U-Pb age of zircon and the history of impact transformations of the Chelyabinsk meteorite

Abstract

The fall of the Chelyabinsk meteorite LL5 (Febru ary 15, 2013), the largest in the past century, caused a wide resonance in the scientific world and initiated the complex investigation of meteorite material. The results of such study have been reported in many pub lications ([1, 2] and others). In discussing the results of the isotope-geochemical study of this meteorite, we should primarily mention the local U-Pb dating of apatite in situ, which was performed independently by X. H. Li in Beijing, China (4452 ± 21 Ma [2]) and by K. Terada in Hiroshima, Japan (4433 ± 110 Ma [3]). Both ages are consistent within the error and, in opin ion of the authors [2, 3], correspond to the largest impact event which was registered by apatite in other meteorites as well (e.g., Novato L6 [4]) and highly likely this impact event was connected with the forma tion of the Moon. The older age (4538 ± 2 Ma) obtained by A. Bouvier [5] who used the isochron method for leached meteorite glass is correlated by the author with the impact event, rather than with cooling of the parental body of the meteorite after its forma tion. Based on the results of the study of rock forming minerals (olivine, orthopyroxene, and troilite) of the Chelyabinsk meteorite, the Sm-Nd isochron with an age of 3733 ± 110 Ma was plotted [6]. This is the age of an impact event, which resulted in melting of meteor ite material and re equilibration of the Sm-Nd iso tope system. Independent dating of the meteorite by the Sm-Nd method at the Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sci ences, was not performed for monomineral samples and did not provide a precise isochronous depen dence. A linear trend ("geochron") corresponding to an age of ~290 Ma was obtained [1]. The age of frag mentation of the parental body of the Chelyabinsk meteorite (the age of exposure) was estimated by the concentration of cosmogenic nuclides as ~1.2 Ma [7].One zircon grain (no. 1 in Tables 1 and 2) was found at the laboratory of the Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, during extraction of monofractions of rock forming minerals for Sm-Nd dating from samples with a total weight of 20 g by a methodology which excludes a laboratory contamination [6]. With account for the importance of the find, zircon extraction was repeated from the sample with a weight of ~70 g at the laboratory of the ZAO "NATI" by the "ppm mineral ogy" technology [8] (www.natires.com). This technol ogy was primarily worked out for extraction and study of heavy ore minerals, especially gold and PGE bear ing phases, at a low (<1 ppm) concentration of these phases in rock. Later this technology was adapted for extraction of zircon, apatite, and monazite. Distinct groups of heavy minerals` concentrates with a big range of densities were obtained and studied and this approach allows to achieve required mineralogical sensitivity. The process of gravitational fractionation was carried out on a hydroseparator designed in the ZAO "NATI." To prevent pollutio...

The Chelyabinsk meteorite: Thermal history and variable shock effects recorded by the 40Ar‐39Ar system

“…; Skublov et al. ). However, this interpretation may be incorrect owing to an incomplete degree of isotopic reset.…”

“…; Skublov et al. ), creating the impression of a strongly heterogeneous material that experienced a large variety of impact events (Lindsay et al. ; Righter et al.…”

Geochemical characteristics of zircons in the Ashizuri A‐type granitoids: An additional granite topology tool for detrital zircon studies

“…Color regions are from Belousova et al (). This diagram includes data from H adean detrital zircons (Crowley, Myers, Sylvester, & Cox, ; Hoskin & Black, ; Maas, Kinny, Williams, Froude, & Compston, ; Peck, Valley, Wilde, & Graham, ; Wilde, Valley, Peck, & Graham, ), zircons separated from terrestrial igneous rocks (Ballard et al, ; Belousova et al, ; Breiter et al, ; Griffin et al, ; Pankhurst et al, ; Suzuki et al, ; Wang et al, ), zircons in meteorite (Skublov et al, ). See Table S1 for the data of OD3 and MES…”

“…HED meteorite, and ordinary chondrite; Bonin, 2012;Bonin, Bébien, & Masson, 2002;Terada & Bischoff, 2009;Warren, Taylor, Keil, Shirley, & Wasson, 1983) and their geochemical similarities to Atype granites raise the possibility that A-type granitic rocks existed in the Hadean Earth or on other planets (Bonin, 2007 (Ballard et al, 2002;Belousova et al, 2006;Breiter et al, 2014;Griffin et al, 2002;Pankhurst et al, 2013;Suzuki et al, 2014;Wang et al, 2012), zircons in meteorite (Skublov et al, 2015). See Table S1 for the data of OD3 and MES Among the four types of granites, the A-type granites are suggested to have a tectonically different origin than the other three granite types; I-, S-, and M-type granites are basically related to volcanism at a subduction zone, whereas A-type granites are anorogenic in origin.…”

“…Therefore, this kind of information could be useful for granite petrogenetic studies. Skublov et al (2015) report trace elements data in two zircons from the LL5 ordinary chondrite Chelyabinsk. Both zircon grains are characterized by high Nb contents and high Nb/Sr ratios, and one grain exhibits a strong negative Eu anomaly (white squares in Figure 9a).…”