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200 1 _aOrigin of John’s Stone: A quartzitic boulder from the site of the 1908 Tunguska (Siberia) explosion
_fE. Bonatti [et al.]
203 _aText
_celectronic
300 _aTitle screen
330 _aAn exotic meter-size quartzitic boulder known as John’s Stone was found by John Anfinogenov in 1972 buried in permafrost close to the epicenter of the 1908 Tunguska blast in a region of Siberia dominated by Permian–Triassic Siberian Trap basalts. The boulder is made almost entirely of well-cemented quartz grains, mostly around 100 µm in size; it contains zones with coarser or finer grain sizes. Rare zircon and rutile crystals are scattered within the quartz matrix. Quartz is often dissected by strain lamellae. The rock contains abundant scattered internal vugs rimmed by euhedral quartz crystals. We cannot exclude that John’s Stone is a fragment of a Permian granite-derived sandstone unit. However, based on structure, mineralogy and chemistry the quartzitic boulder may have originated due to silica deposition from hydrothermal solutions that had reacted with basaltic rocks. Anfinogenov et?al. (Anfinogenov, J. et?al. [2014]. Icarus 243, 139–147) interpreted features observed in the permafrost at the base of the boulder as indicating it impacted from above, suggesting the boulder may be a meteorite, possibly of martian origin, given the reported presence on Mars of silica-rich deposits. Triple oxygen isotope ratios determined on two samples of the quartzite reveal a terrestrial rather than a martian meteorites composition. Oxygen isotope data suggest also that the precipitation of SiO2 could have occurred in equilibrium with hydrothermal water (d18Ow ˜ -19.5‰) at the temperature of about 50 °C. The thermal event that generated the quartzite may be related either to the century-old Tunguska Event, or, more probably, to Permian–Triassic Siberian Traps magmatism, although an extraterrestrial origin cannot be completely ruled out.
333 _aРежим доступа: по договору с организацией-держателем ресурса
461 _tIcarus
_oScientific Journal
463 _tVol. 258
_v[P. 297-308]
_d2015
610 1 _aэлектронный ресурс
610 1 _aтруды учёных ТПУ
610 1 _aMeteorites
610 1 _aMars
610 1 _aMineralogy
610 1 _aCratering
701 1 _aBonatti
_bE.
_gEnrico
701 1 _aBreger
_bD.
_gDee
701 1 _aTommaso
_bD.R.
_gDi Rocco
701 1 _aFulvio
_bF.
_gFranchi
701 1 _aLuca
_bG.
_gGasperini
701 1 _aPolonia
_bA.
_gAlina
701 1 _aAnfinogenov
_bJ.
_gJohn
701 1 _aAnfinogenova
_bYa. J.
_cLinguist
_cLecturer of Tomsk Polytechnic University, Doctor of medical sciences
_f1970-
_gYana Jonovna
_2stltpush
_3(RuTPU)RU\TPU\pers\33592
712 0 2 _aНациональный исследовательский Томский политехнический университет (ТПУ)
_bФизико-технический институт (ФТИ)
_bКафедра иностранных языков физико-технического института (ИЯФТ)
_h6715
_2stltpush
_3(RuTPU)RU\TPU\col\18736
801 2 _aRU
_b63413507
_c20151012
_gRCR
856 4 _uhttp://dx.doi.org/10.1016/j.icarus.2015.06.018
942 _cCF