Inclusions in salt beds resulting from thermal metamorphism by dolerite sills (eastern Siberia, Russia)

Cambrian rocks in the Siberian platform, represented by carbonate- sulphate and halite beds, are intruded by numerous basaltic sills. The evolution of the fluid chemistry is described as a function of the thickness of the intrusion (h) and the distance of the sample from the contact with the intrusion (d). Four inclusion associations were found in halite as a function of the d/h ratio. The extent of the influence of intrusion is marked by the disappearance of chevron structures in halite which occurs at greater distances above than below the intrusions. For d/h < 0.9 above the intrusion, CaCl (sub 2) , CaCl (sub 2) .KCl and nCaCl (sub 2) .mMgCl (sub 2) solids occur in association with water-free and liquid-CO (sub 2) inclusions, with H (sub 2) S, SCO and orthorhombic or glassy S (sub 8) . For d/h of 0.2-2 above the intrusion, H (sub 2) S-bearing liquid-CO (sub 2) inclusions are typical with various amounts of water. Sometimes, carbonaceous material and orthorhombic S (sub 8) are found. For d/h of 1-5 above the intrusion, the vapour phase is always a low-density CO (sub 2) - bearing vapour with a volume fraction of a few %. All these associations also occur to a smaller extent below the intrusions, indicating mainly conductive heating below and upward vertical fluid circulation above the intrusions. This clear zonation pattern of fluid and solid inclusions as a function of d/h is probably due to the rather dry environment.