Abstract
Garnet-bearing mantle xenoliths have been recovered from Quaternary alkali basalts, both within and peripheral to the Hangay dome of central Mongolia. Microfabric analysis and thermobaromery, combining empirical thermobarometers and the self-consistent dataset of THERMOCALC, indicate that garnet websterites from the Shavaryn-Tsaram volcanic centre at the dome core were formed in the spinel-lherzolite upper mantle at pressures of 17–18 kbars and temperatures of 1,070–1,090°C, whereas garnet lherzolites were derived from greater depths (18–20 kbars). Garnet lherzolites from the Baga Togo Uul vents near the dome edge were formed at 18–22 kbars under significantly cooler conditions (960–1,000°C). These xenoliths reveal reaction coronas of (1) orthopyroxene, clinopyroxene, plagioclase and spinel mantling garnets; (2) spongy rims of olivine replacing orthopyroxene and (3) low-Na, low-Al clinopyroxene replacing primary clinopyroxene. Trace-element abundances indicate that clinopyroxene from these coronas is in chemical equilibrium with the host magma. The thermobarometric and textural data suggest that lherzolite xenoliths from both sites were derived from depths of 60–70 km and entrained in magma at 1,200–1,300°C. The average rate of ascent, as determined by olivine zoning, lies in the range 0.2–0.3 m s−1. The contrast in thermal profiles of the upper mantle between the two sites is consistent with a mantle plume beneath the Hangay dome with elevated thermal conditions beneath the core of the dome being comparable to estimates of the Pleistocene geotherm beneath the Baikal rift.
Similar content being viewed by others
References
Agafonov LV, Pinus GV, Lesnov FP, Lavrent’ev YuG, Usova LS (1975) Abyssal inclusions in basaltoids from the Shavaryn-Saram pipe Mongolia. Doll Akad Nauk SSSR 225:1163–1165 (in Russian)
Badarch G, Cunningham WD, Windley BF (2002) A new terrane subdivision for Mongolia: implications for the Phanerozoic crustal growth of Central Asia. J Asian Earth Sci 21:87–110
Barruol G, Deschamps A, Déverchère J, Mordvinova VV, Ulziibat M, Perrot J, Artemiev AA, Dugarmaa T, Bokelmann GHR (2008) Upper mantle flow beneath and around the Hangay dome, Central Mongolia. Earth Planet Sci Lett 274:221–233
Barry TL, Saunders AD, Kempton PD, Windley BF, Pringle MS, Dorjnamjaa D, Saandar S (2003) Petrogenesis of Cenozoic basalts from Mongolia: evidence for the role of asthenospheric versus metasomatized lithospheric mantle sources. J Petrol 44:55–91
Brearley M, Scarfe CM (1986) Dissolution rates of upper mantle minerals in an alkali basalt melt at high pressure: an experimental study and implications for ultramafic xenolith survival. J Petrol 27:1157–1182
Brey GP, Köhler T (1990) Geothermobarometry in four-phase lherzolites 2. New thermobarometers and practical assessment of existing thermobarometers. J Petrol 31:1353–1378
Chuvashova IS, Rasskazov SV, Yasnygina TA (2007) Holocene volcanism in Central Mongolia and NE China: asynchronous decompressional and fluid melting of the mantle. J Volc Seismol 1:372–396
Cull JP, O’Reilly SY, Griffin WL (1991) Xenolith geotherms and crustal models in Eastern Australia. Tectonophysics 192:359–366
Cunningham WD (2001) Active intracontinental transpressional mountain building in the Mongolian Altai: defining a new class of orogen. Tectonophysics 331:389–411
Gaetani GA, Watson EB (2002) Modeling the major-element evolution of olivine-hosted melt inclusions. Chem Geol 183:25–41
Glaser SM, Foley SF, Günther D (1999) Trace element compositions of minerals in garnet and spinel peridotite xenoliths from the Vitim volcanic field, Transbaikalia, eastern Siberia. Lithos 48:263–285
Griffin WL, Powell WJ, Pearson NJ, O’Reilly SY (2008) GLITTER: data reduction software for laser ablation ICP-MS. In: Sylvester P (ed) Laser ablation-ICP-MS in the earth sciences. Mineral Assoc Canada Short Course Ser 40, Appendix 2, pp 204–207
Günther D, Heinrich CA (1999) Enhanced sensitivity in laser ablation-ICP mass spectrometry using helium-argon mixtures as aerosol carrier. J Anal At Spectrom 14:1363–1368
Harris N (2009) Of all places, why here? Geoscientist 19:21–23
Hart SR, Dunn T (1993) Experimental clionopyroxene/melt partitioning of 24 trace elements. Contrib Mineral Petrol 113:1–8
Hauri EH, Wagner TP, Grove TL (1994) Experimental and natural partitioning of Th, U, Pb and other trace elements between garnet, clinopyroxene and basaltic melts. Chem Geol 117:149–166
Holland TJB, Powell R (1998) An internally consistent dataset for phases of petrological interest. J Metamorphic Geol 16:309–343
Holland TJB, Powell R (2003) Activity–composition relations for phases in petrological calculations: an asymmetric multicomponent formulation. Contrib Mineral Petrol 145:492–501
Hunt AC, Parkinson IJ, Rogers N, Harris N, Barry T, Uondon M (2008) Deciphering the sources and melt generation mechanisms of Cenozoic intraplate volcanism in central Mongolia. Geochim Cosmochim Acta 72:A403 (abstract)
Ionov D (2002) Mantle structure and rifting processes in the Baikal–Mongolia region: geophysical data and evidence from xenoliths in volcanic rocks. Tectonophysics 351:41–60
Ionov DA (2007) Compositional variations and heterogeneity in fertile lithospheric mantle: peridotite xenoliths in basalts from Tariat, Mongolia. Contrib Mineral Petrol 154:455–477
Ionov DA, Hoefs J, Wedepohl KH, Wiechert U (1992) Content and isotopic composition of sulphur in ultramafic xenoliths from central Asia. Earth Planet Sci Lett 111:269–286
Ionov DA, O’Reilly SY, Griffin WL (1998) A geotherm and lithospheric cross-section for central Mongolia. In: Flower MJF, Chung S-L, Lo C-H, Lee TY (eds) Mantle dynamics and plate interactions in East Asia. Amer Geophys Union Geodynamics Ser 27, Washington, DC, pp 127–153
Johnson JS, Gibson SA, Thompson RN, Nowell GM (2005) Volcanism in the victim volcanic field, Siberia: geochemical evidence for a mantle plume beneath the Baikal rift zone. J Petrol 46:1309–1344
Jurewicz AJG, Watson EB (1988) Cations in olivine, Part 2. Diffusion in olivine xenocrysts, with applications to petrology and mineral physics. Contrib Mineral Petrol 99:186–201
Khutorskoy MD, Yarmoluk VV (1989) Heat flow, structure and evolution of the lithosphere of Mongolia. Tectonophysics 164:315–322
Kopylova MG, O’Reilly SY, Genshaft YS (1995) Thermal state of the lithosphere beneath Central Mongolia: evidence from deep-seated xenoliths from the Shavaryn-Saram volcanic centre in the Tariat depression, Hangay, Mongolia. Lithos 36:243–255
Lysak SV, Dorofeeva RP (1997) Geothermal regime of the upper horizons of the earth’s crust in the southern regions of Eastern Siberia. Trans Dokl Russ Acad Sci Earth Sci Sect 352:133–137
McKenzie D, Bickle MJ (1988) The volume and composition of melt generated by extension of the lithosphere. J Petrol 29:625–679
Nickel KG, Green DH (1985) Empirical geothermobarometry for garnet peridotites and implications for the nature of the lithosphere, kimberlites and diamonds. Earth Planet Sci Lett 73:158–170
Nimis P, Taylor WR (2000) Single clinopyroxene thermobarometry for garnet peridotites. Part I. Calibration and testing of a Cr-in-Cpx barometer and an enstatite-in-Cpx thermometer. Contrib Mineral Petrol 139:541–554
O’Reilly SY, Griffin WL (1985) A xenolith-derived geotherm for southeastern Australia and its geophysical implications. Tectonophysics 111:41–63
Parkinson IJ, Hammond SJ, James RH, Rogers NW (2007) High-temperature lithium isotope fractionation: Insights from lithium isotope diffusion in magmatic systems. Earth Planet Sci Lett 257:609–621
Pesliera AH, Luhr JF (2006) Hydrogen loss from olivines in mantle xenoliths from Simcoe (USA) and Mexico: Mafic alkalic magma ascent rates and water budget of the sub-continental lithosphere. Earth Planet Sci Lett 242:302–319
Petit C, Koulakov I, Deverchère J (1998) Velocity structure around the Baikal rift zone from teleseismic and local earthquake travel times and geodynamic implications. Tectonophysics 296:125–144
Potts PJ, Thorpe OW, Watson JS (1981) Determination of the rare-earth element abundances in 29 international rock standards by instrumental neutron activation analysis: A critical appraisal of calibration errors. Chem Geol 34:331–352
Pouchou JL, Pichoir F (1985) “PAP” procedure for improved quantitative analysis. Microbeam Anal 20:104–105
Press SG, Witt HA, Seck DA, Ionov DA, Kovalenko VI (1986) Spinel peridotite xenoliths from the Tariat depression, Mongolia. 1: Major element chemistry and mineralogy of a primitive mantle xenolith suite. Geochim Cosmochim Acta 50:2587–2599
Schlupp A (1996) Néotectonique de la Mongolie occidentale analysée à partir de données de terrain, sismologiques et satellitaires. PhD thesis, Université Louis Pasteur de Strasbourg
Sobolev NV, Nixon PH (1987) Xenoliths from the USSR and Mongolia: a selective and brief review. In: Nixon PH (ed) Mantle xenoliths. Wiley, New York, pp 159–166
Stosch HG, Ionov DA, Puchtel IS, Galer SJG, Sharpouri A (1995) Lower crustal xenoliths from Mongolia and their bearing on the nature of the deep crust beneath central Asia. Lithos 36:227–242
Sun SS, McDonough WF (1989) Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders AD, Norry MJ (eds) Magmatism in the Ocean Basins. Special Publications, Geological Society of London 42, pp 313–345
Van Orman JA, Grove TL, Shimizu N (2001) Rare earth element diffusion in diopside: influence of temperature, pressure and ionic radius, and an elastic model for diffusion in silicates. Contrib Mineral Petrol 141:687–703
Van Orman JA, Grove TL, Shimizu N, Layne GD (2002) Rare earth element diffusion in a natural pyrope single crystal at 2.8 GPa. Contrib Mineral Petrol 142:416–424
Walker RT, Molor E, Fox M, Bayasgalan A (2008) Active tectonics of an apparently aseismic region: distributed active strike-slip faulting in the Hangay Mountains of central Mongolia. Geophys J Int 174:1121–1137
Wells PRA (1977) Pyroxene thermometry in simple and complex systems. Contrib Mineral Petrol 62:129–139
Williams HM, Turner SP, Pearce JA, Kelley SP, Harris NBW (2004) Nature of the source regions for post-collisional, potassic magmatism in Southern and Northern Tibet from geochemical variations and inverse trace element modelling. J Petrol 45:555–607
Windley BF, Allen MB (1993) Mongolian plateau: evidence for a late Cenozoic mantle plume under central Asia. Geol 21:295–298
Windley BF, Alexeiev D, Xiao W, Kröner A, Badarch G (2007) Tectonic models for accretion of the Central Asian Orogenic Belt. J Geol Soc 164:31–47
Acknowledgments
Fieldwork was supported by the Natural Environment Research Council (Alison Hunt) and the W G Fearnsides Fund administered by the Geological Society (Nigel Harris). We thank reviewers Dmitri Ionov and Bill Griffin for their insightful comments on the manuscript.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by C. Ballhaus.
Rights and permissions
About this article
Cite this article
Harris, N., Hunt, A., Parkinson, I. et al. Tectonic implications of garnet-bearing mantle xenoliths exhumed by Quaternary magmatism in the Hangay dome, central Mongolia. Contrib Mineral Petrol 160, 67–81 (2010). https://doi.org/10.1007/s00410-009-0466-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00410-009-0466-6