ISSN 1028334X, Doklady Earth Sciences, 2011, Vol. 437, Part 2, pp. 473–478. © Pleiades Publishing, Ltd., 2011. Original Russian Text © A.V. Korsakov, A.V. Golovin, T. Dieing, J. Toporski, 2011, published in Doklady Akademii Nauk, 2011, Vol. 437, No. 4, pp. 530–535.
GEOCHEMISTRY
Fluid Inclusions in RockForming Minerals of UltrahighPressure Metamorphic Rocks (Kokchetav Massif, Northern Kazakhstan) A. V. Korsakova, A. V. Golovina, T. Dieingb, and J. Toporskib Presented by Academician N.V. Sobolev September 2, 2010 Received October 11, 2010
DOI: 10.1134/S1028334X11040040
Crystallization of diamond with participation of COH fluid [1, 2] or the melt [3–7] at PTparameters of its thermodynamic stability (950–1000°C and 4– 6 GPa) is the dominating point of view on the forma tion of diamondiferous metamorphic rocks. In spite of lengthy study of diamondbearing metamorphic rocks of the Kokchetav massif, highpressure fluid inclu sions were found only in diamonds [8] and assumed in garnets on the basis of the results of IRspectroscopic investigations [9]. The presence of potassiumbearing clinopyroxenes in rocks of the Kokchetav massif also provides evidence for the fact that highpotassic liquid occurred in these rocks at the peak of metamorphism [10], but its traces were registered only as inclusions in diamonds [8]. The compositions of the fluid phase and melt at high temperatures and pressures (above the second critical point) become practically indistinguishable. The problem of the position of the second critical point in the most significant petrological systems is of special importance since fluids and melts transport a variable set of elements (see [11] and references therein). The presence of COHfluid significantly decreases the melting temperature of practically all substrates (metapelites, metabasites, metaperidotites). The appearance of a melt in primary rocks during sub duction in turn results in disappearance of the free fluid phase, because water solubility in the melt increases with pressure [11]. Because of this, it is important to distinguish the areas of fluid and melt existence, as well as contour the area of coexistence of these phases. In this paper we present original data on the com position of fluid inclusions in garnets and clinopy a
Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia b WITec GmbH, Ulm, Germany email:
[email protected]
roxenes from highpressure garnet–clinopyroxene rocks of the Kokchetav massif (Northern Kazakh stan). The modal composition of garnet–clinopyroxene rocks of the Kokchetav massif varies in broad limits from carbonate (
