Fluid inclusions (191) in calcite, quartz, K-feldspar, and epidote from ≈1-mm veinlets in cores and well cuttings from 604--2560 m homogenize from 217¿ to >500 ¿C and vary widely in salinity, suggesting a complex history of fluids surrounding these samples. No daughter minerals were seen, and no clathrates were recognized on freezing. Vapor-rich inclusions under pressure, presumably containing CO2 and/or CH4, were found from a wide range of depths, suggesting that effervescence has occurred. Low-salinity fluids (1.2--4.0 wt % NaCl eq) were present as deep as 1939 m. The data can be explained by a combination of processes such as thermal metamorphism of evaporites and other sediments and mixing of water from metamorphic dehydration reactions with partly evaporated Colorado River water. ¿ American Geophysical Union 1988