Journal of Petrology Advance Access originally published online on September 9, 2004
Journal of Petrology 2004 45(11):2261-2286; doi:10.1093/petrology/egh055
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Petrology 45(11) © Oxford University Press 2004; all rights reserved
The Effect of Cr2O3 on the Partial Melting of Spinel Lherzolite in the System CaOMgOAl2O3SiO2Cr2O3 at 1·1 GPa
RESEARCH SCHOOL OF EARTH SCIENCES, AUSTRALIAN NATIONAL UNIVERSITY, CANBERRA, A.C.T. 0200, AUSTRALIA
Chromium as Cr3+ substitutes for octahedrally coordinated Al in upper-mantle minerals, thereby reducing the activity of Al2O3 in the system and hence the concentration of Al2O3 in partial melts. The effect of Cr2O3 on melt compositions multiply saturated with the spinel lherzolite phase assemblage has been quantified in the system CaOMgOAl2O3SiO2Cr2O3 at 1·1 GPa as a function of 100 Cr/(Cr + Al) in the spinel (Cr#sp). The decrease of Al2O3 in the melt with increasing Cr#sp is accompanied by increasing MgO and SiO2, whereas CaO remains almost constant. Consequently, the CaO/Al2O3 ratio of the melt increases with Cr#sp, and the melt becomes richer in normative diopside, hypersthene and quartz. The effect may explain certain mantle melts with unusually high CaO/Al2O3 ratios. The concentration of Cr2O3 in the melt remains low even at high Cr#sp, which means that the strong effect of Cr2O3 on partial melting equilibria is not readily apparent from its concentration in the melt itself. The existence of a highly refractory major component such as Cr2O3 nullifies simplified conclusions from the inverse approach in the experimental study of basalt petrogenesis, as there is insufficient information in the composition of the partial melt to reconstruct the conditions of melting.
KEY WORDS: basalt petrogenesis; partial melting; reversal experiment; spinel lherzolite; system CMASCr2O3; CaO/Al2O3 of melt; effect of Cr2O3
* Corresponding author. Telephone: (+61) 2 6125 5159. Fax: (+61) 2 6125 5989. E-mail: hugh.oneill{at}anu.edu.au
![]()
CiteULike
Connotea
Del.icio.us What's this?
This article has been cited by other articles:
![]() |
X. Liu and H. St.C. O'Neill EFFECTS OF P2O5 AND TiO2 ON THE PARTIAL MELTING OF SPINEL LHERZOLITE IN THE SYSTEM CaO-MgO-Al2O3-SiO2 AT 1.1 GPa Can Mineral, June 1, 2007; 45(3): 649 - 655. [Abstract] [Full Text] [PDF] |
||||
![]() |
X. LIU, H. ST. C. O'NEILL, and A. J. BERRY The Effects of Small Amounts of H2O, CO2 and Na2O on the Partial Melting of Spinel Lherzolite in the System CaO-MgO-Al2O3-SiO2 {+/-} H2O {+/-} CO2 {+/-} Na2O at 1{middle dot}1 GPa J. Petrology, February 1, 2006; 47(2): 409 - 434. [Abstract] [Full Text] [PDF] |
||||

