海南岛中西部金矿集中区断裂构造的分形研究

利用数盒子法对海南岛中西部金矿集中区断层分布统计表明 :断层系统在 5～ 75km尺度内符合分形分布 ,其分维值为 1 .70。根据成矿系统的差异 ,将全区分为 9个子区块 ,各子区块断层系统在 2 .5～ 2 5km尺度内均符合分形分布 ,其分维值介于 0 .6 6～ 1 .72之间。断层分维值的大小可作为判断矿化强弱的指标 :断层的分维值≥ 1 .5 ,是矿化集中区的标志 ;分维值小于 1 .4 ,不利于规模成矿 ;断层的分维值较大 ,是形成金矿化的有利条件 ,若形成超大型矿床 ,则断层系统需处于临界分维状态(Dc≈ 1 .5 )。白沙元门地区断层分维 (D =1 .4 9)接近于临界分维 ,预示该区有良好的找矿前景。基于离散元方法 (UDEC)的数值模拟显示 :随着断层分维值增大 ,则变形趋强、连通性更好、渗透率增大 ;临界状态下断层间的连通性好 ,变形及渗透率突然增加且变形及流体流动局限于骨干断层中 ,即临界状态下最有利于形成含矿流体的局域化分布

FRACTAL ANALYSIS ON FAULT SYSTEM IN CENTRAL AND WESTERN HAINAN GOLD METALLOGENIC PROVINCE

It is found, by using box-counting method, that the fault system conforms to the power-law distribution on the scale from 5 km to 75 km in the central and western Hainan gold metallogenic province , the fractal dimension of the faults is 1.70. The whole area is divided into nine subblocks according to the difference of the metallogenic systems; the subblocks are all conformable to the power-law distributions on the scale from 2.5 km to 25 km. The fractal dimensions are among 0.66～1.72, which can be applied as an index to distinguish the mineralization intensity: if the fractal dimension is more than 1.5, the area can be regarded as a concentrated mineralization zone. If the value is less than 1.4, the area is regarded as unfavorable for mineralization. It can be seen that although the larger fractal dimension values of faults are the favorable condition for gold mineralization, the fault system needs to be in the state of the critical fractal dimension(D c=1.5) in order to form super-large scale ore deposit. The fractal dimension(D=1.49) of faults in Yuanmen district is near the critical state, it shows that the area exists possibly large scale mineralization. Numerical simulation based on UDEC model shows that the system will get higher deformation, better connectivity and large amount of fluid flow with the increase of the fractal dimension of faults. The connectivity, deformation and fluid flow which are localized in a few backbone faults will increase abruptly in the critical state. That is the most favorable state for the localization of ore-bearing fluids.