Late Permian mafic rocks identified within the Doba basin of southern Chad and their relationship to the boundary of the Saharan Metacraton

J. Gregory Shellnutt, Tung Yi Lee, Chih Cheng Yang, Shin Tai Hu, Jong Chang Wu, Kuo Lung Wang, Ching Hua Lo

    Research output: Contribution to journalArticlepeer-review

    8 Citations (Scopus)

    Abstract

    The Doba gabbro was collected from an exploration well through the Cretaceous Doba basin of southern Chad. The gabbro is composed mostly of plagioclase, clinopyroxene and Fe-Ti oxide minerals and displays cumulus mineral textures. Whole-rock 40Ar-39Ar step-heating geochronology yielded a Late Permian plateau age of 257 ± 1 Ma. The major and trace elemental geochemistry shows that the gabbro is tholeiitic in composition and has trace element ratios (i.e. La/YbN > 7; Sm/YbPM > 3.4; Nb/Y > 1; Zr/Y > 5) indicative of a basaltic melt derived from a garnet-bearing mantle source. The moderately enriched Sr-Nd isotopes (i.e. ISr = 0.70495 to 0.70839; ENd(T) = -1.0 to -1.3) fall within the mantle array (i.e. OIB-like) and are similar to other Late Permian plutonic rocks of North-Central Africa (i.e. ISr = 0.7040 to 0.7070). The enriched isotopic composition of the Doba gabbro contrasts with the more depleted compositions of the spatially associated Neoproterozoic post-Pan-African within-plate granites. The contrasting Nd isotope composition between the older within-plate granites and the younger Doba gabbro indicates that different mantle sources produced the rocks and thus may mark the southern boundary of the Saharan Metacraton.

    Original languageEnglish
    Pages (from-to)1073-1084
    Number of pages12
    JournalGeological Magazine
    Volume152
    Issue number6
    DOIs
    Publication statusPublished - 2015 Nov 1

    Keywords

    • Ar-Ar dating
    • Chad
    • Doba basin
    • Late Permian
    • Saharan Metacraton

    ASJC Scopus subject areas

    • Geology

    Fingerprint Dive into the research topics of 'Late Permian mafic rocks identified within the Doba basin of southern Chad and their relationship to the boundary of the Saharan Metacraton'. Together they form a unique fingerprint.

    Cite this