FLUID INCLUSION STUDY OF KARAKORAM METAMORPHIC COMPLEX HUNZA VALLEY, PAKISTAN

Abstract

This metamorphic sequence contains metapelites, meta-carbonates, and amphibolite layers, cross-cut by metamorphosed granite sheets, collectively known as the Karakoram metamorphic complex (KMC), is bounded to the north by the Hunza plutonic unit – the central part of the huge east–west-trending Karakoram axial batholith – and to the southwest by the Main Karakoram thrust (MKT). Four main type of fluid inclusions identified from the studied samples: type-I (L×V) (two-phase, liquid-rich), type-II (V×L) (two-phase, vapor-rich), type-III (L×S×V) (three-phase, liquid rich, solid and vapor inclusions), and type-IV (L×V) (two phase, liquid rich CO₂ with CO₂ vapor inclusions). These fluid inclusions are unevenly distributed in metamorphic quartz grains and most are irregular in shape, being cylindrical, triangular, or oval, and are sub-rounded, flattened isometric or rounded, typically being up to 23 µm across. Measured salinities ranged from 0.3 to 13.1 wt.% NaCl, while homogenization temperatures (T_h) ranged from ~160–332 °C. Based on this study, it has been determined that the rock have been subjected to temperature 730-780 °C and pressure 5 to 5.5 kb.