Q: Is metamorphic sole rock (SOM) is the obduction age of ophiolite?

Could be but not necessary, metamorphic sole ages gives the ages of emplacement age of the ophiolitic slab on an oceanic crust, however, obduction refers to emplacement of an allocthonous nappes (ophiolitic melange or oceanic slab) on to continental crust (Coleman 1971). If the emplacement of ophiolitic slab takes place directly on a continental crust, in that case SOM and obduction ages are same, but in the case of obduction SOM ages are almost (if not same) always older than obduction ages.

Several phases in the "formation" or "emplacement" of an ophiolite can be distinguished:

-accretion phase (usually made on late magmatic lithologies such as plagiogranite that intrude the gabbros and sheeted dike complex, but taken as close enough to date the building of the crustal section that will make the ophiolite)

-intra-oceanic detachment. Thrusting of the ophiolite, most often, occur somewhere within the ocean (at at a ridge, or in a near-arc setting). Footwall of the detachement is made of metamorphosed oceanic sediments and/or basalt with an inverse T° gradient. This is the metamorphic sole which protolith is made of whatever was at the surface of the footwall detachement.

-The obduction per say, when the ophiolite is thrusted onto a continent margin. The autochtonous continent rock can be metamorphosed: this dates the obduction. It is necessaraly younger than the metamorphic sole (sometimes nearly the sam, as pointed above by Nuretdin).

I would rather refer to these 3 phases (accretion-detachement-obduction) rather than formation or emplacement which can be vague or misleading as they may overlap onto 2 or 3 of those phases.

Hi Inayat,

Is metamorphic sole rock is the obduction age of ophiolite?

Metamorphic sole formation (e.g. amphibolites) is related with intraoceanic subduction of Lithospheric mantle (with Ocanic crust on top). Emplacement of Upper mantle (e.g. ultramafics with metamorphic sole) is a subsequent event and very long travelling history.

For e.g. it is widely accepted that Tethian ocean realm was in the east (Vardar/Axios)

Emplacement of upper mantle of Triassic-Jurassic ultramafics with amphibolite sole today are more than 200 km west from the place of origin.

In the northern Albania (Shkodra area) within about 200 m distance is following section:

Ultramafic rocks with amphibolites sole (c 160 my ago) overthrusted onto Middle Jurassic mélange, underlain by a thin slide (c 50 m) of Triassic limestone, which in turn is overthrusted on Paleogene flysch.

On ultramafic rocks is a small town with a beautiful Roman Catholic Church. In this case forensic geology of Sherlock Holmes and Georg Popp doesn’t work: small town didn’t come from Vardar (for humour).

For more data, please find most up to date excellent video:

Plate Tectonics-What Drives the Plates? Overview of processes (Educational) - YouTube

www.youtube.com

www.iris.edu/earthquake

and dhe August 1, 2019 paper for Plate tectonics

Drop of ancient seawater rewrites Earth's history

Nuretdin KAYMAKCI

Thanks your answer clear my view about difference between both terms.

Naeim Mousavi David Jousselin Lirim Hoxha

Thanks to all, your valuable comments on my queation produced much understanding in my knowledge and further the research references you people shared guided me about my querry.