Origin of Volcanics in the Tethyan Suture Zone of Pakistan

Abstract

The south Tethyan suture zone in Baluchistan has two distinct tectonic segments: (1) a north-south segment along the fold belt from Karachi to the Pamir Mountains and (2) an east-west segment west of the fold belt in the Makran region. Along the fold belt ophiolites are obducted over folded Jurassic and Cretaceous rocks. The Maastrichtian age Parh Formation on which ophiolites are obducted contains volcanic agglomerates, flows and breccia. Preliminary petrographic and chemical analyses as well as field evidence indicates these volcanic units are oceanic island type basalts.

These volcanic units may represent passage of Tethyan ocean floor over the Reunion Island “hot spot” prior to the passage of the Indian continent over it which produced the Deccan rocks and prior to the passage of the Indian Ocean floor over it which has produced the Chaggos, Maldive and Laccadive islands, movement similar to that proposed for the Ninetyeast Ridge as it passed over the Kerguelen Island “hot spot.” Preliminary dates for basalts are: 72 my near Uthal, north of Karachi; 68 my in the Deccan; 32 my at site 706 in the Indian Ocean; 10 my at Mauritius and 0–2 my at Reunion. The oceanic islands formed by the movement over the “hot spot” north of the Deccan are now in the collision zone between the Indian plate and the Afghan micro-continent.