Gahnite and Columbite in an Alkali-Feldspar Granite from New Zealand

A. J. Tulloch
Geology Department, Otago University, Dunedin, New Zealand*
*Present address: NZ Geological Survey, PO Box 30368, Lower Hutt, New Zealand.

Abstract: Gahnite and columbite with compositions (Zn5.96Fe1.55Mg0.21Mn0.13)Σ7.85Al16.09O32 and (Nb7.36Ta0.60Mn2.95Fe0.98Ti0.09)Σ11.98O24 occur as accessory phases in a highly evolved garnetiferous muscovite alkalifeldspar granite. Both phases have developed as a result of a concentration of Zn, Nb, and Ta during the fmal stages of the fractional crystallization which led to the formation of the pluton, and the lack of a major mafic mineral such as biotite, in which these elements are normally camouflaged in granitoid rocks.

Mineralogical Magazine; September 1981 v. 44; no. 335; p. 275-278; DOI: 10.1180/minmag.1981.044.335.06
© 1981, The Mineralogical Society
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