Correlated cosmogenic W and Os isotopic variations in Carbo and implications for Hf–W chronology
Correlated cosmogenic W and Os isotopic variations in Carbo and implications for Hf–W chronology
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Carbo 中相关的宇宙成因 W 和 Os 同位素变化及其对 Hf-W 年代学的影响
DOI：
10.1016/j.gca.2014.11.015
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发表时间：
2015-03
影响因子：
5
通讯作者：
Carlson R. W.
中科院分区：
文献类型：
--
作者：
Qin L.;Dauphas N.;Horan M. F.;Leya I.;Carlson R. W.
利用182 Hf-182 W系统学（t1/2= 890万年）建立铁陨石形成年代学的一个障碍是找到合适的中子注量监测器来校正宇宙射线对W同位素组成的修改。最近的研究表明，亲铁元素如Pt和Os可以起到这样的作用。为了测试和校准这些中子剂量计，在IID铁陨石Carbo的板中测量了W和Os的同位素组成。该板具有特征良好的惰性气体深度剖面，反映了对宇宙射线的不同程度的屏蔽。结果表明，钨、锇同位素比值与距前大气层中心的距离有关。在ε 190 Os-ε 189 Os和ε 186 Os-ε 189 Os之间发现了负相关，其斜率分别为-0.64 ± 0.45和-1.8（+1.9/-2.1）。这些Os同位素的相关性大致同意模型预测捕获的二次中子产生的宇宙射线照射和其他组的铁陨石先前报道的结果。ε 182 W-ε 189 Os（斜率= 1.02 ± 0.37）和ε 182 W-ε 190 Os（斜率= −1.38 ± 0.58）之间也存在相关性。这两个相关性的截距分别产生暴露前ε 182 W值为−3.32 ± 0.51和−3.62 ± 0.23（加权平均ε 182 W = −3.57 ± 0.21）。这个值依赖于一个很大的外推法，导致很大的不确定性，但给出了太阳系形成后金属硅酸盐的分离年龄为-0.5 ± 2.4百万年。结合铁陨石的测量和宇宙成因效应的模拟，提出了用Os同位素计算和校正182 W宇宙成因效应的公式。
An obstacle for establishing the chronology of iron meteorite formation using182Hf–182W systematics (t1/2= 8.9 Myr) is to find proper neutron fluence monitors to correct for cosmic ray modification of W isotopic composition. Recent studies showed that siderophile elements such as Pt and Os could serve such a purpose. To test and calibrate these neutron dosimeters, the isotopic compositions of W and Os were measured in a slab of the IID iron meteorite Carbo. This slab has a well-characterized noble gas depth profile reflecting different degrees of shielding to cosmic rays. The results show that W and Os isotopic ratios correlate with distance from the pre-atmospheric center. Negative correlations, barely resolved within error, were found between ε190Os–ε189Os and ε186Os–ε189Os with slopes of −0.64 ± 0.45 and −1.8(+1.9/−2.1), respectively. These Os isotope correlations broadly agree with model predictions for capture of secondary neutrons produced by cosmic ray irradiation and results reported previously for other groups of iron meteorites. Correlations were also found between ε182W–ε189Os (slope = 1.02 ± 0.37) and ε182W–ε190Os (slope = −1.38 ± 0.58). Intercepts of these two correlations yield pre-exposure ε182W values of −3.32 ± 0.51 and −3.62 ± 0.23, respectively (weighted average ε182W = −3.57 ± 0.21). This value relies on a large extrapolation leading to a large uncertainty but gives a metal–silicate segregation age of −0.5 ± 2.4 Myr after formation of the solar system. Combining the iron meteorite measurements with simulations of cosmogenic effects in iron meteorites, equations are presented to calculate and correct for cosmogenic effects on182W using Os isotopes.
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DOI：
10.1016/j.nimb.2005.08.122
发表时间：
2006
影响因子：
1.3
作者：
O. Tavares;M. Terranova;E. L. Medeiros
通讯作者：
O. Tavares;M. Terranova;E. L. Medeiros
影响因子：
5.3
作者：
Francisco Calviño Tavares;Guillem Pere Cortés Rossell;Agustí Poch Parés;Carme Pretel Sánchez
通讯作者：
Francisco Calviño Tavares;Guillem Pere Cortés Rossell;Agustí Poch Parés;Carme Pretel Sánchez
影响因子：
64.8
作者：
M. Willbold;T. Elliott;S. Moorbath
通讯作者：
M. Willbold;T. Elliott;S. Moorbath
影响因子：
5.3
作者：
S. Mughabghab
通讯作者：
S. Mughabghab
影响因子：
5.3
作者：
Kruijer, Thomas S.;Fischer-Goedde, Mario;Wieler, Rainer
通讯作者：
Wieler, Rainer