Fluid inclusion constraints on temperatures of petroleum migration from authigenic quartz in bitumen veins

Solid bitumens in fracture systems commonly contain microscopic crystals of authigenic quartz which were precipitated coevally with the bitumen early in the paragenesis of the fracture-fillings. The quartz contains primary fluid inclusions (both aqueous and hydrocarbon), yielding homogenization temperatures particularly in the range 95–130°C, indicating minimum temperatures of entrapment during petroleum migration. Volumes of up to 50% entrained quartz, and a predominance of aqueous inclusions, indicate that the petroleum fluid had a substantial aqueous component.