Petrogenesis of the Panjal Traps, Kashmir (North West India)Export this event to calendar

Tuesday, October 4, 2011 — 9:45 AM EDT

Department Seminar

Dr. Greg Sheellnut
Earth Sciences Department
National Taiwan Normal University
Petrogenesis of the Panjal Traps, Kashmir (NW India)

Abstract:

The Panjal Traps of North West (NW) India represent a significant outpouring of mafic and felsic volcanic rocks and are thought to have contributed to the mid-Capitanian (~260 Ma) mass extinction. Basaltic, dacitic and rhyolitic samples collected from Guryal Ravine and Pahalgam indicate that the volcanic rocks erupted subaerially (e.g. columnar joints) and subaqueously (i.e. pillow lavas) suggesting that are related to the formation of a rift basin which was periodically inundated with either lacustrine or marine water. The basalts, dacites and rhyolites have compositions similar to the rocks from a within-plate setting. The basaltic rocks can be divided into high- (TiO2>2.0 wt%) and low-Ti (TiO2<1.8 wt%) groups. The two groups of basalts can be modeled using a primitive mantle source and different degrees of partial melting where the high-Ti rocks are produced by ~1% partial melting of a spinel peridotite source whereas the low-Ti rocks are produced by ~8% partial melting of the same source. The trace element ratios (e.g. Nb/U, Th/NbPM) and εNd(T) values of the basalts (εNd(t)=+1.3 to -6.1) indicate that there may be 10% or more assimilation of enriched material. The felsic volcanic rocks are stratigraphically below the basalts at Guryal Ravine. Major element modeling and trace element and εNd(T) values suggest the felsic rocks were derived by partial melting of the crust. Zircons were dated from one rhyolite sample and yielded a mean U-Pb age of 289.

The Early Permian age confirms that they are not associated with the mid-Capitanian mass extinction and that they are significantly older than other Permian volcanic rocks throughout the Himalaya. The isotope and trace element compositions of the basaltic rocks indicate that they may be derived from a mantle plume source which assimilated enriched material during emplacement. The injection of the basaltic magmas likely induced partial melting of the crust to produce felsic rocks thus explaining their Stratigraphic position. 

Location 
EIT - Centre for Environmental and Information Technology
room 3142
200 University Ave West

Waterloo, ON N2L 3G1
Canada

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