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GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 263-3
Presentation Time: 9:00 AM-6:30 PM

K2CA(CO3)2 AND NA2MG(CO3)2 IN DIAMOND FROM YAKUTIAN KIMBERLITE: THE FIRST OBSERVATION


LOGVINOVA, A.M.1, WIRTH, R.2, UGAP'EVA, S.S.3, TOMILENKO, A.А.1 and SOBOLEV, N.V.1, (1)V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, 630090, Russian Federation, (2)Helmholtz Center, Potsdam, GFZ, German Research Centre for Geosciences, Section 4.4, Telegrafenberg, Potsdam, D-14473, Germany, (3)Institute of Diamond and Precious Metal Geology SB RAS, Yakutsk, 667077, Russian Federation

Carbonates, similarly to other carbon-rich phases, are significant for processes which are directly related to the nucleation and growth of diamonds, however carbonate mineral inclusions are quite rare in diamonds. But they represent an evidence for carbonate abundance in the mantle. It is believed that carbonatitic inclusions originated from high-density fluids (HDFs) that were encapsulated in diamond during its growth. Several kinds of carbonate inclusions were identified in Yakutian diamonds: magnesite (Bulanova, 1995), dolomite, Ba-, Sr- and Fe-rich Ca-carbonates (Logvinova et al., 2008). Most of them are represented by polyphase inclusions of chemically varying carbonates, associated with minor amounts of silicate, oxide, phosphate, saline and volatile phases. Volatiles, such as chlorine, fluorine and hydrogen, play a significant role in diamond growth.

In this study polyphase inclusion, composed of CaMg(CO3)2 (dolomite), K2Ca(CO3)2 (buetschliite), Na2Mg(CO3)2 (eitelite) and MgCO3 (magnesite), was identified in Yakutian diamond, using TEM and Raman spectroscopy. Buetschliite and eitelite as inclusions in diamond are reported for the first time. The characteristic Raman bands lie for buetschliite at 1092cm -1, weak lines at 693, 222, 165 cm-1. For eitelite – at 1105 cm-1 and weak lines at 261, 207 cm-1. The polyphase inclusion is located in the centre of a monocrystalline diamond from Sytykanskaya pipe (Yakutia). It is enolgated 35 microns in size shaped and alkalis presence inclusion. Dolomite predominates in polyphase inclusion. Careful CL imaging reveals the total absence of cracks around the dolomite inclusion. Buetschliite and eitelite are located closer to the peripheral zone of inclusion. The origin of the studied diamond may be due to high-Mg carbonatitic HDFs, which have been described in fibrous cubic and coated Yakutian diamonds (Klein-BenDavid et al., 2009), but having the complex alkali-rich carbonate compositions. Variations of carbonate - inclusion compositions among diamonds indicate the variability in the source media at the formation of diamond.

Financial support for this study was provided by RFBR (16-05-00841; 17-05-00668), RSF (14-17-00602P)

Session No. 263--Booth# 244

T147. Planetary Mantles—Using Samples to Explore Earth, the Moon, and Mars (Posters): Memorial Session in Memory of Lawrence A. Taylor
Wednesday, 7 November 2018: 9:00 AM-6:30 PM
Halls J-K (Indiana Convention Center)
Geological Society of America Abstracts with Programs. Vol. 50, No. 6
doi: 10.1130/abs/2018AM-322000
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