Although there is a consensus about Pangea assemblage in northwestern Gondwana spanning from the Late Carboniferous to the Early Permian, the tectonics of the Permo–Triassic period, including the onset of Pangea breakup, is still controversial. In this context, three regional tectonic features need to be considered: (1) The Ouachita-Marathon-Sonora suture, (2) east-dipping subduction of the Panthalassa oceanic crust beneath Gondwana, and (3) an extensional setting documented in Colombia, Ecuador, and México suggesting Pangea breakup at ca. 240–220 Ma. A chemical, isotopic, and geochronological dataset is presented in this contribution to constrain the effects of these tectonic processes in the metamorphic basement of the Mérida Andes in western Venezuela. U–Pb Secondary Ion Mass Spectrometry analyses on unpolished surfaces of zircons from orthogneisses yielded an average age of 251 ± 4 Ma. The corresponding δ¹⁸O values suggest metamorphic recrystallization of zircon instead of high-T fluid interaction. Rb–Sr and Sm–Nd geochronology in white mica and garnet yielded ages of 234 ± 3 Ma and 249 ± 2 Ma, respectively, whereas a younger Rb–Sr date of 197 ± 1 Ma was obtained from biotite. U–Pb and Sm–Nd ages constrain the latest Permian–earliest Triassic metamorphism in the Mérida Andes at 251 ± 4 Ma. Geothermobarometry data suggest amphibolite-facies peak metamorphic conditions at ~ 685 °C and ~ 6.0 kbar. Metamorphism might be related to post-orogenic collapse, after the collision of Gondwana and Laurentia to form Pangea. Rb–Sr ages suggest retrogression and cooling, possibly caused by thermal relaxation of a tectonically overthickened crust and onset of extensional setting, followed by Pangea breakup during the Late Triassic–Early Jurassic.

尽管人们对冈瓦纳西北部从石炭纪晚期到早二叠纪的Pangea组合有一个共识，但是Permo-Triassic时期的构造，包括Pangea破裂的发生，仍然是有争议的。在这种情况下，需要考虑三个区域构造特征：（1）Ouachita-Marathon-Sonora缝合线；（2）冈瓦纳下的Panthalassa大洋壳向东俯冲俯冲；以及（3）哥伦比亚记录的扩张性环境，厄瓜多尔和墨西哥建议在大约 240–220马。这项化学，同位素和年代学数据集被提出来限制委内瑞拉西部安第斯山脉梅里达变质基底中这些构造过程的影响。对原生片麻岩的未抛光锆石进行U-Pb二次离子质谱分析后，平均年龄为251±4 Ma。对应的δ^18岁O值表明锆石的变质重结晶，而不是高T流体相互作用。白云母和石榴石中的Rb-Sr和Sm-Nd年代学分别产生了234±3 Ma和249±2 Ma的年龄，而从黑云母中获得了更年轻的Rb-Sr日期197±1 Ma。U–Pb和Sm–Nd年龄限制了MéridaAndes地区最新的二叠纪-最早的三叠纪变质作用为251±4 Ma。地热大气压力数据表明在〜685°C和〜6.0 kbar时，闪石相的峰变质条件。在冈瓦纳和劳伦西亚碰撞形成Pangea后，变质作用可能与造山后的崩塌有关。Rb–Sr年龄表明退缩和冷却，可能是由于构造上增厚的地壳的热松弛和伸展期的开始，随后在三叠纪—早侏罗世期间发生了Pangea破裂。