Continental subduction recorded by Neoproterozoic eclogite and garnet amphibolites from Western Hoggar (Tassendjanet terrane, Tuareg Shield, Algeria)

Abstract : eoproterozoic eclogite and garnet amphibolites, representing retrogressed eclogites, from the Tassendjanet-Tidéridjaouine terrane in the Pan-African Western Hoggar (Tuareg shield, Southern Algeria) form lenses enclosed in 1.8 Ga subalkaline Paleoproterozoic orthogneisses. They lie along a major sinistral shear zone marking the boundary with the Archean/Paleoproterozoic granulitic In Ouzzal terrane and are associated with high-pressure metasediments. According to thermodynamic calculations, peak condition of the eclogitic stage is 650 °C, 20-22 kbar followed by post-peak heating and exhumation at 730 °C, 10-14 kbar and cooling to 610 °C, 7-10 kbar. Their major, trace-element and isotopic compositions are consistent with emplacement of former basalts in the shoulder of a 700-800 Ma continental rift that evolved to an oceanic basin. The eclogite and garnet amphibolites were thus part of the continental portion of a subducting slab that was pulled down by a denser oceanic lithosphere. Sheath and recumbent folds associated with the exhumation of HP units are verging toward the west, meaning that the former slab was dipping to the east. U-Pb zircon dating on metamorphic zircons bordering ilmenite and rutile in the eclogite gave an age of 623 ± 2 Ma, interpreted as the syn-collisional exhumation stage of the high-pressure unit. This event was rapidly followed by transpressional tectonics and abundant magmatism linked to the northward motion of the adjacent In Ouzzal terrane.
Complete list of metadatas

https://hal.archives-ouvertes.fr/hal-01054338
Contributor : Gm Aigle <>
Submitted on : Wednesday, August 6, 2014 - 11:37:45 AM
Last modification on : Friday, October 11, 2019 - 8:23:06 PM

Identifiers

Citation

Julien Berger, Khadidja Ouzegane, Abderrahmane Bendaoud, Jean-Paul Liegeois, Jean-Robert Kienast, et al.. Continental subduction recorded by Neoproterozoic eclogite and garnet amphibolites from Western Hoggar (Tassendjanet terrane, Tuareg Shield, Algeria). Precambrian Research, Elsevier, 2014, 247, pp.139-158. ⟨10.1016/j.precamres.2014.04.002⟩. ⟨hal-01054338⟩

Share

Metrics

Record views

1193