Paleomagnetic Dating of the Genesis of the Early Cretaceous Aliva Zn-Pb Ore Deposit, Northern Spain

David T A Symons, University of Windsor, Earth Sciences, Windsor, ON, Canada, Fernando Tornos, CSIC-INTA, Astrobiologia, Madrid, Spain, Kazuo Kawasaki, University of Toyama, Earth System Science, Toyama, Japan, Francisco Velasco, Universidad del Pais Vasco, Mineralogia y Petrologia, Bilbao, Spain and Idoia Rosales, Instituto Geológico y Minero de Espana,, Madrid, Spain

Contact First Author: David T A Symons; dsymons@uwindsor.ca

Previously Published Material: paper submitted

Abstract ID#: 34349

 

English Abstract:
The Aliva Mississippi Valley-type (MVT) Zn-Pb deposit is hosted in strata of the 309±3Ma (Late Carboniferous) Picos de Europa limestone formation in the Picos de Europa Unit of the Cantabrian zone. Paleomagnetic analyses of 193 specimens from 23 sites in MVT mineralization and surrounding dolomite gives a characteristic remanent magnetization (ChRM) with a paleopole at 80.7°N, 268.1°E (A95 =5.3°) that resides mainly in magnetite-titanomagnetite with minor pyrrhotite. A negative fold test shows that the ChRM postdates Variscan orogenic deformation at >95% confidence and that the ore is not syngenetic or syndiagenetic. Plausible tectonic corrections indicate further that the Aliva MVT deposit: 1) resides in dolomitzed zones in olistoliths of the Picos de Europa limestone that slumped into the overlying 305±1Ma Lebena shale formation during Variscan orogenesis; 2) was formed epigenetically at 112±8 Ma (Early Cretaceous) as Iberia rotated away from Eurasia to open the Bay of Biscay, most likely from rift-related hydrothermal fluids ascending into Iberia’s coastal margin; and, 3) was tilted 10°±3° downward to the north by N-S compression as Iberia collided with Eurasia during the Oligocene-Miocene Pyrenean Orogeny.
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