应用奇异值分解与二维经验模型分解提取金矿化致矿重力异常

The application of both singular value decomposition and bi-dimensional empirical mode decomposition in extraction of gravity anomalies associated with gold mineralization

奇异值分解(singular value decomposition,SVD)和二维经验模型分解(bi-dimensional empirical mode decomposition,BE-MD)2种方法用于鲁西铜石金矿田的金矿化致矿重力异常提取。通过对比研究得出如下结论:①基于重力数据,由BEMD和SVD 2种方法获取的铜石金矿田的控矿因素是一致的,为重力负异常的近圆形铜石侵入杂岩体和环绕铜石侵入杂岩体的表现为正异常的接触交代矿化带。②2种方法一致地揭示了控矿因素和不同类型金矿化之间的空间关系:斑岩型金矿化位于杂岩体内,矽卡岩型铁-铜-金矿化位于内接触交代带,卡林型和隐爆角砾岩型金矿床位于外接触交代带。③BEMD的分解结果不但反映了控矿地质体单元(铜石杂岩体)的空间分布特征,亦反映了铜石金矿田的其它地质单元,如NW向表现为明显重力负异常的中生代火山沉积盆地,位于铜石侵入体与中生代火山沉积盆地之间的表现为重力正异常的NW向基底隆起。而由SVD获取的致矿重力异常,更确切地揭示了铜石侵入体和环形接触交代带内部的精细结构特征,环形接触交代带内部具岛状形态的正重力异常可能代表铁-铜-金矿化矽卡岩体。④虽然2种方法在原理和过程方面都不同,但具有明显地质成矿意义的金致矿异常皆可通过各自定义的带通滤波器获取。⑤在成矿地质背景的约束下,由这2种方法获取的综合研究结果比其中任意一种方法获取的结果更全面客观地揭示了控矿因素与金矿化的空间关系。

Two methods of the singular value decomposition（SVD） and the Bi-dimensional empirical mode decomposition（BEMD） were applied respectively in extraction of gravity anomalies associated with gold mineralization in the Tongshi gold orefield in this paper.Conclusions drawn by the comparative study are as follows：（a） The two methods consistently reveal the ore-controlling factor in the Tongshi gold orefield on the basis of original gravity data：the Tongshi intrusion has a negative circular gravity anomaly and the ringed contact metasomatic mineralization zone around the Tongshi intrusion has a positive gravity anomaly.（b） The two methods consistently reveal the spatial relationship between the ore-controlling factors and various gold mineralizations：the skarn and porphyry types of gold deposits are located within the complex pluton and the Carlin and crypto-breccia types of gold deposits are situated within the contact metasomatic mineralization zone.（c） The image produced by BEMD not only reflects the structural features of the ore-controlling factor（Tongshi complex pluton） but also shows the distribution of other geological units in the Tongshi gold orefield such as the Mesozoic volcanic sedimentary basin in NW direction with obvious negative gravity anomaly and the concealed metamorphic base swell in NW direction with positive gravity anomaly located between the Tongshi intrusion and the Mesozoic volcanic sedimentary basin.（d）The image produced by SVD might depict the inner structure of the Tongshi intrusion and the ringed contact metasomatic zone in more detail than that produced by BEMD.The higher gravity anomaly areas like island-shaped bodies within the ringed contact metasomatic zone may be skarn bodies with iron-copper-gold mineralization.（e） Under the constraints of the ore-forming geological setting,the result obtained from the original gravity data by combination of the two methods can depict the relationship between the ore-controlling factors and the gold mineralizations more exactly than the result obtained only by one method.