Portal de Periódicos da CAPES

Alkali Metasomatism in a Thermal Gradient Two Possible Examples

1963; University of Chicago Press; Volume: 71; Issue: 5 Linguagem: Inglês

10.1086/626940

1537-5269

John C. Green,

earthquake and tectonic studies

Two cases of alkali metasomatism, one in Norway and the other in New Hampshire, are considered in the light of Orville's (1962) recent experimental work. Near Kragerö, Norway, granite pegmatites have intruded albitite with evident addition of K to the albitite, converting albite to microcline at the contact. This metasomatism is attributed principally to the effect of the thermal gradient that evidently existed across the contact at the time of intrusion. In northern New Hampshire andalusite has been altered to muscovite over large areas in the vicinity of adamellite plutons that themselves are depleted in K at their borders. This metasomatism was probably not driven primarily by a thermal gradient, but by the chemical potential gradient existing between andalusite and K-feldspar under hydrous conditions.