A composite Fe,Ni‐FeS and enstatite‐forsterite‐diopside‐glass vitrophyre clast in the Larkman Nunatak 04316 aubrite: Origin by pyroclastic volcanism     

Klaus KEIL  Timothy J. McCOY  Lionel WILSON  Jean‐Alix BARRAT  Doug RUMBLE  Matthias M. M. MEIER  Rainer WIELER  Gary R. HUSS 《Meteoritics & planetary science》2011,46(11):1719-1741

Abstract– We studied the mineralogy, petrology, and bulk, trace element, oxygen, and noble gas isotopic compositions of a composite clast approximately 20 mm in diameter discovered in the Larkman Nunatak (LAR) 04316 aubrite regolith breccia. The clast consists of two lithologies: One is a quench‐textured intergrowth of troilite with spottily zoned metallic Fe,Ni which forms a dendritic or cellular structure. The approximately 30 μm spacings between the Fe,Ni arms yield an estimated cooling rate of this lithology of approximately 25–30 °C s^?1. The other is a quench‐textured enstatite‐forsterite‐diopside‐glass vitrophyre lithology. The composition of the clast suggests that it formed at an exceptionally high degree of partial melting, perhaps approaching complete melting, and that the melts from which the composite clast crystallized were quenched from a temperature of approximately 1380–1400 °C at a rate of approximately 25–30 °C s^?1. The association of the two lithologies in a composite clast allows, for the first time, an estimation of the cooling rate of a silicate vitrophyre in an aubrite of approximately 25–30 °C s^?1. While we cannot completely rule out an impact origin of the clast, we present what we consider is very strong evidence that this composite clast is one of the elusive pyroclasts produced during pyroclastic volcanism on the aubrite parent body ( Wilson and Keil 1991 ). We further suggest that this clast was not ejected into space but retained on the aubrite parent body by virtue of the relatively large size of the clast of approximately 20 mm. Our modeling, taking into account the size of the clast, suggests that the aubrite parent body must have been between approximately 40 and 100 km in diameter, and that the melt from which the clast crystallized must have contained an estimated maximum range of allowed volatile mass fractions between approximately 500 and approximately 4500 ppm.  相似文献   

Remote sensing of snow and ice / La télédétection de neige et de glace     

MARK F. MEIER 《水文科学杂志》2013,58(3):307-330

Abstract

Monitoring of snow and ice on the Earth's surface will require increasing use of satellite remote sensing techniques. These techniques are evolving rapidly. Active and passive sensors operating in the visible, near infrared, thermal infrared, and microwave wavelengths are described in regard to general applications and in regard to specific USA or USSR satellites. Meteorological satellites (frequent images of relatively crude resolution) and Earth resources satellites such as Landsat (less frequent images of higher resolution) have been used to monitor the areal extent of seasonal snow, but problems exist with cloud cover or dense forest canopies. Snow mass (water equivalent) can be measured from a low-flying aircraft using natural radioactivity, but cannot yet be measured from satellite altitudes. A combination of active and passive microwave sensors may permit this kind of measurement, but not until more is known about radiation scattering in snow. Satellite observations are very useful in glacier inventories, correcting maps of glacier extent, estimating certain mass balance parameters, and monitoring calving or surging glaciers. Ground ice is virtually impossible to monitor from satellites; ice on rivers and lakes can be monitored only with very high-resolution sensors. Microwave sensors, due to their all-weather capability (the ability to see through clouds) provide exciting data on sea ice distribution. Analysis of digital tapes of satellite data requires the archiving and scanning of huge amounts of data. Simple methods for extracting quantitative data from satellite images are described.  相似文献   

A global rain of micrometeorites following breakup of the L‐chondrite parent body—Evidence from solar wind‐implanted Ne in fossil extraterrestrial chromite grains from China     

C. ALWMARK  B. SCHMITZ  M. M. M. MEIER  H. BAUR  R. WIELER 《Meteoritics & planetary science》2012,47(8):1297-1304

Abstract– Previous studies of limestone beds of mid‐Ordovician age from both Sweden and China show that the Earth saw an at least two orders of magnitude increase in the influx of extraterrestrial material approximately 470 Ma, following the disruption of an L‐chondrite parent body in the asteroid belt. Recovered extraterrestrial material consists of fossil meteorites and sediment‐dispersed extraterrestrial chromite (SEC) grains, both with L‐chondritic origin. Ne isotope analysis of SEC grains from one of the Swedish limestone sections revealed that the vast majority of the grains were delivered to Earth as micrometeorites. In this study, we extend the previous work, both in time and geographically, by measuring concentrations and isotopic ratios of Ne in individual SEC grains (60–120 μm in diameter) from three different beds from a contemporary Middle Ordovician limestone section in China. All of the Chinese SEC grains, 44 in total, contain surface‐implanted Ne of fractionated solar wind composition, implying that these grains were, as in the case of the Swedish SEC grains, delivered to Earth as micrometeorites. This gives further compelling evidence that the two to three orders of magnitude increase in the influx of micrometeoritic material following the breakup of the L‐chondrite parent body was indeed a global event. The rain of micrometeorites prevailed for at least 2 Myr (the estimated time of the deposition of the topmost Chinese bed) after the breakup event.  相似文献   

Costs and global impacts of black carbon abatement strategies     

By KRISTIN RYPDAL  NATHAN RIVE  TERJE K. BERNTSEN  ZBIGNIEW KLIMONT  TORBEN K. MIDEKSA  GUNNAR MYHRE  RAGNHILD B. SKEIE 《Tellus. Series B, Chemical and physical meteorology》2009,61(4):625-641

Abatement of particulate matter has traditionally been driven by health concerns rather than its role in global warming. Here we assess future abatement strategies in terms of how much they reduce the climate impact of black carbon (BC) and organic carbon (OC) from contained combustion. We develop global scenarios which take into account regional differences in climate impact, costs of abatement and ability to pay, as well as both the direct and indirect (snow-albedo) climate impact of BC and OC. To represent the climate impact, we estimate consistent region-specific values of direct and indirect global warming potential (GWP) and global temperature potential (GTP). The indirect GWP has been estimated using a physical approach and includes the effect of change in albedo from BC deposited on snow. The indirect GWP is highest in the Middle East followed by Russia, Europe and North America, while the total GWP is highest in the Middle East, Africa and South Asia. We conclude that prioritizing emission reductions in Asia represents the most cost-efficient global abatement strategy for BC because Asia is (1) responsible for a large share of total emissions, (2) has lower abatement costs compared to Europe and North America and (3) has large health cobenefits from reduced PM₁₀ emissions.  相似文献   

THREE NATURAL ZIRCON STANDARDS FOR U-TH-PB, LU-HF, TRACE ELEMENT AND REE ANALYSES   总被引：143，自引：0，他引：143  

M. WIEDENBECK  P. ALLÉ  F. CORFU  W.L. GRIFFIN  M. MEIER  F. OBERLI  A. VON QUADT  J.C. RODDICK†  W. SPIEGEL 《Geostandards and Geoanalytical Research》1995,19(1):1-23

We report here the results of a study to develop natural zircon geochemical standards for calibrating the U-(Th)-Pb geochronometer and Hf isotopic analyses. Additional data were also collected for the major, minor and trace element contents of the three selected sample sets. A total of five large zircon grains (masses between 0.5 and 238 g) were selected for this study, representing three different suites of zircons with ages of 1065 Ma, 2.5 Ma and 0.9 Ma. Geochemical laboratories can obtain these materials by contacting Geostandards Newsletter.  相似文献   

Comparison of the radiative properties and direct radiative effect of aerosols from a global aerosol model and remote sensing data over ocean   总被引：1，自引：1，他引：1  

GUNNAR MYHRE  NICOLAS BELLOUIN  TORE F. BERGLEN  TERJE K. BERNTSEN  OLIVIER BOUCHER  ALF GRINI  IVAR S. A. ISAKSEN  MONA JOHNSRUD  MICHAEL I. MISHCHENKO  FRODE STORDAL  DIDIER TANRÉ 《Tellus. Series B, Chemical and physical meteorology》2007,59(1):115-129

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Cosmic‐ray exposure age and preatmospheric size of the Bunburra Rockhole achondrite     

Kees C. WELTEN  Matthias M. M. MEIER  Marc W. CAFFEE  Matthias LAUBENSTEIN  Kunihiko NISHIZUMI  Rainer WIELER  Phil A. BLAND  Martin C. TOWNER  Pavel SPURNÝ 《Meteoritics & planetary science》2012,47(2):186-196

Abstract– Bunburra Rockhole is the first meteorite fall photographed and recovered by the Desert Fireball Network in Australia. It is classified as an ungrouped achondrite similar in mineralogical and chemical composition to eucrites, but it has a distinct oxygen isotope composition. The question is if achondrites like Bunburra Rockhole originate from the same parent body as the howardite‐eucrite‐diogenite (HED) meteorites or from several separate, differentiated parent bodies. To address this question, we measured cosmogenic radionuclides and noble gases in the Bunburra Rockhole achondrite. The short‐lived radionuclides ²²Na and ⁵⁴Mn confirm that Bunburra Rockhole is a recent fall. The concentrations of ¹⁰Be, ²⁶Al and ³⁶Cl as well as the ²²Ne/²¹Ne ratio indicate that Bunburra Rockhole was a relatively small object (R approximately 15 cm) in space, consistent with the photographic fireball observations. The cosmogenic ³⁸Ar concentration yields a cosmic‐ray exposure (CRE) age of 22 ± 3 Myr, whereas ²¹Ne and ³He yield approximately 30% and approximately 60% lower ages, respectively, due to loss of cosmogenic He and Ne, mainly from plagioclase. With a CRE age of 22 Myr, Bunburra Rockhole is the first anomalous eucrite that overlaps with the main CRE peak of the HED meteorites. The radiogenic K‐Ar age of 4.1 Gyr is consistent with the U‐Pb age, while the young U,Th‐He age of approximately 1.4 Gyr indicates that Bunburra Rockhole lost radiogenic ⁴He more recently.  相似文献   

Tardigrada from the Husvik area, South Georgia, sub-Antarctic     

PREBEN S. OTTESEN  TERJE MEIER 《Polar research》1990,8(2):291-294

Eleven species of tardigrades in South Georgia, of which two are new to science, were found in samples collected at fifteen localities. The highest number of species was found in moss from a scree field. Twenty species of tardigrades are presently known from South Georgia, but the island remains insufficiently investigated. The species composition is similar to that of southern South America. The high number of cosmopolitan species makes the geographical distribution pattern of the South Georgian tardigrades more similar to that of macrolichens than to that of insects and vascular plants.  相似文献   

Impacts of increased anthropogenic emissions in Asia on tropospheric ozone and climate   总被引：4，自引：0，他引：4  

TERJE BERNTSEN  IVAR S. A. ISAKSEN  WEI-CHYUNG WANG  XIN-ZHONG LIANG 《Tellus. Series B, Chemical and physical meteorology》1996,48(1):13-32

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ESTIMATION OF PREDICTION ERROR FOR SAMPLES WITHIN THE CALIBRATION RANGE     

JOSTEINTOFT  OLAVM.KVALHEIM 《地理学报(英文版)》1992,(4)

A modification of a technique proposed by Lorber and Kowalski for the estimation of prediction errorsis presented.The method is applied to five data sets.The results show that for some data sets theestimated prediction errors are close to the actual prediction errors for samples within the calibrationrange,while samples outside the calibration range must be background corrected before quantificationof the prediction error.  相似文献