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A B S T R A C TNeves-Corvo is one of the biggest mining districts on the Portuguese side of the Iberian Pyrite Belt hosting six different lower Carboniferous copper, zinc, lead and tin orebodies including Lombador, Neves, Graça, Corvo, Zambujal, and Semblana. During the past 50 years, geological, geochemical, and geophysical methods were utilized in the exploration of volcanogenic massive sulfide deposits at Neves-Corvo. Electromagnetic, earth resistivity, and principally gravimetry methods played major roles in the geophysical exploration of the area. However, in 2011, as the exploration depth for volcanogenic massive sulfide mineralization became ever deeper, the surface reflection seismic technique was trialled.Initially, elastic property measurements were employed on numerous core samples to determine the seismic properties of the major formations of Neves-Corvo. The contrast in acoustic impedance values derived from these measurements showed that there should be a significant difference in the seismic response of mineralization relative to the surrounding host rocks. Based on this, a high-resolution 3D seismic survey was acquired over the Neves-Corvo mine and its southeastern extension in order to image known deep volcanogenic massive sulfide mineralization to validate the seismic reflection technique and to potentially identify new mineralization targets. As a result, the Semblana and Lombador deposits were successfully imaged, along with key lithological contacts and geologic structures. Additionally, copper sulfide extensions south of Semblana were discovered. Unfortunately, all of the high-priority targets that were identified from the seismic data were subsequently drilled and many of them found to be non-economic.In order to overcome the non-uniqueness of the original seismic data, full-waveform sonic and pseudo-logs were used to model different interfaces and calibrate the seismic data. These results indicated that preserved relative amplitude processing might be of importance to help reduce the ambiguity in direct detection of volcanogenic massive sulfide based on seismic amplitude anomalies. The customized relative amplitude *

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Instrumenting wells with distributed acoustic sensors (DAS) and illuminating them with passive or active seismic sources allows precise tracking of temporal variations of direct-wave traveltimes and amplitudes, which can be used to monitor variations in formation stiffness and density. This approach has been tested by tracking direct-wave amplitudes and traveltimes as part of a CCS project where a 15 kt supercritical CO2 injection was monitored with continuous offset VSPs using nine permanently mounted surface orbital vibrators (SOVs) acting as seismic sources and several wells instrumented with DAS cables cemented behind the casing. The results show a significant (from 15 to 30%) increase of strain amplitudes within the CO2 injection interval, and travetime shifts of 0.3 to 0.4 ms below this interval, consistent with full-wave 1.5D numerical simulations and theoretical predictions. The results give independent estimates of the CO2 plume thickness and P-wave velocity reduction within it.

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