凤太矿集区航空地球物理异常特征及找矿方向

Aerogeophysical anomalies and prospecting direction in the Fengtai ore concentration area

凤太矿集区是秦岭造山带中部重要的铅锌矿和金矿产地,发育有铅硐山—东塘子、八方山—二里河、八卦庙、双王等多个大型—超大型矿床,随着矿床开发,储量大幅度下降,地表找矿也转入深部找矿,但矿床赋存的地球物理场背景不清楚,严重制约了矿床成矿规律研究及外围的找矿勘查工作。本文运用最新完成的1∶5万航空物探(磁、放)数据,结合重力数据,开展区域、矿集区、矿床3个尺度的多源地球物理场特征研究,旨在总结不同尺度地球物理异常分布规律,为成矿规律研究和找矿预测提供依据。结果表明,凤太矿集区与西成矿集区具有相似的磁性结构,二者被徽成盆地结晶基底产生的强磁异常带所分隔。重力垂向一阶导数显示凤太、西成矿集区与徽成盆地具有相似的密度结构,推断浅部为一个统一的盆地,2个矿集区之间有较大的找矿空间。凤太矿集区发育大量NW向线性磁异常带,与断裂构造的位置十分吻合,受后期改造明显,被NE向构造错断,重力垂向二阶导数推断深部发育大量中酸性侵入岩株或岩脉。通过航磁垂向一阶导数、0°方向水平导数、小波变换等方法可以有效识别构造边界,矿体大都沿构造带呈NW向分布,对找矿勘探有重要指导作用。

The Fengtai ore concentration area is an important producing area of plumbum-zinc and gold ores in the middle of the Qin-ling orogenic belt.It hosts many large to super-large deposits,such as Qiandongshan-Dongtangzi,Bafangshan-Erlihe,Baguamiao,and Shuangwang deposits.With the exploitation proceeding,the reserves of these deposits have decreased significantly,and the ore pros-pecting in these deposits has shifted from the surface to the deep part.However,the geophysical fields in the deposits are yet to be as-certained,severely restricting research on the metallogenic regularity of the deposits and the ore prospecting and exploration in the pe-ripheral zones.Based on the latest 1∶50,000 aeromagnetic and airborne radioactivity survey data,as well as gravity data,this study in-vestigated the multi-source geophysical fields on the scales of the region,the ore concentration area,and deposits,aiming to summarize the distribution patterns of geophysical anomalies of different scales and provide evidence for research on metallogenic regularity and prospecting prediction.The results show that the Fengtai and the Xicheng ore concentration areas,with similar magnetic structures,are separated by the zone with strong magnetic anomalies caused by the crystalline basement of the Huicheng Basin.The first vertical deriv-ative of gravity reveals that the Fengtai and Xicheng ore concentration areas have density structures similar to the Huicheng Basin.It can be inferred that the shallow part is a unified basin and that a large prospecting space exists between the two ore concentration areas.Many NW-trending linear magnetic anomaly zones occur in the Fengtai ore concentration area.Their locations are highly consistent with those of fault structures,and they were offset by NE-trending structures due to late transformation.The second vertical derivative of gravity reveals that many intermediate-acid intrusive stocks or veins have developed in the deep part of the Fengtai ore concentration ar-ea.Structural boundaries can be effectively identified based on the first vertical derivative,X-directional derivative,and wavelet trans-form of aeromagnetic data.Furthermore,ore bodies are mostly distributed in the NW direction along the tectonic belt.All these will play an important role in guiding ore prospecting and exploration in the Fengtai ore concentration area.