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The transition from peraluminous to peralkaline granitic melts: Evidence from melt inclusions and accessory minerals


Thomas, R and Webster, JD and Rhede, D and Siefert, W and Ricker, K and Forster, HJ and Heinrich, W and Davidson, P, The transition from peraluminous to peralkaline granitic melts: Evidence from melt inclusions and accessory minerals, Lithos, 91, (1-4) pp. 137-149. ISSN 0024-4937 (2006) [Refereed Article]

DOI: doi:10.1016/j.lithos.2006.03.013


Fractional crystallization of peraluminous F- and H 2O-rich granite magmas progressively enriches the remaining melt with volatiles. We show that, at saturation, the melt may separate into two immiscible conjugate melt fractions, one of the fractions shows increasing peraluminosity and the other increasing peralkalinity. These melt fractions also fractionate the incompatible elements to significantly different degrees. Coexisting melt fractions have differing chemical and physical properties and, due to their high density and viscosity contrasts, they will tend to separate readily from each other. Once separated, each melt fraction evolves independently in response to changing T/P/X conditions and further immiscibility events may occur, each generating its own conjugate pair of melt fractions. The strongly peralkaline melt fractions in particular are very reactive and commonly react until equilibrium is attained. Consequently, the peralkaline melt fraction is commonly preserved only in the isolated melt and mineral inclusions. We demonstrate that the differences between melt fractions that can be seen most clearly in differing melt inclusion compositions are also visible in the composition of the resulting ore-forming and accessory minerals, and are visible on scales from a few micrometers to hundreds of meters. © 2006 Elsevier B.V. All rights reserved.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and metamorphic petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Davidson, P (Dr Paul Davidson)
ID Code:43449
Year Published:2006
Web of Science® Times Cited:81
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2006-08-01
Last Modified:2007-05-29

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