Episodic emplacement of the Ladakh and Karakoram Batholiths

Lloyd White¹, Gordon Lister¹, Marnie Forster¹, Talat Ahmad² and Trevor Ireland¹

1 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
2 Department of Geology, University of Delhi, India

Aplite dyke cross-cutting an earlier migmatitic phase of the Karakoram Batholith, Tangste Gorge, Northwest India.

Preliminary U-Pb SHRIMP dating of zircon grains from the Ladakh and Karakoram batholiths confirms some of the previously published ages for the two batholiths, but also indicates that older crust (possibly associated with the Tibetan slab) may have been involved with the Karakoram Bathoiith.

Samples of the Ladakh Batholith were collected from Khardung La and Chang La in Ladakh, NW India. These samples obtained an age of circa 58 Ma, similar to the age data published by earlier workers (e.g. Singh et al. 2007). This confirms that there was a strong phase of magmatism in the Ladakh Batholith at approximately 58 Ma.

Samples of the Karakoram Batholith were collected near Tangste Gompa and obtained an age of circa 32 Ma. One zircon grain from this sample also gave a late Permian age, which could indicate that older crust is associated with the Karakoram Batholith. One sample of a cross-cutting dyke collected in the Tangste Gorge (Figure 1 and 2) gave an age of circa 18 Ma. This is consistent with earlier published data that was associated with movement on the Karakoram Fault. Another sample of the Karakoram Batholith obtained an age of circa 102 Ma. Again, this is consistent with a date published for the same Batholith in Pakistan.

This study confirms many of the earlier published dates of the Ladakh and Karakoram batholiths. However, our preliminary work also shows that attention must be paid to younger phases of magmatism that cross-cut older phases of magmatism.

Tangste Gorge, Ladakh, Northwest India

Singh, S. Kumar, R., Barley, M. E., Jain, A. K. 2007. SHRIMP U-Pb ages and depth of emplacement of Ladakh Batholith, Eastern Ladakh, India. Journal of Asian Earth Sciences 30: 490-503