A new 3D geological model and interpretation of structural evolution of the world-class Rio Tinto VMS deposit, Iberian Pyrite Belt (Spain)

Abstract A new 3D geological model and interpretation of structural evolution of the Rio Tinto world-class VMS deposit are presented in this work. The Rio Tinto volcanogenic massive sulfide (VMS) deposit is located in the Spanish segment of the Iberian Pyrite Belt and is hosted by felsic porphyritic volcanic rocks and tuffs. Computer generated 3D modeling of the different orebodies and host rocks has been carried out using data from around 3000 drill-core logs, allowing us to build 93 cross-sections and 6 plants (both 50 m spacing). This has enabled us to recognize the geometry and relationships between the mineralization and the earliest Carboniferous transtensional tectonics through the development of an extensional pull-apart basin with two sub-basins separated by the NW-SE trending Eduardo Fault. The sub-basins, Cerro Colorado and San Dionisio, were limited by two E-W strike-slip faults, the Northern and Southern faults, and bounded in the east and west by the NW-SE-trending Nerva and Western faults, respectively. The generated pull-apart basin was first filled by a basaltic magmatism of mantle origin and later, following the deposition of the intermediate complex sedimentary unit, by rhyodacitic volcanic rocks of crustal origin. The evolution of the subsiding basins caused the development of an E-W oriented rollover anticline that affected these filling rocks. As a result of a counterclockwise rotation of the stress axes, the primitive pull-apart basin evolved into a basin affected by E-W transtensional sinistral shearing. Its northern and southern limits were favorable areas for increased hydrothermal fluid flow, which gave way to the huge concentration of VMS mineralization located near the limits. The Northern and, to a lesser degree, the Southern extensional faults thus become channel areas for feeding and discharging of the VMS and stockwork ores. The main mineralizing period was related to this stage. Subsequently, during the Variscan transpressional phase, the E-W extensional faults were reactivated as inverse faults, affecting the volcanic sequence of mafic to felsic composition and the intermediate complex sedimentary unit. Fault propagation folds developed above these faults, affecting the massive sulfides, the transition series and the Culm flysch sediments, with buttressing playing a significant role in the geometry of tectonically inverted structures. The VMS mineralization and cupriferous stockworks were folded and dismembered from the original conduits in the volcanic series, and a dextral reactivation of the NW-SE trending faults also developed. Finally, it should be emphasized that this new 3D geological model is an approach to provide a better insight into the 3D structure of the world-class VMS Rio Tinto deposit and could be a key-point for further studies providing a new tool to increase knowledge of the VMS mineralizations and exploration guidelines elsewhere in the IPB.

[1]  Olivier Kaufmann,et al.  3D geological modelling from boreholes, cross-sections and geological maps, application over former natural gas storages in coal mines , 2008, Comput. Geosci..

[2]  A. Martín-Izard,et al.  Structural control and geological significance of the Zn–Pb ores formed in the Benasque Pass area (Central Pyrenees) during the post-late Ordovician extensional event of the Gondwana margin , 2014 .

[3]  Roger W. Marjoribanks,et al.  Geological methods in mineral exploration and mining , 1997 .

[4]  C. Quesada,et al.  A reappraisal of the structure of the Spanish segment of the Iberian Pyrite Belt , 1997 .

[5]  J. Matos,et al.  Devonian and Carboniferous palynostratigraphy of the South Portuguese Zone, Portugal - An overview. , 2007 .

[6]  J. Chilès,et al.  Geological modelling from field data and geological knowledge. Part I. Modelling method coupling 3D potential-field interpolation and geological rules , 2008 .

[7]  Peter Connolly,et al.  Prediction of static and dynamic fluid pathways within and around dilational jogs , 1999, Geological Society, London, Special Publications.

[8]  R. D. Dallmeyer,et al.  Pre-Mesozoic Geology of Iberia , 1991 .

[9]  J. Munhá.  Metamorphic Evolution of the South Portuguese/Pulo Do Lobo Zone , 1990 .

[10]  A. Azor,et al.  Tectonic style and structural analysis of the Puebla de Guzmán Antiform (Iberian Pyrite Belt, South Portuguese Zone, SW Spain) , 2011 .

[11]  L. J. Drew.  A tectonic model for the spatial occurrence of porphyry copper and polymetallic vein deposits - applications to Central Europe , 2006 .

[12]  D. Sanderson,et al.  Analysis of the fractal clustering of ore deposits in the Spanish Iberian Pyrite Belt , 2010 .

[13]  Joan Martí,et al.  Magmatic Evolution and Tectonic Setting of the Iberian Pyrite Belt Volcanism , 1997 .

[14]  A. Martín-Izard,et al.  Geological context and plumbotectonic evolution of the giant Almadén Mercury Deposit , 2015 .

[15]  Michael A. Arthur,et al.  Methane-rich Proterozoic atmosphere? , 2003 .

[16]  C. Boulter.  Comparison of Rio Tinto, Spain, and Guaymas Basin, Gulf of California: An explanation of a supergiant massive sulfide deposit in an ancient sill-sediment complex , 1993 .

[17]  J. Murphy,et al.  Supercontinent model for the contrasting character of Late Proterozoic orogenic belts , 1991 .

[18]  C. Lajaunie,et al.  Foliation fields and 3D cartography in geology: Principles of a method based on potential interpolation , 1997 .

[19]  J. Turner,et al.  Temperature, density and buoyancy fluxes in “black smoker” plumes, and the criterion for buoyancy reversal , 1987 .

[20]  F. Tornos,et al.  Environment of formation and styles of volcanogenic massive sulfides: The Iberian Pyrite Belt , 2006 .

[21]  C. Soriano,et al.  Variscan tectonics in the Iberian Pyrite Belt, South Portuguese Zone , 2002 .

[22]  N. Jones,et al.  Building solid models from boreholes and user-defined cross-sections , 2003 .

[23]  B. Hobbs,et al.  Fault-related dilation, permeability enhancement, fluid flow and mineral precipitation patterns: numerical models , 2008 .

[24]  C. Soriano,et al.  Erratum to: Variscan tectonics in the Iberian Pyrite Belt, South Portuguese Zone , 2002 .

[25]  Philippe Renard,et al.  A workflow to facilitate three-dimensional geometrical modelling of complex poly-deformed geological units , 2009, Comput. Geosci..

[26]  C. Dusel-Bacon,et al.  Proterozoic zircon from augen gneiss, Yukon-Tanana Upland, east-central Alaska , 1981 .

[27]  Guillaume Caumon,et al.  Curvature Attribute from Surface-Restoration as Predictor Variable in Kupferschiefer Copper Potentials , 2015, Natural Resources Research.

[28]  F. Barriga,et al.  Metallogenesis in the Iberian Pyrite Belt , 1990 .

[29]  Jeff B. Boisvert,et al.  Quantitative assessment of mineral resources by combining geostatistics and fractal methods in the Tongshan porphyry Cu deposit (China) , 2013 .

[30]  A. Sánchez,et al.  The volcanic-hosted massive sulphide deposits of the Iberian Pyrite Belt Review and preface to the Thematic Issue , 1997 .

[31]  Y. Amelin,et al.  U–Pb Geochronology of VMS mineralization in the Iberian Pyrite Belt , 2002, Mineralium Deposita.

[32]  Takeo Sato.  Kuroko deposits: their geology, geochemistry and origin , 1977, Geological Society, London, Special Publications.

[33]  Christopher Juhlin,et al.  Crustal structure of the transpressional Variscan orogen of SW Iberia: SW Iberia deep seismic reflection profile (IBERSEIS) , 2003 .

[34]  J. Munhá.  Hercynian magmatism in the Iberian pyrite belt , 1983 .

[35]  Jean-Daniel Boissonnat,et al.  Shape reconstruction from planar cross sections , 1988, Comput. Vis. Graph. Image Process..

[36]  J. L. Fernández,et al.  Nuevas investigaciones y trabajos de evaluación de reservas de gossan en Minas de Riotinto , 1986 .

[37]  Takeo Sato,et al.  The Kuroko and Associated Ore Deposits of Japan; A Review of Their Features and Metallogenesis , 1974 .

[38]  J. B. Silva,et al.  Transcurrent continental tectonics model for the Ossa-Morena Zone Neoproterozoic–Paleozoic evolution, SW Iberian Massif, Portugal , 2004 .

[39]  F. Tornos,et al.  Explanation for many of the unusual features of the massive sulfide deposits of the Iberian pyrite belt , 2002 .

[40]  R. Sáez,et al.  Geological constraints on massive sulphide genesis in the Iberian Pyrite Belt , 1996 .

[41]  Ken McClay,et al.  Extensional fault systems in sedimentary basins: a review of analogue model studies , 1990 .

[42]  F. Barriga,et al.  Bimodal Siliciclastic Systems—The Case of The Iberian Pyrite Belt , 1997 .

[43]  Alan D. Gibbs,et al.  Balanced cross-section construction from seismic sections in areas of extensional tectonics , 1983 .

[44]  C. Rosa,et al.  Type of volcanoes hosting the massive sulfide deposits of the Iberian Pyrite Belt , 2010 .

[45]  Mónica Arias,et al.  A multifractal simulation model for the distribution of VMS deposits in the Spanish segment of the Iberian Pyrite Belt , 2011, Comput. Geosci..

[46]  F. Barriga,et al.  Hydrothermal Alteration and Mineralization in the Neves-Corvo Volcanic-Hosted Massive Sulfide Deposit, Portugal. I. Geology, Mineralogy, and Geochemistry , 2006 .

[47]  J. Walsh,et al.  Hanging wall fault kinematics and footwall collapse in listric growth fault systems , 2003 .

[48]  D. Cassard,et al.  Geometry and genesis of feeder zones of massive sulphide deposits: constraints from the Rio Tinto ore deposit (Spain) , 1997 .

[49]  Simon W. Houlding,et al.  3D Geoscience Modeling: Computer Techniques for Geological Characterization , 1995 .

[50]  E. Carranza,et al.  3D geological modeling for prediction of subsurface Mo targets in the Luanchuan district, China , 2015 .

[51]  E. Marcoux.  Lead isotope systematics of the giant massive sulphide deposits in the Iberian Pyrite Belt , 1997 .

[52]  F. Palomero.  Caracteres geológicos y relaciones morfológicas y genéticas de los yacimientos del "anticlinal de Rio Tinto" , 1980 .

[53]  S. Giorgis,et al.  Tectonic inversion and basement buttressing: an example from the central Appalachian Blue Ridge province , 2002 .

[54]  A. Gibbs.  Structural evolution of extensional basin margins , 1984, Journal of the Geological Society.

[55]  A. Martín-Izard,et al.  3D geological modelling of a polyphase deformed pre‐Variscan IOCG mineralization located at the southeastern border of the Ossa Morena Zone, Iberian Massif (Spain) , 2010 .

[56]  N. Adamides.  Rio Tinto (Iberian Pyrite Belt): a world-class mineral field reopens , 2013 .

[57]  Renaud Bouroullec,et al.  Kinematics of a growth fault/raft system on the West African margin using 3-D restoration , 2002 .

[58]  F. M. Vokes,et al.  Scandinavian Caledonide Metallogeny in a plate tectonic perspective , 1999 .