Vannucchi Paola

No Thumbnail Available
Last Name
Vannucchi
First Name
Paola
ORCID

Filters

1 1 1
2004 - 2008 2
1 1
2
Reset filters

Settings

Search Results

Now showing 1 - 2 of 2
  • Preprint
    Arc-continent collisions, sediment recycling and the maintenance of the continental crust
    ( 2008-02-13) Clift, Peter D. ; Schouten, Hans A. ; Vannucchi, Paola
    Subduction zones are both the source of most new continental crust and the locations where crustal material is returned to the upper mantle. Globally the total amount of continental crust and sediment subducted below forearcs currently lies close to 3.0 Armstrong Units (1 AU = 1 km3/yr), of which 1.65 AU comprises subducted sediments and 1.33 AU tectonically eroded forearc crust. This compares with average ~0.4 AU lost during subduction of passive margins during Cenozoic continental collision. Individual margins may retreat in a wholesale, steady-state mode, or in a slower way involving the trenchward erosion of the forearc coupled with landward underplating, such as seen in the central and northern Andean margins. Tephra records of magmatism evolution from Central America indicate pulses of recycling through the roots of the arc. While this arc is in a state of long- term mass loss this is achieved in a discontinuous fashion via periods of slow tectonic erosion and even sediment accretion interrupted by catastrophic erosion events, likely caused by seamount subduction. Crustal losses into subduction zones must be balanced by arc magmatism and we estimate global average melt production rates to be 96 and 64 km3/m.y./km in oceanic and continental arc respectively. Key to maintaining the volume of the continental crust is the accretion of oceanic arcs to continental passive margins. Mass balancing across the Taiwan collision zones suggests that almost 90% of the colliding Luzon Arc crust is accreted to the margin of Asia in that region. Rates of exhumation and sediment recycling indicate the complete accretion process spans only 6–8 m.y. Subduction of sediment in both erosive and inefficient accretionary margins provides a mechanism for returning continental crust to the upper mantle. Sea level governs rates of continental erosion and thus sediment delivery to trenches, which in turn controls crustal thicknesses over 107– 109 yrs. Tectonically thickened crust is reduced to normal values (35–38 km) over timescales of 100–200 Ma.
  • Article
    Controls on tectonic accretion versus erosion in subduction zones : implications for the origin and recycling of the continental crust
    (American Geophysical Union, 2004-04-08) Clift, Peter D. ; Vannucchi, Paola
    Documenting the mass flux through convergent plate margins is important to the understanding of petrogenesis in arc settings and to the origin of the continental crust, since subduction zones are the only major routes by which material extracted from the mantle can be returned to great depths within the Earth. Despite their significance, there has been a tendency to view subduction zones as areas of net crustal growth. Convergent plate margins are divided into those showing long-term landward retreat of the trench and those dominated by accretion of sediments from the subducting plate. Tectonic erosion is favored in regions where convergence rates exceed 6 ± 0.1 cm yr−1 and where the sedimentary cover is <1 km. Accretion preferentially occurs in regions of slow convergence (<7.6 cm yr−1) and/or trench sediment thicknesses >1 km. Large volumes of continental crust are subducted at both erosive and accretionary margins. Average magmatic productivity of arcs must exceed 90 km3 m.y.−1 if the volume of the continental crust is to be maintained. Convergence rate rather than height of the melting column under the arc appears to be the primary control on long-term melt production. Oceanic arcs will not be stable if crustal thicknesses exceed 36 km or trench retreat rates are >6 km m.y.−1. Continental arcs undergoing erosion are major sinks of continental crust. This loss requires that oceanic arcs be accreted to the continental margins if the net volume of crust is to be maintained.