کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
9522129 1634962 2005 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Search for traces of the late heavy bombardment on Earth-Results from high precision chromium isotopes
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
Search for traces of the late heavy bombardment on Earth-Results from high precision chromium isotopes
چکیده انگلیسی
High precision mass spectrometric analyses of the chromium isotopic composition of metamorphosed turbiditic and pelagic sedimentary rocks and banded iron stones from the ∼3.7 Gyr Isua Supracrustal Belt (ISB) in West Greenland cannot be distinguished from the standard terrestrial 53Cr / 52Cr ratio at our present level of resolution. As a consequence, our search for chemical traces of possible impact-derived meteoritic components (asteroidal and/or cometary material, or accreted cosmic dust) in the Earth's oldest chemical and detrital sediments was negative. Our results, based on the 53Mn-53Cr short-lived radionuclide system (half-life of 3.7 Myr), cannot confirm the recent findings by [1] [R. Schoenberg, B.S. Kamber, K.D. Collerson, S. Moorbath. Tungsten isotope evidence from approximately 3.8-Gyr metamorphosed sediments for early meteorite bombardment of the Earth. Nature 418 (2002) 403-405.] of tungsten isotope anomalies (based on the 182Hf-182W short-lived radionuclide system; half-life of 9 Myr) in these sediments, which were interpreted as indicating a component derived from meteorites. Possible reasons for the failure to trace cosmic material in the ISB metasediments are various: 1. The samples studied are not representative; 2: The sedimentation period did not overlap with the period of late heavy bombardment of the Moon; and 3. The potential chromium anomalies, if present, are too small to be traceable by our present levels of detection. Unequivocal evidence of a late heavy bombardment on the early Earth therefore remains elusive and uncertain.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 236, Issues 1–2, 30 July 2005, Pages 28-40
نویسندگان
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