DOME SPP 2238 – Phase 1: 2021-2023
Melts-Fluids-Models: keys to understanding ore-forming processes at the world-class Neves Corvo massive sulphide deposit, Iberian Pyrite Belt
The Iberian Pyrite Belt (IPB) in Portugal and Spain is a world-class metallogenic province that contains more than 1600 Mt of massive sulfide ore in over 100 deposits (see map). The orebodies are hosted by submarine lithologies comprising felsic volcanic rocks and black shales and, therefore, share characteristics with the sedimentary-hosted (SEDEX) and the volcanogenic massive sulfide (VMS) deposits. Hydrothermal activity at mid-ocean ridges and submarine arc volcanoes has been inferred to be a modern analog for forming these giant submarine deposits, but none of the known modern hydrothermal fields contain the tonnage, density of occurrence, or size of the IPB district. The classic conceptual models assume that metal-bearing, high-salinity hydrothermal fluids (brines) vent into anoxic-euxinic domains of the paleo-ocean where they precipitate massive sulfide ores during sedimentation of black shales. However, most deposits lack unequivocal evidence for exhalation into anoxic seawater, and sulfide reduction may instead be related to early diagenetic processes of shales in oxygenated oceanic environments with high organic, where basin restriction may impose mass balance limitations of sulfur availability, hence inhibiting the formation of large, massive sulfide deposits. Nevertheless, the future supply of raw materials will come from giant ore deposits, so the formation mechanisms of world-class systems remain a key issue in economic geology.
General geology of the Iberian Pyrite Belt showing the location of Neves Corvo, Sesmarias, and Albernoa areas (white boxes) and other massive sulfide deposits.
Goals of the project
This project aims to understand the origin and evolution of the ore-forming fluids and formation mechanisms of the cassiterite mineralization at the giant Cu-Zn-Pb-(Sn)Neves Corvo deposit in Portugal using fluid and melt inclusions and numerical simulations.
Neves Corvo deposit comprises seven massive sulfide orebodies predominantly located in the northern limb of the Rosário-Neves Corvo antiform (RNC). The lenses occur on top of the lower Volcano-Sedimentary Complex (VSC), either hosted by the black shales or by the felsic volcanic rocks (rhyolites and volcaniclastics). The Sn mineralization is structurally controlled and occurs along the so-called “tin corridor” in the Corvo orebody. Neves Corvo is a hybrid deposit with high- and low-temperature mineralization (Cu, Zn, Sn) where the nature of the contribution of magmatic fluids and/or seawater-derived fluids has been the topic of much debate. Thus, deciphering and constraining the first-order chemical and physical processes that form the deposit in a geodynamic context will help find similar giant deposits on land or in the oceans at greater depths.
We studied a total of 8 ore samples from the cassiterite ores and eight samples from the footwall host rocks. We used a combination of transmitted and reflected light microscopy, SEM imaging, microprobe imagining, and analysis to study fluid and melt inclusions, as well as the mineralogy and textural relationships of cassiterite, sulfides, and gangue minerals. We also studied the trace element geochemistry of cassiterite and phosphate minerals in detail using LA-ICP-MS and obtained stable isotope geochemistry analyses of cassiterite, quartz, and apatite using SIMS. Host rocks were analyzed using a combination of XRD, XRF, and ICP-MS.
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Results from the fluid and melt inclusion study showed that fluid inclusions were mostly decrepitated during metamorphism, making their investigation irrelevant to the aims of this study. The melt inclusions were metamorphosed during the Variscan orogeny and are mostly altered to an assemblage of albite, white mica, carbonate, and chlorite (see below).
​Textural and mineralogical studies have led to the discovery of phosphate minerals associated with cassiterite mineralization. This will be the topic of our next article. More details will follow soon.
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Geology, lithogeochemistry, and genesis of the Sesmarias VMS deposit, Iberian Pyrite Belt
This subproject is part of the project above, funded by DFG (German Science Foundation), and it aims to characterize the volcanic sequence and mineralization and reconstruct the hydrothermal alteration, as well as propose a genetic model for the formation of the recently discovered Sesmarias VMS deposit in the Iberian Pyrite Belt. For this work, we will use a combination of lithogeochemistry, microprobe, LA-ICP-MS, and SIMS studies to characterize rocks, alteration, and mineralization.
Details about the Sesmarias property (Alvalade Project) can be consulted here.
Publications from these projects:
Codeço, M. S., Gleeson, S. A., Barrote, V., Harlov, D., Kusebauch, C., Koch-Müller, M., Relvas, J.M., Schmidt, C., Schleicher, A., Stammeier, J. A., Syczewski, M. D., and Wilke, F. D. (under review). Textural, mineralogical, and geochemical evidence for apatite metasomatism and REE mobility within the Corvo orebody at the Neves Corvo Cu-Zn-Pb(-Sn) VMS deposit (Iberian Pyrite Belt).
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Codeço, M. S., Gleeson, S. A., Relvas, J.M.R.S., Wilke, F.D.H., Schleicher, A., Stammeier, J.A., Barrote, V., Harlov, D.E., Schmidt, C., Weis, P. (2023): Tracking the evolution of the “Tin corridor” at the Neves Corvo deposit (Iberian Pyrite Belt) through metasomatism of phosphate minerals – Goldschmidt 2023 Conference (Lyon, France). https://conf.goldschmidt.info/goldschmidt/2023/meetingapp.cgi/Paper/15856
Codeço, M. S., Gleeson, S. A., Rosa, C., Kuhn, P., Trumbull, R., Weis, P., Schleicher, A. M., Stammeier, J. A., Wilke, F. (2022): The Sesmarias massive sulfide discovery in Portugal (Iberian Pyrite Belt): preliminary geochemical and petrological studies – Abstracts, EGU General Assembly 2022 (Vienna, Austria, Online 2022). https://doi.org/10.5194/egusphere-egu22-6130
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Codeço, M. S., Weis, P., Trumbull, R. B., Relvas, J., Veksler, I., & Gleeson, S. A. (2021). The Crown Jewels: Understanding ore-forming processes at the world-class Panasqueira and Neves Corvo deposits, Portugal. In 3rd European Mineralogical Conference (p. 100). Cracow, Poland.
Research Group
Marta Codeço (Postdoc) GFZ Potsdam now @ Univ. Arizona
Sarah Gleeson (PI) GFZ Potsdam
Robert Trumbull (co-PI) GFZ Potsdam
Philipp Weis (co-PI) GFZ Potsdam
Jorge Relvas University of Lisbon
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Funding and collaborations:
