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

*此作品的通信作者

研究成果: 雜誌貢獻期刊論文同行評審

8 引文 斯高帕斯(Scopus)

摘要

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.

原文英語
頁(從 - 到)1073-1084
頁數12
期刊Geological Magazine
152
發行號6
DOIs
出版狀態已發佈 - 2015 十一月 1

ASJC Scopus subject areas

  • 地質學

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