As a type of crustal fluid, brines are high-salinity fluids that commonly contain various chlorides and sulphates of sodium, magnesium, potassium, and other metals. They are widely developed in orogenic belts and their neighbouring foreland basins, or occur as seawater. They are an indispensable medium for oil/gas formation and accumulation in oil fields or direct carriers of ore-forming materials in several types of mineral deposits (e.g. SEDEX, MVT, and brine-type lithium deposits). Brine activities can be represented by fluid inclusions as well as microstructure fillings in various minerals in ore deposits and oil basins.

To date, our knowledge regarding the role the brines play in ore-forming processes or oil/gas generation/accumulation is still limited in aspects such as: geochemistry of brines related to different ore deposits; factors that decide the metal or organic matter-transport capacity of brines; the interaction between brines and rocks at their sources and along their pathways; and changes in physio-chemical conditions of brines during metal precipitation and oil/gas migration and accumulation. Nevertheless, with development of micro-beam analytical techniques (e.g. single fluid inclusion LA-ICP-MS analysis, high-resolution BSE), non-traditional isotope geochemistry (e.g. Li isotopes), and fluid modelling, the above-mentioned scientific questions can be further addressed, in combination with traditional methods including microthermometry and isotopes of oxygen, hydrogen, and carbon.

Therefore, this Special Issue focuses on innovative techniques, methods and models that can be used to investigate/depict brines linked to mobilization, transport and precipitation of metal elements in various types of ore deposits and basin fluids related to oil/gas formation, migration, and accumulation. Case studies which address the sources, compositions, and physio-chemical conditions of geofluids related to ore deposition or oil/gas reservoir formation in foreland basins are encouraged. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Brines linked to mineralization and oil/gas accumulation in orogens and their foreland basins
• Identifying brine sources and understanding flow patterns of brines in mineral deposits and oil/gas-bearing basins
• Paleotemperature/pressure and thermochronology of geofluids from mineralized systems or petroleum systems
• Petrography and geochemistry of geofluids related to mineralization, alteration, and diagenesis during fluid activities
• Microstructure variations of minerals related to fluid flow or diagenesis