Grain described below was polished twice, first very lightly just to expose the grain surface for initial SEM examination. A second polish subsequently was carried out to expose more of the grain for additional detailed study. The EDS analyses of matrix olivines were collected using this system, to take advantage of the high spatial resolution imaging and digital beam location for analysis of such small grains. Natural and synthetic minerals were used both for calibration and as running standards to monitor data accuracy.
For further details regarding standards etc. Instrumental and intrinsic mass fractionation in both 25 Mg and 26 Mg were calculated using a linear law, and the data are reported in standard delta notation: 1. The sample was pretreated in acid to dissolve any carbonates, then rinsed thoroughly and dried. Ages are reported as 14 C years before present BP , where present is defined by convention as Backscattered electron images of the blue variant of the host clay are given in Fig.
The grains primarily are lithic clasts, a variety of which are present, including minor amounts of very fresh rhyolitic ash Fig. However, the dominant lithology in the blue variant is serpentinite Fig. The green and tan varieties of the clay are quite different in composition; they contain mainly shale clasts and mineral grains, rather than serpentinite. The metal is concentrated in the core of the grain Fig.
The diopside forms very thin rims around spinel, whereas the hedenbergite occurs as larger blocky grains. The principal differences are an overall finer grain size and much thinner diopside rims around spinel in the Khatyrka grain. The interior of the MSNF sample is a dense, achondritic intergrowth of metal with forsteritic olivine and diopside.
The meteorite grains that were recovered from the expedition are dark gray in incident light with diverse silicate and metallic fragments visible Fig. No fusion crust is preserved on the samples examined thus far. Detailed SEM examination of polished surfaces of two of the grains labeled herein 5 and reveals clearly the chondritic character Fig. Both consist Fig.
All of the chondrules in our samples are of the type IA porphyritic olivine variety, although, given the small size of the meteorite fragments and the limited number of chondrules, this sampling probably is not representative of the original meteorite. The largest chondrule we observed is just under one mm in maximum size Fig.
Note that this ferroan overgrowth extends along internal crystalline fractures Fig. Interstitial to the olivine is primary enstatite Figs. The matrix texture Fig. The matrix is highly porous and is nearly identical to that observed in CV3 chondrites, such as Allende. Magnetite has not been found, although with such small meteorite fragments, we cannot rule out the possibility of nonrepresentative sampling. Metal and pentlandite occur together with calcium phosphate probably whitlockite in distinctive rounded in some cases concentric masses Fig. The sulfide and phosphate assemblage encloses irregular particles of metal, suggesting secondary replacement of the metal.
The interior Fig.
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Finally, grain Fig. This metal grain was the sample used for magnesium isotopic analysis see below. Calcium and aluminum decrease with increasing iron, whereas manganese correlates directly with iron. Similar minor element patterns are observed in chondrule olivines from the most unequilibrated chondrites, where they are interpreted as the result of primary igneous crystallization see review by Brearley and Jones The calcium and aluminum contents of the core olivine might seem rather high approximately 0.
The fayalitic olivine rims, and also the matrix olivine, are Fo 50—56 in composition Fig. The composition range Fo 50—56 is typical of ferroan olivine compositions in CV3 chondrite matrices e. This compositional range is distinct from that observed in unequilibrated ordinary chondrites e.
Pyroxene in the chondrules is enstatite Wo 1 En 98 Fs 1 ; it shows no discernible compositional zoning of any kind. This gives the structural formula as Al 63 Cu 24 Fe 13 , which is that of icosahedrite. EDS analyses of the grains present in the polished section of 5 see Fig. Oxygen isotopic compositions are plotted in Fig. Forsteritic and ferroan olivine both plot on the carbonaceous chondrite anhydrous mineral CCAM line, below the terrestrial fractionation line. This represents the minimum age for the arrival of the meteorite on Earth.
Thus, it is necessary to establish here that the metal is indeed an integral part of the meteorite.
Moreover, the reader may be skeptical that any alloy containing metallic aluminum can even be natural, much less extraterrestrial. We address these questions here. There are complications, however. One is the fact that the recovered grains are so diverse in character. Grains 5 and are fragments of an oxidized CV3 chondrite. A second complication is the way the metal occurs in the chondritic grains 5, , , In all four cases, the original grains prior to making polished sections had metal particles firmly attached to their exterior surfaces Fig.
But in no cases did the polished sections reveal a metal particle enclosed within meteorite matrix. Grain had a tiny cupalite grain enclosed within a chondrule Figs. The section of grain 5 Fig. Also disconcerting is that these same grains are all separated from the meteorite fragment by several micrometers of epoxy, even though they were firmly attached prior to sectioning. The reason for this gap, thermally induced differential movement during the epoxy curing process, also suggests a possible explanation for the occurrence of the metal particles on outer surfaces.
We think that over time within the original clay layer, repeated expansion and contraction of the metal particles relative to the meteoric silicates led to creation of internal fractures. Breakage along these fractures naturally meant that the metal ended up being sited on the surfaces of those breaks. We recognize that this idea is somewhat ad hoc, and we intend to continue to search for more definitive evidence.
This is beyond the scope of the current manuscript, however. We have established that the metal is extraterrestrial in origin, and it is associated not just with a meteorite, but in some cases with CAI fragments. Therefore, it was natural to question whether the metal might actually be an unusual primitive nebula product. It was for this reason that we searched for, but did not find, evidence of extinct 26 Al.
An equally perplexing mystery that we are actively investigating is the association of aluminum with copper, two metals with profoundly differing cosmochemical properties. Apart from their unusual metal, Khatyrka grains such as 5, , and are primarily CV3 ox chondrites. As stated earlier, all specimens are in the form of thick polished sections, so none of the relevant optical properties could be determined.
The individual fragments show few signs of terrestrial weathering rare hematite, but not present in the samples described herein , although they occur in a sedimentary deposit. Based strictly on the scale proposed by Wlotzka , Khatyrka would have a weathering grade of W0, because there is no iron oxide around the metal grains in any of the fragments described herein. The fact that the CuAl alloy grains are also unweathered supports a W0 grade. We emphasize, however, that such small grains are unlikely to be representative of the meteorite as a whole. We have benefitted from comments and many contributions to detailed imaging studies of the samples by N.
The expedition also hugely benefitted from the logistical aid provided by Olga Komelkova, Victor Komelkov, and Bogdan Makovskii, all from Anadyr, who organized and provided all transportation and provisions both in base camp in the Koryak Mountains and en route between the base camp and Anadyr. We also are grateful to Prof. Jull, George Burr, and the rest of the team at the Accelerator Mass Spectrometry Laboratory, University of Arizona, for their excellent work in producing the 14 C age dates of the blue clay layer.
Finally, this manuscript benefitted greatly from constructive reviews by Drs. Volume 48 , Issue 8. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username.
Original Article Free Access. Glenn J. Christopher L. Vadim V. Michael P. John M. Lincoln S. William M. Paul J. Tools Request permission Export citation Add to favorites Track citation. Share Give access Share full text access. Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article.
Abstract A new meteorite find, named Khatyrka, was recovered from eastern Siberia as a result of a search for naturally occurring quasicrystals. Introduction A meteorite was found as a result of an expedition to Chukotka in far eastern Russia by ten scientists from the United States, Russia, and Italy, from July 20 to August 7, Figure 1 Open in figure viewer PowerPoint.
Map of the find locality in Chukotka in the northern half of the Kamchatka peninsula in far eastern Russia.
Khatyrka, a new CV3 find from the Koryak Mountains, Eastern Russia - CaltechAUTHORS
The dashed rectangular outline shows the location of the geologic map in Fig. Figure 2 Open in figure viewer PowerPoint. One of his most heartfelt accomplishments happened just recently with the acceptance of a letter he wrote for his friend and point man in Vietnam, Willie Earl Granger, who lost his life on a land mine while they were together.
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This June, Distler went to join his buddy, loosing his life to a fast, aggressive brain tumor. So many in our community were and are devastated with the news, as is his wife and daughter, who now all struggle to adjust to a life without him.
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