重力异常方向导数的刻痕分析方法及在江西省地热调查中的应用

Scratch analysis method on directional derivative of gravity data and its application in geothermal investigation in Jiangxi Province

江西省已知地热资源主要分布在剩余重力低异常区和梯度带上,剩余重力低异常区主要反映了地下中酸性岩体,而梯度带主要反映了岩体的边缘和断裂构造,这些信息为进一步研究地热水成因及导水储水结构机理提供了一定依据.本文基于江西省重力异常数据,利用剩余重力异常刻痕分析的边界系数识别线性构造,提取的断裂构造与地质图上的主构造基本吻合,呈现北东向主构造背景特征.为了特定识别北西向微弱断裂构造,本文提出基于剩余重力异常方向导数的刻痕分析方法,利用其脊形系数识别线性构造,提取特定方向上构造信息,并论证了该方法的有效性.江西省处于北东向大断裂构造背景下,北西向断裂构造在地热资源的形成机理中充当着重要角色.基于该技术方法,可靠地提取北东向和北西向两组断裂构造,根据已知地热点的分布特征,圈定多处北东、北西向两组构造交汇位置,结合构造交叉型蓄水空间理论,为微弱构造的识别以及后续地热靶区的确定提供了地球物理的依据.

The known geothermal resources in Jiangxi Province are mainly distributed in the low residual gravity anomaly area and gradient zone.The low residual gravity anomaly area mainly reflects the underground medium-acid rock mass.The gradient zone mainly reflects the edge and fault structure of rock mass.These information provide a certain basis for further research on the origin of geothermal water and the mechanism of water conduction and storage structure.Based on the gravity anomaly data in Jiangxi Province,this paper uses the boundary coefficient of the residual gravity anomaly scratch analysis to identify the linear structure.The extracted fault structure is basically consistent with the main structure on the geological map,Presenting the main background tectonic characteristics of the northeast direction.In order to highlight the identification of NW trending weak fault structures,this paper proposes the scratch analysis based on the derivative anomaly in the direction of residual gravity,uses its ridge coefficient to identify linear structures,extracts the structural information in a specific direction,and demonstrates the effectiveness of this method.Jiangxi Province is under the background of NE trending large fault structure,and NW trending fault structure plays an important role in the formation mechanism of geothermal resources.Based on this method,the NE and NW fault structures are reliably extracted,and combined with the distribution characteristics of known geothermal hotspots,the intersection positions of many NE and NW structures are delineated,which provides a geophysical basis for the identification of weak structures and the subsequent determination of geothermal target areas.