Alkali carbonates and sulfides in kimberlite-hosted chloride-carbonate nodules (Udachnaya pipe, Russia) V.V. SHARYGIN 1 , V.S. KAMENETSKY 2 , M.B. KAMENETSKY 2 1 Institute of Geology and Mineralogy, Novosibirsk, Russia (sharygin@uiggm.nsc.ru) 2 CODES, University of Tasmania, Hobart, Australia (Dima.Kamenetsky@utas.edu.au) A block of unaltered kimberlites has been recently exposed in the eastern body of the Udachanya pipe mine pit at >400–500 m depths. This kimberlite is characterized by abundant chloride-rich nodules (up to 90–95% NaCl + KCl) and rare chloride-carbonate nodules (roughly similar amounts of chloride and carbonate min- erals). Two types of chloride-carbonate nodules are distinguished in the carbonate-sulfide assemblage: nyerereite-shortite-calcite- rasvumite and shortite-northupite-calcite-djerfisherite. Nyerereite Na 2 Ca(CO 3 ) 2 forms the cores of zoned crystals in the fist type of the nodules are characterized by strong composi- tional variations, especially in K 2 O and SO 3 . (in wt/Na 2 O, 23–27; K 2 O, 2.5–7; SO 3 , 1–7). Nyerereite is partly or completely replaced by pirssonite Na 2 Ca(CO 3 ) 2 2H 2 O and contains minute aphthitalite K 3 Na(SO 4 ) 2 crystals. Shortite Na 2 Ca 2 (CO 3 ) 3 and cal- cite are main minerals of the rims of zoned crystals. We envisage the formation of the rims resulting from breakdown of nyerereite at reducing temperatures. Associated shortite, northupite Na 3 Mg(CO 3 ) 2 Cl and calcite in other type of carbonate-rich nod- ules are close to ideal compositions. Rasvumite forms prismatic, often split crystals (up to 5 mm) at the contacts between nyerereite and chlorides. It is chemically homogeneous: (n = 28, in wt%) Na 0.06; K 15.5; Fe 45.5; S 38.6; Cl 0.05; Rb 0.7; Tl 0.02; and corresponds to ideal KFe 2 S 3 . Djerfisherite K 6 Na(Fe,Ni,Cu) 24 S 26 Cl often forms octahedral crys- tals (up to 100 lm) or subhedral grains (up to 80 lm) in shortite. It is enriched in Fe (53.4–53.9 wt%) and depleted in Ni and Cu (0.9–1.1 and <0.4 wt%, respectively). Only some grains show ele- vated Ni, Cu and Co (8.6, 2.2 and 1.0 wt%, respectively). The chloride-carbonate nodules can originate either due pro- longed fractionation of the kimberlite magma or from recrystal- lized evaporite fragments, trapped by ascending magmas. The appearance of nyerereite, rasvumite and djerfisherite unambigu- ously points to magmatic origin of the nodules. In many aspects these nodules are similar to the Oldoinyo Lengai natrocarbona- tites. Preservation of highly hydroscopic alkali carbonates in the 350 Ma Udachnaya-East kimberlite is enigmatic, but possible if the system remained closed since emplacement. As chlorides are dominant in all types of studied nodules, the presence of Cl- free rasvumite in some nodules and Cl-bearing djerfisherite in oth- ers requires further investigation. doi:10.1016/j.gca.2006.06.1067 Mineral inclusions in diamonds from chemically heterogeneous eclogite xenolith V.S. SHATSKY, A.S. STEPANOV, D.A. ZEDGENIZOV, A.L. RAGOZIN Institute of Geology and Mineralogy, Novosibirsk, Russia (stepanovas@uiggm.nsc.ru) The studied eclogite from Udachnaya kimberlite pipe (Yaku- tia), which was primarily composed of omphacitic clinopyroxene (65%) and pyrope-almandine garnet (35%). By composition of major matrix minerals this eclogite fall in between group A and group B eclogites (Taylor and Neal, 1989). Accessory minerals are diamond and sulfide (MSS). In the xenolith there are simulta- neous compositional variations of garnet and clinopyroxene. The content of CaO and FeO in garnets decrease with the increasing of Mg (Mg# 56.7–75.5). Jadeite component in clinopyroxene increase from 12% to 22% with the decreasing of Mg number (from 74% to 83%). The variation of diamond characteristics (size, morphology, nitrogen content and aggregation state, carbon isotope composition) reflects the diamond formation in two stages. Mineral inclusions have mostly been recovered from diamonds of first generation. Inclusions generally differ from matrix miner- als by chemistry. Clinopyroxene inclusions contain higher amount of Na 2 O (6.0–7.3 wt% in inclusions and 4–6.8 wt% in matrix), Al 2 O 3 (9.3–13.2 wt% and 5.8–10.4 wt%, respectively) and K 2 O (0.19–0.58 wt% and 0.1–0.17 wt%, respectively) and have lower Mg#. Garnets in inclusions have higher CaI content (5.6– 8.6 wt%) and lower MgO content (10.0–12.3 wt%) than garnets in matrix (3.2–4.5 wt% and 13.4–18.6 wt%, respectively). Some inclusions of garnet and clinopyroxene are relatively enriched in MREE. The estimates of temperature by garnet-clinopyroxene pair (Ellis and Green, 1979) from three individual diamonds give the average value around 1220 °C. The compositional differences of inclusions and matrix miner- als may be explained by the evolution of eclogites after diamond formation or by the diamond growth from fluid/melt, which were no in equilibria with the host rock. The evolution of composition of eclogite is possibly resulted either from partial melting or from metasomatism or from solid state diffusion of components. As the partial melting and metasomatism reasonably involve a signifi- cantly bigger volume than the studied sample is, we suggest the outflow/inflow of some components by diffusion in solid state in originally heterogeneous environments. Acknowledgments The work is supported by VMTK (Grant No. 1735) and SBRAS (Grant No. 137). References Ellis, D.J., Green, D.H., 1979. Contrib. Mineral. Petrol. 71, 13–22. Taylor, L.A., Neal, C.R., 1989. J. Geol. 97, 551–567. doi:10.1016/j.gca.2006.06.1068 A576 Goldschmidt Conference Abstracts 2006