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1.
Abstract— We report the first petrologic examination of all stone meteorites of Fayette County, Texas. The 10 stones represent four or five different fall events. The three recovered Bluff stones represent two falls. Bluff (a), which includes the 145.5-kg Bluff #1 stone, is classified as L5(S4), whereas Bluff (b) is classified as L4(S3) and is represented by a single stone. The studied Cedar stones are classified as H4(S3), and all four Cedar stones appear to define a strewnfield. Round Top (a), classified as L5(S3) and represented by two stones, is unrelated to either Bluff or Cedar. Round Top (b) [H4(S3); 1 stone], whose exact provenance is unknown, might be a transported fragment of the Cedar shower.  相似文献   

2.
Abstract— We report the histories and classifications of poorly known meteorites from the Oscar Monnig meteorite collection. Forestburg (a), Texas, is an L4(S2) ordinary chondrite. Forestburg (b), Texas, is a shock-blackened L5(S5) ordinary chondrite containing an impact-melt clast. Davy (a), Texas, L4(S2), is represented by several highly weathered stones. Davy (b), Texas, is a single stone classified as H4(S2). Harrison Township, Kansas, (L6(S4)) was found in the vicinity of several meteorites grouped as Ladder Creek but appears distinct. We have identified the second and largest fragment of the 1814 October Gurram Konda, India, L6(S3) meteorite fall and uncovered details of its early history.  相似文献   

3.
Abstract— Based on optical microscopy, modal and electron microprobe analyses, six ordinary chondrites from Texas preserved in the Monnig Meteorite Collection at Texas Christian University, Fort Worth, Texas, were classified in compositional groups, petrologic types, and shock facies. These meteorites are Comanche (stone), L5c; Haskell, L5c; Deport (a), H4b; Naruna (a), H4b; Naruna (b), H4b; and Clarendon (b), H5d.  相似文献   

4.
Abstract— We classified four ordinary chondrites from the Monnig Meteorite Collection into compositional groups, petrologic types and shock stages, based on optical microscopy in transmitted and reflected light, and electron microprobe and modal analyses. These meteorites are Allen, Texas, H4(S2); May Day, Kansas, H4(S2); Pony Creek, Texas, H4(S3); and Springer, Oklahoma, H5(S3).  相似文献   

5.
Based on optical microscopy and electron microprobe analyses of mafic minerals, six previously undescribed or poorly known ordinary chondrites from Texas were classified into compositional groups, petrologic types, and shock facies. These meteorites are Junction, L5d; Anton, H4b; Venus, H4d; Dalhart, H5a; Rosebud, H5c; and Cranfills Gap, H6c.  相似文献   

6.
Six meteorites have been found in Castro County, Texas and named after the town of Nazareth, but each of the four classified specimens has been given two different full names. To clarify this, we have classified the other two specimens and helped to establish approved names for all six specimens. The classes and names of the six specimens, which probably come from six separate falls, are as follows: Nazareth (a), L6; Nazareth (b), L6; Nazareth (c), H5; Nazareth (d), H5; Nazareth (e), H6; Nazareth (iron), IIIA.  相似文献   

7.
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8.
Based on optical microscopy and electron microprobe analyses, eight previously undescribed or poorly known chondrites were classified into compositional groups, petrologic types, and degree of shock alteration. These chondrites are: Leander, L4b; Nazareth(a), L6d; La Villa, H4b; Mereta, H4c; Gail, H4d; Shafter Lake, H5a; Uvalde, H5d; and Howe, H5d.  相似文献   

9.
Abstract— Five new ordinary chondrites from Roosevelt County, New Mexico, USA, have been assigned to a chemical group, petrologic type and shock stage. All five are moderately to heavily weathered. They are: RC 073, H5(S2); RC 074, L5(S3); RC 076, L4(S3); RC 077 , L4(S2); RC 078, L4(S2).  相似文献   

10.
Abstract— We have classified 12 new, moderately to severely weathered meteorites from Roosevelt County, New Mexico (RC 079–090) that were recovered between 1969 and 1993. They include nine H chondrites and three L chondrites of petrologic types 4 to 6 and shock classification S1 to S4. Among these are a flight-oriented specimen of an H5 chondrite, an L4 chondrite with a porphyritic impact-melt rock clast, an H5 fragmental breccia with an unusual weathering assemblage (probably a Ca sulfate), and an H4 chondrite with unequilibrated pyroxenes.  相似文献   

11.
Abstract— Studies of 52 specimens recovered from the find site of the original Travis County meteorite reveal the presence of two distinct meteorites. Travis County (a), which includes the original Travis County meteorite, is the more abundant meteorite and is classified as an H5(S4) shock-blackened chondrite. Travis County (b) is classified as an H4(S2) chondrite with rare chondritic clasts of H group parentage, indicating that the meteorite is a breccia.  相似文献   

12.
The loess-paleosol sequences of the last 1.2 Ma in China have recorded two kinds of climate extremes: the strongly developed S4, S5-1 and S5-3 soils (corresponding to the marine δ18O stages 11, 13, and 15, respectively) as evidence of three episodes of great warmth and two coarse-grained loess units (L9 and L15, corresponding to the marine δ18O stages 22, 23, 24 and 38, respectively) which indicate severest glacial conditions. The climatic and geographical significance of these events are still unclear, and their cause remains a puzzle.Paleopedological, geochemical and magnetic susceptibility data from three loess sections (Xifeng, Changwu and Weinan) suggest that the S4, S5-1 and S5-3 soils were formed under sub-tropical semi-humid climates with a tentatively estimated mean annual temperature (MAT) of at least 4–6°C higher and a mean annual precipitation (MAP) of 200–300 mm higher than for the present-day, indicating a much strengthened summer monsoon. The annual rainfall was particularly accentuated for the southern-most part of the Loess Plateau, suggesting that the monsoon rain belt (the contact of the monsoonal northward warm-humid air mass with the dry-cold southward one) might have stood at the southern part of the Plateau for a relatively long period each year. The loess units L9 and L15 were deposited under semi-desertic environments with a tentatively estimated MAT and MAP of only about 1.5–3°C and 150–250 mm, indicating a much strengthened winter monsoon, and that the summer monsoon front could rarely penetrate into the Loess Plateau region.Correlation with marine carbon isotope records suggests that these climate extremes have large regional, even global, significance rather than being local phenomena in China. They match the periods with greatest/smallest Atlantic–Pacific δ13C gradients, respectively, indicating their relationships with the strength of Deep Water (NADW) production in the North Atlantic. These results suggest that the monsoon climate in the Loess Plateau region was significantly linked with the North Atlantic thermohaline circulation on timescales of 104 years.  相似文献   

13.
High‐temperature solid‐state electrochemistry techniques (EMF method) were used to measure the oxygen fugacity (fO2) of the ordinary chondrites Ochansk (H4), Savtschenskoje (LL4), Elenovka (L5), Vengerovo (H5), and Kharkov (L6). The fO2 results are presented in the form of the following equations: It was found that fO2 regularly increases from H chondrites to LL chondrites. Measured fO2 are ~1.5 higher than those previously calculated from mineral assemblages. Kharkov (L6) is a little more oxidized than Elenovka (L5) in agreement with the progressive oxidation model. At the same time, Ochansk (H4) is more oxidized than Vengerovo (H5) and exhibits a slightly different slope compared to other chondrites and at T > 1200 K, becomes more reduced than Kharkov (L6) or Elenovka (L5). Measured oxygen fugacity values of meteorites fall within (0.1–1.0)·log fO2 of one another. The possible explanation of discrepancies between measured and calculated values is discussed.  相似文献   

14.
Abstract— The Meteoritical Bulletin No. 80 lists data for 178 meteorites. Noteworthy are 3 HED meteorites (ALH 88102, Hammadah al Hamra (HaH) 059, and Monticello); 3 ureilites (HaH 064, HaH 126, and Dar al Gani (DaG) 084); 4 irons (Baygorria (IAB), Ste. Croix (IIIAB), Sargiin Gobi (IAB), and Tarahumara (IIE)); an unusual metal-rich meteorite (Vermillion); 8 carbonaceous chondrites (HaH 043 (C03), HaH 073 (C4), DaG 055 (C3) and 5 C03 chondrites (probably paired) from DaG); an R chondrite (DaG 013); and 6 unequilibrated ordinary chondrites (ALH 88105 (L3), Camel Donga 016 (L3), HaH 093 (LL3.9), HaH 096 (LL(L)3), Richfield (LL3.7), and Sarir Quattusah (LL(L)3)). Three recent falls of ordinary chondrites (Coleman (LL5), St. Robert (H5), and Tsukuba (H5-6)) are described.  相似文献   

15.
Thermochemical data for several ion-molecule clustering of hydrocarbon ions with N2 or CH4 were obtained from clustering equilibria studies in gas mixtures irradiated by alpha-particles. High-pressure mass spectrometry was used to determine the enthalpy and entropy changes of clustering (delta H0 and delta S0, respectively) for the reactions X+(N2)n-1 + 2N2 <==> X(+)(N2)n + N2 with X = CH5, n = 1-2; X = C2H5, n = 1-4; and X = C3H7, n = 1. For X = CH5, the values (delta H0; delta S0) are found to be (-6.8 kcal mol-1; -19.7 cal mol-1 K-1) for n = 1, and (-5.3 kcal mol-1; -15.9 cal mol-1 K-1) for n = 2. For X = C2H5, (delta H0; delta S0) = (-6.9 kcal mol-1; -18.2 cal mol-1 K-1), for n = 1, and (-4.6 kcal mol-1; -20.8 cal mol-1 K-1) for n = 2. From the equilibrium measurements at 129 K, estimates of the thermochemical values could be obtained for n = 3-4. The results obtained for the free energy, delta G0, were -1.4 kcal mol-1 for n = 3, and -1.1 kcal mol-1 for n = 4. For X = C3H7 we found delta G0 = -0.7 kcal mol-1 at 213 K. The association reactions X+ + 2CH4 <==> X+(CH4) + CH4 with X = CH5, C2H5, C2H7, and C3H7 were also studied, resulting in free energy values at 206 K of -3.1, -1.9, -0.5 and -1.3 kcal mol-1, respectively. The results for CH5, C2H5 and C3H7 are compared with previously reported measurements.  相似文献   

16.
Microprobe analyses of the major silicates in Clovis (no. 1), New Mexico, establish it as an H3 chondrite. Inclusions identified in Clovis are: breccia fragments; angular and vesicular chondrule or rock fragments composed almost entirely of glass and olivine (Fa12–22); chondrules, composed principally of pyroxene (Fs2–33) and olivine (Fa1–28); and Ca, Al and Ti-rich inclusions. These refractory enriched inclusions, similar in composition to those found in some carbonaceous chondrites, are rare in ordinary chondrites but in this study were observed in Sharps, Virginia (H3), Gobabeb, South Africa (H4), Dimmitt, Texas (H4), Weston, Connecticut (H4–6) and Clovis. Sodium, known to rim similar inclusions in carbonaceous chondrites, also occurs in the interiors of inclusions observed in this study, sometimes in moderate amounts. The Na distribution is regarded as primary and is not attributable, at least in total, to secondary Na extraction from the host matrix.  相似文献   

17.
Recent dynamical analyses of the Kuiper belt have introduced a rigorous classification scheme, determined the mean orbital plane, and identified “Core” and “Halo” populations as a function of inclination with respect to this plane (Elliot, J.L., Kern, S.D., Clancy, K.B., Gulbis, A.A.S., Millis, R.L., Buie, M.W., Wasserman, L.H., Chiang, E.I., Jordan, A.B., Trilling, D.E., Meech, K.J., 2005. Astron. J. 129, 1117-1162). Here, we use new observations and existing data to investigate the colors of Kuiper belt objects (KBOs) within this framework. With respect to the bulk KBO color distribution (all objects for which we have B-V and V-R colors; median B-R=1.56), we find that the population of objects classified following (Elliot, J.L., Kern, S.D., Clancy, K.B., Gulbis, A.A.S., Millis, R.L., Buie, M.W., Wasserman, L.H., Chiang, E.I., Jordan, A.B., Trilling, D.E., Meech, K.J., 2005. Astron. J. 129, 1117-1162) as Classical tends to be red (B-R>1.56) while the Scattered Near population is mostly neutral (B-R<1.56). Colors of Scattered Extended and Resonant objects are consistent with the bulk distribution. Separating objects into specific resonances demonstrates that the color of the Resonant sample is dominated by KBOs in the 3:2 resonance, which is consistent with previous findings. Unlike the objects in the 3:2 resonance, however, the majority of objects in the 5:2 resonance are neutral and all but one of the objects in the 4:3, 5:3, 7:4, 2:1, and 7:3 resonances are red. In particular, the objects in the 7:4 resonance are remarkably red. We find that the colors of KBOs in the Core (low-inclination) and Halo (high-inclination) are statistically different, with Core objects being primarily red and Halo objects having a slight tendency to be neutral. Notably, virtually all of the non-Resonant Core objects are red. This combination of low inclination, unperturbed orbits and red colors in the Core may be indicative of a relic grouping of objects.  相似文献   

18.
Abstract Buck Mountain Wash (BMW) is a new genomict breccia (H3‐5) found in the Franconia (H5) strewn field in Arizona that shows complex brecciation and shock effects. It contains three distinct chondritic lithologies in sharp contact: a) a main lithology that consists primarily of petrographic type 5 material but which has finely intermixed type 3 and 4 material, b) a shock‐blackened (shock stage S5) type 3 lithology (lithology A), and c) a shock‐blackened type 3/4 lithology (lithology B). Buck Mountain Wash was lithified after impact‐mixing and impact‐melting of weakly and strongly metamorphosed materials, possibly at depth in the regolith of the parent body. Shock effects included brecciation on a fine scale, localized impact‐melting of silicates, partial melting, and mobilization of metal‐sulfide, and chemical fractionations that produced non‐H‐group composition kamacite by two disequilibrium mechanisms. Shock heating did not cause significant thermal metamorphism in the shock‐blackened lithologies of BMW, except possibly in areas adjacent to whole‐rock shock melt. During lithification, cooling must have been rapid at high temperatures to preserve glass and inhomogeneous silicate compositions, but not so fast at lower temperatures as to produce dendritic metal‐sulfide globules or martensite.  相似文献   

19.
Abstract— We have classified four new ordinary chondrites from Roosevelt County, New Mexico (RC 091–094) that were found in June and July of 1994 by I. Wilson. They include one H4(S2) and three L5(S4) chondrites. Degree of weathering is variable and ranges from W2–6.  相似文献   

20.
The brecciation and shock classification of 2280 ordinary chondrites of the meteorite thin section collection at the Institut für Planetologie (Münster) has been determined. The shock degree of S3 is the most abundant shock stage for the H and LL chondrites (44% and 41%, respectively), while the L chondrites are on average more heavily shocked having more than 40% of rocks of shock stage S4. Among the H and LL chondrites, 40–50% are “unshocked” or “very weakly shocked.” Considering the petrologic types, in general, the shock degree is increasing with petrologic type. This is the case for all meteorite groups. The main criteria to define a rock as an S6 chondrite are the solid‐state recrystallization and staining of olivine and the melting of plagioclase often accompanied by the formation of high‐pressure phases like ringwoodite. These characteristics are typically restricted to local regions of a bulk chondrite in or near melt zones. In the past, the identification of high‐pressure minerals (e.g., ringwoodite) was often taken as an automatic and practical criterion for a S6 classification during chondrite bulk rock studies. The shock stage classification of many significantly shocked chondrites (>S3) revealed that most ringwoodite‐bearing rocks still contain more than 25% plagioclase (74%). Thus, these bulk chondrites do not even fulfill the S5 criterion (e.g., 75% of plagioclase has to be transformed into maskelynite) and have to be classified as S4. Studying chondrites on typically large thin sections (several cm2) and/or using samples from different areas of the meteorites, bulk chondrites of shock stage S6 should be extremely rare. In this respect, the paper will discuss the probability of the existence of bulk rocks of S6.  相似文献   

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