EVIDENCE OF STRUCTURE-H HYDRATE, GULF-OF-MEXICO CONTINENTAL-SLOPE

A research submarine was used to sample an amber-colored gas hydrate exposed on the sea-floor at 540 m water depth in the Gulf of Mexico continental slope, offshore Louisiana. The hydrate composition is novel for a natural occurrence because i-C-5 comprises 41.1% of the total C-i-C-5 hydrocarbon distribution. The relative abundance of i-C-5 is consistent with an hexagonal (H) lattice structure that is capable of enclosing larger hydrocarbon molecules than either structure I or II hydrates. Structure H hydrate, which has not been identified previously in nature, coexists with structure II hydrate on the Gulf slope.