Comment on 'Interplay of deformation and magmatism in the Pangong Transpressional Zone, Eastern Ladakh, India: Implications for remobilization of the trans-Himalayan magmatic arc and initiation of the Karakoram Fault' by K. Sen, B.K. Mukherjee and A.S. Collins, Journal of Structural Geology 62 (2014) 13-24

摘要

Sen et al. (2014) address the issue of the age of the Karakoram Fault Zone (KFZ), western Tibet, and suggest that the fault has accommodated significant eastward extrusion of the Tibetan plateau since initiating prior to c. 23 Ma. Anisotropy of magnetic susceptibility (AMS) data provided by Sen et al. potentially provide a new approach to investigating the relationship between the KFZ and the c. 22-16 Ma Tangtse-Darbuk leucogranite (TDL) (Phillips et al., 2004). However, we show that misinterpretation of key mi-crostructures has led Sen et al. to reach conclusions starkly at odds with the evidence that they present. Furthermore, we demonstrate that the study lacks the cautionary procedures and considerations that are crucial to the valid interpretation of AMS data. We show that the findings of Sen et al. are entirely consistent with pre-kinematic rather than syn-kinematic emplacement of the TDL We conclude that the KFZ initiated after cooling of the TDL to ambient lower amphibolite grade conditions after 15.55 ± 0.74 Ma (Phillips et al., 2004) and is a relatively recent structure of the India-Asia collision zone.