安徽宿松志留系—泥盆系碎屑锆石物源分析及其大地构造意义*

安徽宿松志留系—泥盆系分布于下扬子地层区西部,大别造山带东南缘,郯庐断裂带南端东侧。为了获得宿松地区志留系—泥盆系的物源信息,对出露于宿松地区的坟头组、茅山组及五通组细砂岩及粉砂岩进行了碎屑锆石LA-ICP-MS U-Pb定年。结果显示,3个样品均获得了约970 Ma、820 Ma的主要峰值年龄和约450 Ma的次要峰值年龄。碎屑锆石主要来源于花岗质岩石。根据花岗岩中锆石的判别图,研究层段碎屑锆石大多属于I型和S型花岗岩锆石,而江南造山带内新元古代及华南地区加里东期的花岗质岩石大多为I型和S型。通过与华南碎屑锆石年龄谱的对比,认为研究地层物源主要来自华南板块内部。根据锆石结晶年龄与沉积年龄差异模式图,判别出安徽宿松志留系—泥盆系形成于碰撞背景。

Detrital-zircon provenance analysis and its tectonic significance of the Silurian-Devonian in Susong area,Anhui Province

The Silurian-Devonian in Susong area,Anhui Province are distributed in the western part of the Lower Yangtze stratigraphic subregion,the southeastern edge of the Dabie orogenic belt,and the eastern side of the southern end of the Tanlu fault zone. In order to obtain the provenance information of the Silurian-Devonian in Susong area,detrital zircon LA-ICP-MS U-Pb dating was performed on the fine sandstone and siltstone of the Fentou,Maoshan and Wutong formations exposed in Susong area. The results showed that the three samples all obtained major peak ages of about 970 Ma,820 Ma,and a secondary peak age of about 450 Ma. Detrital zircons are mainly derived from granitic rocks. Using the discriminant map of zircon in granite, most of dated zircons are recognized to be I-type and S-type granite zircons,while most of the Neoproterozoic and Caledonian granitic rocks in the Jiangnan orogenic belt and South China are type I and type S. Through comparison with the ages of detrital zircons from South China,the provenance of the studied strata mainly comes from the interior of the South China plate. Using the pattern map of the difference between zircon crystallization age and sedimentary age,the tectonic setting of the Silurian-Devonian in Susong area, Anhui Province was identified as the collision background.