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为揭示鄂西南齐岳山地区晚三叠世须家河组物源与构造背景,以周家湾与颜家沟剖面为代表,对须家河组碎屑岩的颗粒组分、元素组成以及锆石年龄进行测试与统计.结果显示:砂岩碎屑颗粒石英含量高、岩屑与长石含量低,平均值分别为76.15%、8.90%与3.45%,具有锆石-板钛矿-磁铁矿-榍石-电气石重矿物组合,反映源岩以酸性岩或低级变质岩为主,Dickinson判别图解表明物源主要来自再旋回造山带;砂岩(TFe_2O_3+MgO)*与TiO_2*含量低,Al2O_3/SiO_2比值低,K_2O/Na_2O比值高,最接近被动大陆边缘特征值;泥岩成分变异指数ICV分布于0.32~0.79之间,平均值为0.56,反映物源主要为再旋回沉积物;样品稀土元素配分模式、特征微量元素含量及比值指示晚三叠世沉积构造背景为被动与活动大陆边缘;碎屑锆石分为磨圆与自形两类,磨圆者具有2 480Ma、1 880Ma、832Ma年龄峰值(n=133),年龄频数分特征与扬子陆块最接近;自形锆石具有435Ma、217Ma年龄峰值(n=42),年龄频数分布特征与秦岭造山带和雪峰造山带花岗岩年龄具有很好的对应关系.结合物源与构造背景判别图解,上述特征综合表明须家河组形成于被动大陆边缘(为主)与活动大陆边缘环境,其物源来自东南的雪峰造山带(为主)与北侧的秦岭造山带.
In order to reveal the source and tectonic setting of the Late Triassic Xujiahe Formation in the Qiyueshan area, southwestern Hubei Province, the grain composition, elemental composition and zirconium The results show that the content of quartzite and feldspar in sandstone clasts is low and the average values are 76.15%, 8.90% and 3.45%, respectively. -cristallite-tourmaline heavy mineral assemblage, which indicates that the source rock is mainly composed of acidic rocks or low-grade metamorphic rocks. The Dickinson discriminant diagram shows that the source rocks mainly come from the re-orogenic belt; the content of sandstone (TFe_2O_3 + MgO) * and TiO_2 * / SiO 2 ratio is low, and K 2 O / Na 2 O ratio is the highest, which is the closest to the eigenvalues of the passive continental margin. The ICV of mudstone composition varies from 0.32 to 0.79 with an average of 0.56, indicating that the source rocks are mainly re-swirling sediments. The distribution pattern, the content of trace elements and their ratios indicate that the sedimentary tectonic setting of the Late Triassic was the passive and active continental margin. The detrital zircons were divided into two types: rounding and self-shaping. The rounding rounds had the ages of 2 480Ma, 1 880Ma and 832Ma Peak (n = 133), age frequency sub-characteristics and Yangtze land With the age of 435Ma and 217Ma (n = 42), and the distribution of age frequency has a good correspondence with the granite ages of the Qinling orogenic belt and the Xuefeng orogenic belt.By combining the provenance and tectonic setting . The above characteristics show that the Xujiahe Formation formed on the passive continental margin (mainly) and the active continental margin. Its source comes from the Xuefeng orogenic belt in the southeast and the Qinling orogenic belt on the north side.