Dissolving Macrocrists of Olivine in a Kimberlite Melt at High P–T Parameters
Olivine is found in kimberlite in the form of two types of phenocrysts: olivine I in the form of relatively large grains of round or irregular shape and olivine II in the form of small (up to 0,5 rarely 1 mm) idiomorphic crystals, but having irregularly shaped cores. It is believed that type I olivine xenocrysts appear due to the disintegration of nodules of mantle rocks, and their specific morphology is results by the processes of dissolution and / or abrasion of grains in kimberlite (or even in protokimberlite) magma. The determination of the composition of the initial kimberlite magma and, ultimately, the concept of the genesis of the kimberlites themselves, depends on the solution of this question. It was previously experimentally established that among silicate minerals from mantle xenoliths, olivine is most stable when dissolved in kimberlite melt at high temperatures and pressures. However, the occurrence of a specific rounded form of olivine grains which were dissolved in a kimberlite melt was not experimentally confirmed yet. This report presents the first results of experiments on this topic. The experiments were carried out on a pressless multi-anvil high-pressure apparatus of the “split sphere” type (BARS). A series of four experiments was carried out at a pressure of 4 GPa, temperatures of 1300 °С and 1500 °С, with a duration of 1 and 2 hours. Kimberlite N-1 from Nyurbinskaya pipe (Yakutia, Russia) was used as a starting sample. Olivine grains were extracted from the nodules of spinel lherzolite from alkaline basaltoids of Mongolia. Following the hypothesis of the xenogenic nature of olivine phenocrysts, the composition of the protokimberlite magma should be enriched with iron in comparison with the composition of kimberlite. In addition, a substantially carbonatite composition of the protokimberlite magma is assumed. Therefore, Fe2O3 and CaCO3 are added to the kimberlite samples. The results of the experiments show that the olivine xenocrysts used are not in equilibrium with the N-1 molten kimberlite enriched with iron and calcium. On the contrary, the kimberlite melt is an aggressive medium capable of dissolving the xenocrysts of magnesian olivine. At the same time, their initially irregular shape is transformed into a rounded one, which is also characteristic for natural kimberlites. The large, rounded xenocrysts of kimberlite olivine are also often contains many cracks. In our experiments, this phenomenon probably occurred even at the stage of pressure increase due to the existing stress in the olivine crystals. After that, when the kimberlite powder was melted, the melt penetrated into these cracks and disintegrated the xenocrysts into separate fragments. A similar process may have occurred in natural objects under pressure gradient conditions during the rising of kimberlite magma. Thus, it was experimentally confirmed the possibility of the formation of rounded phenocrysts of olivine during their interaction with a carbonated melt.
Gryaznov Ivan Alexandrovich, Research Engineer, Sobolev Institute of Geology and Mineralogy SB RAS, 3, pr. Acad. Koptyug, Novosibirsk, 630090, Russian Federation, tel.: 8(383)306-64-03, e-mail: Gryaznov_9@mail.ru
Karpovich Zakhar Alekseevich, Research Engineer, Sobolev Institute of Geology and Mineralogy SB RAS, 3, pr. Acad. Koptyug, Novosibirsk, 630090, Russian Federation, tel.: 8(383)306-64-03, e-mail: email@example.com
Ishutin Ilya Andreevich, Research Engineer, Sobolev institute of Geology and Mineralogy SB RAS, 3, pr. Acad. Koptyug, Novosibirsk, 630090, Russian Federation, tel.: 8(383)306-64-03, e-mail: firstname.lastname@example.org
Zhimulev Egor Igorevich, Doctor of Sciences (Geology and Mineralogy), Senior Researcher, Sobolev Institute of Geology and Mineralogy SB RAS, 3, pr. Acad. Koptyug, Novosibirsk, 630090, Russian Federation, tel.: 8(383)306-64-03, e-mail: email@example.com
Gryaznov I.A., Karpovich Z.A., Ishutin I.A., Zhimulev E.I. Dissolving Macrocrists of Olivine in a Kimberlite Melt at High P–T Parameters. The Bulletin of Irkutsk State University. Series Earth Sciences, 2019, vol. 28, pp. 34-47. https://doi.org/10.26516/2073-3402.2019.28.34 (in Russian)
Kutolin V.A., Agafonov L.V., Chepurov A.I. Otnositelnay ustoychivost olivina, piroksenov i granata v bazaltovoy magme i sostav verhney mantii [Relative stability of olivine, pyroxenes and garnet in basaltic magma and upper mantle composition]. Proc. USSR Academy of Sciences, 1976, vol. 231, no. 5, pp. 1218-1221. (in Russian)
Sobolev N.V. Glubinie vklyuchenia v kimberlitah i problema sostava verhney mantii [Deep inclusions in kimberlites and the problem of upper mantle composition]. Novosibirsk, Nauka Publ., 1974, 264 p. (in Russian)
Sobolev N.V. Paragenezisy almaza I problema glubinogo mineraloobrazovania [Parageneses of diamond and the problem of deep mineral formation]. Zap. WMO, 1983, H SH, vol. 4, pp. 389-397. (in Russian)
Tonkov E.Y., Fazovie diagrammi elementov pri visokom davlenii [Phase diagrams of elements at high pressure]. Moscow, Science Publ., 1979, 192 p. (in Russian)
Brett R.C., Russelle J.R., Moss S. Origin of olivine in kimberlite: phenocryst or impostor? Lithos, 2009, vol. 112S, pp. 201-212. https://doi.org/10.1016/j.lithos.2009.04.030.
Chang F. Petrography, geochemistry, age, and petrogenesis of ultramafic from Sarfartoq, central west Greenland. Thesis for the degree of bachelor of science, The University of British Columbia, April, 2000.
Chepurov A.A., Pokhilenko N.P. Experimental estimation of the Kimberlite melt viscosity. Doklady Earth Sciences, 2015, vol. 462, no. 2, pp. 592-595. https://doi.org/10.1134/s1028334x15060033.
Gurney J.J., Helmstaedt H.H., Richardson S.H., Shirey S. B. Diamond through Time. Soc. of Econ. Geolog., inc. Economic Geology, 2010, vol. 105, pp. 689-712. https://doi.org/10.2113/gsecongeo.105.3.689.
Chepurov A.I., Sonin V.M., Tychkov N.S., Kulakov I.Y. Experimental estimate of the actual infiltration (migration) of volatilities (H2O + CO2) in rocks of the mantle wedge. Doklady Earth Sciences, 2015, vol. 464, no. 1, pp. 932-935. https://doi.org/10.1134/S1028334X15090032.
Chepurov A.I., Zhimulev E.I., Sonin V.M., Chepurov A.A., Tomilenko A.A., Pokhilenko N.P. Experimental Estimation of the Rate of Gravitation Fractionating of Xenocrysts in Kimberlite Magma at High P-T Parameters. Doklady Earth Sciences, 2011, vol. 440, no. 2, pp. 1427-1430. https://doi.org/10.1134/S1028334X11100138
Sobolev A.V., Sobolev N.V., Smith C.B., Dubessy J. Fluid and melt compositions in lamproites and kimberlites based on the study of inclusions in olivine. GSA Special Publ. N 14 Kimberlites and Related Rocks, 1989, vol. 1, pp. 220-240.
Kennedy C.S., Kennedy G.C. The equilibrium boundary between graphite and diamond. J. Geophys. Res., 1976, vol. 81, no. 14, pp. 2467-2470.
Russell J.K., Porritt L.A., Lavallee Y., Dingwell D.B. Kimberlite ascent by assimilation – fuelled buoyancy. Nature, 2012, vol. 481, pp. 352-356. https://doi.org/10.1038/nature10740
Kopylova M.G., Matveev S., Raudsepp M. Searching for parental kimberlite melt. Geochim. Cosmochim. Acta, 2007, vol. 71, pp. 3616-3629. https://doi.org/10.1016/j.gca.2007.05.009
Mitchell R.H. Petrology of hypabyssal kimberlites: relevance to primary magma compositions. J. Volcanol. Geotherm. Res., 2008, vol. 174, pp. 1-8. https://doi.org/10.1016/j.jvolgeores.2007.12.024
Jones T.J., Russell J.K., Porritt L.A., Brown R.J. Morphology and surface features of olivine in kimberlite: implication for ascent processes. Solid Earth, 2014, vol. 5, pp. 313-326. https://doi.org/10.5194/se-5-313-2014.
Arndt N.T., Guitreau M., Boullie A. M., le Roex A., Tommasi A., Cordier P., Sobolev A. Olivine and the origin of kimberlite. J. Petrol, 2010, vol. 51, pp. 573-602. https://doi.org/10.1093/petrology/egp080.
Kamenetsky V.S., Kamenetsky M.B., Sobolev A.V., Golovin A.V., Demouchy S., Faure K., Sharygin V.V., Kuzmin D.V. Olivine in the Udachnaya-East kimberlite (Yakutia, Russia): types compositions and origins. J. Petrol, 2008, vol. 49, no. 4, pp. 823-839. https://doi.org/10.1093/petrology/egm033.
Sobolev N.V., Sobolev A.V., Tomilenko A.A., Kovjazin S.V., Batanova V.G., Kuzmin D.V. Paragenesis and complex zoning of olivine macrocrysts from unaltered kimberlite of the Udachnaya-East pipe, Yakutia: relationship with the kimberlite formation conditions and evolution. Russian Geology and Geophysics, 2015, vol. 56, no. 1-2, pp. 260-279. https://doi.org/10.1016/j.rgg.2015.01.019.
Patterson M., Francis D., McCanless T. Kimberlites: Magmas or mixtures? Lithos, 2009, vol. 112S, p. 191-200. https://doi.org/10.1016/j.lithos.2009.06.004.
Skinner E.M.W., Clement C.R. Mineralogical classification of southern African kimberlites. Boyd FR, Meyer HOA (eds.) The Mantle Sample. 2nd International Kimberlte Conference, 1979, American Geophysical Union. Washington. D. C., pp. 129-139.
Chepurov A.I., Tomilenko A.A., Zhimulev E.I., Sonin V.M., Chepurov A.A., Kovjazin S.V., Timina T.Y., Surkov N.V. The conservation of an aqueous fluid in inclusions in minerals and their interstices at high pressures and temperatures during the decomposition of antigorite. Russian Geology and Geophysics, 2012, vol. 53, no. 3, pр. 234-246. https://doi.org/10.1016/j.rgg.2012.02.002.
Sparks R.S.J., Brooker R.A., Field M., Kavanagh J., Schumacher J.C., Walter M.J., White J.The nature of erupting kimberlite melts. Lithos, 2009, vol. 112S, pp. 429-438. https://doi.org/10.1016/j.lithos.2009.05.032.
Chepurov A.I., Zhimulev E.I., Agafonov L.V., Sonin V.M., Chepurov A.A., Tomilenko A.A. The stability of ortho- and clinopyroxenes, olivine, and garnet in kimberlitic magma. Russian Geology and Geophysics, 2013, vol. 54, no. 4, pp. 406-415. https://doi.org/10.1016/j.rgg.2013.03.004.