The Variscan metamorphism in the Pyrenees is dominantly of the low-pressure–high-temperature (LP–HT) type. The relics of an earlier, Barrovian-type, metamorphism that could be related to orogenic crustal thickening are unclear and insufficiently constrained. A microstructural and petrological study of micaschists underlying an Ordovician augen orthogneiss in the core of the Canigou massif (Eastern Pyrenees, France) reveal the presence of two syntectonic metamorphic stages characterized by the crystallization of staurolite (M1) and andalusite (M2), respectively. Garnet is stable during the two metamorphic stages with a period of resorption between M1 and A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. M2. The metamorphic assemblages M1 and M2 record similar peak temperatures of 580 °C at different pressure conditions of 5.5 kbar and 3 kbar, respectively. Using chemical zoning of garnet and calculated P–T pseudosections, a prograde P–T path is constrained with a peak pressure at ~6.5 kbar and 550 °C. This P–T path, syntectonic with respect to the first foliation S1, corresponds to a cold gradient (of ~9 °C/km), suggestive of crustal thickening. Resorption of garnet between M1 and M2 can be interpreted either in terms of a simple clockwise P–T path or a polymetamorphic two stage evolution. We argue in favour of the latter, where the medium-pressure (Barrovian) metamorphism is followed by a period of significant erosion and crustal thinning leading to decompression and cooling. Subsequent advection of heat, probably from the mantle, lead to a new increase in temperature, coeval with the development of the main regional fabric S2. LA-ICP-MS U-Th-Pb dating of monazite yields a well-defined date at c. 300 Ma. Petrological evidence indicates that monazite crystallization took place close to the M1 peak-pressure conditions. However, the similarity between this age and that of the extensive magmatic event well documented in the eastern Pyrenees suggests that it probably corresponds to the age of monazite recrystallization during the M2 LP–HT event.

中文翻译：

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Canigou 地块的两阶段 Variscan 变质作用：比利牛斯山脉地壳增厚的证据

比利牛斯山脉的 Variscan 变质作用主要是低压-高温 (LP-HT) 型。可能与造山地壳增厚有关的较早的巴罗式变质作用的遗迹尚不清楚，也没有受到足够的约束。对 Canigou 地块（法国东比利牛斯山脉）核心奥陶纪正方麻岩下的云母片岩的微观结构和岩石学研究揭示了两个同构造变质阶段的存在，其特征分别是十字石 (M1) 和红柱石 (M2) 的结晶。石榴石在两个变质阶段是稳定的，在 M1 和 A 之间有一段吸收期。 cc ep te d Art ic le 本文受版权保护。版权所有。M2。变质组合 M1 和 M2 分别在 5.5 kbar 和 3 kbar 的不同压力条件下记录了类似的峰值温度 580 °C。使用石榴石的化学分区和计算出的 P-T 假截面，顺行 P-T 路径受到峰值压力为 ~6.5 kbar 和 550 °C 的限制。这条 P-T 路径，相对于第一个叶理 S1 同构造，对应于冷梯度（~9°C/km），暗示地壳增厚。M1 和 M2 之间石榴石的吸收可以解释为简单的顺时针 P-T 路径或多变质的两阶段演化。我们支持后者，其中中压（巴罗维）变质作用之后是一段显着的侵蚀和地壳变薄，导致减压和冷却。随后的热量平流，可能来自地幔，导致温度的新升高，与主要区域结构 S2 的发展同时发生。独居石的 LA-ICP-MS U-Th-Pb 定年在 c 处产生了明确定义的日期。300 马。岩石学证据表明独居石结晶发生在 M1 峰值压力条件附近。然而，这个年龄与东比利牛斯山脉广泛记录的岩浆事件的相似性表明它可能对应于 M2 LP-HT 事件期间独居石再结晶的年龄。