Geologic features of the Socorro perlite deposit

The Socorro deposit of the Great Lakes Carbon Corporation was the first commercial source of perlite io be placed in production in New N'Iexico. For several years during the period of active production from r949 to r96r, it was the leading domestic source of crude perlite aggregate. The deposit has the form of a volcanic dome ap-proximately zooo to z6oo feet in exposed horizontal diameter, and an exposed vertical extent of more than 45o feet. The eastern and western margins are bounded by high-angle normal faults of northerly trend, between which the perlite body occupies the position of a horst block. To the north and south, the perlite is overlain by a sequence of vitric breccias, and massive to thin-bedded, weakly to highly indurated vitric tuffs that grade upward into clays, sands, gravels, and their indurated equivalents. The vitric tuffs and breccias are composed largely of angu-lar fragments of glass identical with that of the perlite dome, plus fragments of older volcanic rocks composition These pyroclastics clearly point to