Gas geochemistry is developing into a powerful tool to understand geological processes and affirm source origins of geo-fluids. Major and trace gases, including abundances and isotopes, have shown considerable application in natural gas systems. For example, progress in unconventional gases such as shale gas, tight gas, and extreme conditions in the deep oceans represent more emerging areas and application of these novel gas-related techniques. Examples where gas geochemistry continues to place key constraints on the origin and migration characteristics of natural gas, the P-T characteristics of fluids in both subaerial and deep geothermal reservoirs, and the dynamics of the accumulation cycles, to name but a few. This volume will reflect this diversity in scope and application of gas geochemistry, focusing on deeper and broader applications in unconventional domains of novel gas geochemical techniques and applications. (C) 2017 Elsevier Ltd. All rights reserved.