Variation of fluid compositions and homogenization temperatures ( T
) in a vein from locality W4. (a) Photomicrograph of the quartz vein in which elongate crystals grew inward from both walls and impinged at the center of the vein. (b) SEM-CL image of the same vein in the region from the vein wall to the vein center. Cal, calcite. (c) Variations of (=CO2 / (CO2 + CH4)) (gray squares) and homogenization temperature (black diamonds) in two-phase aqueous inclusions across the vein (A to B in (a)). Note that the homogenization temperatures were measured in only one half of the vein along A to B. Gray stars indicate the positions of one-phase carbonic inclusions (CH4) in the vein.