Abstract:
In the land stretching from Spangar peak to Garkai in Pishin District, Pakistan, ultramafic (kimberlitic) lamprophyre and mildly alkalic basaltic rocks intrude the lowermost Jurassic sediments. Both rock groups occur closely associated spatially and exhibit similar mode of occurrence. Both intrude calcareous sediments of the lowermost Jurassic age. About 25 km north-eastwards, near Kozh Kach, sodic alkalic dolerites intrude the lower Jurassic sediments. Wholerock major and trace element variations in the three rock groups are determined. The rocks at Spangar represent magmatism within continental plate, caused probably by a hot spot. Their source seems to be the trace element enriched mantle. They are visualized to have originated during the break-up or rifting of western margin of the Indian plate away from its Gondwanaland position in proximity to east Ethiopia-Somalia. The basalts may represent "trap" volcanism of mildly alkaline character related to horizontal extension.
Page(s):
25-45
DOI:
DOI not available
Published:
Journal: Acta mineralogica pakistanica, Volume: 5, Issue: , Year: 1991