Abstract In order to determine the tectonic regime change of the early Mesozoic in the South China Block, this study analyzed sedimentary rocks in the Middle Jurassic of southwestern Fujian by modal analysis of sandstones, elemental geochemical analysis of mudstones, and detrital zircons U–Pb dating. The results show that the detrital zircons in Southwestern Fujian mainly consist of Paleoproterozoic to early Mesozoic zircons in the Middle Jurassic. Within the Dongkeng profile of the Zhangping Formation, DK5 sample (lower part) showed a major age peak at ca. 1,848 Ma and two secondary age peaks at ca. 235 and 180 Ma, while DK15 sample (middle part) showed a major age peak at ca. 1,876 Ma and two secondary age peaks at ca. 233 and 190 Ma; the age compositions of these two samples’ were similar. Modal analysis of sandstones indicated that sediments of Zhangping Formation might source from arc orogen and recycled orogen, and element geochemical analysis showed that source rocks of Zhangping Formation might be sedimentary rocks and granites. The Indosinian zircons were mainly derived from the Wuyi region, and the Yanshanian zircons were mainly derived from the Nanling region. The major age group changes from ca. 230 to 220 Ma of the Late Triassic – Early Jurassic to ca. 190 to 180 Ma of the Middle Jurassic in Southwestern Fujian, and main sources changed from Indosinian magmatic rocks in the Late Triassic – Early Jurassic to early Yanshanian magmatic rocks in the Middle Jurassic.

中文翻译：

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闽西南中侏罗统沉积岩碎屑锆石LA-ICP-MS U-Pb年龄：沉积物源及其地质意义

摘要 为确定华南地块早中生代构造制度变化，本研究通过砂岩模态分析、泥岩元素地球化学分析、碎屑锆石U-Pb定年分析了闽西南中侏罗统沉积岩。 . 结果表明，闽西南碎屑锆石主要为中侏罗世古元古代至早中生代锆石。在漳平组东坑剖面中，DK5 样品（下部）在约 约 1,848 Ma 和两个次生年龄峰值。235 和 180 Ma，而 DK15 样品（中间部分）在约 1,876 Ma 和两个次级年龄峰值在大约。233 和 190 毫安；这两个样本的年龄构成相似。砂岩模态分析表明漳平组沉积物可能来源于弧形造山带和再生造山带，元素地球化学分析表明漳平组烃源岩可能为沉积岩和花岗岩。印支期锆石主要来源于武夷地区，燕山期锆石主要来源于南岭地区。主要年龄组从大约变化。晚三叠世 230 至 220 Ma – 早侏罗世至约。闽西南中侏罗世190～180 Ma，主要来源由晚三叠世-早侏罗世印支期岩浆岩转变为中侏罗世燕山期早岩浆岩。元素地球化学分析表明，漳平组烃源岩可能为沉积岩和花岗岩。印支期锆石主要来源于武夷地区，燕山期锆石主要来源于南岭地区。主要年龄组从大约变化。晚三叠世 230 至 220 Ma – 早侏罗世至约。闽西南中侏罗世190～180 Ma，主要来源由晚三叠世-早侏罗世印支期岩浆岩转变为中侏罗世燕山期早岩浆岩。元素地球化学分析表明，漳平组烃源岩可能为沉积岩和花岗岩。印支期锆石主要来源于武夷地区，燕山期锆石主要来源于南岭地区。主要年龄组从大约变化。晚三叠世 230 至 220 Ma – 早侏罗世至约。闽西南中侏罗世190～180 Ma，主要来源由晚三叠世-早侏罗世印支期岩浆岩转变为中侏罗世燕山期早岩浆岩。