| 华北克拉通东南部淮南地区晚前寒武纪寿县组碎屑岩粒度特征及锆石U-Pb年代学分析 |
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| 引用本文：顾承串,赵嘉祺,詹 润,李澳晨,邓世纪,余 博.2025.华北克拉通东南部淮南地区晚前寒武纪寿县组碎屑岩粒度特征及锆石U-Pb年代学分析[J].地球学报,46(4):777-799. |
| DOI：10.3975/cagsb.2025.012121 |
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| 基金项目:国家自然科学基金项目(编号: 41902212); 矿山地质灾害防治安徽省重点实验室开放基金课题(编号: 2023-MGDP-06); 安徽省科技厅重点研发项目(编号: ZMXJ-LZ-JS-2020-16) |
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| 中文摘要:寿县组是华北克拉通东南部广泛发育的一套前寒武纪碎屑岩地层, 长期以来对其沉积时限的认识有较大分歧。由于寿县组上、下相邻层位中均产有丰富宏体藻类化石, 因而查明其岩性特征、沉积环境、沉积时限以及沉积物源等方面内容对认识晚前寒武纪古地理变迁、生物地层层序对比以及沉积大地构造演化均具有重要意义。本文以寿县组为研究对象, 通过野外调查确定淮南地区寿县组的出露位置、岩性和层序特征, 采集5处岩石样品进行显微镜下观察和粒度分析, 并开展了LA-ICP-MS碎屑锆石U-Pb年龄测定, 以分析寿县组的沉积环境、沉积时限以及沉积物源特征。研究表明, 寿县组是一套中-厚层钙质细碎屑岩偶夹中-薄层泥质岩沉积序列, 粒度分析结果显示其沉积粒度属于细砂岩与粗粉砂岩过渡类型, 粒度组成中以悬浮搬运组分为主, 跳跃搬运组分较少, 成熟度较高, 沉积水动力条件较弱, 结合海绿石矿物的出现以及萨胡判别函数计算结果推断寿县组沉积处于临滨带和过渡带之间的陆棚环境。5个样品中最年轻的碎屑锆石年龄分别为(962±25) Ma、(963±31) Ma、(954±25) Ma、(952±24) Ma和(976±26) Ma。淮南地区寿县组最年轻一组碎屑锆石的加权平均年龄为(953±9) Ma, 结合徐州—淮北地区侵入相当层序中的基性岩床群943~876 Ma的侵入年龄, 将寿县组沉积时间限定在953~943 Ma。淮南地区寿县组碎屑锆石年龄频谱显示1.8 Ga以来的锆石数量占比具有逐步增多的趋势, 并且富含1.2~1.0 Ga的年龄, 综合分析认为寿县组主要的沉积物源应来自与华北克拉通曾经相连的陆块或陆块群, 但不能排除华北克拉通内部可能为次要的物源区。 |
| 中文关键词:寿县组 粒度分析 碎屑锆石U-Pb定年 最大沉积时间 沉积物源 |
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| Grain Size Characteristics and Zircon U-Pb Geochronological Analysis of Late Precambrian Clastic Rocks from the Shouxian Formation in the Huainan Region, Southeastern North China Craton |
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| Abstract:The Shouxian Formation is a set of Precambrian clastic strata widely distributed in the southeastern part of the North China Craton. However, its depositional age remains unclear. Due to the abundance of macroalgal fossils in the upper and lower adjacent strata of the Shouxian Formation, identifying its lithology, sedimentary environment, timing, and sources is of great importance. This will help in understanding Late Precambrian paleogeography, biostratigraphic sequence correlation, and sedimentary tectonic evolution. In this study, a detailed field investigation was conducted to determine the outcrop locations, lithologies, and sequence characteristics of the Shouxian Formation, based on Late Precambrian successions in the Huainan area. Microscopic observations, grain size analyses, and LA-ICP-MS detrital zircon U-Pb dating were performed on five rock samples to analyze the depositional environment, time constraints, and sediment source characteristics. The findings indicate that the Shouxian Formation consists of medium- to thick-bedded calcareous fine clastic rocks, occasionally interbedded with medium- to thin-bedded muddy layers. Grain size analysis showed that the formation belongs to the transitional type between fine sandstone and coarse siltstone. In terms of composition, it is dominated by suspended load components, with fewer saltation load components, indicating high maturity and weak depositional hydrodynamic conditions. The presence of glauconite minerals, along with the results from the Sahu discrimination function, suggests that sedimentation occurred in a shelf environment between the littoral and transitional zones. The youngest single-grain detrital zircon ages for the five samples are: (962±25) Ma, (963±31) Ma, (954±25) Ma, (952±24) Ma, and (976±26) Ma. The weighted average age of the youngest detrital zircon group, considering all samples, is (953±9) Ma. Combined with the intrusive age of the mafic sill complexes (943–876) Ma in the Xuzhou–Huaibei area, which intrude into the equivalent stratigraphic sequence, the depositional age of the Shouxian Formation is constrained between 953 and 943 Ma. The detrital zircon age spectrum of the Shouxian Formation shows a gradual increase in the number of detrital zircons since 1.8 Ga, with a significant abundance of zircons dated between 1.2 and 1.0 Ga. A comprehensive analysis suggests that the main sediment source for the Shouxian Formation likely originated from a landmass or landmass groups that were once connected outside the North China Craton. However, the interior of the North China Craton could also have served as a secondary source area. |
| keywords:Shouxian Formation grain size analysis detrital zircon U-Pb dating maximum depositional age sediment provenance |
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