安徽淮南舜耕山奥陶系古溶洞发育特征及成因^*

Developmental characteristics and formation of the Ordovician paleocaves in Shungeng mountain,Huainan of Anhui Province,China

摘要

古溶洞对隐伏地区岩溶地下水储存与运移至关重要,查明其形态及内部结构特征对于认识隐伏煤田岩溶形成过程及矿山岩溶水害防治具有一定的指导意义。近年来,通过对华北板块南缘安徽淮南舜耕山地区奥陶系岩溶野外露头详细的地质勘查,在奥陶系发现1处典型古溶洞。采用野外观测、显微鉴定、古水文和古构造等方法,对古溶洞几何形态特征、内部结构进行系统分析,该溶洞发育于奥陶系古溶洞沿马家沟组和萧县组的沉积层面间,洞体形态宽窄不一,西侧较宽、东侧较窄,最大层间高度达9.8 m,洞体长度为125 m。洞顶面保留古水流冲刷溶蚀痕迹,洞体内存在多处因重力作用垮落坍塌充填物,按其成因,可分为碎屑垮落充填、化学充填以及混合充填等,充填岩屑以灰岩、白云岩类为主,其矿物成分为方解石、白云石、隐晶硅质等。结合区域地质构造演化史,古溶洞形成于加里东运动抬升阶段,经过了裂隙发育、层面岩溶形成、层面间溶洞生长以及崩塌跨落充填压实4个阶段,主要受层面裂隙、侵蚀流体以及岩溶垂向分带控制。研究成果可为淮南煤田乃至华北煤田古岩溶突水防治提供有益参考。

Abstract

Paleocave play a crucial role in the storage and transport of karst groundwater in the covered area,and the exploration and identification of their morphological and internal structural characteristics are of certain guidance for understanding the formation process of karst in covered coal fields and the prevention and control of karst water inrush damage in mines. In recent years,through a detailed geological investigation of the Ordovician karst outcrops in the Shungeng mountain in Huainan,Anhui Province,on the southern edge of the North China Plate,a typical paleokarst cave was found at the Ordovician formations. This study analyzes the morphological features and internal structures of the paleocave using field observations,microstructural identification,paleohydrology,and paleotectonics. The cave developed along the sedimentary interfaces between the Majiagou and Xiaoxian formations,exhibiting varying widths—wider on the west side and narrower on the east. The maximum vertical height between layers reached 9.8 meters,and the cave extended over a length of 125 meters. Evidence of paleowater erosion and corrosion is preserved on the cave ceiling,and gravity-induced collapses have resulted in various fill types,including debris collapse fill,chemical fill,and mixed fill,primarily consisting of limestone and dolomite,with minerals such as calcite,dolomite,and cryptocrystalline silica. Combined with the regional geological and tectonic evolution,paleocave formation experienced four stages: the fissure development,interlayer karst formation,,interlayer cave growth,and collapse filling and compaction,which are mainly controlled by layer fissure,erosive fluid and vertical karst zoning. The results can provide useful reference for prevention and treatment of deap karst water inrush in Huainan and other North China coalfields.

关键词

古岩溶角砾岩 / 溶洞填充物 / 古水流 / 构造演化 / 淮南舜耕山

Key words

paleokarst breccia rock / cave fillings / paleofluid / tectonic evolution / Shungeng mountain in Huainan

基金资助

*国家自然科学基金项目(编号: 42172279)资助