Crystallographic Controls on Staurolite to Fibrolite Transformation: Petrographic Evidence from the Pangong Metamorphic Complex in Eastern Karakoram, Ladakh, India

Abstract

Incomplete discontinuous reactions in metamorphic rocks provide good opportunities to investigate reaction kinetics in natural samples. This contribution discusses crystallographic controls of reacting phases on solid-state metamorphic reactions involving staurolite to fibrolite transformation in metapelites from the Pangong metamorphic complex, Ladakh. The understanding of mineral kinetics is fundamental for assessing the extent to which equilibrium is attained in metamorphic systems and constrains the disequilibrium processes in rocks. In the present study, the periodic bond chain theory is used to explain lower reaction rates on the faces parallel to the trace of c-axis (hk0) than the faces across the trace of c-axis (hkl¹0) of staurolite.