Itawa Bhopji (L3–5) chondrite regolith breccia: Fall,classification, and cosmogenic records     

N. Bhandari  S. V. S. Murty  P. N. Shukla  A. D. Shukla  R. R. Mahajan  M. M. Sarin  G. Srinivasan  K. M. Suthar  M. S. Sisodia  S. Jha  A. Bischoff 《Meteoritics & planetary science》2002,37(4):549-563

Abstract— A stony meteorite fell at Itawa Bhopji, Rajasthan, India on 2000 May 30. This is the fifth recorded fall in a small area of Rajasthan during the past decade. The meteorite is an ordinary chondrite with light clasts in a dark matrix, consisting of a mixture of equilibrated (mainly type 5) and unequilibrated components. Olivine is Fa_24–26 and pyroxene Fs_20–22 but, within the unequilibrated components, olivine (Fa_5–29) and low calcium pyroxene (Fs_5–37) are highly variable. Based on petrographic studies and chemical analyses, it is classified as L(3–5) regolith breccia. Studies of various cosmogenic records, including several gamma‐emitting radionuclides varying in half‐life from 5.6 day ⁵²Mn to 0.73 Ma ²⁶Al, tracks and rare gases have been carried out. The exposure age of the meteorite is estimated from cosmogenic components of rare gases to be 19.6 Ma. The track density varies by a factor of ?3 (from 4 to 12 times 10⁶/cm²) within the meteorite, indicating a preatmospheric body of ?9 cm radius (corresponding to a meteoroid mass of ?11 kg) and small ablation (1.5 to 3.6 cm). Trapped components in various rare gases are high and the solar component is present in the dark portion of the meteorite. Large excess of neutron‐produced ⁸²Kr and ¹²⁸Xe in both the light and the dark lithology but very low ⁶⁰Co, indicating low neutron fluxes received by the meteoroid in the interplanetary space, are clear signatures of an additional irradiation on the parent body.  相似文献   

Lava bubble-wall fragments formed by submarine hydrovolcanic explosions on Lō'ihi Seamount and Kīlauea Volcano     

David A. Clague  Alice S. Davis  James L. Bischoff  Jacqueline E. Dixon  Renee Geyer 《Bulletin of Volcanology》2000,61(7):437-449

 Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted on Lō'ihi Seamount and along the submarine east rift zone of Kīlauea Volcano. The limu o Pele fragments are undegassed with respect to H₂O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths by cooling-contraction granulation. The limu o Pele fragments from Lō'ihi Seamount are dominantly tholeiitic basalt containing 6.25–7.25% MgO. None of the limu o Pele samples from Lō'ihi Seamount contains less than 5.57% MgO, suggesting that higher viscosity magmas do not form lava bubbles. The dissolved CO₂ and H₂O contents of 7 of the limu o Pele fragments indicate eruption at 1200±300 m depth (120±30 bar). These pressures exceed that generally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing conditions, at pressures as great as 120 bar. Received: 22 December 1998 / Accepted: 16 July 1999  相似文献   

Soil-Structure Interaction of Steel Fiber Reinforced Concrete Slab Strips on a Geogrid Reinforced Subgrade     

Olivia Hernandez  Hany El Naggar  Peter H. Bischoff 《Geotechnical and Geological Engineering》2015,33(3):727-738

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Seismic risk assessment of building stocks in Indian context     

Radhikesh P. Nanda  Nilendu Krishna Paul  Ningthoujam Monika Chanu  Sukanti Rout 《Natural Hazards》2015,78(3):2035-2051

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Influence of diversified relief on the urban heat island in the city of Kraków,Poland     

Anita Bokwa  Monika J. Hajto  Jakub P. Walawender  Mariusz Szymanowski 《Theoretical and Applied Climatology》2015,122(1-2):365-382

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Optical absorption of electronic Fe–Ti charge-transfer transition in natural andalusite: the thermal stability of the charge-transfer band     

Michail N. Taran  Monika Koch-Müller 《Physics and Chemistry of Minerals》2011,38(3):215-222

Differently colored natural Brazilian andalusite crystals heat-treated under reducing and oxidizing conditions were analyzed by optical spectroscopy. The intensity of a broad intense band at around 20,500 cm⁻¹ in the optical absorption spectra of all color zones of the sample is proportional to the product of Ti- and Fe-concentrations and herewith proves its attribution to electronic Fe²⁺/Ti⁴⁺ IVCT transition. The band is strictly E||c-polarized, causing an intense red coloration of the samples in this polarization. The polarization of the Fe²⁺/Ti⁴⁺ IVCT band in andalusite, E||c, shows that the electronic charge-transfer process takes place in Al–O octahedral groups that share edges with neighbors on either side, forming chains parallel to the c-axis of the andalusite structure. Under thermal treatments in air, the first noticeable change is some intensification of the band at 800°C. However, at higher temperatures its intensity decreases until it vanishes at 1,000°C in lightly colored zones and 1,100°C in darkly colored ones. Under annealing in reducing conditions at 700 and 800°C, the band also slightly increases and maintains its intensity at treatments at higher temperatures up to 1,000°C. These results demonstrate that weakening and disappearance of the Fe²⁺/Ti⁴⁺ IVCT band in spectra of andalusite under annealing in air is caused by oxidization of Fe²⁺ to Fe³⁺ in IVCT Fe²⁺/Ti⁴⁺-pairs. Some intensification of the band at 800°C is, most probably, due to thermally induced diffusion of Fe²⁺ and Ti⁴⁺ in the structure that leads to aggregation of “isolated” Ti⁴⁺ and Fe²⁺ ions into Fe²⁺–Ti⁴⁺-pairs. At higher temperatures, the competing process of Fe²⁺ → Fe³⁺ oxidation overcomes such “coupling” and the band continues to decrease. The different thermal stability of the band in lightly and darkly colored zones of the samples evidence some self-stabilization over an interaction of Fe²⁺/Ti⁴⁺-pairs involved in IVCT process.  相似文献   

Tracing metamorphism,exhumation and topographic evolution in orogenic belts by multiple thermochronology: a case study from the Nízke Tatry Mts., Western Carpathians     

Martin Danišík  Jaroslav Kadlec  Christoph Glotzbach  Anett Weisheit  István Dunkl  Milan Kohút  Noreen J. Evans  Monika Orvošová  Brad J. McDonald 《Swiss Journal of Geoscience》2011,104(2):285-298

A combination of four thermochronometers [zircon fission track (ZFT), zircon (U–Th)/He (ZHe), apatite fission track (AFT) and apatite (U–Th–[Sm])/He (AHe) dating methods] applied to a valley to ridge transect is used to resolve the issues of metamorphic, exhumation and topographic evolution of the Nízke Tatry Mts. in the Western Carpathians. The ZFT ages of 132.1 ± 8.3, 155.1 ± 12.9, 146.8 ± 8.6 and 144.9 ± 11.0 Ma show that Variscan crystalline basement of the Nízke Tatry Mts. was heated to temperatures >210°C during the Mesozoic and experienced a low-grade Alpine metamorphic overprint. ZHe and AFT ages, clustering at ~55–40 and ~45–40 Ma, respectively, revealed a rapid Eocene cooling event, documenting erosional and/or tectonic exhumation related to the collapse of the Carpathian orogenic wedge. This is the first evidence that exhumation of crystalline cores in the Western Carpathians took place in the Eocene and not in the Cretaceous as traditionally believed. Bimodal AFT length distributions, Early Miocene AHe ages and thermal modelling results suggest that the samples were heated to temperatures of ~55–90°C during Oligocene–Miocene times. This thermal event may be related either to the Oligocene/Miocene sedimentary burial, or Miocene magmatic activity and increased heat flow. This finding supports the concept of thermal instability of the Carpathian crystalline bodies during the post-Eocene period.  相似文献   

TEM investigations on the monomict ureilites Jalanash and Hammadah al Hamra 064     

I. Weber  A. Bischoff  D. Weber 《Meteoritics & planetary science》2003,38(1):145-156

Abstract— We studied the petrography and mineralogy of two monomict ureilites, Hammadah al Hamra 064 (HH064) and Jalanash, by using reflected light and scanning electron microscopy. Quantitative analyses were performed by electron microprobe and the microstructures were investigated with transmission electron microscopy (TEM). HH064 features two different textures, a poikilitic and a typical one, whereas Jalanash shows only the typical ureilite texture. Our synergetic chemical and microstructural investigations reveal a complex cooling history for both ureilites. The temperature for the first equilibrium deduced from the pigeonite‐augite assemblage in HH064 is ～1200°C. The presence of antiphase domains in low‐Ca pyroxenes proves that they are clearly pigeonite. The occurrences of tweed micro structure and orthopyroxene lamellae, which are incompletely developed, imply a faster cooling rate from the first equilibrium with a sudden end. Although both ureilites contain shock induced diamonds, dislocations in silicates are rare. This observation suggests that the meteorites were hot at the time of strong shock metamorphism or that they were heated after strong shock metamorphism. After this event, new microstructural features were generated by different cooling processes and were frozen by a final rapid decrease in temperature possibly due to excavation from the ureilite parent body, or bodies.  相似文献   

26Mg excess in hibonites of the Rumuruti chondrite Hughes 030     

A. Bischoff  G. Srinivasan 《Meteoritics & planetary science》2003,38(1):5-12

Abstract— The Rumuruti chondrites (R chondrites) constitute a new, well-established, chondrite group different from carbonaceous, ordinary, and enstatite chondrites. Most samples of this group are gas-rich regolith breccias showing the typical light/dark structure and consist of abundant fragments of various parent body lithologies embedded in a fine-grained, olivine-rich matrix. Most R chondrites contain the typical components of primitive chondrites including chondrules, chondrule and mineral fragments, sulfides, and rare calcium-aluminum-rich inclusions (CAIs). In Hughes 030, an interesting CAI consisting of abundant hibonite and spinel was found. Mg isotopic analyses revealed excess ²⁶Mg in components of R chondrites for the first time. The hibonite grains with high Al/Mg values (∼1500 to 2600) show resolved ²⁶Mg excess. The slope of the correlation line yields an initial ²⁶Al/ ²⁷Al = (1.4 ± 0.3) × 10⁻⁶, which is ∼40 times lower than the initial value measured in CAIs from primitive meteorites. The inferred difference in ²⁶Al abundance implies a time difference of ∼4 million years for the closure of the Al-Mg system between CAIs from primitive chondrites and the Hughes 030 CAI. Based on mineralogy and the petrographic setting of the hibonite-rich CAI, it is suggested that 4 million years reflect the time interval between the formation of the CAI and the end of its secondary alteration. It is also suggested that most of this alteration may have occurred in the nebula (e.g. Zn- and Fe-incorporation in spinels). However, the CAI could not have survived in the nebula as a free floating object for a long period of time. Therefore, the possibility of storage in a precursor planetesimal for a few million years, resetting the magnesium-aluminum isotopic system, prior to impact brecciation, excavation, and accretion of the final R chondrite parent body cannot be ruled out.  相似文献   

TRANSCRIPTION OF THE NAMES OF CHINA'S ANCIENT METEORITES     

Monika Kumlehn 《Meteoritics & planetary science》1987,22(2):137-149

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