Argon redistribution during a metamorphic cycle: Consequences for determining cooling rates
Argon redistribution during a metamorphic cycle: Consequences for determining cooling rates
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变质循环期间的氩气重新分布：确定冷却速率的后果
DOI：
10.1016/j.chemgeo.2016.09.028
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
McDonald C
中科院分区：
文献类型：
--
作者：
McDonald C
40 Ar/39 Ar热年代学通常用于限制折返变质岩石的冷却速率和时间，年龄通常通过Dodson的闭合温度（TC）公式与温度联系起来。虽然许多变质40 Ar/39 Ar数据与结晶或冷却的时间一致，但在由其他更高温度的计时器定义的年代框架内，其他40 Ar/39 Ar数据更难以解释。我们报告了挪威西部片麻岩地区长英质片麻岩的白色云母和黑云母单颗粒熔融和激光烧蚀40 Ar/39 Ar年龄。这些岩石记录了在c时从榴辉岩相峰值条件（白色云母稳定）到角闪岩相条件（黑云母稳定）的等温减压。七百度。白色云母和黑云母的分散单颗粒熔融年龄分别为416 ~ 373 Ma和437 ~ 360 Ma。原位激光烧蚀分析提供了一个类似的范围，与白色云母斑点年龄范围从424至370 Ma和黑云母斑点年龄范围从437至370 Ma。的日期跨度的变质周期的持续时间建议由以前的研究，并不能与简单的模型的Ar损失在冷却过程中的扩散的结果。显示不同物理过程（如白色云母的化学分解、部分熔融和流体进入）证据的样品与没有经历或记录这些过程的明显岩石学证据的样品产生不同的年龄群体。样品记录显着的重结晶和变形产生年轻的白色云母（但老黑云母）单颗粒熔融年龄比更原始的样品。角闪岩相的片麻岩，保存证据显着的部分熔融产生年轻的黑云母年龄比样品记录的证据显着水合作用。我们的数据支持其他报告的意见，高温变质云母40 Ar/39 Ar的日期不能被假定为通过一个特定的温度窗口记录冷却的时间。仔细评估的岩相背景的过时的矿物和考虑他们的结晶后的历史可能会提供一个更强大的洞察力是否“年龄”链接到“阶段”在时间上有意义的方式。
40Ar/39Ar thermochronology is commonly used to constrain the rates and times of cooling in exhumed metamorphic terranes, with ages usually linked to temperature via Dodson's closure temperature (TC) formulation. Whilst many metamorphic40Ar/39Ar data are consistent with the timing of crystallisation or cooling within a chronological framework defined by other, higher temperature, chronometers, other40Ar/39Ar data are more difficult to interpret. We report white mica and biotite single grain fusion and laser ablation40Ar/39Ar ages from felsic gneisses from the Western Gneiss Region, Norway. The rocks record isothermal decompression from peak eclogite-facies conditions (white mica stable) to amphibolite-facies conditions (biotite stable) at c. 700 °C. White mica and biotite yield dispersed single grain fusion dates from 416 to 373 Ma and 437 to 360 Ma respectively. In-situ laser ablation analyses provide a similar range, with white mica spot ages ranging from 424 to 370 Ma and biotite spot ages ranging from 437 to 370 Ma. The dates span the duration of the metamorphic cycle suggested by previous studies, and cannot be reconciled with the results of simple models of Ar loss by diffusion during cooling. Samples that show evidence for different physical processes, such as the chemical breakdown of white mica, partial melting, and fluid ingress, generated different age populations to samples that did not experience or record obvious petrological evidence for these processes. Samples that record significant recrystallization and deformation yielded younger white mica (but older biotite) single grain fusion ages than more pristine samples. Amphibolite-facies gneisses that preserve evidence for significant partial melting generated younger biotite ages than samples that recorded evidence for significant hydration. Our data support other reported observations that high-temperature metamorphic mica40Ar/39Ar dates cannot be assumed to record the timing of cooling through a specific temperature window. Careful assessment of the petrographic context of the dated minerals and consideration of their post-crystallisation history may provide a more robust insight into whether ‘age’ links to ‘stage’ in a temporally meaningful way.
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Kl Ar 年龄来自挪威西部 Stadlandet 地区的基底片麻岩地区
DOI：
--
发表时间：
1985
期刊：
影响因子：
--
作者：
D. Lux;D. Lux
通讯作者：
D. Lux
挪威西部超高压转变的结构和 40Ar/39Ar 热年代学
影响因子：
2.7
作者：
D. Young;B. Hacker;T. Andersen;P. Gans
通讯作者：
P. Gans
影响因子：
3.7
作者：
D. Mark;D. Barfod;F. Stuart;J. Imlach
通讯作者：
D. Mark;D. Barfod;F. Stuart;J. Imlach
影响因子：
3.1
作者：
Whitney, Donna L.;Evans, Bernard W.
通讯作者：
Evans, Bernard W.
影响因子：
5
作者：
K. Foland
通讯作者：
K. Foland