TY  - JOUR
A1  - Aygül, Mesut
A1  - Oberhänsli, Roland
T1  - Tectonic Stacking of HP/LT Metamorphic Rocks in Accretionary Wedges and the Role of Shallowing Slab-Mantle Decoupling
JF  - Tectonics
N2  - High-pressure/low-temperature (HP/LT) chloritoid-bearing micaschists crop out widely in the central part of northern Turkey and represent deep-seated subduction-accretionary complexes. Three peak metamorphic assemblages are identified in the area studied: (1) garnet-chloritoid-glaucophane with pseudomorphs after lawsonite; (2) chloritoid with pseudomorphs after glaucophane; and (3) chloritoid with pseudomorphs after jadeite in addition to phengite, paragonite, quartz, chlorite, rutile, and apatite. The latter is interpreted as transformation of a chloritoid + glaucophane assemblage to chloritoid + jadeite with increasing pressure; PT modeling indicates similar to 17 and 22-25 kbars for the two peak parageneses. The diversity of peak metamorphic assemblages and the PT estimates suggest that basal accretion occurred at different depths within the wedge. The depth of the basal accretion is possibly controlled by the slab-mantle decoupling depth. Stretching and thinning of the lithospheric fore arc induced by the slab rollback possibly caused shallowing of the slab-mantle decoupling depth which limited depth of the basal accretion from 70-80km to similar to 55km within the subduction channel. A slab-mantle coupling depth-controlled basal accretion may also explain the scarcity of eclogite and high-grade blueschist facies metamorphic rocks in active intraoceanic subduction zones. Because the overriding plate is young and hot in intraoceanic subductions, the slab and mantle are coupled at a relatively shallow depth before eclogitization of the oceanic crust. This prevents accretion and exhumation of eclogite along the subduction channel.
KW  - chloritoid micaschist
KW  - accretionary complex
KW  - slab-mantle decoupling
KW  - basal accretion
Y1  - 2017
U6  - https://doi.org/10.1002/2017TC004689
SN  - 0278-7407
SN  - 1944-9194
VL  - 36
SP  - 2332
EP  - 2346
PB  - American Geophysical Union
CY  - Washington
ER  -