Experimental study of the system phlogopite-diopside from 3.5 to 17 GPa

University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada

On the basis of both natural samples and experimental studies, clinopyroxene is a potential reservoir for potassium in the Earth's mantle. The amount of K partitioning into clinopyroxene depends on the phase assemblage present, the bulk composition, pressure, and temperature. To investigate some of these dependencies, subsolidus and melting phase relations in the system phlogopite-diopside have been studied to 17 GPa. In this system, phlogopite becomes unstable with increasing pressure, breaking down to potassium richterite, which in turn breaks down to another K-bearing hydrous phase (phase X), such that a K-rich phase coexists with clinopyroxene to 17 GPa. Clinopyroxenes contain < or =1.3 wt% K ₂ O in assemblages of phlogopite + clinopyroxene + or - olivine + or - liquid at 3-5 GPa, phlogopite + clinopyroxene + garnet + or - olivine + or - liquid at 7-9 GPa, clinopyroxene + garnet + olivine + or - potassium richterite + or - liquid at 11 GPa, and clinopyroxene + olivine + garnet + phase X at 14 and 17 GPa. In these assemblages, K is partitioned into hydrous phases or liquid, rather than into the clinopyroxene. By inference, phlogopite (or its higher-pressure breakdown products) is the primary host for K in the mantle (if H ₂ O is present), and any coexisting clinopyroxene has very low concentrations of K. Conversely, the natural occurrence of clinopyroxene with >>1 wt% K ₂ O requires that phlogopite, potassium richterite, or phase X is not stable in the local source environment of such samples.

This record provided courtesy of AGI/GeoRef.

This article has been cited by other articles:

				R. Oberti, F. C. Hawthorne, E. Cannillo, and F. Camara Long-Range Order in Amphiboles Reviews in Mineralogy and Geochemistry, October 1, 2007; 67(1): 125 - 171. [Full Text] [PDF]

				L. Bindi, A. Bobrov, and Y. A. Litvin Incorporation of Fe3+ in phase-X, A2 xM2Si2O7Hx, a potential high-pressure K-rich hydrous silicate in the mantle Mineralogical Magazine, June 1, 2007; 71(3): 265 - 272. [Abstract] [Full Text] [PDF]

				J. G. Liou, R. Y. Zhang, and W. G. Ernst High-Pressure Geoscience Special Feature: Very high-pressure orogenic garnet peridotites PNAS, May 29, 2007; 104(22): 9116 - 9121. [Abstract] [Full Text] [PDF]

				S. C. Gunn and R. W. Luth Carbonate reduction by Fe-S-O melts at high pressure and high temperature American Mineralogist, July 1, 2006; 91(7): 1110 - 1116. [Abstract] [Full Text] [PDF]

				D. J. Frost The Stability of Hydrous Mantle Phases Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 243 - 271. [Full Text] [PDF]

				T. Tsujimori and J. G. Liou Low-pressure and low-temperature K-bearing kosmochloric diopside from the Osayama serpentinite melange, SW Japan American Mineralogist, October 1, 2005; 90(10): 1629 - 1635. [Abstract] [Full Text] [PDF]

				I. KATAYAMA, M. OHTA, and Y. OGASAWARA Mineral inclusions in zircon from diamond-bearing marble in the Kokchetav massif, northern Kazakhstan European Journal of Mineralogy, December 1, 2002; 14(6): 1103 - 1108. [Abstract] [Full Text] [PDF]

				R. Y. Zhang, J. G. Liou, and J. F. Shu Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites, with retrograde woodhouseite, from the Sulu terrane, eastern China American Mineralogist, April 1, 2002; 87(4): 445 - 453. [Abstract] [Full Text] [PDF]

				Y. Ogasawara, K. Fukasawa, and S. Maruyama Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav Massif, northern Kazakhstan American Mineralogist, April 1, 2002; 87(4): 454 - 461. [Abstract] [Full Text] [PDF]

				F. Mancini, G. E. Harlow, and C. Cahill The crystal structure and cation ordering of Phase-X-(K1-x-n)2(Mg1-n[Al,Cr]n)2Si2O7H2x: A potential K- and H-bearing phase in the mantle American Mineralogist, February 1, 2002; 87(2-3): 302 - 306. [Abstract] [Full Text] [PDF]

				H. Yang, J. Konzett, and C. T. Prewitt Crystal structure of phase X, a high pressure alkali-rich hydrous silicate and its anhydrous equivalent American Mineralogist, November 1, 2001; 86(11-12): 1483 - 1488. [Abstract] [Full Text] [PDF]

				I. Katayama, C. D. Parkinson, K. Okamoto, Y. Nakajima, and S. Maruyama Supersilicic clinopyroxene and silica exsolution in UHPM eclogite and pelitic gneiss from the Kokchetav massif, Kazakhstan American Mineralogist, October 1, 2000; 85(10): 1368 - 1374. [Abstract] [Full Text] [PDF]

				J. KONZETT and Y. FEI Transport and Storage of Potassium in the Earth’s Upper Mantle and Transition Zone: an Experimental Study to 23 GPa in Simplified and Natural Bulk Compositions J. Petrology, April 1, 2000; 41(4): 583 - 603. [Abstract] [Full Text] [PDF]