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Combination of Δ47 and U-Pb dating in tectonic calcite veins unravel the last pulses related to the Pyrenean Shortening (Spain)
Earth and Planetary Science Letters ( IF 5.3 ) Pub Date : 2021-01-01 , DOI: 10.1016/j.epsl.2020.116636
Guilhem Hoareau , Nemo Crognier , Brice Lacroix , Charles Aubourg , Nick M.W. Roberts , Nathan Niemi , Mathieu Branellec , Nicolas Beaudoin , Isabel Suárez Ruiz

Abstract Clumped isotopes thermometry (Δ47) and U-Pb dating of carbonates have been used to elucidate the temperature-time conditions of 10 tectonic calcite veins in the hanging wall of the South Pyrenean Frontal Thrust (Spain), the youngest thrust unit in the south-central Pyrenees. The Δ47 values indicate precipitation temperatures below ∼90 °C, in agreement with fluid inclusion analyses. 6 veins have been successfully dated, giving ages between 61 and 14.5 Ma with all but one value below 24 Ma. On the basis of our new results, we propose that several the studied veins record the end of Pyrenean tectonics in the area during the Burdigalian, possibly up to the Serravalian, younger than estimates based on magnetostratigraphic data from continental syn-tectonic deposits. Calculated δ 18 O values of the precipitating fluid are either very positive, suggesting a local source that has interacted with the host rock, or negative, suggesting the downward incursion of meteoric waters. For undated or pre-burial veins, the Δ47 values derived from temperature history reordering model (THRM) show that the measured Δ47 values may have been significantly altered during burial, preventing their use as a reliable thermal or paleohydrological marker. Although applied to a limited number of samples, these results highlight the great potential of the U-Pb/Δ47 approach to decipher the history of vein or cement formation and fluid flow in complex tectonic zones, provided that (i) the thermal evolution is known and (ii) the extent of clumped isotope reordering is systematically modelled.

中文翻译:

构造方解石脉中 Δ47 和 U-Pb 测年的组合揭示了与比利牛斯缩短(西班牙)相关的最后脉冲

摘要 利用碳酸盐的成簇同位素测温 (Δ47) 和 U-Pb 测年,阐明了南比利牛斯山脉锋冲断层(西班牙)上盘中 10 条构造方解石脉的温度-时间条件,南比利牛斯山前冲断层是南部最年轻的逆冲冲断单元。 -中央比利牛斯。Δ47 值表明沉淀温度低于 ~90 °C,与流体包裹体分析一致。6 条矿脉已成功测年,年龄在 61 到 14.5 Ma 之间,只有一个值低于 24 Ma。根据我们的新结果,我们提出,一些研究的矿脉记录了该地区比利牛斯构造在布尔迪加期的结束,可能直到塞拉瓦期,比基于大陆同构造矿床的磁地层数据估计的更年轻。计算出的沉淀流体的 δ 18 O 值要么非常正,要么 表明当地源与主岩相互作用,或否定,表明大气水向下侵入。对于未注明日期或埋藏前的静脉,从温度历史重新排序模型 (THRM) 得出的 Δ47 值表明,测量的 Δ47 值可能在埋藏期间发生了显着变化,从而阻止了它们作为可靠的热学或古水文标记的使用。尽管应用于有限数量的样本,但这些结果突出了 U-Pb/Δ47 方法在破译复杂构造带中静脉或胶结物形成和流体流动的历史方面的巨大潜力,前提是 (i) 热演化是已知的(ii) 对聚集同位素重新排序的程度进行系统建模。表明大气水向下侵入。对于未注明日期或埋藏前的静脉,从温度历史重新排序模型 (THRM) 得出的 Δ47 值表明,测量的 Δ47 值可能在埋藏期间发生了显着变化,从而阻止了它们作为可靠的热学或古水文标记的使用。尽管应用于有限数量的样本,但这些结果突出了 U-Pb/Δ47 方法在破译复杂构造带中静脉或胶结物形成和流体流动的历史方面的巨大潜力,前提是 (i) 热演化是已知的(ii) 对聚集同位素重新排序的程度进行系统建模。表明大气水向下侵入。对于未注明日期或埋藏前的静脉,从温度历史重新排序模型 (THRM) 得出的 Δ47 值表明,测量的 Δ47 值可能在埋藏期间发生了显着变化,从而阻止了它们作为可靠的热学或古水文标记的使用。尽管应用于有限数量的样本,但这些结果突出了 U-Pb/Δ47 方法在破译复杂构造带中静脉或胶结物形成和流体流动的历史方面的巨大潜力,前提是 (i) 热演化是已知的(ii) 对聚集同位素重新排序的程度进行系统建模。防止它们用作可靠的热学或古水文标记。尽管应用于有限数量的样本,但这些结果突出了 U-Pb/Δ47 方法在破译复杂构造带中静脉或胶结物形成和流体流动的历史方面的巨大潜力,前提是 (i) 热演化是已知的(ii) 对聚集同位素重新排序的程度进行系统建模。防止它们用作可靠的热学或古水文标记。尽管应用于有限数量的样本,但这些结果突出了 U-Pb/Δ47 方法在破译复杂构造带中静脉或胶结物形成和流体流动的历史方面的巨大潜力,前提是 (i) 热演化是已知的(ii) 对聚集同位素重新排序的程度进行系统建模。
更新日期:2021-01-01
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