During the Upper Ordovician–Lower Silurian, chert was widely distributed in the Zhongbao Formation in the eastern part of the North Qilian Orogen. The origin and the tectonic setting of these chert were largely unknown. In order to analyse the material provenance, sedimentary environment, their formation and the tectonic setting, we present petrology and geochemical research on chert samples collected from Shihuigou Section. The evidence provided by radiolarite occurrences, Aluminium (Al)–iron (Fe)–manganese diagram and the silicon(Si)/Si + Al + Fe + calcium ratios suggesting a non-hydrothermal input and the biogenic origin chert. The geochemical features and the petrographic signatures have shown that the chert was also influenced by a terrigenous origin. It is considered that the deposition of the Late Ordovician chert is mainly affected by tectonic collision and volcanic ash events. During the Late Ordovician–Early Silurian transition, huge amounts of volcanic ash were released by massive volcanic activity that fell into the ocean, triggering the proliferation of radiolarians. Finally, in the Late Ordovician–Lower Silurian the tectonic setting of the North Qilian Orogen was not a typical deep-water basin, nor a typical continental margin, but a multi-island deep-water basin, which is closed to the mainland.

中文翻译：

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上奥陶统—下志留统燧石成因：对北祁连造山带沉积环境的启示

上奥陶统—下志留统期间，燧石广泛分布于北祁连造山带东部的中宝组。这些燧石的起源和构造环境在很大程度上是未知的。为分析石回沟剖面的物质来源、沉积环境、成因和构造背景，对石回沟剖面的燧石样品进行岩石学和地球化学研究。放射虫的出现、铝 (Al)-铁 (Fe)-锰图和硅 (Si)/Si + Al + Fe + 钙比率提供的证据表明非热液输入和生物成因燧石。地球化学特征和岩石学特征表明，燧石也受到陆源的影响。认为晚奥陶世燧石的沉积主要受构造碰撞和火山灰事件的影响。在晚奥陶世-早志留世过渡期间，大量火山活动释放了大量火山灰，落入海洋，引发了放射虫的增殖。最后，晚奥陶世—下志留世北祁连造山带的构造背景不是典型的深水盆地，也不是典型的大陆边缘，而是与大陆相接的多岛深水盆地。