Tuesday, September 18, 2012


Although volumetrically insignificant relative to the dominant siliciclastics of continental rift basins, strata of chemical origin can provide important information.  Mack et al. explore the origin of a syndepositional geothermal opal deposit in Pliocene axial-fluvial facies of the southern Rio Grande rift, New Mexico, using field and geochemical observations.  The data suggest that the opal and calcite precipitated from high-temperature fluid of either a deep crustal or an advecting bedrock source.  These results provide a conceptual model for recognition of similar deposits in ancient continental rifts, and insights into their hydrologic and thermal evolution.

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