[Geodynamics] GSA Connects 2023 - Session T163: Subduction-Accretion Complexes

[Andrea Festa]

Dear Colleagues (apologies for cross-posting),



As we approach the abstract deadline for *GSA Connects 2023 *(15-18 October
2023, Pittsburgh, Pennsylvania, USA), I wanted to re-advertise our *Topical
Session T163 *- *Significance of Subduction-Accretion Complexes & Mélanges
in Orogenic Belts and in Continental Growth during the Precambrian and
Phanerozoic.*



Conveners:

Andrea Festa (University of Torino, Italy)

Yildirim Dilek (Miami University, USA)



*See below for a detailed session description.*



*Deadline* for abstract submissions is *25th July 2023, 11:59 PM, Pacific
Time*

https://protect-au.mimecast.com/s/1ycDCXLW2mU4p6pogc6ET7v?domain=gsa.confex.com





We are look forward to meeting you in Pittsburgh,



Best Regards,

Andrea Festa and Yildirim Dilek





*Summary of the session:*

Subduction-accretion complexes (SAC) and mélanges are significant
components of active continental margins and provide critical constraints
for the timing and mode of the development of orogenic belts and
continental growth. Modern accretionary orogenic belts mark the
Circum–Pacific region, and ancient examples include the Central Asian
Orogenic Belt. The collisional Rif–Maghrebides–Apennines, Alpine–
Himalayan–Tibetan, Uralides, Taiwan, Papuan, and Appalachian orogenic belts
underwent major episodes of collision tectonics, following the development
of vast SACs with ~400-km-width (i.e., Makran) and nearly 30 km thickness
(i.e., Taiwan). Hence, the growth of average continental crust in these
orogenic belts had already started in submarine conditions, prior to the
collisional events, and the construction of accretionary prisms through
time produced average continental crust.



Diagnostic rock assemblages in the SACs in these two major types of
orogenic belts are excellent archives for the dynamic, and lateral/vertical
construction of accretionary wedges through off-scraping–underplating,
seamount and oceanic plateau accretion, mass–transport movements, mélange
formation, and return flow exhumation in subduction channels. SACs commonly
display major differences in their time and mode of formation, crustal
anatomies, and geochemical signatures of their rock units. Documentation of
the P-T-t paths of various rock assemblages in orogenic belts provides
significant quantitative constraints for the subduction–accretion, tectonic
burial, and exhumation phases of mountain belt development. Subduction
and/or accretion of structural inheritances, seamounts, oceanic plateaus,
and microcontinents at oceanic trenches, as well as the occurrence of
stratigraphic heterogeneities in the subducting Ocean Plate Stratigraphy
(OPS) and the lithological makeup of Ocean–Continent transition Zones
(OCTZ) are significant drivers for migrations–jumps of subduction plate
interface and polarity flips during orogenic buildup, and strongly affect
the structural architecture of SACs. Overall, all these processes
contribute to the complexities in the anatomies of SACs along and across
their strike, the formation of different types of mélanges, and the
structural makeup of orogenic belts. They also pose major challenges for
Earth scientists in deciphering the spatial and temporal evolutionary
histories of orogenic belts.



We welcome contributions, documenting the significance of SACs and mélanges
in the evolution of orogenic belts and in continental growth during the
Precambrian and Phanerozoic. Presentations based on interdisciplinary
approach (field–based structural, stratigraphic, geochemical–petrological,
geochronological, geophysical, geodynamic, and numerical & analogue
modelling) to the delineation of SACs in the Precambrian and Phanerozoic
rock records, and addressing the sedimentological, tectonic, metamorphic,
and magmatic mechanisms and processes involved in their formation are
encouraged. We are particularly interested in those studies, which utilize
different methods of quantifying the rates of crustal growth, uplift, and
topographic buildup in SACs at modern and active convergent margins.



*Endorsed by*: GSA Structural Geology and Tectonics Division; GSA
Geophysics and Geodynamics Division; GSA Geochronology Division; GSA
Mineralogy, Geochemistry, Petrology, and Volcanology Division

____________________________________

Andrea Festa
Department of Earth Sciences
University of Torino
Via Valperga Caluso, 35
10125 - TORINO (Italy)
Phone: - +39-011-670.51.86
e-mail: andrea.festa at unito.it
Personal Web Page:
https://protect-au.mimecast.com/s/cyI1CYW8NocDG0G2vSGb6Il?domain=andreafesta.magix.net
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