郯庐断裂带是热异常带吗:来自断裂带南段热流的约束

Is the Tan-Lu fault zone a thermal anomaly belt:Constraints from heat flow in its southern section

郯庐断裂带是东亚最重要的断裂之一,在构造地质、岩石矿物、地震分布等领域得到了广泛的关注,然而少有针对郯庐断裂带地热学的研究.本文作者对郯庐断裂带南段7口钻井进行了系统测温,采用光学扫描法测试了6口钻井的142块岩心和13块露头样品的热导率,获得了6个高质量的热流数据.结合已发表的热流和地震剖面资料,我们获得了郯庐断裂带南段的岩石圈结构.研究表明,郯庐断裂带南段现今地温梯度从南到北有增大的趋势,介于21.8~30.3℃·km^-1.大地热流值介于44.0~81.7mW·m^-2,平均61.4±10.8mW·m^-2,表现为正常大地热流的特征,并非热异常带.最大热流值出现在庐枞盆地的大陆科学钻探井ZK03处,上地壳浅部极高的生热层很可能是高热流的主要因素.沿郯庐断裂南段地震带浅源地震发震带的底界和350℃等温面耦合较好,指示了深部结构的差异.

The Tan-Lu fault zone is one of the most important faults in East Asia.It has received extensive attention of many fields such as structural geology,mineralogy,and seismology.However,few geothermal studies on this structure have been made so far.This work conducted temperature measurement on 7 wells systematically in the southern Tan-Lu fault zone.Thermal conductivity of 142 cores and 13 outcrop samples for these wells were tested by the optical scanning method and 6 high-quality heat flow data were obtained.Combined with the published heat flow and seismic profiles,we obtained the lithospheric structure of the southern Tan-Lu fault zone.The study shows that the current temperature gradient in the study area increases from south to north,ranging from 21.8 to 30.3℃·km^-1.The heat flow value is between 44.0~81.7 mW·m^-2,with an average of 61.4±10.8 mW·m^-2,represnting a normal geothermal heat flow rather than a thermal anomaly belt.The maximum heat flow value appears in the Continental Scientific Drilling Well ZK03 in the Luzong Basin and the extremely high heat production of rocks in the shallow upper crust is probably the main factor for such a high heat flow.The bottom boundary of the shallow earthquake seismic zone in the southern Tan-Lu fault zone is well coupled with the 350℃isothermal surface,indicating the difference in deep structure.