Comment on: “Does the Karakoram fault interrupt mid-crustal channel flow in the western Himalaya?” by Mary L. Leech, Earth and Planetary Science Letters 276 (2008) 314–322

Leech (Mary L. Leech, Earth and Planetary Science Letters 276 (2008) 314–322) presents new U–Pb Ion Microprobe zircon ages from the Leo Pargil dome in NW India in an attempt to delineate the potential tectonic relationships between initiation of the Karakoram Fault and the timing of mid-crustal flow in the Himalayan orogen. Unfortunately, as presented, the data are incapable of answering the question posed because: 1) no field, petrographic or other contextual information is presented for the dated samples making their relevance to the problem uncertain and 2) the U–Pb data themselves are limited by inadequate discussion of complexities including apparent analytical issues (non-linearity of secondary electron multiplier) and, in my view unjustified rejection of ca. 88% of the dataset. The combination of these two factors undermines the usefulness of the data to the relationship of the Karakoram Fault to mid-crustal ‘channel flow’ in the western Himalaya.