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首页> 外文期刊>Journal of Metamorphic Geology >Coupled Lu-Hf and Sm-Nd geochronology constrains garnet growth in ultra-high-pressure eclogites from the Dabie orogen
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Coupled Lu-Hf and Sm-Nd geochronology constrains garnet growth in ultra-high-pressure eclogites from the Dabie orogen

机译：Lu-Hf和Sm-Nd地质年代学相结合，限制了大别造山带超高压榴辉岩中的石榴石生长。

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摘要

Ultra-high-pressure eclogites from the Dabie orogen that formed over a range in temperatures (similar to 600 to > 700 degrees C) have been investigated with combined Lu-Hf and Sm-Nd geochronology. Three eclogites, sampled from Zhujiachong, Huangzhen and Shima, yield Lu-Hf ages of 240.0 +/- 5.0, 224.4 +/- 1.9 and 230.8 +/- 5.0 Ma and corresponding Sm-Nd ages of 222.5 +/- 5.0, 217.6 +/- 6.1 and 224.2 +/- 2.1 Ma respectively. Well-preserved prograde major- and trace-element zoning in garnet in the Zhujiachong eclogite suggests that the Lu-Hf age mostly reflects an early phase of garnet growth that continued over a time interval of c. 17.5 Myr. For the Huangzhen eclogite, despite preserved elemental growth zoning in garnet, textural study reveals that the Lu-Hf age is biased towards a later garnet growth episode rather than representing early growth. The narrow time interval of < 6.6 Myr defined by the difference between Lu-Hf and Sm-Nd ages indicates a short final garnet growth episode and suggests a rapid cooling stage. By contrast, the rather flat element zoning in garnet in the Shima eclogite suggests that Lu-Hf and Sm-Nd ages for this sample have been reset by diffusion and are cooling ages. The new Lu-Hf ages point to an initiation of prograde metamorphism prior to c. 240 Ma for the Dabie orogen, while the exact peak metamorphic timing experienced by specific samples ranges between c. 230 to c. 220 Ma.
机译：通过结合Lu-Hf和Sm-Nd地质年代学研究了在一定温度范围内（约600至> 700摄氏度）形成的大别造山带超高压榴辉岩。从朱家冲，黄镇和志摩采样的三个榴辉岩的Lu-Hf年龄分别为240.0 +/- 5.0、224.4 +/- 1.9和230.8 +/- 5.0 Ma，相应的Sm-Nd年龄为222.5 +/- 5.0、217.6 +分别为6.1和224.2 +/- 2.1 Ma。竹家冲榴辉岩中石榴石保存完好的主要和微量元素区划表明，Lu-Hf年龄主要反映了石榴石生长的早期阶段，持续了大约c的时间间隔。 17.5马币对于黄镇榴辉岩，尽管保留了石榴石中的元素生长区域，但结构研究显示，Lu-Hf年龄偏向于石榴石后期生长，而不是代表早期生长。 Lu-Hf和Sm-Nd年龄之间的差异定义了小于6.6 Myr的狭窄时间间隔，这表明最终的石榴石生长期很短，并显示出快速的冷却阶段。相比之下，在Shima榴辉岩中石榴石中相当平坦的元素区带表明，该样品的Lu-Hf和Sm-Nd年龄已经通过扩散而重置，并且处于冷却年龄。新的Lu-Hf年龄指向在c之前开始进行蜕变。大别造山带240 Ma，而特定样品经历的确切的变质时间正好在c到100之间。 230至c 220毫安。

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