Tectonic erosion of the overriding plate by the downgoing slab is believed to occur at half the Earth’s subduction zones1,2. In situ investigation of the geological processes at active erosive margins is extremely difficult owing to the deep marine environment and the net loss of forearc crust to deeper levels in the subduction zone. Until now, a fossil erosive subduction channel—the shear zone marking the plate boundary3—has not been recognized in the field, so that seismic observations have provided the only informa- tion on plate boundary processes at erosive margins. Here we show that a fossil erosive margin is preserved in the Northern Apennines of Italy. It formed during the Tertiary transition from oceanic subduction to continental collision, and was preserved by the late deactivation and fossilization of the plate boundary. The outcrop- ping erosive subduction channel is ,500 m thick. It is represent- ative of the first 5 km of depth, with its deeper portions reaching 150 6C. The fossil zone records several surprises. Two de ́ colle- ments were simultaneously active at the top and base of the sub- duction channel. Both deeper basal erosion and near-surface frontal erosion occurred. At shallow depths extension was a key deformation component within this erosive convergent plate boundary, and slip occurred without an observable fluid pressure cycle. At depths greater than about 3 km a fluid cycle is clearly shown by the development of veins and the alternation of fast (co-seismic) and slow (inter-seismic) slip. In the deepest portions of the outcropping subduction channel, extension is finally overprinted by compressional structures. In modern sub- duction zones the onset of seismic activity is believed to occur at ,150 6C, but in the fossil channel the onset occurred at cooler palaeo-temperatures.

Geologic record of fluid flow and seismogenesis along an erosive subducting plate boundary / P. VANNUCCHI; F. REMITTI; G. BETTELLI. - In: NATURE. - ISSN 0028-0836. - STAMPA. - 451:(2008), pp. 699-703. [10.1038/nature06486]

Geologic record of fluid flow and seismogenesis along an erosive subducting plate boundary

VANNUCCHI, PAOLA;
2008

Abstract

Tectonic erosion of the overriding plate by the downgoing slab is believed to occur at half the Earth’s subduction zones1,2. In situ investigation of the geological processes at active erosive margins is extremely difficult owing to the deep marine environment and the net loss of forearc crust to deeper levels in the subduction zone. Until now, a fossil erosive subduction channel—the shear zone marking the plate boundary3—has not been recognized in the field, so that seismic observations have provided the only informa- tion on plate boundary processes at erosive margins. Here we show that a fossil erosive margin is preserved in the Northern Apennines of Italy. It formed during the Tertiary transition from oceanic subduction to continental collision, and was preserved by the late deactivation and fossilization of the plate boundary. The outcrop- ping erosive subduction channel is ,500 m thick. It is represent- ative of the first 5 km of depth, with its deeper portions reaching 150 6C. The fossil zone records several surprises. Two de ́ colle- ments were simultaneously active at the top and base of the sub- duction channel. Both deeper basal erosion and near-surface frontal erosion occurred. At shallow depths extension was a key deformation component within this erosive convergent plate boundary, and slip occurred without an observable fluid pressure cycle. At depths greater than about 3 km a fluid cycle is clearly shown by the development of veins and the alternation of fast (co-seismic) and slow (inter-seismic) slip. In the deepest portions of the outcropping subduction channel, extension is finally overprinted by compressional structures. In modern sub- duction zones the onset of seismic activity is believed to occur at ,150 6C, but in the fossil channel the onset occurred at cooler palaeo-temperatures.
2008
451
699
703
P. VANNUCCHI; F. REMITTI; G. BETTELLI
File in questo prodotto:
File Dimensione Formato  
2008_Vannucchi_Nature.pdf

Accesso chiuso

Tipologia: Versione finale referata (Postprint, Accepted manuscript)
Licenza: Tutti i diritti riservati
Dimensione 962.88 kB
Formato Adobe PDF
962.88 kB Adobe PDF   Richiedi una copia

I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/257211
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 129
  • ???jsp.display-item.citation.isi??? 123
social impact