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首页> 外文学位 >Extinct Radionuclides in the Early Solar System: The Initial Solar System Abundance of Iron-60 from Angrites and Unequilibrated Ordinary Chondrites and Aluminum-26-Magnesium-26 Chronology of Ungrouped Achondrites.
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Extinct Radionuclides in the Early Solar System: The Initial Solar System Abundance of Iron-60 from Angrites and Unequilibrated Ordinary Chondrites and Aluminum-26-Magnesium-26 Chronology of Ungrouped Achondrites.

机译：早期太阳系中已灭绝的放射性核素：来自太阳神的铁60和未平衡的普通球粒陨石的初始太阳系的丰度以及未分组的球粒陨石的铝26镁26的年表。

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摘要

The presence of a number of extinct radionuclides in the early Solar System (SS) is known from geochemical and isotopic studies of meteorites and their components. The half-lives of these isotopes are short relative to the age of the SS, such that they have now decayed to undetectable levels. They can be inferred to exist in the early SS from the presence of their daughter nuclides in meteoritic materials that formed while they were still extant. The extinct radionuclides are particularly useful as fine-scale chronometers for events in the early SS. They can also be used to help constrain the astrophysical setting of the formation of the SS because their short half-lives and unique formation environments yield information about the sources and timing of delivery of material to the protoplanetary disk. Some extinct radionuclides are considered evidence that the Sun interacted with a massive star (supernova) early in its history.;The abundance of 60Fe in the early SS is particularly useful for constraining the astrophysical environment of the Sun's formation because, if present in sufficient abundance, its only likely source is injection from a nearby supernova. The initial SS abundance of 60Fe is poorly constrained at the present time, with estimates varying by 1-2 orders of magnitude. I have determined the 60Fe-60Ni isotope systematics of ancient, well-preserved meteorites using high-precision mass spectrometry to better constrain the initial SS abundance of 60Fe. I find identical estimates of the initial 60Fe abundance from both differentiated basaltic meteorites and from components of primitive chondrites formed in the Solar nebula, which suggest a lower 60Fe abundance than other recent estimates.;With recent improved meteorite collection efforts there are more rare ungrouped meteorites being found that hold interesting clues to the origin and evolution of early SS objects. I use the 26Al-26 Mg extinct radionuclide chronometer to constrain the ages of several recently recovered meteorites that sample previously unknown asteroid lithologies, including the only know felsic meteorite from an asteroid and two other ungrouped basaltic achondrites. These results help broaden our understanding of the timescales involved in igneous differentiation processes in the early SS.
机译：从陨石及其成分的地球化学和同位素研究中可以知道，早期太阳系（SS）中存在许多已灭绝的放射性核素。这些同位素的半衰期相对于SS的寿命短，因此它们现在已经衰减到无法检测的水平。从它们尚存时形成的陨石中存在子核素，可以推断它们存在于SS早期。灭绝的放射性核素特别适合用作早期SS事件的精密天文钟。它们还可以用于帮助限制SS的天体物理环境，因为它们的短半衰期和独特的形成环境会产生有关物质向原行星盘输送的来源和时间的信息。某些已灭绝的放射性核素被认为是太阳在其历史早期与大质量恒星（超新星）相互作用的证据。; SS初期60Fe的丰度对于限制太阳形成的天体物理环境特别有用，因为如果存在足够的丰度，它唯一可能的来源是附近超新星的注入。目前，最初对60Fe的SS丰度缺乏很好的约束，估计值相差1-2个数量级。我已经使用高精度质谱仪确定了古老的，保存完好的陨石的60Fe-60Ni同位素系统，以更好地限制60Fe的初始SS丰度。我从分化的玄武陨石和太阳星云中形成的原始球粒陨石的成分中发现了对初始60Fe丰度的相同估计，这表明60Fe丰度比其他最近的估计值要低。被发现为早期SS对象的起源和演化提供了有趣的线索。我使用26Al-26 Mg灭绝放射性核素天文钟表来约束几个最近恢复的陨石的年龄，这些陨石对以前未知的小行星岩性进行采样，包括唯一已知的小行星陨石陨石和另外两个未分组的玄武质陨石。这些结果有助于拓宽我们对早期SS火成分化过程涉及的时间尺度的理解。

著录项

  • 作者

    Spivak-Birndorf, Lev.;

  • 作者单位

    Arizona State University.;

  • 授予单位 Arizona State University.;
  • 学科 Geology.;Geochemistry.;Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 193 p.
  • 总页数 193
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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