关键词: 物源分析, 构造背景, 秦岭造山带, 南召盆地, 上三叠统

Abstract: The Triassic is the critical period when the Qinling Orogenic Belt was marked by a completely collisional orogeny. With the
amalgamation of the Yangtze and Qingling blocks and the North China Block along the Mianlue and Shangdan sutures, respectively, the
Qinling Orogenic Belt started to form and transformed from plate tectonic systems to intracontinental orogenic systems. The active
orogenies controlled the formation and evolution of the basins adjacent to the orogenic belt. Based on the geochemistry of clastic rocks,
the provenance and tectonic setting of the Upper Triassic from the Nanzhao Basin were investigated in this study. Results show that the
composition of provenance was mainly felsic igneous rocks of the upper crust. The source rocks experienced a moderate chemical
weathering, and the corrected chemical index of alternation (CIAcorr) values indicated that the provenance was formed in warm and
humid climate and in relatively active tectonic environments. Tectonic setting of the provenance in the Taishanmiao Formation was
mainly continental island arc and active continental margin, while the Taizishan Formation was continental island arc and passive
continental margin. According to the near-source depositional characteristics of the Nanzhao Basin and the evolutionary process of the
Qinling Orogenic Belt, we suggest that the Qinling Orogenic Belt and the southern margin of the North China Block are the important
provenances of the Nanzhao Basin during the Late Triassic. The provenance of the Taishanmiao Formation is mainly provided by the
basement of the North Qinling Belt, and the provenance of the Taizishan Formation is probably derived from the South Qinling Belt,
North Qinling Belt and the southern margin of the North China Block, with the recycling of sediments. The transition of the UpperTriassic provenance from the Nanzhao Basin is the response to the gradually enhanced thrusting of the Qinling Orogenic Belt during the
Late Triassic. This has a crucial significance to reconstruct the process of mountain building and uplifting of the Qinling Orogenic Belt
and the evolutionary process of basin-orogeny systems in adjacent basins.

Key words: provenance analysis, tectonic setting, Qinling Orogenic Belt, Nanzhao Basin, Upper Triassic