Spectrochimica Acta Part A 80 (2011) 21–26 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy j ourna l ho me page: www.elsevier.com/locate/saa First findings of monocrystalline aragonite inclusions in garnet from diamond-grade UHPM rocks (Kokchetav Massif, Northern Kazakhstan) Andrey V. Korsakov a,∗ , Peter Vandenabeele b , Maria Perraki c , Luc Moens d a Institute of Geology and Mineralogy of Siberian Branch Russian Academy of Sciences, Koptyug Pr. 3, Novosibirsk 630090, Russia b Ghent University, Department of Archaeology and Ancient History of Europe, Blandijnberg 2, B-9000 Ghent, Belgium c School of Mining and Metallurgical Engineering, National Technical University of Athens, 9 Heroon Politechniou St., Zografou, Athens GR-15773, Greece d Ghent University, Department of Analytical Chemistry Raman Research Group, Proeftuinstraat 86, B-9000 Ghent, Belgium a r t i c l e i n f o Article history: Received 13 August 2010 Received in revised form 19 November 2010 Accepted 8 December 2010 Keywords: Aragonite Calcite Diamond UHPM petrology Raman spectroscopy SEM Cathodoluminescence a b s t r a c t The presence of aragonite inclusions in garnet from diamond-grade metamorphic rocks from the Kokchetav Massif, Northern Kazakhstan was identified for the first time by means of Raman analyses and mapping. Aragonite appears within the inclusions up to 50 m in size as a single crystal. These inclusions have rounded shape. The grain boundary between the host–garnet is smooth. No cracks occur around the aragonite inclusions. No significant shift in the main aragonite Raman band was measured. These observations indicate that residual pressure within the inclusion is minor. These findings imply either non-UHPM origin of the host garnet or significant plastic deformation of host minerals during retrograde stage. These features should be taken into account for recovery peak metamorphic conditions and modeling of exhumation processes of UHPM complexes. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Aragonite, the high-pressure CaCO 3 polymorph, is expected to form from calcite during incipient subduction of carbon- ated sediments and, at much higher pressure (P > 5 GPa), through the breakdown of dolomite, CaMg(CO 3 ) 2 , to MgCO 3 (magne- site) + CaCO 3 (e.g. 1,2). However, the presence of aragonite in subducted slab is generally restricted to low temperature high pressure (HP) or ultrahigh pressure (UHP) metamorphic rocks. The rapid kinetics of the back-transformation of aragonite to calcite makes the preservation of metamorphic aragonite to the surface an indicator of decompression under quite low temperatures [3,4]. Recently, relics of aragonite were identified as inclusions in garnet from high temperature diamond-grade metamorphic rocks from Erzgebirge [5] and as nanometer-sized inclusions in diamond from the Kokchetav massif [6]. Carbonates (e.g. calcite, dolomite, aragonite) are quite com- mon in high pressure metamorphic rocks. Whereas CaCO 3 and (Mg, Ca)[CO 3 ] 2 can be easily distinguished by CL, EMP and SEM analyses, the identification of CaCO 3 polymorphs especially in very tiny inclusions is tricky. In these cases, Raman spec- ∗ Corresponding author. Tel.: +7 383 333 25 17; fax: +7 383 333 27 92. E-mail address: korsakov@uiggm.nsc.ru (A.V. Korsakov). troscopy has been proven to be a useful tool. Recently aragonite inclusions were identified in diamond-grade UHPM localities [5,7], however, the origin of aragonite inclusions remains poorly understood [6,8,9]. The presence of aragonite inclusions in metamorphic diamonds by [6] indicates that diamond-bearing rocks were subducted to depth >280 km. The ultradeep subduction was deducted from the dolomite breakdown to form aragonite and magnesite at peak metamorphic conditions [6,8]. Complex aragonite–calcite inclusions occurring in the diamond-bearing metamorphic rocks were identified by Raman spectroscopy [7]. All mineralogical observations indicate that origin of aragonite is not related to dolomite breakdown. Here we present the results of Raman spec- troscopic study of monocrystalline aragonite inclusions in garnet from diamond-bearing metamorphic rocks (Kokchetav massif, Northern Kazakhstan). Raman mapping was performed in aim to check the possible presence of any optical undetectable cal- cite and strain pattern inside inclusions and surrounding host garnet. 2. Analytical methods Raman mapping was performed with a Sentera Raman system equipped with two lasers at 532 nm and 785 nm. The map size is 35 × 35 points with 1 m step. The Raman signal was collected in 1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2010.12.024