New Mexico Geological Society Annual Spring Meeting — Abstracts

Magnetite deposits occur as massive replacements of Permian sedimentary rocks at Jones Camp dike, east of Bingham in eastern Socorro County, New Mexico. The mineralization occurs at the contact between the sediments and the dike, which is composed of several cogenetic dioritic intrusicns. The dike was emplaced during the late Oligocene Epoch and is cne of several intrusive and volcanic features along the Capitan lineament in central New Mexico.

Paleomagnetic field directions and intensities were measured on oriented rock cores from eleven sites at Jones Camp. Magnetite ore, alteration and three of the intrusive pulses were sampled. Most sites show a wide range of remanent field directions and characteristically have high alpha-95 values. Only two of the sites have well defined remanent field directicns. Both outcrcps are extensively altered. Magnetic minerals were ccmpletely removed and the remanent magnetization is carried by secondary hematite introduced during the waning stages of hydrothermal alteration. The wide range of remanent directions is the result of ccmplex chemical remanent magnetizations which were affected by hydrothermal activity associated with several intrusive pulses. Some evidence suggests that remanence acquisition was further complicated by a reversal of the earth's magnetic field during the emplacment of the dike.

Proton precession magnetcmeter surveys show a depressed magnetic signal. Such surveys are useful only for qualitative interpretation at Jones Camp dike. They are most useful in locating buried orebodies.

Field observations and paleomagnetic data indicate a ccmplex history of igneous intrusion and hydrothermal alteraticn at Jones Camp.