TUNGSTEN AND HAFNIUM DISTRIBUTION IN CALCIUM - ALUMINUM INCLUSIONS ( CAIs ) FROM ALLENDE
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منابع مشابه
TUNGSTEN AND HAFNIUM DISTRIBUTION IN CALCIUM-ALUMINUM INCLUSIONS (CAIs) FROM ALLENDE AND EFREMOVKA
Introduction: A widely accepted paradigm for the origin of chondrites maintains that chondrites represent the earliest planetesimals to form from the solar nebula and that differentiated bodies formed by the subsequent melting of chondrites. A challenge to this paradigm comes from physical models of accretion that require rapid accretion of ~10 km planetesimals that are then melted by the heat ...
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Application of Hf–W chronometry to constrain the duration of early solar system processes requires the precise knowledge of the initial Hf and W isotope compositions of the solar system. To determine these values, we investigated the Hf–W isotopic systematics of bulk samples and mineral separates from several Ca,Al-rich inclusions (CAIs) from the CV3 chondrites Allende and NWA 2364. Most of the...
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The Hf–W systematics of meteoritic and planetary samples provide firm constraints on the chronology of the accretion and earliest evolution of asteroids and terrestrial planets and lead to the following succession and duration of events in the earliest solar system. Formation of Ca,Al-rich inclusions (CAIs) at 4568.3 ± 0.7 Ma was followed by the accretion and differentiation of the parent bodie...
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AbstructThe etch rates for 317 combinations of 16 materials (single-crystal silicon, doped, and undoped polysilicon, several types of silicon dioxide, stoichiometric and silicon-rich silicon nitride, aluminum, tungsten, titanium, TVW alloy, and two brands of positive photoresist) used in the fabrication of microelectromechanical systems and integrated circuits in 28 wet, plasma, and plasmaless-...
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تاریخ انتشار 2006