The Late Permian Sunjiagou Formation and Early Triassic Liujiagou Formation were studied to understand the palaeoclimatic and palaeoenvironmental changes in the southwest margin of the North China Craton across the Permian–Triassic boundary, as well as the tectonic evolution of their provenance sediment. Major, trace, and rare earth elements in 20 clastic rock samples from the strata above and below the boundary were analysed. Overall, the Sunjiagou Formation samples showed an average index of compositional variability (ICV) and chemical index of alteration (CIA) of 1.53 and 73.59, respectively, indicating high-maturity sediments in a warm and humid environment with moderate chemical weathering, whereas Liujiagou Formation samples had an average ICV and CIA of 2.40 and 70.1, respectively, indicating low-maturity sediments in a cold and dry environment with mild chemical weathering. These strata were composed of first-cycle sediments in a tectonically active area. The provenance of the Sunjiagou Formation was dominated by quartz-rich sedimentary rocks, whereas that of Liujiagou Formation had both quartz-rich sedimentary rocks and intermediate volcanic rocks. The provenance tectonic settings were mainly the continental island arc and active continental margin. Thus, the study area was in a terrestrial, freshwater sedimentary environment from the Late Permian to Early Triassic, and the climate gradually changed from warm and humid to dry and hot, with multiple small-scale periodic evolutions. Taken together, these findings further confirm that the entire study area was in an oxidizing environment and the oxidation degree in the Early Triassic was higher than that in the Late Permian.

中文翻译：

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华北克拉通西南缘二叠系-三叠系边界地层地球化学：物源与构造意义

研究晚二叠世孙家沟组和早三叠世刘家沟组，了解华北克拉通西南缘跨二叠—三叠世界线的古气候、古环境变化及其物源沉积物构造演化。对边界上下地层的20个碎屑岩样品中的主量、微量和稀土元素进行了分析。总体而言，孙家沟组样品的平均成分变异指数（ICV）和化学蚀变指数（CIA）分别为1.53和73.59，表明高成熟度沉积物处于温暖潮湿的环境中，化学风化程度适中，而刘家沟组则为高成熟度沉积物。样本的平均 ICV 和 CIA 分别为 2.40 和 70.1，表明在寒冷干燥的环境中具有温和的化学风化作用的低成熟度沉积物。这些地层由构造活动区的第一旋回沉积物组成。孙家沟组物源以富石英沉积岩为主，刘家沟组物源既有富石英沉积岩，也有中间火山岩。物源构造环境主要为大陆岛弧和活动大陆边缘。因此，研究区晚二叠世至早三叠世处于陆相淡水沉积环境，气候由暖湿向干热逐渐转变，具有多次小尺度周期性演化。综合起来，