New Mexico Geological Society Annual Spring Meeting — Abstracts

Huntite is an unusual calcium-magnesium carbonate, CaMg₃ (CO₃)₄, first described in 1953 at Currant Creek, Nevada. Hitherto, huntite occurrences have included: a metastable, speleothemic carbonate as in the Carlsbad Caverns; a diagenetic mineral as at Currant Creek, Nevada, where it occurs as a near surface weathering product of magnesium-rich rocks such as brucite, serpentine, dolomite and magnesite; huntite nodules found associated with a deep weathering zone in dolomitic rocks and shales underlying a calcitic soil with a magnesite base in Australia. Huntitehas also been documented in Recent supratidal evaporite sequences in the Trucial Coast area of the Persian Gulf.

In 1988, a continuous 303.4 ft: core was drilled in the Fruitland Formation, Fossil Forest study area of the San Juan Basin, New Mexico. The core was intensively sampled for paleontological, sedimentological and geochemical studies. At 80.3 ft and 143.3 ft, a very fine-grained, yellow-brown carbonate units were encountered. X-ray diffraction analyses of samples from these units clearly document the presence of huntite. This is the first documented occurrence of huntite in Cretaceous strata. This discovery requires modification of Fruitland Formation paleoenvironmental reconstructions. A reappraisal of huntite stability through time is also warranted.