Skip to main content
SpringerLink
Log in

3D Constrained Gravity Inversion and TEM, Seismic Reflection and Drill-Hole Analysis for New Target Generation in the Neves–Corvo VMS Mine Region, Iberian Pyrite Belt

  • Original Paper
  • Published:
Natural Resources Research Aims and scope Submit manuscript

Abstract

Located in the Iberian pyrite belt, the Neves–Corvo mine is a world-class massive sulfide deposit and the largest operating mine in Portugal with underground mining down to 1000 m depth focused on massive and stockwork Cu, Zn, Pb rich ores. Gravimetric data have had a leading role in the discovery of the seven known deposits, together with time-domain electromagnetic (TEM) ground data. In this work, we present the results of a 3D constrained gravity inversion carried out with legacy ground gravity data. The 3D gravity inversions were carried out using an updated density database containing approximately 142,000 measurements. A recently constructed 3D geological model based on reprocessed 2D seismic reflection, 3D seismic, TEM and updated geology from detailed surface mapping and drill-hole data, was used to constrain the inversions. The results show multiple high-density anomalies that may indicate the presence of mineralization at depth. These anomalies were therefore cross-checked with holes previously drilled. Approximately 97% of more than 1000 available surface drill-holes located on or at a distance of less than 200 m from the high-density anomalies intersected mineralization. However, gravity anomalies have been drilled in the past and particularly dense black shales or rhyolitic/gabbroic rocks have been intersected. To increase the success of future drilling, gravimetric anomalies have been correlated spatially with high-conductivity TEM zones and strong-amplitude seismic reflections, because igneous rocks usually present weak-to-moderate conductivity and a massive column of black shales presents a seismic signature quite different from that of mineralization. We concluded that some of these locations represent high-quality targets to consider following up with drilling and further exploration.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Figure 1

adapted from Oliveira et al., 2016; Matos et al., 2020). (c) Simplified stratigraphy of the Neves–Corvo mine region, after Oliveira et al. (2013), Mendes et al. (2020) and Pereira et al. (2021). Legend: MT = Mértola Fm. (MT1, MT2 and MT3); r = Brancanes Fm.; g = Godinho Fm.; bv = “Borra de vinho” Fm.; s = Grandaços Fm.; Va = Felsic volcanic rocks; Vb = Mafic volcanic rocks; MS = Massive Sulfides; ST = Stockwork; n = Neves Fm.; Co = Corvo Fm.; PQ = Phyllite Quartzite Gr.; ca = limestones; d = dolerites; J = Jaspers

Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9

Similar content being viewed by others

Availability of Data and Material

Gravimetric data are commercially available at LNEG; density database is available upon request.

References

  • Albouy, L., Conde, L. N., Foglierinni, F., Leca, X., Morikis, A., Callier, L., Carvalho, P., & Songy, J. C. (1981). Le gisement de sulfures massifs polymétalliques de Neves Corvo, Baixo Alentejo, Portugal. Chronique de La Recherche Minière, BRGM, 460, 5–27.

    Google Scholar 

  • Al-Chalabi, M. (1979). Velocity determination from seismic reflection data. In A. A. Fitch (Ed.), Developments in geophysical exploration methods, 1. Dordrecht: Springer.

    Google Scholar 

  • Blackburn, G. (1980). Errors in stacking velocities-true velocities conversion over complex geologic situations. Geophysics, 45, 1465–1488.

    Article  Google Scholar 

  • Brodic, B., Malehmir, A., Pacheco, N., Juhlin, C., Carvalho, J., Dynesius, L., van den Berg, J., de Kunder, R., Donoso, G. A., Sjölund, T., & Araújo, V. (2021). Innovative seismic imaging of VMS deposits, Neves-Corvo, Portugal: Part I—in-mine array. Geophysics. https://doi.org/10.1190/geo2020-0565.1

    Article  Google Scholar 

  • Carvalho, J., Dias, P., Revaux, C., Inverno, C., Pacheco, N., Matos, J.X., Malehmir, A., Marques, F., Araujo, V., Batista, M.J., Spicer, B., Donoso, G.A., Albardeiro, L., Morais, I., Ramalho, E., Filipe, A., Oliveira, D. (2020). A new 3D geological model for the Neves–Corvo mine region, Iberian Pyrite Belt, Portugal, Extended Abstracts of the Near Surface Geoscience Conference & Exhibition 2020, Amsterdam, 7–10 December.

  • Carvalho, J., Dias, P., Reveaux, C., Matos, J. X., Araújo, V., Inverno, C., Marques, F., Donoso, G. A., Pacheco, N., Morais, I., Albardeiro, L., Batista, M. J., Malehmir, A., Spicer, B., & Oliveira, D. (2021). A Drill-hole, geological and geophysical databased 3D geological model for the Neves-Corvo mine region, Portugal. International Journal of Earth Sciences. https://doi.org/10.1007/s00531-021-02120-x

    Article  Google Scholar 

  • Carvalho, P., Pacheco, N., Beliz, A., Ferreira, A. (1996). Últimos desenvolvimentos em prospeção realizados pela Somincor. Bol. Geologico y Minero, ITGE (Madrid), 107 (5–6), 39–54.

  • Dias, P., Represas, P., Pacheco, N., Thunehed, H., Carvalho, J., Ramalho, E., Donoso, G., Inverno, C., Marques, F., & Araújo, V. (2020). 3D TEM and Gravity Modeling over the Lombador Deposit, Neves–Corvo, Portugal, Extended Abstracts of the 82nd EAGE Conference & Exhibition 2020, Amsterdam, 6–9 December, We_E106_19.

  • Dias, P., Thunehed, H., Represas, P., Carvalho, J., Inverno, C., Spicer, B., Ramalho, E., Donoso, G. A., Araújo, V., Marques, F., Morais, I., Malehmir, A., & Pacheco, N. (2021). Geophysical investigation of the down-dip extension of the Lombador massive sulphide deposit, Neves-Corvo, Portugal. International Journal of Earth Sciences, 110(3), 911–922.

    Article  Google Scholar 

  • Donoso, G. A., Malehmir, A., Brodic, B., Pacheco, N., Carvalho, J., & Araujo, V. (2021). Innovative seismic imaging of VMS deposits, Neves-Corvo, Portugal: Part II—surface array. Geophysics o,. https://doi.org/10.1190/geo2020-0336.1

    Article  Google Scholar 

  • Donoso, G. A., Malehmir, A., Pacheco, P., Araujo, V., Penney, M., Carvalho, J., Spicer, B., & Beach, S. (2020). Potential of legacy 2D seismic data for deep targeting and structural imaging at the Neves-Corvo massive sulphide-bearing deposit, Portugal. Geophysical Prospecting, 66, 44–61.

    Article  Google Scholar 

  • Ellis, R. (2011). Method and system for modeling anomalous density zones in geophysical exploration. US Patent 9372945: filed August 31, 2011 and issued June 21, 2016. https://patents.justia.com/patent/9372945.

  • Ellis, R. G., MacLeod, I. N. (2013). Constrained voxel inversion using the Cartesian cut cell method. ASEG Extended Abstracts, 2013:1, 1–4, https://doi.org/10.1071/ASEG2013ab222.

  • Inverno, C., Díez Montes, A., Rosa, C., García-Crespo, J., Matos, J., García-Lobón, J. L., Carvalho, J., Bellido, F., Castello-Branco, J. M., Ayala, C., Batista, M. J., Rubio, F., Granado, I., Tornos, F., Oliveira, J. T., Rey, C., Araújo, V., Sánchez-García, T., Pereira, Z., Represas, P., Solá, A. R., & Sousa, P. (2015a). Chapter 9: Introduction and geological settings of the Iberian Pyrite Belt. In: P. Weihed (Ed.) 3D, 4D and predictive modelling of major mineral belts in Europe (pp. 191–208). Springer. https://doi.org/10.1007/978-3-319-17428-0_9

  • Inverno, C., Rosa, C., Matos, J., Carvalho, J., Castello-Branco, J.M., Batista, M.J., Granado, I., Oliveira, J.T., Araújo, V., Pereira, Z., Represas, P., Solá, A.R., & Sousa, P. (2015b). Chap. 11—Modelling of the Neves Corvo Project Area.), 3D, 4D and Predictive Modelling of Major Mineral Belts in Europe, P. Weihed (Ed.), (pp. 231–261). Springer. https://doi.org/10.1007/978-3-319-17428-0_9.

  • Leca, X., Ribeiro, A., Oliveira, J. T., Silva, J. B., Albouy, L., Carvalho. P., & Merino, H. (1983). Cadre géologique des minéralisations de Neves Corvo (Baixo-Alentejo, Portugal)– Lithostratigraphie, paléogéographie et tectonique. Mémoire du BRGM, 121, Orléans, France : BRGM. 79 p.

  • Marques, F., Matos, J. X., Sousa, P., Represas, P., Araújo, V., Carvalho, J., Pacheco, N., Morais, I., Albardeiro, L., & Gonçalves, P. (2019). The role of land gravity data in the Neves- Corvo mine discovery and its use in present-day exploration and new target generation. First Break, 37, 97–102.

    Article  Google Scholar 

  • Matos, J. X., Carvalho, J., Represas, P., Batista, M. J., Sousa, P., Ramalho, E. C., Marques, F., Morais, I., Albardeiro, L., Gonçalves, P., & Dias, P. (2020). Geophysical surveys in the Portuguese sector of the Iberian Pyrite Belt: A global overview focused on the massive sulphide exploration and geologic interpretation. Comunicações Geológicas LNEG, 107, 41–78.

    Google Scholar 

  • Matos, J.X., Albardeiro, L., Morai,s I., Mendes, M., Marques, F., Pereira, Z., Solá, R., Batista, M.J., Carvalho, J., Salgueiro, R., de Oliveira D.P.S., Inverno, C., Mirão, J., Rosado, L., Pacheco, N., & Araujo, V. (2019). Prospeção de sulfuretos maciços no setor português da Faixa Piritosa Ibérica: o desafio do projeto EXPLORA/Alentejo2020. Liv. Actas II Jornadas de Arqueología, História y Minería de La Faja Pirítica Ibérica. La Geología como suporte económico, histórico y social de la región. Garrido e Suárez Eds., Assoc. Herrerias, Huelva (Spain), 35–53, ISBN: 978–84–09–16728–9.

  • Matos, J.M., Oliveira, D.P.S., Pereira, Z., Batista, M.J., Carvalho, J., Represas, P., Sousa, P., Solá, R., Salgueiro, R., Mendes, M., Morais, I., Albardeiro, L., & Inverno, C. (2017). The Iberian Pyrite Belt geological, geophysical and geochemical LNEG mapping program, Portugal. PDAC 2017 Technical Program “Riches of the Iberian Peninsula”, 5Th March.

  • Matos, J. X., Pereira, Z., Rosa, C. J. P., Rosa, D. R. N., Oliveira, J. T., & Relvas, J. M. R. S. (2011). Late Strunian age: A key time frame for VMS deposit exploration in the Iberian Pyrite Belt. 11TH SGA Biennial Meeting, Autofagasta, Chile, 790–792.

  • Mendes, M., Pereira, Z., Matos, J. X., Albardeiro, L., Morais, I., Solá, R., Salgueiro, R., Pacheco, N., Araújo, V., Inverno, C., & Oliveira, J. T. (2020). New insights on the middle Givetian/middle Frasnian palynofloras from the Phyllite-Quartzite Formation in the Neves-Corvo mine region (Iberian Pyrite Belt, Portugal). Revue de Micropaléontologie, 68, 1–13.

    Article  Google Scholar 

  • Oliveira, V., Matos, J. X., Bengala, M., Silva, M. N., Sousa, P., & Torres, L. (1998). Geology and geophysics as successful tools in the discovery of the Lagoa Salgada Orebody (Sado Tertiary Basin—Iberian Pyrite Belt), Grândola, Portugal. Mineralium Deposita, 33, 170–187.

    Article  Google Scholar 

  • Oliveira, J. T., Pereira, Z., Carvalho, P., Pacheco, N., & Korn, D. (2004). Stratigraphy of the tectonically imbricated lithological succession of the Neves Corvo mine area, Iberian Pyrite Belt, Portugal. Mineralium Deposita, 39, 422–436.

    Article  Google Scholar 

  • Oliveira, J. T., Rosa, C., Rosa, D., Pereira, Z., Matos, J. X., Inverno, C., & Andersen, T. (2013). Geology of the Neves-Corvo antiform, Iberian Pyrite Belt, Portugal: New insights from physical volcanology, palynostratigraphy and isotope geochronology studies. Mineralium Deposita, 48, 749–766.

    Article  Google Scholar 

  • Oliveira, J. T., Romão, J., Matos, J. X., Leal, J., & Rosa, C. (2016). Sheet 46-C (Almodôvar) from the Geological Map of Portugal, 1:50 000 scale, Un. Geologia, Hidrogeologia & Geologia Costeira, Lisboa: Laboratório Nacional de Energia e Geologia.

  • Oliveira, J. T., Quesada, C., Pereira, Z., Matos, J. X., Solá, A.R., Rosa, D., Albardeiro, L., Díez-Montes, A., Morais, I., Inverno, C., Rosa, C., Relvas, J. (2019). South Portuguese terrane: A continental affinity exotic unit. Cap. 6. In: C. Quesada, & J. T. Oliveira (Eds.), The Geology of Iberia: A Geodynamic Approach, Regional Geology Reviews (pp. 173–206). Springer. https://doi.org/10.1007/978-3-030-10519-8_6.

  • Pereira, Z., Matos, J., Solá, A., Batista, M., Salgueiro, R., Rosa, C., Albardeiro, L., Mendes, M., Morais, I., Oliveira, D., Pacheco, N., Araújo, V., Castelo Branco, J. M., Neto, R., Amaral, J. L., Inverno, C., & Oliveira, J. (2021). Geology of the recently discovered massive and stockwork sulphide mineralization at Semblana, Rosa Magra and Monte Branco, Neves-Corvo mine region, Iberian Pyrite Belt, Portugal. Geological Magazine. https://doi.org/10.1017/S0016756820001284

    Article  Google Scholar 

  • Represas, P., Sousa, P., Torres, L., Bengala, M., & Matos, J. X. (2016). Gravimetric Map (Bouguer anomaly, density 2.6) of the South Portuguese Zone, Iberian Pyrite Belt, scale 1/400 000, Lisboa: LNEG/URMG. ISBN: 978–989–675–046–6.

  • Seequent Limited (2020). VOXI Earth Modelling Service, http://www.seequent.com/voxi.

  • West, D., & Penney, M. (2017). Brownfields and Beyond—Undercover at Neves Corvo, Portugal. Proceedings of Exploration 17: Sixth Decennial International Conference on Mineral Exploration, V. Tschirhart and M.D. Thomas (Eds.), 21, 291–304.

  • Torres, L., Carvalho, J. (1998). A contribuição dos dados geofísicos obtidos na prospecção de sulfuretos polimetálicos na Faixa Piritosa para ampliar o conhecimento estrutural da Zona Sul-Portuguesa. IV Simp. Int. dos Sulfuretos Polimetálicos da Faixa Piritosa Ibérica. Lisboa: APIMINERAL, A.3.1-A.3.6.

  • Yavuz, S., Kinkela, J., Dzunic, A., Penney, M., Neto, R., Araújo, V., Ziramov, S., Pevzner, R., & Urosevic, M. (2015). Physical property analysis and preserved relative amplitude processed seismic imaging of volcanogenic massive sulphides—a case study from Neves-Corvo, Portugal. Geophysical Prospecting, 63(4), 798–812.

    Article  Google Scholar 

  • Zhdanov, M. S. (2002). Geophysical inverse theory and regularization problems. Elsevier

  • Ziramov, S., Kinkela, J., & Urosevic, M. (2016). Neves–Corvo 3D - A High-resolution Seismic Survey at a Mine Camp Scale. Conference Proceedings, Near Surface Geoscience 2016—22nd European Meeting of Environmental and Engineering Geophysics, cp-495–00188, 4–8 September, Barcelona (Spain). https://doi.org/10.3997/2214-4609.201602090.

Download references

Acknowledgments

The authors are grateful to Somincor/Lundin Mining Corporation for providing drill-hole, geological and EM data used in this work, and LNEG for the land gravity and geological data. The authors thank the EU for funding projects EXPLORA/Alentejo2020 (Op ALT20-03-0145-FEDER-000025), and Smart Exploration (Agreement No. 775971) under H2020 research and innovation program. We are also grateful to EMIT and Emerson for providing academic licenses of Maxwell and GoCad software, respectively, and Naphtali from Seequent for support to Oasis Montaj and VOXI licenses. This work is also dedicated to all SFM/IGM/LNEG field work teams that permitted the production of hundreds of gravity maps in detailed 1/5 000 and 1/25 000 scales, coordinated by José Marcos Bengala, Manuel Nolasco Silva, Vitor Alvoeiro and Luís Torres. We are also indebted to Ian Fergusson and four anonymous reviewers who greatly contributed to improve the quality of this work.

Author information

Author notes

  1. Nelson Pacheco

    Present address: Somincor-Lundin Mining Corporation, Santa Bárbara dos Padrões, Castro Verde, Portugal

Authors and Affiliations

  1. Laboratório Nacional de Energia E Geologia, LNEG, Bairro da Val d´Oca Ap. 14, 7601-909, Aljustrel, Portugal

    Fábio Marques, João Xavier Matos, Igor Morais, Luís Albardeiro, Pedro Sousa & Pedro Gonçalves

  2. Laboratório Nacional de Energia E Geologia, LNEG, Estrada da Portela, Zambujal Apartado, 7586, 2610-999, Amadora, Portugal

    Pedro Dias, João Carvalho & Patrícia Represas

  3. Somincor-Lundin Mining Corporation, Santa Bárbara dos Padrões, Castro Verde, Portugal

    Vítor Araújo

  4. Lundin Mining Corporation, Toronto, Canada

    Bill Spicer

  5. Seequent, Rio de Janeiro, Brazil

    Diego Barbosa

Authors
  1. Fábio Marques
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Pedro Dias
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. João Carvalho
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Patrícia Represas
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Bill Spicer
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Vítor Araújo
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. João Xavier Matos
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Igor Morais
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Luís Albardeiro
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Pedro Sousa
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. Nelson Pacheco
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. Pedro Gonçalves
    View author publications

    You can also search for this author in PubMed Google Scholar

  13. Diego Barbosa
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to João Carvalho.

Ethics declarations

Conflict of Interest

None.

Code Availability

Commercial code was used.

Appendix

Appendix

See Figure 10.

Figure 10
figure 10

Results for the third run of the gravimetric inversion (d > 3.5 g/cm3) overlaid by the analytical signal of the residual Bouguer anomaly map shown in Figure 2b. Geological contours of Figure 1b are also superimposed

Full size image

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Marques, F., Dias, P., Carvalho, J. et al. 3D Constrained Gravity Inversion and TEM, Seismic Reflection and Drill-Hole Analysis for New Target Generation in the Neves–Corvo VMS Mine Region, Iberian Pyrite Belt. Nat Resour Res 31, 2321–2346 (2022). https://doi.org/10.1007/s11053-022-10081-4

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11053-022-10081-4

Keywords

Search

Navigation