Magnetic Profiles Across the Northern Suture, Kohistan, NW Pakistan
Abstract
The northern boundary fault (Northern Suture) of the Kohistan island arc terrain separates Cretaceous arc sediments and volcanics from Palaeozoic shelf sediments of the Asian plate. Arc rocks are more magnetized than Asian plate rocks, and ultramafics along the suture are very strongly magnetized. Four magnetic profiles moss the suture show the following features:
- a) a gradual north to south decrease in total field of about 15 nT/km
- b) Asian plate sediments are magnetically quiet and in only one profile does the Northern Suture have a magnetic anomaly
- c) within the arc sequence, anomalies are associated with the sediment/volcanic boundary and large anomalies occur over granodioritic plutons.
We have modelled the best-defined anomaly across the arc sediment/volcanic boundary using a cartoon structure consistent with the surface geology.
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