Evidence for catastrophism at the Famennian-Dinantian boundary in the Iberian Pyrite Belt

Moreno, Carmen; Sierra, Sonia; Sáez, Reinaldo

doi:10.1144/gsl.sp.1996.107.01.12

Cited by 31 publications

(29 citation statements)

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“…The lowest unit is the Late Devonian Phyllite-Quartzite (PQ) formation, which is about 1000 to 5000 m thick and composed mainly of alternating sandstone and shale. This formation is characterized by typical stable epicontinental platform features (Moreno et al 1996). The boundary between the PQ formation and the intermediate unit is defined by quartz-arenite layers (Moreno et al 1996).…”

Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

“…This formation is characterized by typical stable epicontinental platform features (Moreno et al 1996). The boundary between the PQ formation and the intermediate unit is defined by quartz-arenite layers (Moreno et al 1996). The middle unit is the Late Famennian to Late Visean Volcano-Sedimentary Complex (VSC; Van den Boogaard 1963;Oliveira 1990) that is composed of three acidic volcanic cycles separated by two basic volcanic cycles (Lécolle 1972;Routhier et al 1980) with mudstone and some chemical sediments.…”

Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

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A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

et al. 2011

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International audienceIn the Rio Tinto district of the Iberian Pryrite Belt of South Spain, the weathering of massive sulfide bodies form iron caps, i.e., true gossans and their subsequent alteration and re-sedimentation has resulted in iron terraces, i.e., displaced gossans. To study the stucture and evolution of both types of gossans, magnetic investigations have been carried out with two foci: (1) the characterisation and spatial distribution of magnetic fabrics in different mineralised settings, including massive sulfides, gossans, and terraces, and (2) paleomagnetic dating. Hematite has been identified as the suceptibility carrier in all sites and magnetic fabric investigation of four gossans reveals a vertical variation from top to bottom, with: (1) a horizontal foliation refered to as "mature" fabric in the uppermost part of the primary gossans, (2) highly inclined or vertical foliation interpreted as "immature" fabric between the uppermost and lowermost parts, and (3) a vertical foliation interpreted to be inherited from Hercynian deformation in the lowermost part of the profiles. In terraces, a horizontal foliation dominates and is interpreted to be a "sedimentary" fabric. Rock magnetic studies of gossan samples have identified goethite as the magnetic remanence carrier for the low-temperature component, showing either a single direction close to the present Earth field (PEF) direction or random directions. Maghemite, hematite, and occasionally magnetite are the remanence carriers for the stable high-temperature component that is characterized by non PEF directions with both normal and reversed magnetic polarities. No reliable conclusion can be yet be drawn on the timing of terrace magnetization due to the small number of samples. In gossans, the polarity is reversed in the upper part and normal in the lower part. This vertical distribution with a negative reversal test suggests remanence formation during two distinct periods. Remanence in the upper parts of the gossans is older than in the lower parts, indicating that the alteration proceeded from top to bottom of the profiles. In the upper part, the older age and the horizontal "mature" fabric is interpreted to be a high maturation stage of massive sulfides' alteration. In the lower part, the age is younger and the inherited "imature" vertical Hercynian fabric indicates a weak maturation stage. These two distinct periods may reflect changes of paleoclimate, erosion, and/or tectonic motion

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Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

et al. 2011

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“…It is interpreted to represent deposition in an epicontinental sea (Leistel et al 1998). Its upper contact with the Volcano-Sedimentary Complex is in many places tectonic, but in some areas is marked by the occurrence of deposits and structures indicating ground rupture and shaking, and therefore the onset of regional tectonic instability (Moreno et al 1996).…”

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Geochemistry and U–Pb dating of felsic volcanic rocks in the Riotinto–Nerva unit, Iberian Pyrite Belt, Spain: crustal thinning, progressive crustal melting and massive sulphide genesis

Valenzuela

Donaire

et al. 2011

JGS

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We present new geochemical, Sm–Nd and U–Pb data on the felsic volcanic rocks containing the world-class volcanic-hosted massive sulphide deposits in the Riotinto–Nerva unit, Iberian Pyrite Belt, Spain. Three new U–Pb ages from older plagioclase–quartz-phyric dacites and plagioclase-phyric rhyolites to youngest plagioclase–quartz-phyric rhyolites indicate a time span for felsic volcanism ranging from 351.5 ± 0.4 to 345.7 ± 0.6 Ma. The youngest felsic rocks exhibit lower ε Nd , as well as contrasting Ti, Sr, Zr, Hf and Eu/Eu* values. We interpret that in the Riotinto–Nerva unit crustal melting successively affected shallower, more evolved horizons in the crust. Progressive crustal melting is consistent with current interpretations of the Iberian Pyrite Belt in terms of a late Devonian–Early Carboniferous transtensional setting, coupled with underplating by basic magma. We suggest that low ε Nd , evolved crustal magmatism could be used as a proxy in studies of the genesis of these and possibly other Phanerozoic massive sulphide deposits. Supplementary material: Details of the analytical methods and whole-rock data for basalts are available at http://www.geolsoc.org.uk/SUP18452 .

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“…The underlying Phyllite-Quartzite Group clastic sequence (sandy turbidites and black mudrocks) formed in the Devonian at a passive margin (Oliveira & Quesada 1998). For the metallogeny of the region, the key tectonic event was the transition, late in Devonian times, from this drift phase of passive margin evolution to active extensional tectonics (Moreno et al 1996). This switch was induced by oblique convergence as the South Portuguese Zone was sutured to the main Iberian Massif (Fig.…”

Section: Tectonic Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

Provenance and geochemistry of sedimentary components in the Volcano-Sedimentary Complex, Iberian Pyrite Belt: discrimination between the sill–sediment-complex and volcanic-pile models

Boulter

Hopkinson

Ineson

et al. 2004

JGS

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Two highly contrasting models have been proposed for the palaeovolcanological setting of the massive sulphide deposits in the Iberian Pyrite Belt. The long-standing view of the host rocks is that they are a pile of effusive and pyroclastic rocks but this position has now been challenged by the proposal that highlevel peperitic sills predominate. Discrimination between the volcanic-pile and sill-sediment-complex models is important because they lead to very different conclusions about such key metallogenic features as the timing of mineralization, the nature of the ore-forming convective system and the source of the metals. Sedimentary geochemistry, particularly REE and Ti/Nb, shows that there is no correspondence between the chemistries of mafic igneous sheets and intercalated stratified-volcaniclastic rocks that range from andesite to rhyodacite in composition. Therefore none of the mafic sheets supplied detritus to the sedimentary environment. Sedimentary rocks of continental provenance persist throughout the host-rock sequence, especially in mineralized regions, implying confinement of the majority of primary volcanic facies in the form of high-level intrusions. Some andesitic and felsic intrusions created a minor, stratified volcaniclastic component via hydrovolcanic eruptions. The volcanic-pile model is invalidated because the expected provenance patterns for this volcanic style are not present and the sill-sediment-complex setting of the sulphide deposits is confirmed.

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Evidence for catastrophism at the Famennian-Dinantian boundary in the Iberian Pyrite Belt

Abstract: Terrigenous shelf sedimentation during the Devonian created a homogeneous The Volcanic-Siliceous Complex (VSC)This complex contains the economically important massive sulphide and manganese deposits. The VSC is late Famennian to Vis~an in age, and consists of a heterogeneous group of rocks

Cited by 31 publications

References 35 publications

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

Geochemistry and U–Pb dating of felsic volcanic rocks in the Riotinto–Nerva unit, Iberian Pyrite Belt, Spain: crustal thinning, progressive crustal melting and massive sulphide genesis

Provenance and geochemistry of sedimentary components in the Volcano-Sedimentary Complex, Iberian Pyrite Belt: discrimination between the sill–sediment-complex and volcanic-pile models

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