Detailed mineralogical-geochemical study of a large spinel Lherzolite xenolith in alkali basalt of Shavaryn Tsaram paleovolcano, Mongolia

Lesnov, Felix P.; Palesskii, S. V.; Николаева, И. В.; Kozmenko, O. A.; Kuchkin, A. M.; Korolyuk, V. N.

doi:10.1134/s0016702909010029

Cited by 4 publications

(4 citation statements)

References 9 publications

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“…The data obtained in the present research revealed an active influence of the fluid phase during megacrysts crystallisation and further evolution. It is evident that: (1) the pyroclastic and scoria prevail over degassed lavas in the Shavaryn Tsaram (Ionov et al, 1994;Lesnov et al, 2009); (2) a visible isochemical character of alterations (i.e., with significant changes in the chemical composition of initial megacrysts), (3) the presence of water-containing phases such as amphibole, glass and mica. Furthermore, megacryst enclaves, as well as ultrabasic xenoliths, are in an apparent disequilibrium with the host basalts, since almost all of them have rather thick quenching coats and rounded shapes.…”

Section: Discussionmentioning

confidence: 99%

“…The Shavaryn Tsaram Paleovolcano is an eruptive centre on the right bank of the Naryn-Gichingine River (48°0 2'55.3''N; 100°09'43.9''E), which is extremely saturated with megacrysts and ultrabasic xenoliths. This structure has been repeatedly studied over the years (Agafonov et al, 1975;Kepezhinskas, 1979;Genshaft and Saltykovsky, 1990;Ionov, 2007;Lesnov et al, 2009;Vysotskii et al, 2011;Aseeva et al, 2014).…”

Section: Geological Settingmentioning

confidence: 99%

“…The neck of the volcano as well as the adjacent lava flows of the Hangay plateau are composed mostly of porous and porphyritic basalts (Lesnov et al, 2009). Chemically, the lavas are close to the nepheline-leucite basanites and tephrites (Ionov et al, 1994;Ionov, 2007;Lesnov et al, 2009). Both basalts and pyroclastic material are rich in megacrysts and deep-seated xenolith inclusions.…”

Section: Geological Settingmentioning

confidence: 99%

“…1). This unusual cone was the object of study for nearly fifty years (Agafonov et al, 1975;Kepezhinskas, 1979;Genshaft and Saltykovsky, 1990;Ionov, 2007;Lesnov et al, 2009;Vysotskii et al, 2011;Aseeva et al, 2014). The occurrences like this are very uncommon all over the world (Lesnov et al, 2009;Jankovics et al, 2013), and megacryst inclusions are considered by many to be highly informative petrological objects as they reflect the composition of the Earth's depth substance captured by basaltic melts and delivered to the surface.…”

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confidence: 99%

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Melt Pockets in Garnet Megacrysts from Cenozoic Alkali Basalts of the Shavaryn Tsaram Vicinity, Mongolia

Aseeva

Avchenko

Карабцов

et al. 2022

Acta Geologica Sinica (Eng)

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Garnet megacryst with a multiphase inclusion from intraplate alkali basalts of the Shavaryn Tsaram (Tariat, Mongolia) was the object of the study. This unusual aggregate consists of porous glass, Ti-rich biotite, orthopyroxene, spinel, clinopyroxene, olivine, and ilmenite. WinTWQ 2.32 thermodynamic simulation of this system revealed a few intervals of equilibrium. Pressure and temperature adjustment reflected in the paragenetic minerals of the melt pocket. The capture of already crystallised garnet megacryst was at P = 0.8-1 GPa and T = 1120-1160°C. Mineral crystallisation inside the melt pocket, accompanied by external inputs, occurred at P = 0.75-0.95 GPa; T = 790-1120°C. Symplectite assemblage formed in the garnet megacryst due to decomposition at (P = 0.55-0.7 GPa; T = 850-930°C). The study of the oxygen isotope content in primary garnet and biotite of the melt pocket showed that the δ 18 O VSMOW values are the same and correspond to that of typical mantle xenoliths. However, the chemical and microcomponent composition of the melt pocket minerals reveals a material that differs from basalts and peridotites. Thus, it has been revealed that the multiphase inclusion in the garnet megacryst formed not only on account of the garnet's substance, but also due to the entrapped material of the Earth's interior.

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Section: Discussionmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

mentioning

confidence: 99%

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Melt Pockets in Garnet Megacrysts from Cenozoic Alkali Basalts of the Shavaryn Tsaram Vicinity, Mongolia

Aseeva

Avchenko

Карабцов

et al. 2022

Acta Geologica Sinica (Eng)

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Residence of incompatible trace elements in a large spinel lherzolite xenolith from alkali basalt of Shavaryn Tsaram-1 paleovolcano (western Mongolia)

Lesnov

Kozmenko

Николаева

et al. 2009

Russian Geology and Geophysics

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We have studied a large (12 × 22 × 30 cm) spinel lherzolite xenolith with undeformed margins in alkali basalt (basanite) from the eroded crater of Late Cenozoic Shavaryn Tsaram-1 volcano in western Mongolia. The xenolith was sampled along its median transversal profile, at every 15–20 mm for bulk chemistry of lherzolite and basalt (ICP-MS) and at 4–10 mm for the chemistry of olivine, orthopyroxene, clinopyroxene, and Cr-spinel minerals, and of material filling cracks (LA ICP-MS). Incompatible elements (especially, LREE) are distributed unevenly over the xenolith, both in lherzolite and in its constituent minerals, as well as in crack-filling material, with abnormal LREE enrichment in some specimens. Judging by the measured trace-element spectra compared with the model patterns, incompatible elements reside in different amounts as interstitial impurity in cracks inside and between mineral grains in lherzolite, also being a substitutional impurity in the lherzolite constituent minerals. Experimental acid leaching of specimens from sites of high crack density showed (La/Yb)n ratios in the crack fill to be much higher than in the basalt host and more so in bulk lherzolite (180 against 33 and 1.5–3.6, respectively). The proportional contents of P and Ca in the leaching solution, especially in that from the xenolith’s center mark the presence of an apatite microphase, which can be a LREE repository. The observed patterns of LREE and other incompatible elements in the xenolith and in the host alkali basalt fit a model implying that mobile elements residing as interstitial impurity came with fluids which were released from rising basaltic magma and percolated into the xenolith along cracks.

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Rare earth elements in hypabyssal and subvolcanic rocks with high in magnesium composition

2010

Rare Earth Elements in Ultramafic and Mafic Rocks and Their Minerals

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Detailed mineralogical-geochemical study of a large spinel Lherzolite xenolith in alkali basalt of Shavaryn Tsaram paleovolcano, Mongolia

Cited by 4 publications

References 9 publications

Melt Pockets in Garnet Megacrysts from Cenozoic Alkali Basalts of the Shavaryn Tsaram Vicinity, Mongolia

Melt Pockets in Garnet Megacrysts from Cenozoic Alkali Basalts of the Shavaryn Tsaram Vicinity, Mongolia

Residence of incompatible trace elements in a large spinel lherzolite xenolith from alkali basalt of Shavaryn Tsaram-1 paleovolcano (western Mongolia)

Rare earth elements in hypabyssal and subvolcanic rocks with high in magnesium composition

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