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Innovative seismic imaging of volcanogenic massive sulfide deposits, Neves-Corvo, Portugal — Part 2: Surface array
Geophysics ( IF 3.3 ) Pub Date : 2021-04-21 , DOI: 10.1190/geo2020-0336.1
George A. Donoso 1 , Alireza Malehmir 1 , Bojan Brodic 1 , Nelson Pacheco 2 , João Carvalho 3 , Vitor Araujo 2
Affiliation  

Seismic methods are an affordable and effective way of studying the subsurface for mineral exploration. With the goal of testing new technologies for mineral exploration in highly challenging mining areas, in early 2019, an innovative seismic survey was conducted at the Neves-Corvo mine, south Portugal. We have focused on the data and results from the surface array data, whereas other work deals with the underground seismic data. The surface seismic survey consisted of two perpendicular 2D profiles positioned above the known world-class tier-1 Lombador deposit. Simultaneously, a survey inside the active underground mine took place, being unique because it included the testing of a prototype system that enabled accurate GPS-time (microsecond accuracy) synchronization inside the mine tunnels, approximately 650 m below the surface profiles. Due to the active mining operations, the surface data are noisy. To handle this, a carefully tailored processing algorithm was developed and applied to enhance reflections in the data, interpreted to originate from lithologic contacts and the Lombador deposit. The results and interpretations from 2D processing were validated taking advantage of the known deposit geometry using 3D exploding reflector modeling and pseudo-3D cross-dip analysis. These analyses suggest that there is an out-of-plane signature of the Lombador deposit on the surface data. Additionally, source points activated in the exploration tunnels and simultaneously recorded on the surface profiles allowed for the creation of a 2D velocity model that was used for migration and time-to-depth conversion, providing a reliable 2D seismic section of the subsurface under the surface profiles. We determine that limited surface coverage 2D surveys and a velocity model derived from the tunnel-to-surface seismic recordings allow for imaging of key subsurface geologic structures and delineating mineral deposits of economic interest.

中文翻译:

葡萄牙内维斯-科尔沃,火山成块状硫化物矿床的创新地震成像—第2部分:表面阵列

地震方法是研究地下勘探矿物的一种经济有效的方法。为了在极富挑战性的矿区测试用于矿产勘探的新技术,2019年初,在葡萄牙南部的Neves-Corvo矿山进行了一次创新的地震勘测。我们专注于表面阵列数据的数据和结果,而其他工作则涉及地下地震数据。地表地震勘测由位于已知的世界一流的1级Lombador矿床上方的两个垂直2D剖面组成。同时,在活跃的地下矿井内部进行了一次勘测,它是独一无二的,因为它包括对原型系统的测试,该系统能够在矿井隧道内(地表下约650 m)实现精确的GPS时间(微秒精度)同步。由于活跃的采矿作业,地表数据比较嘈杂。为了解决这个问题,开发了一种精心定制的处理算法,并将其应用到数据中以增强反射率,这些反射率被解释为源自岩性接触和Lombador矿床。利用3D爆炸反射器建模和伪3D交叉倾角分析,利用已知的沉积几何体验证了2D处理的结果和解释。这些分析表明,表面数据上存在Lombador沉积物的面外特征。此外,通过在勘探隧道中激活并同时记录在地表轮廓上的源点,可以创建2D速度模型,该模型用于迁移和时间到深度的转换,在表面轮廓下提供可靠的地下2D地震剖面。我们确定有限的地面覆盖2D测量和从隧道到地面地震记录得出的速度模型可以成像关键的地下地质结构并描绘出具有经济意义的矿床。
更新日期:2021-04-22
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