10.6084/m9.figshare.3454703.v1
Anthi Liati
Anthi
Liati
Dieter Gebauer
Dieter
Gebauer
C.Mark Fanning
C.Mark
Fanning
Geochronological evolution of HP metamorphic rocks of the Adula nappe, Central Alps, in pre-Alpine and Alpine subduction cycles
Geological Society of London
2016
Hercynian protolith zircon ages
Central Alps
Alpine subduction cycles SHRIMP
35 Ma
HT
middle Adula nappe
REE
country rock gneisses
zircon domains record
overprinting Alpine HP event
370 Ma
Adula nappe
Alpine HP event
Hercynian basement slivers
Geology
2016-06-21 12:18:08
Dataset
https://geolsoc.figshare.com/articles/dataset/Geochronological_evolution_of_HP_metamorphic_rocks_of_the_Adula_nappe_Central_Alps_in_pre-Alpine_and_Alpine_subduction_cycles/3454703
<p>SHRIMP dating of zircon from eclogites, their country rock gneisses and quartz veins from the northern and middle Adula nappe,
Central Alps, accompanied by cathodoluminescence imaging and REE geochemistry of these dated zircon crystals revealed that
the Adula nappe has been affected by two pre-Alpine high-pressure (HP) metamorphic events (northern: <em>c</em>. 330–340 Ma; middle: <em>c</em>. 370 Ma). In the northern Adula nappe, loss of radiogenic Pb of the <em>c</em>. 330–340 Ma zircon domains in combination with previous geochronological data argue for an overprinting Alpine HP event.
In the middle Adula nappe, metamorphic zircon domains record in addition a 33–32 Ma event, interpreted to reflect HT metamorphism,
already identified in the southern part of the nappe, where such SHRIMP ages have been related to HT (Lepontine) metamorphism.
The Alpine HP event indicated by previous SHRIMP data in the southern Adula nappe at <em>c</em>. 35 Ma is not recorded in the zircons of the rocks dated herein. The absence in this dataset is probably because either no
HP (<em>c</em>. 35 Ma) zircon domains were formed or such domains were completely reset during the 33–32 Ma HT event. Protolith ages of
orthogneisses and eclogites are 470–457 Ma and 595–587 Ma, respectively, and maximum sedimentation ages of paragneisses 500–460
Ma. The lack of Hercynian protolith zircon ages implies pre-Hercynian formation for the precursors of the dated HP rocks.
Our data suggest that the Adula nappe contains various Hercynian basement slivers that underwent subduction to HP conditions
at <em>c</em>. 330–340 Ma and <em>c</em>. 370 Ma prior to the Alpine orogeny, similar to many other parts of the Hercynian basement in Central and Southern Europe.
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