The Formation and Evolution of the Neotethyan Arc Systems (Ladkh-Kohistan Batholith)

The continental crust is generally assumed to be created in island arcs, which mature towards a composition more akin to bulk continental crust. A major difference between the “juvenile” and “mature” arc stages concerns the voluminous amount of granitoid formed in mature arcs. An unsolved paradox in the idea that continental crust forms in subduction zones is that bulk estimates of island-arc crust compositions are basaltic while the bulk continental crust is andesitic. The voluminous occurrence of evolved rocks drives the average crustal arc composition towards andesitic. Accordingly,understanding the formation of evolved plutonic rocks should lead to further understanding of the continental crust formation. Similar the “low-Mg#” number of the continental crust conflicts with the high-Mg# of mantle derived melts.

The so-called Mg#-gap and the silica-enrichment of the continental crust are first order unsolved problems in earth science. Work is on the evolution and formation of the Kohistan-Ladakh arc, (NE Pakistan, NW India).

In this interdisciplinary petro-stuctural research project, focus is on the Neotethyan arc exposures in the western Himalaya. The goal is to understand the long term evolution of the batholith system. Given the current political situation in Pakistan, we concentrate field studies on the Ladakh Batholith (India). We are mapping, for the first time, the different intrusive units of the Batholith, and determine the petrological, geochemical and isotopic evolution of the system. Additionally, we are trying to better constrain the closure of the so-called Shyok suture.