Distribution of scandium between coexisting biotite and hornblende in igneous rocks

GSA Bulletin
By: , and 



Scandium analyses of more than 90 pairs of coexisting biotite and hornblende from igneous rocks of various provinces (including Southern California, Boulder, Sierra Nevada, Boulder Creek batholiths and the Jemez Mountains volcanic rocks) indicate that the distribution ratio (Kd = Schornblende/Scbiotite) for most samples closely approached that of an equilibrium distribution. Median Kd values for the igneous samples range from 4.8 to 8.0, which are higher than similar values derived from published data on metamorphic samples and apparently not related to the mode of crystallization (volcanic, hypabyssal, or plutonic). A correlation between Kd and mafic index, (FeO + Fe2O3)/(FeO + Fe2O3 + MgO) X 100, of both the minerals and the host rock, and between Kd and SiO2 content of the host rock, can be established only for the Southern California batholith samples. However, whether this correlation reflects temperature dependence, compositional dependence, or both, cannot be specified uniquely with present data. The present data also cast doubt on the validity of the so-called “scandium geothermometer.”

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Distribution of scandium between coexisting biotite and hornblende in igneous rocks
Series title GSA Bulletin
DOI 10.1130/0016-7606(1969)80[651:DOSBCB]2.0.CO;2
Volume 80
Issue 4
Year Published 1969
Language English
Publisher Geological Society of America
Contributing office(s) California Volcano Observatory
Description 18 p.
First page 651
Last page 668
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