartz and clay minerals. Si and Al have not dissolved during weathering, due to pH-Eh conditions.


Type de document :
Article de périodique

Source :
Fennia (Helsinki. 1889), issn : 0015-0010, 1985, vol. 163, n°. 2, p. 315-321, Références bibliographiques : 15 réf.

Date :
1985

Editeur :
Pays édition : Finlande, Helsinki, Societas Geographica Fenniae