Economic Geology of the Carlsbad Potash District, New Mexico James M
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New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/44 Economic geology of the Carlsbad potash district, New Mexico James M. Barker and George S. Austin, 1993, pp. 283-291 in: Carlsbad Region (New Mexico and West Texas), Love, D. W.; Hawley, J. W.; Kues, B. S.; Austin, G. S.; Lucas, S. G.; [eds.], New Mexico Geological Society 44th Annual Fall Field Conference Guidebook, 357 p. This is one of many related papers that were included in the 1993 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. 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No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages. New Mexico Geological Society Guidebook, 44th Field Conference, Carlsbad Region, New Mexico and West Texas, 1993 283 ECONOMIC GEOLOGY OF THE CARLSBAD POTASH DISTRICT, NEW MEXICO JAMES M. BARKER and GEORGE S. AUSTIN New Mexico Bureau of Mines and Mineral Resources, Campus Station, Socorro, New Mexico 87801 Abstract—New Mexico produced 83% of domestic potash and 27% of domestic consumption in 1992. Fertilizer used 95% of U.S. production; 5% was used in chemicals. The p otash industry of New Mexico produces sylvite (KCI), langbeinite (K 2 SO42Mg(SO4) 2 ) and artificial K2 504 . Sylvite grade in New Mexico decreased from 20-25% K20 in the 1950s to about 14% today. The average grade of langbeinite (first produced in 1940) remains 8-10% K 2 0. Reserves in the Known Potash Leasing Area (KPLA) will sustain production for 25 to 35 years and represent 57% of domestic reserves. Potash horizons extend far outside the KPLA, but none are economic. Commercial potash occurs in the middle or McNutt Member of the Salado Formation (Upper Permian Ochoan Stage). The potash distribution in the Salado is asymmetrical, suggesting a reflux model related to a bar-restricted marine embayment with dense brine underflow toward the bar. The dominantly seawater brine was magnesium-rich, producing primary carnallite or polyhalite, later recycled into the modern complex salt assemblage. The 400–ft-thick McNutt Member dips about I° east and contains 11 of 12 potential ore zones in the Salado. Potash zones are 3-10 ft thick and contain minable sylvite and/or langbeinite, together with halite and accessory minerals. The zones are consistent laterally, but are locally interrupted by barren halite (salt horses) formed later by undersaturated migrating fluids. Room-and-pillar mining, with pulled pillars, recovers >90% of the potash from depths ranging from 885 to 1400 ft by continuous -mining coal equipment or drilling and blasting. Beneficiation is by various separation, flotation, crystallization, leaching and heavy -media circuits optimized for each ore. The mineralogy and proportion of clay minerals, up to 7% of the ore, influence optimum milling procedures and ore grade cutoff. Agriculture, petroleum and nuclear waste disposal affect production of potash from southeastern New Mexico. Agricultural demand for fertilizer is a complex interaction between weather and climate, advances in crop genetics, soil science, farming practices, GNP of importing nations, farm income, population growth, efficient distribution systems, freight rates and backhauls, substitutes, taxes and tariffs. Petroleum companies compete for petroleum under potash and the Waste Isolation Pilot Project (WIPP) led to withdrawal of potash reserves. INTRODUCTION three types of soluble potash salts (Table 2); other producers are more Potash is the common industrial term for potassium in various com- specialized. binations with sodium, magnesium, chloride and sulfate (Table 1). The United States ranked fourth in world potash production (1.94 Potassium is one of the three essential plant nutrients; it is the "K" in million st) in 1992. New Mexico accounted for about 83% of domestic the "NPK" fertilizer rating, with nitrogen (N) and phosphorus (P). The production (1.61 million st), supplied about 27% of domestic con- sumption (Table 4) and has about 57% of domestic reserves (Searls, potassium in potash is reported as K20 eq. wt % (K20 hereafter), although potassium oxide is not directly present in natural potassium salts (Table 2). For potash fertilizers, K20 is closest chemically to the form of potassium used by plants (Sullivan and Michael, 1986) and is the best means to compare fairly the diverse mineralogy of potash. Important natural, commercial, soluble potassium salts are sylvite and langbeinite. Sylvinite, a mixture of sylvite and halite, is the typical ore mined in the Carlsbad Potash District (CPD) in southeastern New Mexico (Fig. I). The CPD is near the northeastern border of the Del- aware basin (Fig. 1) and contains the largest domestic potash reserves. Soluble potash occurs primarily in Eddy and Lea Counties, which contain the only potash mines in the state. The Potash Enclave (Fig. 2), also designated the Known Potash Leasing Area (KPLA), consists of part of the CPD where federal and state lands require competitive bidding for mineral leases under BLM management. The KPLA lies between Carlsbad and Hobbs, and comprises about 425 mi2 (Cheeseman, 1978). The area underlain by other salts and less soluble potash minerals, such as polyhalite, is much larger than the KPLA (Fig. I). The Salado Formation underlies about 58,000 mi2, halite about 37,000 mi2 and polyhalite about 27,000 mil (Jones, 1972). Areal limits of the CPD are determined by drilling to the north, east and south. The CPD is bounded on the west by dissolution truncation of shallow Salado evaporites by circulating ground water in the Pecos River drainage basin (Griswold, 1982). Potassium products (Table 2) from New Mexico are muriate of potash (KCI; also called MOP, muriate or sylvite by industry), langbeinite (K,SO4.2Mg(SO4)2, called sulfate of potash magnesia or SOPM) and manufactured potassium sulfate (K2504, called sulfate-of-potash or SOP). MOP, sold in various grades (Table 3), comprises about 70% of New Mexico potash output; SOPM and SOP account for the remaining 30%. IMC Fertilizer (IMC), the largest producer in the CPD, supplies all 1993). The remaining 73% of consumption was imported primarily Potash was cored in April 1926 and the Federal Potash Exploration Act (91%) from Saskatchewan, Canada. Domestic potash production is was passed in June. composed of about 75% as muriate, 20% as sulfate or langbeinite and The American Potash Co. was formed in 1926 for potash exploration 5% in other forms (Searls, 1993). About 95% of soluble potash minerals in southeastern New Mexico. A 1062-ft shaft was started in December are used in fertilizer, so potash trends closely parallel agricultural supply 1929 and completed in 1930, and the first commercial potash from and demand (Searls, 1993). Most of the additional 5% is used in chem- New Mexico was shipped in March 1931. Assets of American Potash, icals (O'Driscoll, 1990), mainly aqueous electrolysis of potash to po-. incorporated in 1930 as United States Potash Co., are owned by Mis- tassium hydroxide. Potassium chemicals are used in medicines, sissippi Chemical Corp. (Table 5). The Potash Company of America pharmaceuticals, salt substitutes, soap, matches, glass and storage bat- (PCA) formed in 1931 and completed a shaft in early 1934. The Santa teries. Fe Railroad constructed a 20-mi spur from Carlsbad to the mine; later spurs were run to other mines and mills. The PCA mine is now operated HISTORY by Eddy County Potash. By 1934, at least II companies were exploring The following discussion of potash mining history draws heavily on for potash in southeastern New Mexico. In 1936, Union Potash & Walls (1985) and on Williams-Stroud et al. (1993). Early large scale Chemical Co., Texas Potash Co., Independent Potash & Chemical Co., use of potash started in Germany in the mid-nineteenth century. The New Mexico Potash Co. and the Carlsbad Potash Co. merged into what modern U.S. potash industry is primarily a product of a World War I is now IMC Fertilizer, Inc. and began producing sylvite, langbeinite embargo on German potash—the only large source—that drove prices and K2S0., in 1940. to over $500/st. Wartime potash (for saltpeter) was produced at over Domestic production supplied virtually all potash in the United States 100 plants, mainly in Nebraska and California, each with very small between 1941 and 1949.