THE IMPACT-FLOOD CONNECTION: DOES IT EXIST?*     

Alexander Deutsch  Christian Koeberl  Joel D. Blum  Bevan M. French  Billy P. Glass  Richard Grieve  Peter Horn  Elmar K. Jessberger  Gero Kurat  Wolf Uwe Reimold  Jan Smit  Dieter Stöffler  Stuart Ross Taylor 《地学学报》1994,6(6):644-650

In a recent article in Terra Nova, Kristan-Tollmann and Tollmann (1994) suggested that the Biblical Flood can be explained by seven fragments of a comet that impacted the ocean at seven locations on Earth at 03.00h (C.E.T.) on 23 September, 9545 yr BP. We demonstrate that all the ‘geological proofs’ that allegedly support their conclusions are not supported by the available data on impact cratering. Their hypothesis is based on insufficient and ambiguous data, selective citation, and incomplete comprehension of previous research.  相似文献   

Primordial noble gases in a graphite‐metal inclusion from the Canyon Diablo IAB iron meteorite and their implications     

Jun‐ichi Matsuda  Miwa Namba  Teruyuki Maruoka  Takuya Matsumoto  Gero Kurat 《Meteoritics & planetary science》2005,40(3):431-443

Abstract— We have carried out noble gas measurements on graphite from a large graphite‐metal inclusion in Canyon Diablo. The Ne data of the low‐temperature fractions lie on the mixing line between air and the spallogenic component, but those of high temperatures seem to lie on the mixing line between Ne‐HL and the spallogenic component. The Ar isotope data indicate the presence of Q in addition to air, spallogenic component and Ar‐HL. As the elemental concentration of Ne in Q is low, we could not detect the Ne‐Q from the Ne data. On the other hand, we could not observe Xe‐HL in our Xe data. As the Xe concentration and the Xe/Ne ratio in Q is much higher than that in the HL component, it is likely that only the contribution of Q is observed in the Xe data. Xenon isotopic data can be explained as a mixture of Q, air, and “El Taco Xe.” The Canyon Diablo graphite contains both HL and Q, very much like carbonaceous chondrites, retaining the signatures of various primordial noble gas components. This indicates that the graphite was formed in a primitive nebular environment and was not heated to high, igneous temperatures. Furthermore, a large excess of ¹²⁹Xe was observed, which indicates that the graphite was formed at a very early stage of the solar system when ¹²⁹I was still present. The HL/Q ratios in the graphite in Canyon Diablo are lower than those in carbonaceous chondrites, indicating that some thermal metamorphism occurred on the former. We estimated the temperature of the thermal metamorphism to about 500–600 °C from the difference of thermal retentivities of HL and Q. It is also noted that “El Taco Xe” is commonly observed in many IAB iron meteorites, but its presence in carbonaceous chondrites has not yet been established.  相似文献   

Reply to comment: “The Nakhla Martian meteorite is a cumulate igneous rock” by A. Treiman     

M. E. Varela  G. Kurat  R. Clocchiatti 《Mineralogy and Petrology》2003,77(3-4):279-285

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Buchbesprechungen     

G. Kurat  E. F. Stumpfl 《Mineralogy and Petrology》1977,24(4):299-302

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I‐Xe ages of Campo del Cielo silicates as a record of the complex early history of the IAB parent body     

O. Pravdivtseva  A. Meshik  C. M. Hohenberg  G. Kurat 《Meteoritics & planetary science》2013,48(12):2480-2490

Using in situ laser analyses of a polished thin section from the IAB iron meteorite Campo del Cielo, we identified two silicate grains rich in radiogenic ^129*Xe, Cr‐diopside, and oligoclase, excavated them from the metal, and irradiated them with thermal neutrons for I‐Xe dating. The release profiles of ^129*Xe and ^128*Xe are consistent with these silicates being diopside and oligoclase, with activation energies, estimated using Arrhenius plots, of ～201 and ～171 kcal mole^?1, respectively. The 4556.4 ± 0.4 Ma absolute I‐Xe age of the more refractory diopside is younger than the 4558.0 ± 0.7 Ma I‐Xe age of the less refractory oligoclase. We suggest that separate impact events at different locations and depths on a porous initial chondritic IAB parent body led to the removal of the melt and recrystallization of diopside and oligoclase at the times reflected by their respective I‐Xe ages. The diopside and oligoclase grains were later brought into the studied inclusion by a larger scale catastrophic collision that caused breakup and reassembly of the debris, but did not reset the I‐Xe ages dating the first events. The metal melt most probably was <1250 °C when it surrounded studied silicate grains. This reassembly could not have occurred earlier than the I‐Xe closure in diopside at 4556.4 ± 0.4 Ma.  相似文献   

Noble gases in metal and schreibersite of the Acuña (IIIAB) iron meteorite     

Jun-ichi Matsuda  Keisuke Nagao  Gero Kurat 《Meteoritics & planetary science》1996,31(2):227-233

Abstract— We measured abundances and isotopic compositions of noble gases in metal and schreibersite of the Acuña (IIIAB) iron meteorite. The concentrations of noble gases in Acuña metal are very low compared to those reported so far for other iron meteorites. The isotopic ratios of He, Ne and Ar indicate that they are mostly of cosmogenic origin. Cosmogenic components are even present in Kr and Xe, which could not have been produced from Fe, Ni and P and are probably due to the spallation of trace elements of higher masses. The high ⁴He/²¹Ne ratio of 420 in Acuña metal indicates that the samples were at a deep position within a very large meteoroid. The exposure ages of Acuña were estimated to be 50–200 Ma from ³He, ²¹Ne and ³⁸Ar abundances and by utilizing the diagrams of production rates vs. the ⁴He/²¹Ne ratio based on the Signer-Nier model. The low exposure age of Acuña may indicate a history different from that of other IIIAB irons whose exposure ages cluster at ～670 Ma. Otherwise, Acuña may be one of the samples with the low production rate, which can not be estimated from the diagrams of the Signer-Nier model.  相似文献   

The origin of non-porphyritic pyroxene chondrules in UOCs: Liquid solar nebula condensates?     

Almut Engler  Gero Kurat  Paul Sylvester 《Icarus》2007,192(1):248-286

A total of 56 non-porphyritic pyroxene and pyroxene/olivine micro-objects from different unequilibrated ordinary chondrites were selected for detailed studies to test the existing formation models. Our studies imply that the non-porphyritic objects represent quickly quenched liquids with each object reflecting a very complex and unique evolutionary history. Bulk major element analyses, obtained with EMPA and ASEM, as well as bulk lithophile trace element analyses, determined by LA-ICP-MS, resulted in unfractionated (solar-like) ratios of CaO/Al₂O₃, Yb/Ce as well as Sc/Yb in many of the studied objects and mostly unfractionated refractory lithophile trace element (RLTE) abundance patterns. These features support an origin by direct condensation from a gas of solar nebula composition. Full equilibrium condensation calculations show that it is theoretically possible that pyroxene-dominated non-porphyritic chondrules with flat REE patterns could have been formed as droplet liquid condensates directly from a nebular gas strongly depleted in olivine. Thus, it is possible to have enstatite as the stable liquidus phase in a 800 × Cl dust-enriched nebular gas at a ptot of 10⁻³ atm, if about 72% of the original Mg is removed (as forsterite?) from the system. Condensation of liquids from vapor (primary liquid condensation) could be considered as a possible formation process of the pyroxene-dominated non-porphyritic objects. This process can produce a large spectrum of chemical compositions, which always have unfractionated RLTE abundances. Late stage and subsolidus metasomatic events appear to have furthered the compositional diversity of chondrules and related objects by addition of moderately volatile and volatile elements to these objects by exchange reactions with the chondritic reservoir (e.g., V, Cr, Mn, FeO as well as K and Na). The strong fractionation displayed by the volatile lithophile elements could be indicative of a variable efficiency of metasomatic processes occurring during and/or after chondrule formation. Histories of individual objects differ in detail from each other and clearly indicate individual formation and subsequent processing.  相似文献   

Glass-bearing xenoliths from Cape Verde: Evidence for a hot rising mantle jet     

Prof. Dr. J. D. Ryabchikov  Dr. T. Ntaflos  Prof. Dr. G. Kurat  Prof. Dr. L. N. Kogarko 《Mineralogy and Petrology》1995,55(4):217-237

Summary Peridotitic xenoliths from melanephelinites of Sal Island, Cape Verde Archipelago, have a compositional range from moderately depleted Iherzolites to refractory harzburgites. Most xenoliths have protogranular textures but porphyroclastic and mylonitic textures are not uncommon. Small amounts of glass are present in the intergranular space of these rocks which possibly, at least in part, represent quenched silicate melt which invaded these rocks just before they were excavated. These glasses contain microphenocrysts of olivine, clinopyroxene, and spinel, as well as small grains of sulphides and metallic Fe-Ni alloys. Metallic phases were most likely produced by the desulphurization of sulfides, which also resulted in very low oxygen fugacities (several logarithmic units below QFM buffer) in the interstitial glasses and associated microphenocrysts. This is reflected in the chemical composition of the newly formed spinels which are characterised by low amounts of ferric iron. In contrast, primary spinel-bearing mineral assemblages of the peridotites were formed at much higher f_O2. which were similar to those estimated for the host nephelinites which have high titanomagnetite contents.

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Glasführende Xenolithe von Kap Verde: Evidenz für einen heißen Erdmantel Diapir

Zusammenfassung Die ultramafischen Xenolithe aus den Melanepheliniten von der Kap Verde Insel Sal sind Spinell-Lherzolithe und Spinell-Harzburgite. Am verbreitesten sind Xenolithe mit protogranularer Textur, aber auch Xenolithe mit porphyroklastischer und mylonitischer Textur treten häufig auf. Die Xenolithe enthalten kleine Mengen von intergranularem Glas, welches, wenigstens zum Teil, abgeschreckte silikatische Schmelzen repräsentiert, welche die Gesteine vor ihrem Aufstieg aus dem Erdmantel durchdrungen haben. Dieses Glas enthält Mikrophenokristalle von Olivin, Klinopyroxen und Orthopyroxen, sowie auch kleinere Körner von Sulfiden und metallischen Fe-Ni Legierungen. Metallische Phasen sind sehr wahrscheinlich durch Entschwefelung von Sulfiden unter sehr niedrigem f_O2 (einige Größenordnungen unter dem QFM Buffer) entstanden. Das wirkt sich auf die Zusammensetzung der neu gebildeten Spinelle aus, die durch einen niederen Gehalt an Fe³⁺ charakterisiert sind. Die Xenolithe wurden jedoch unter viel höhere f_O2 gebildet. Ihre foe sind ähnlich der für die Wirtsnephelinite berechneten f_O2, die hohe Titanomagnetit-Gehalte aufweisen.

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Granat-Spinell-Websterit und Lherzolith aus dem Basalttuff von Kapfenstein,Steiermark     

Dr. G. Kurat 《Mineralogy and Petrology》1971,16(4):192-214

Zusammenfassung Aus dem Basalttuff von Kapfenstein werden ein Granat-Spinell-Websterit und ein Lherzolith-Einschluß beschrieben. Elektronenstrahl-Mikrosondenanalysen der Phasen und Pauschalanalysen dieser Gesteine und des Basaltes werden angegeben.Die Zusammensetzung der koexistierenden Phasen deutet auf eine Gleichgewichtsbildung unter sehr hohen Temperaturen und Drücken hin (Lherzolith: 1100–1150° C, 20 kb; Websterit: 1250–1350° C, 24 kb). Beide Einschluß-Gesteine zeigen Deformationen und metamorphe Rekristallisationen. Es wird angenommen, daß sie Reste verschiedener Lagen des oberen Erdmantels darstellen.Die Basaltschlacken des Tuffs sind reich an Mineralbruchstücken dieser und anderer Gesteine. Sie fürhren jedoch auch Hp-HT-Minerale, welche kogenetisch sind. Die ungewöhnliche Zusammensetzung der Lapilli und der Schlacken deutet auf eine direkte Herkunft dieser Laven aus dem Erdmantel hin.

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Garnet-spinel-websterite and lherzolite from the Basalt tuff from Kapfenstein, Styria

Summary A garnet-spinel websterite and a spinel lherzolite nodule as well as some scoriaceous basaltic fragments from the tuff of Kapfenstein have been investigated petrologically. Electron-microprobe analyses of the phase and bulk analyses of the rocks are presented.Compositions of the coexisting phases suggest equilibration at high temperatures and pressures; lherzolite at 1100–1150° C and 20 kb whereas websterite at 1250–1350° C and 24 kb. Both xenoliths show metamorphic recrystallization and stress deformation. It is believed that they represent accidental xenoliths of different strata of the upper mantle.The scoriaceous basaltic fragments contain abundant mineral fragments of the xenoliths and other rocks. They also contain cogenetic high pressure minerals. The unusual composition of the basaltic fragments suggests a direct derivation of their melts from the upper mantle by partial melting of different degrees.

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Herrn Prof. DDr.H. Wieseneder zum 65. Geburtstag gewidmet.  相似文献   

Impaktite von Köfels,Tirol     

Dr. G. Kurat  Dr. W. Richter 《Mineralogy and Petrology》1972,17(1):23-45

Zusammenfassung Die glasführenden Gesteine von Köfels, Tirol, wurden petrologisch untersucht. Sowohl Elektronenstrahl-Mikrosondenanalysen der Phasen als auch chemische Pauschalanalysen einiger Gesteine werden angegeben.Das Vorhandensein von Cr- und Si-führendem Nickeleisen, Lechatelierit, Kalifeldspatglas, Fe-reichen Gläsern, Olivin sowie die kräftigen Inhomogenitäten in der Glasphase sind nur durch eine Impakt-Entstehung dieser Gesteine erklärbar.

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Impactites from Koefels, Tyrol, Austria

Summary The glass-bearing rocks from Koefels, Tyrol, have been investigated petrologically. Electron-microprobe Analyses of the phases and chemical bulk analyses of some rocks are presented.The presence of Cr- and Si-bearing nickel-iron, lechatelierite, potassium-feldspar-glass, olivine, as well as the pronounced inhomogenities of the glasses strongly suggest an impact origin of these rocks.

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Mit 7 Abbildungen  相似文献