Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah Andrew Rupke and Taylor Boden
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Proceedings of the 48th Annual Forum on the Geology of Industrial Minerals Scottsdale, Arizona | April 30 - May 4, 2012 Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah Andrew Rupke and Taylor Boden Arizona Geological Survey Special Paper 9 Chapter # Proceedings of the 48th Annual Forum on the Geology of Industrial Minerals Scottsdale, Arizona | April 30 - May 4, 2012 Arizona Geological Survey M. Lee Allison, State Geologist and Director This publication was prepared by an agency of the State For information on the mission, objectives or geologic of Arizona. The State of Arizona, or any agency thereof, products of the Arizona Geological Survey visit www.azgs. or any of their employees, makes no warranty, expressed az.gov. or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any Manuscript approved for publication in 2014. Printed by the information, apparatus, product, or process disclosed in Arizona Geological Survey. All rights reserved. this report. Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the State of Arizona. Officers and Organizers of the 48th Annual Forum on the Geology of Industrial Minerals Board of Directors Forum Steering Committee Bates Scholarship Trustees - RLBMSF President – Mark Wolf Lynne Carpenter George Edwards Vice President – Thomas Newman Dale Scott Roger Sharpe Secretary – Stan Krukowski Dave Crouse Peter Harben Treasurer – Vanessa Santos Greta Orris Vanessa Santos Gretchen Hoffman Members Marion Wiggins Lynne Carpenter Tom Newman Nelson Shaffer Dale Scott Special Paper 9 Recommended Citation: Rupke, A. and Boden, T., 2015, Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah. Proceedings of the 48th Annual Forum on the Geology of Industrial Minerals, Phoenix, Arizona, April 30 - May 4, 2012. Arizona Geological Survey Special Paper #9, Chapter 8, 23 p. TABLE of CONTENTS ABSTRACT 2 INTRODUCTION 2 Purpose and scope 2 Study area 3 Methods 5 REGIONAL GEOLOGY AND STRUCTURE 5 POTASH RESOURCES 7 General 7 Potash maps 7 Cycle 5 potash 8 Cycle 9 potash 12 Cycle 13 potash 14 Cycle 18 potash 15 CONCLUSIONS 20 ACKNOWLEDGEMENTS 20 REFERENCES 22 Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah 1 Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah Andrew Rupke1 and Taylor Boden Utah Geological Survey, P.O. Box 146100, Salt Lake City, UT 84114-6100 [email protected] ABSTRACT anticline, the potash deposits in that area have the advantage of being relatively shallow, although Strong international demand and high potash structural complexity at the anticline may present prices have prompted a number of companies to difficulties for extraction. conduct or plan potash exploration in the already In the Hatch Point and Hart Point areas, potash productive Paradox Basin of southeastern Utah. in salt cycles 13 and 18 may represent potential In response to potash interest in the area, the Utah resources. A few data points show potash grades of School and Institutional Trust Lands Administration cycle 13 above 10% K2O in the west-central part of the contracted the Utah Geological Survey to evaluate study area, and projected thicknesses are generally less potash beds in the Pennsylvanian Paradox Formation than 10 ft. Mapping indicates that high-grade areas of in about 900 square miles of northern San Juan cycle 18 potash (>15% K2O) may be widespread in the County, including the Hatch Point, Hart Point, and southwestern part of the study area, including in the Lisbon Valley areas. The Paradox Formation is an Hatch Point and Hart Point areas. Limited chemical evaporite sequence containing up to 29 recognized analyses are available for cycle 18, but a number of salt cycles that are numbered sequentially from top (1) boreholes show high gamma-ray signatures indicating to bottom (29), and the most significant potash beds high-grade potash. Projected thickness of high-grade in the study area are in salt cycles 5, 6, 9, 13, 16, 18, potash in cycle 18 is variable, but ranges up to about 19, 20, 21, and 24. Data on these beds were compiled 30 ft. In contrast to Lisbon Valley, topography is from published and unpublished sources containing the primary control for overburden thickness where information on 132 potash exploration boreholes and potential resource is present in cycles 13 and 18— oil and gas wells in and around the area. From the overburden is thick at Hatch Point and Hart Point compiled data we created isopach, grade, overburden mesas, and is relatively thin in the valley to the west. thickness, and structure contour maps of potash beds. For the maps, we interpolated the data using an INTRODUCTION inverse-distance-squared weighting, with an anisotropy Purpose and scope applied to take the Paradox Basin’s northwest-trending The Utah School and Institutional Trust Lands geometry into account. Results suggest that multiple Administration (SITLA) commissioned the Utah salt cycles in the study area may represent a potash Geological Survey (UGS) to prepare a report on resource; however, the resource comprises different potash resources over a region that covers the Hatch beds in different areas. The primary potash-bearing Point, Hart Point, and Lisbon Valley areas of San Juan mineral of most of the potential resources in the basin County, Utah. Due to recent increases in potash prices, is sylvite, but carnallite is also present in some areas. the potash-bearing Paradox Formation of the Paradox In the Lisbon Valley area, data suggest a potential Basin has drawn interest from a number of mining resource in salt cycles 5 and 9. Analyses from both and exploration companies. These companies have cycles show greater than 20% weight equivalent leased and applied for rights to large tracts of SITLA K2O, and mapping suggests reasonably sized areas of and Bureau of Land Management (BLM) property. above 15% K2O. Potash thickness in high-grade areas Two companies have recently drilled for potash is typically 10 ft. or less for cycle 5 and from about within the study area: K2O Utah, LLC (90% owned 5 to 15 ft. for cycle 9. Generally, data indicate that by Potash Minerals Ltd., formerly known as Transit potash in cycle 9 would be a better target as it tends Holdings Ltd.) drilled in the Hatch Point area, and to be higher grade and more extensive than potash in North American Potash Developments Incorporated cycle 5. Because Lisbon Valley represents a structural (formerly known as Ringbolt Ventures Limited) drilled in the Lisbon Valley area. 2 Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah This paper presents isopach, grade, overburden from oil and gas well gamma-ray logs. While a thickness, and structure contour maps of the potash reasonable amount of data are available, additional beds in the study area that likely have the most drill holes in key areas would provide a more complete economic potential. The maps were generated from and reliable picture of the potash resource within the compilation and analysis of existing potash data from study area. wells drilled in and around the study area to provide Study area a better picture of the potash resource. Limited The study area is situated in northern San Juan potash drilling has occurred in the study area and County and encompasses nearly 873 square miles few chemical analyses are available for most of the (559,000 acres) (figure 1). The area includes primarily study area, so much of the potash data is interpreted BLM and SITLA land with a small amount of private Spanish Valley Utah Colorado River Manti-La Sal Study National Forest Hatch Point Area Lisbon Valley Hart Point Canyonlands National Park Ü Manti-La Sal National Forest 0 5 10 15 20 Miles Figure 1. Study area. Blue dots represent locations of potash exploration boreholes and oil and gas wells used for potash bed mapping. Potash Bed Mapping in the Paradox Basin, Northern San Juan County, Utah 3 land that is concentrated on the east side of the area. the primary targets being potash in salt cycles 5 and Canyonlands National Park defines the western 9. Other companies, primarily the Pure Oil Company, boundary of the study area, Manti-La Sal National drilled a number of oil and gas wells in Lisbon Forest defines the southwestern boundary, and the Valley during the early 1960s. Hodges and Banfield flanks of the La Sal Mountains occur along much of (1962) and Hite (1978) provided potash information the northeastern boundary. A short segment of the from analytical data and gamma-ray log data that Colorado River is within the extreme northwestern were gleaned from both the potash and oil-and-gas part of the study area, and is near much of the western exploration and production wells. In response to the boundary. Some of the primary physical features results of potash exploration, the BLM designated an in the study area are Hatch Point, which is a large, area of Lisbon Valley as a Known Potash Leasing Area relatively flat mesa that extends from the central part (KPLA) in 1960, which allowed the leasing of potash of the area towards the northwest, and Lisbon Valley, on BLM ground. Gwynn and Tripp (2009) prepared which is an asymmetric, northwest-trending valley in a potash resource evaluation of Lisbon Valley for the the eastern part of the study area (figure 1). Elevations BLM and the BLM increased the area of the Lisbon range from over 7000 ft. in the southwest on the flanks Valley KPLA in response. of the Abajo Mountains and the northeast on the At Hatch Point and other parts of this study flanks of the La Sal Mountains to about 4000 ft.