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

A new 3D geological model and structural evolution of the world-class Rio Tinto VMS deposit, Iberian Pyrite Belt (Spain)
A new 3D geological model and structural evolution of the world-class Rio Tinto VMS deposit, Iberian Pyrite Belt (Spain)
A new 3D geological model and structural evolution of the Rio Tinto world-class VMS deposit is 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 3,000 drill-core logs, allowing us to build 93 cross-sections and 6 plants (both 50 m spacing). This has enabled us to recognize of 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 elsewerein the IPB.
rio tinto deposit, 3D modeling, transtensional tectonics, pull-apart basin, VMS, stockwork, variscan orogeny
0169-1368
1-55
Martin-Izard, A.
4f76e60d-86a4-4588-b214-981af987e5b7
Arias, D.
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Arias, M.
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Gumiel, P.
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Sanderson, D.J.
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Castañon, C.
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Lavandeira, A.
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Sanchez, J.
6ee55962-52a5-460d-ad5d-10151b721f75
Martin-Izard, A.
4f76e60d-86a4-4588-b214-981af987e5b7
Arias, D.
6d78bd4d-dc04-4600-bcad-82a91bf6ecb5
Arias, M.
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Gumiel, P.
d8b4a65d-b701-4bf0-9d94-7a3c016ed8ef
Sanderson, D.J.
5653bc11-b905-4985-8c16-c655b2170ba9
Castañon, C.
918718c3-b447-4fdd-96af-31f665b052b5
Lavandeira, A.
ff01aa0f-b970-4c04-baf3-be7eb30a9a93
Sanchez, J.
6ee55962-52a5-460d-ad5d-10151b721f75

Martin-Izard, A., Arias, D., Arias, M., Gumiel, P., Sanderson, D.J., Castañon, C., Lavandeira, A. and Sanchez, J. (2015) A new 3D geological model and structural evolution of the world-class Rio Tinto VMS deposit, Iberian Pyrite Belt (Spain). Ore Geology Reviews, 1-55. (doi:10.1016/j.oregeorev.2015.06.006).

Record type: Article

Abstract

A new 3D geological model and structural evolution of the Rio Tinto world-class VMS deposit is 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 3,000 drill-core logs, allowing us to build 93 cross-sections and 6 plants (both 50 m spacing). This has enabled us to recognize of 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 elsewerein the IPB.

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Accepted/In Press date: 9 June 2015
e-pub ahead of print date: 10 June 2015
Keywords: rio tinto deposit, 3D modeling, transtensional tectonics, pull-apart basin, VMS, stockwork, variscan orogeny
Organisations: Faculty of Engineering and the Environment

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Local EPrints ID: 378061
URI: http://eprints.soton.ac.uk/id/eprint/378061
ISSN: 0169-1368
PURE UUID: 6a61d121-0137-44d3-94d4-da52309c7d56
ORCID for D.J. Sanderson: ORCID iD orcid.org/0000-0002-2144-3527

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Date deposited: 24 Jun 2015 13:25
Last modified: 19 Nov 2019 01:43

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Contributors

Author: A. Martin-Izard
Author: D. Arias
Author: M. Arias
Author: P. Gumiel
Author: D.J. Sanderson ORCID iD
Author: C. Castañon
Author: A. Lavandeira
Author: J. Sanchez

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