淮南-溧阳大地电磁剖面与地质结构分析  

The geological structures along Huainan-Liyang magnetotelluric profile: Constraints from MT data

作　　者：强建科[1] 王显莹[1] 汤井田[1] 潘伟[1] 张钱江[1] 

机构地区：[1]中南大学地球科学与信息物理学院,有色金属成矿预测教育部重点实验室,长沙410083

出　　处：《岩石学报》2014年第4期957-965,共9页Acta Petrologica Sinica

基　　金：国家"深部探测技术与实验研究"专项课题(SinoProbe-03-02);国家自然科学基金项目(40930418;40974076;41174104)联合资助

摘　　要：研究跨长江中下游成矿带宽频大地电磁测深剖面得出，华北板块与扬子板块的电性差异明显，二者以张八岭隆起为界线，其西侧为合肥沉积盆地，主体电阻率较低。合肥盆地上地壳深度约12km，电阻率约50～500Ω·m，为相对高阻，中下地壳为大片低电阻率，约10～20Ω·m，推测与高温、含盐度、结晶水有关。电性莫霍面深度约34～38km。在张八岭隆起以东，扬子板块导电性较差，电阻率较高，约500～5000Ω·m。主要原因与火山岩侵入活动和中生代灰岩出露地表有关；宁芜盆地和溧阳盆地上地壳电阻率相对较低，中下地壳电阻率较高；溧阳盆地电性莫霍面明显，深度约30～32km；宁芜盆地之下电性莫霍面不明显，可能与岩体侵入有关。宁芜盆地成矿带与燕山期多期次火山侵入活动密切相关，大量富含金属离子的岩浆和热液沿地层界面或断层裂隙上涌，并与沉积围岩发生强烈矿化作用，最终形成了铁、铜、银等多金属矿床。Our study has shown that there is the significant electrical difference between North China block （NCB） and South China block （SCB）. For NCB, the upper crust with a thickness of 12km is of relatively high-resistivity with values of 50 - 500Ω· m while the middle and lower crust is of low-resistivity with values of 10 - 20Ω· m which probably due to the high temperature, high salinity and the presence of crystal water. The study of petrophysics shows that the temperature of the earth＇ s middle and lower crusts is around 400 - 500℃, and the resistivity difference is 3 to 4 orders of magnitude about granite and gabbro under the condition of wet and dry. Ultra-deep scientific drilling also confirmed that there are still a lot of brine in the depths of more than 8000m, and there are the rock pore, water and gas flow in the depths of more than 9000m. Even the geothermal gradient is to increase faster than expected. The electrical Moho is at depths of 34 -38km. On the east of Zhangbaling uplift, the SCB is more resistive （500 -500Ω· m） due to the volcanic activities and the cenzoic carbonic rocks. The upper crust of Ningwu basin and Liyang basin is relative of low resistivity while the middle and lower crust is of high resistivity. The electrical Moho of Liyang basin is at depths of 30 - 32km, but that of Ningwu basin is not obvious probably due to the intrusions. The Ningwu metallogenic belt has genetic relationships with multi-periods of volcanic activity during Yanshanian Period when ore magma and fluids which bearing huge metallic ion upwelled through fractures and altered wall rocks, finally formed iron, copper, gold and other multi-metal deposits. Generally, the environment of volcanic eruption is different, it can form different minerals. Such as the Dabie-Sulu orogenic belt （Zhangbaling uplift belt）, it is formed by the collision between the Yangtze plate and North China plate. It has experienced the ultrahigh pressure metamorphism and the process of continuous rise. So a lot of nonmetal

关 键 词：大地电磁法 长江中下游矿集区 深部地质结构 电性莫霍面 

分 类 号：P631[天文地球—地质矿产勘探]