山东莱芜盆地碳酸盐岩热液溶蚀特征及水文地质意义

鲁中山区莱芜盆地在燕山期发生大规模岩浆侵入活动,岩浆岩体外围碳酸盐岩区分布有水源地、富水块段等岩溶发育富水区,且靠近岩体含水层多发生大理岩化。富含CO₂、H₂S等酸性成分的岩浆热液流体,能对碳酸盐岩产生明显的溶蚀作用。基于岩石样品化学组分分析、水文地质调查及数据统计分析、热液溶蚀地质点详细观测,构建热液溶蚀模式,对莱芜盆地及外围热液溶蚀特征及机理进行研究。结果表明:高温高压岩浆侵入使得接触带碳酸盐岩发生热液变质大理岩化;沿渗透性断裂、裂缝以及不整合面等运移的热液流体,对碳酸盐岩地层产生酸性热液溶蚀和混合溶蚀作用,形成不同规模溶蚀孔洞,构成地下水富集空间,为寻找城镇地下水后备水源地提供新方向。

Characteristics and Hydrogeological Significance of Hydrothermal Dissolution in Carbonate Rocks from Laiwu Basin,Shandong Province

In the Yanshanian period,large-scale magmatic intrusion occurred in the Laiwu Basin.Certain water source areas,karst and water-rich blocks were developed in carbonate rocks around the intrusions.Marbleization often occurs in the carbonate aquifers near the intrusions.Magmatic-hydrothermal fluids,which are rich in acidic components such as CO2 and H2S,can cause significant dissolution of carbonate rocks.The mechanism and characteristics of hydrothermal dissolution in the Laiwu Basin were identified via analyzing the chemical composition of rock samples,hydrogeological surveying and data statistical analysis,together with detail observation on the hydrothermal dissolution spots.Consequently,the hydrothermal dissolution model for the region was constructed.The results show that the high-temperature/-pressure magmatic intrusions likely caused the marble metamorphism of carbonate rocks in the contact zone.Hydrothermal fluids migration along permeable faults,fissures and unconformities could cause acidic hydrothermal dissolution and mixed dissolution in the carbonate formation,and formed dissolution cavities of different scales.The cavities constitute the current sites of groundwater enrichment,and provide a new direction of water reserve exploration for towns and cities.