sup 40 Ar/ sup 39 Ar polyorogenic mineral age record within the southern Mauritanide orogen (M'Bout-Bakel region) West Africa

Journal Article · Sat Dec 01 04:00:00 EST 1990 · American Journal of Science; (USA)

DOI:https://doi.org/10.2475/ajs.290.10.1136· OSTI ID:5600177

Dallmeyer, R D ^[1]; Lecorche, J P ^[2]

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1. Univ. of Georgia, Athens (USA)
2. Universite d'Aix-Marseille III (France)

The southern Mauritanide orogen exposed between M'Bout and Bakel is characterized by several internally imbricated, polydeformed, and variably metamorphosed infrastructural allochthons. {sup 40}Ar/{sup 39}Ar incremental-release ages recorded by hornblende within undeformed granodiorite of the Guidimakha Complex suggest post-magmatic cooling through appropriate argon closure temperatures at approx 670 Ma. {sup 40}Ar/{sup 39}Ar ages recorded by muscovite within lithologic elements of both the Guidimakha Complex and the Diala-Bouanze Series suggest initial regional metamorphism (associated with Pan-African I orogenesis) was following by cooling through muscovite argon closure temperatures between approx 600 and 620 Ma. Slight rejuvenation of muscovite argon systems occurred locally between approx 325 and 350 Ma. Muscovite and whole-rock slate/phyllite argon systems within metavolcanic and metavolcaniclastic components of the infrastructural calc-alkaline igneous complex (easternmost sectors of the M'Bout Series) record {sup 40}Ar/{sup 39}Ar plateau age of approx 300 to 320 Ma. Muscovite and whole-rock slate/phyllite argon systems within westernmost portions of the study area (western portions of the M'Bout Series) record {sup 40}Ar/{sup 39}Ar plateau ages of approx 267 to 312 Ma. All foreland units within the M'Bout-Bakel area were affected by post-Emsian folding. Effects of this tectonic activity are widespread throughout the parautochthon and western metamorphic sequences. These effects include emplacement of suprastructural ( ) allochthons and local reactivation of older thrust faults within infrastructural units.

• OSTI ID: 5600177
• Journal Information: American Journal of Science; (USA), Journal Name: American Journal of Science; (USA) Vol. 290:10; ISSN 0002-9599; ISSN AJSCA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AFRICA
AGE ESTIMATION
AMPHIBOLE
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DEVELOPING COUNTRIES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GRANITES
GRANODIORITES
HORNBLENDE
IGNEOUS ROCKS
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
LITHOLOGY
MAURITANIA
METAMORPHIC ROCKS
MICA
MINERALS
MUSCOVITE
NUCLEI
PLUTONIC ROCKS
RADIOISOTOPES
ROCKS
SILICATE MINERALS
STABLE ISOTOPES
TECTONICS
VOLCANIC ROCKS
YEARS LIVING RADIOISOTOPES