The Jurassic Louann Salt is an evaporite sequence deposited in the Gulf of Mexico Basin (GOMB). It is an important component of the GOMB petroleum system and influences the facies pattern in overlying strata and the distribution of petroleum stratigraphic traps. The Louann Salt is composed primarily of halite with intercalated anhydrites and silty- or sandy-halite intervals that can reach thicknesses in excess of four kilometers (~13,000 feet). Suture zones occur sporadically within the Louann Salt formed by the collision of allochthonous evaporite layers. The mineralogy and geochemistry of the suture zones are currently understudied and can be hazardous during drilling operations, potentially causing over-pressurization of the zone. Furthermore, these evaporite bodies are potential sources for critical minerals or rare earth elements, which can also lend insight into depositional conditions during the Jurassic.

The focus of this study was to determine the bulk geochemistry of the allochthonous evaporite layers within the Louann Salt in the Puma Field, offshore of the GOMB. Geochemical analyses were performed by handheld X–ray fluorescence (XRF) on approximately 600 cutting samples from the Puma West GC821–1 well, ranging from 2057 meters to 6528 meters (6750 feet to 21,420 feet) below the surface. X–ray diffraction (XRD) was used to determine bulk mineralogy of 10 samples to determine mineralogy and create a mineral model throughout the section of the suture zone within the Louann Salt.

XRD results in the suture zone within the Louann Salt shows that the mineralogy of the suture zone is predominantly composed of quartz, hematite, and smectite, with minor amounts of other clay minerals. The results of the XRF analysis show that the upper and lower boundaries of the Louann Salt can be determined by the inverse relationship between the chlorine and silicon element values. Chlorine values represent the Louann Salt interval, whereas the silicon values represent clay minerals. XRF analyses shows that the Louann Salt contains rare earth elements in the hundreds of parts per million (ppm). Rare earth elements such as Lanthanum (min = 0 ppm, max = 218 ppm, average = 80.8 ppm), Praseodymium (min = 0 ppm, max = 401 ppm, average = 74.8 ppm), Cerium (min = 0 ppm, max = 188 ppm, average = 64.5 ppm), and Neodymium (min = 0 ppm, max = 519 ppm, average = 150.5 ppm) are in concentrations equivalent to those where rare earth elements are being mined for economic value. This study provides insight into the depositional history of the Louann Salt and characteristics of the allochthonous bodies within the Louann for future mapping of the extent of these bodies in the GOMB.