论文标题
陨石的统计计时。 ii。短寿命放射性核素的初始丰度和同质性
Statistical Chronometry of Meteorites. II. Initial Abundances and Homogeneity of Short-lived Radionuclides
论文作者
论文摘要
行星形成的天体物理模型需要通过短寿命（Al-MG，MN-CR，HF-W）和长寿（PB-PB）天文学的准确辐射测定，并需要长期使用（PB-PB）天文序列，以在太阳星云中形成围绕Ca-Rich，Al-Al-Al-Al-Al-Al-Al-Planimimes，CAIS，CAIS，CHONDERES，CHONDERES，CHONDERES，CANODETES，CANODETERES，CANODETERES，CANODESERES，CARORES，CANODERES，CARORES，CANODERES，CANODERES，CANODERES，CANODERES，CAIS）的时间表。 （“ T = 0”）当存在短寿命的放射性核素26AL（T1/2 = 0.72 MYR）时，并且大概是在已知的水平上分布的，我们将其定义为（26AL/27AL）SS = 5.23 x10^-5。可以通过确定其初始（26AL/27AL）0比并将其比较（26AL/27AL）SS来找到另一个对象的t = 0之后的形成时间。使用MN-CR或HF-W系统的陨石对象的日期由于t = 0时的丰度（53MN/55MN）SS和（182HF/180HF）SS而受到阻碍。为了限制这些数量，我们为14个Achondrites编译了文献Al-Mg，Mn-CR，HF-W和PB-PB数据，并使用新颖的统计技术来最大程度地减少它们在这些系统中形成时间之间的差异。我们发现（53MN/55MN）ss =（8.09 +/- 0.65）X10^-6，（182HF/180HF）ss =（10.42 +/- 0.25）X10^-5，TSS = 4568.36 +/-0.20 myr，以及53mn firs of 3.80 +/--0.23 +/---0.230 +/----0.23 +/----0.230 +/---23 +/---23 +/-- 37个由不同系统记录的14个无吨位的形成时间。这些参数还使得从CB/CH ACHONDRITES衍生的软骨衍生的年龄相一致，并同时形成撞击，并且显然与I-XE天文钟也一致。我们的发现为太阳星云中的26AL，53MN和182HF的同质性提供了非常有力的支持，我们的方法为更精确的计时量提供了一个框架。
Astrophysical models of planet formation require accurate radiometric dating of meteoritic components by short-lived (Al-Mg, Mn-Cr, Hf-W) and long-lived (Pb-Pb) chronometers, to develop a timeline of such events in the solar nebula as formation of Ca-rich, Al-rich Inclusions (CAIs), chondrules, planetesimals, etc. CAIs formed mostly around a time ("t=0") when the short-lived radionuclide 26Al (t1/2 = 0.72 Myr) was present and presumably homogeneously distributed at a known level we define as (26Al/27Al)SS = 5.23 x10^-5. The time of formation after t=0 of another object can be found by determining its initial (26Al/27Al)0 ratio and comparing it to (26Al/27Al)SS. Dating of meteoritic objects using the Mn-Cr or Hf-W systems is hindered because the abundances (53Mn/55Mn)SS and (182Hf/180Hf)SS at t=0 are not known precisely. To constrain these quantities, we compile literature Al-Mg, Mn-Cr, Hf-W and Pb-Pb data for 14 achondrites and use novel statistical techniques to minimize the discrepancies between their times of formation across these systems. We find that for (53Mn/55Mn)SS = (8.09+/-0.65)x10^-6, (182Hf/180Hf)SS = (10.42+/-0.25)x10^-5, tSS = 4568.36+/-0.20 Myr, and a 53Mn half-life of 3.80+/-0.23 Myr, these four free parameters make concordant 37 formation times recorded by the different systems in 14 achondrites. These parameters also make concordant the ages derived for chondrules from CB/CH achondrites, formed simultaneously in an impact, and are apparently concordant with the I-Xe chronometer as well. Our findings provide very strong support for homogeneity of 26Al, 53Mn, and 182Hf in the solar nebula, and our approach offers a framework for more precise chronometry.
