Publication Date:
2017-04-04
Description:
Subduction zones appear primarily controlled by the polarity of their direction, i.e., W-directed or E- to NNE-directed, probably due to the westward drift of the lithosphere relative to the asthenosphere. The decollement planes behave
differently in the two end-members. In the W-directed subduction zone, the decollement of the plate to the east is warped
and subducted, whereas in the E- to NNE-directed, it is ramping upward at the surface. There are W-directed subduction
zones that work also in absence of active convergence like the Carpathians or the Apennines. W-directed subduction zones
have shorter life 30–40 Ma.than E- or NE-directed subduction zones even longer than 100 Ma.. The different
decollements in the two end-members of subduction should control different PTt paths and, therefore, generate variable
metamorphic assemblages in the associated accretionary wedges and orogens. These asymmetries also determine different
topographic and structural evolutions that are marked by low topography and a fast ‘eastward’ migrating structural wave
along W-directed subduction zones, whereas the topography and the structure are rapidly growing upward and expanding
laterally along the opposite subduction zones. The magmatic pair calc-alkaline and alkaline–tholeiitic volcanic products of
the island arc and the back-arc basin characterise the W-directed subduction zones. Magmatic rocks associated with E- or
NE-directed subduction zones have higher abundances of incompatible elements, and mainly consist of calc-alkaline–
shoshonitic suites, with large volumes of batholithic intrusions and porphyry copper ore deposits. The subduction zones
surrounding the Adriatic plate in the central Mediterranean confirm the differences among subduction zones as primarily
controlled by the geographic polarity of the main direction of the slab. The western margin of the Adriatic plate
contemporaneously overridden and underthrust Europe toward the ‘west’ to generate, respectively, the Alps and the
Apennines, while the eastern margin subducted under the Dinarides–Hellenides. These belts confirm the characters of the
end-members of subduction zones as a function of their geographic polarity similarly to the Pacific subduction zones.
Description:
Published
Description:
167–208
Description:
3.3. Geodinamica e struttura dell'interno della Terra
Description:
JCR Journal
Description:
reserved
Keywords:
tectonics
;
subduction zones
;
orogens
;
Mediterranean geodynamics
;
04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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