Origin of lunar fragmental matrix breccias—Highly siderophile element constraints     

Philipp Gleißner  Harry Becker 《Meteoritics & planetary science》2019,54(9):2006-2026

Ejecta at North Ray crater (Apollo 16) sampled a unique section of the lunar highlands not accessible at most other landing sites and provide important constraints on the composition of late accreted materials. New data on multiple aliquots of four fragmental matrix breccias and a fragment‐laden melt breccia from this site display a variety of highly siderophile element patterns which may represent the signatures of volatile element‐depleted carbonaceous chondrite‐like material, primitive achondrite, differentiated metal, and an impactor component that cannot be related to known meteoritic material. The latter component is prevalent in these rocks besides characterized by depletions in Re and Os compared to Ir, Ru and Pt, chondritic Re/Os, and a gradual depletion of Pd and Au. The observed characteristics are more consistent with fractionations by nebular processes, like incomplete condensation or evaporation, than with lunar crustal processes, like partial melting or volatilization. The impactor signature preserved in these breccias may stem from primitive meteorites with a refractory element composition moderately different from known chondrites. The presence of distinct impactor components within the North Ray crater breccias together with observed correlations of characteristic element ratios (e.g., Re/Os, Ru/Pt, Pd/Ir) in different impact lithologies of four Apollo landing sites constrains physical mixing processes ranging from the scale of gram‐sized samples to the area covered by the Apollo missions.  相似文献   

Strain measurements with the borehole slotter     

A. Becker  D. Werner 《地学学报》1994,6(6):608-617

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Methods to determine the angular resolution of the HEGRA extended air shower scintillator array     

M. Merck  A. Karle  S. Martinez  F. Arqueros  K. H. Becker  M. Bott-Bodenhausen  R. Eckmann  E. Faleiro  J. Fernandez  P. Fernandez  V. Fonseca  V. Haustein  G. Heinzelmann  I. Holl  F. Just  F. Krennrich  M. Kühn  E. Lorenz  H. Meyer  N. Müller  R. Plaga  J. Prahl  M. Probst  M. Rozanska  M. Samorski  H. Sander  K. Sauerland  C. Sesea  W. Stamm 《Astroparticle Physics》1996,5(3-4):379-392

A precise knowledge of the angular resolution of scintillator arrays used to observe extended air showers (EAS) is of key importance in the search for VHE/UHE γ point sources. Four independent methods have been used to determine the mean resolution for which a value of ΔΘ₆₃ of 0.8°(1.0°) at a proton threshold of 50 (40) TeV has been found for the HEGRA EAS-array.  相似文献   

A proposed new type of arsenian pyrite: Composition, nanostructure and geological significance   总被引：8，自引：0，他引：8  

Artur P. Deditius  Udo Becker  Stephen E. Kesler 《Geochimica et cosmochimica acta》2008,72(12):2919-2933

This report describes a new form of arsenian pyrite, called As³⁺-pyrite, in which As substitutes for Fe [(Fe,As)S₂], in contrast to the more common form of arsenian pyrite, As¹⁻-pyrite, in which As¹⁻ substitutes for S [Fe(As,S)₂]. As³⁺-pyrite has been observed as colloformic overgrowths on As-free pyrite in a hydrothermal gold deposit at Yanacocha, Peru. XPS analyses of the As³⁺-pyrite confirm that As is present largely as As³⁺. EMPA analyses show that As³⁺-pyrite incorporates up to 3.05 at % of As and 0.53 at. %, 0.1 at. %, 0.27 at. %, 0.22 at. %, 0.08 at. % and 0.04 at. % of Pb, Au, Cu, Zn, Ni, and Co, respectively. Incorporation of As³⁺ in the pyrite could be written like: As³⁺+yAu⁺+1-y(□)⇔2Fe²⁺; where Au⁺ and vacancy (□) help to maintain the excess charge. HRTEM observations reveal a sharp boundary between As-free pyrite and the first overgrowth of As³⁺-pyrite (20-40 nm thick) and co-linear lattice fringes indicating epitaxial growth of As³⁺-pyrite on As-free pyrite. Overgrowths of As³⁺-pyrite onto As-free pyrite can be divided into three groups on the basis of crystal size, 8-20 nm, 100-300 nm and 400-900 nm, and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals. The Yanacocha deposit, in which As³⁺-pyrite was found, formed under relatively oxidizing conditions in which the dominant form of dissolved As in the stability field of pyrite is As³⁺; in contrast, reducing conditions are typical of most environments that host As¹⁻-pyrite. As³⁺-pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments, including high-sulfidation epithermal deposits and shallow groundwater systems, where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of As³⁺ and toxic heavy metals in oxidizing natural systems.  相似文献   

Die neuen Arbeiten zur Geologie von Sachsen     

Hans Becker 《International Journal of Earth Sciences》1926,17(5):349-368

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Das Gebiet des Yangtze-Deltas mit den Nanking-Bergen     

Hans Becker 《International Journal of Earth Sciences》1937,28(5):385-406

Ohne Zusammenfassung  相似文献   

The Tamayo transform fault in the mouth of the Gulf of California     

K. A. Kastens  K. C. Macdonald  K. Becker  K. Crane 《Marine Geophysical Researches》1979,4(2):129-151

The Tamayo transform fault is located at the north end of the East Pacific Rise where it enters the Gulf of California. This paper presents bathymetric, seismic reflection, magnetic, and gravity data from a detailed survey of the transform fault. The dominant feature of the offset region is a bathymetric ridge trending 120°, parallel to the predicted transform plate boundary. This transform ridge is associated with a large (600 ) positive magnetic anomaly, and a very small positive free-air gravity anomaly. Magnetic and gravity models indicate either a basalt or serpentinite composition for the ridge, but cannot distinguish between these possibilities. At its eastern end, the modern zone of strike-slip motion is in a narrow valley south of the transform ridge. The transform plate margin appears to pass through a saddle in the transform ridge and meet the western spreading center segment in the trough north of the transform ridge. On the basis of this survey and previous work, the history of the Tamayo from continental breakup to the present has been reconstructed. Initial rifting occurred along a trend of 130° at approximately 3.5 m.y.b.p. Once the transform fault was free of the constraints imposed by continent-continent and continent-oceanic lithospheric interaction, the trend of the transform fault rotated counter-clockwise. This rotation resulted in a leaky transform fault and intrusion of a large continuous transform ridge. Further adjustments in the spreading center/transform fault plate boundary configuration have given rise to an incipient zone of rifting cutting across the transform ridge and emplacement of diapiric structures.Contribution of the Scripps Institution of Oceanography, new series.  相似文献   

Volcanic stratigraphy of DSDP/ODP Hole 395A: An interpretation using well-logging data   总被引：1，自引：0，他引：1  

Bartetzko  Anne  Pezard  Philippe  Goldberg  David  Sun  Yue-Feng  Becker  Keir 《Marine Geophysical Researches》2001,22(2):111-127

Deep Sea Drilling Project/Ocean Drilling Program Hole 395A was drilled approximately 500 m deep into young oceanic crust west of the Mid-Atlantic Ridge. Core recovery is very poor in this hole and therefore continuous downhole measurements are important to understand the drilled lithology. Geophysical downhole measurements were carried out during several cruises. A new set of logs was recorded during Leg 174B in summer 1997. The new logging data show a significant improvement in data quality compared to older measurements from Leg 109. The lithostratigraphy established from cores gives only limited information because of the poor core recovery in this hole. The gaps in the core lithostratigraphy are filled by reconstructing a synthetic lithological profile using the standard well-logging data. Three types of lava morphologies, massive basalts, altered lava flows, and pillow basalts, may be distinguished using the logs because the lava morphologies show differences in their physical properties due to differences in fracturing and alteration. The synthetic lithological profile gives a more detailed and precise vertical definition of single layers than the core profile. The integration of further logging and core data enables a detailed reconstruction of the accretion history at the drill site. Cyclic, upward decreasing trends in the resistivity logs were already observed during earlier cruises and were referred to magmatic cycles. Similar trends occur in the density log and, inversely, in the total gamma ray log. The trends reflect gradual changes in fracturing, porosity, permeability, and alteration and cover depth intervals of several tens of meters. Boundaries between cycles are interpreted to correspond to periods of volcanic quiescence. Two types of boundaries may be identified. Boundaries correlating with reversals in the magnetic field and/or changes in the geochemical composition of the basalts are interpreted as long pauses. Basalts separated by these boundaries were probably fed by separate magma reservoirs. Boundaries identified only by changes in alteration but not in geochemistry are interpreted to represent shorter pauses. They separate basalts that were probably fed by the same magma chamber. This revised version was published online in November 2006 with corrections to the Cover Date.  相似文献   

The contact binary AE phoenicis — An analysis from deconvoluted spectra     

H. J. Becker 《Astrophysics and Space Science》1984,99(1-2):157-161

A method is described for an analysis of deconvoluted stellar spectra, and applied to new spectroscopic observations of the close eclipsing system AE Phuenicis, obtained with the 1.52 m telescope of the Southern European Observatory at La Silla, Chile, Results are presented for the rotational velocities of this variable, together with a proposed model of the system.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.  相似文献   

The Chan Hol cave near Tulum (Quintana Roo,Mexico): evidence for long‐lasting human presence during the early to middle Holocene          下载免费PDF全文

Fabio Hering  Wolfgang Stinnesbeck  Jens Folmeister  Eberhard Frey  Sarah Stinnesbeck  Jerónimo Avilés  Eugenio Aceves Núñez  Arturo González  Alejandro Terrazas Mata  Martha Elena Benavente  Carmen Rojas  Adriana Velázquez Morlet  Norbert Frank  Patrick Zell  Julia Becker 《第四纪科学杂志》2018,33(4):444-454

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