RME- 4062 U. S. ATOMIC ENERGY COMMISSION DIVISION OF PRODUCTION AND MATERIALS MANAGEMENT POSSIBILITIES FOR URA\NIU14 IN COSTA RICA By Edward K. Judd Washington, D. C. 20545 January 1955 metadc1 393263 REPRODUCED FROM BEST AVAILABLE COPY Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. -2- RME- 4062 POSSIBILITIES FOR URANIUM IN COSTA RICA CONTENTS Page INTRODUCTION . 4 Geography . 4 Transportation, communication and industry . 4 Physiography and climate . 6 GENERAL GEOLOGY .............. '. 7 Deep-seated intrusives . 8 Extrusive and eruptive rocks . 9 METALLIC LODE DEPOSITS . ... .. .. ... 10 SUMMARY .. * . .0 . .0 0 .0 0 . 13 REFERENCES . .0. 14 ILLUSTRAT IONS Figure 1. Political map of Costa Rica . 0 . * . 5 Plate I. Geologic map of the highlands of Costa Rica . (in pocket) - 3 - RME-4062 POSSIBILITIES FOR URANIUM IN COSTA RICA INTRODUCT ION Geography The Republic of Costa Rica occupies the full width of the Central American isthmus, a minimum of 120 kilometers (75 miles) at this lati- tude, between Nicaragua on the north and Panama on the south (Fig. 1 . The approximate limits are N. 80 (Point Burica) to 110 15' and W. 82 30' to 86 . Its area is about 50,890 square kilometers. Cocos Island is in the Pacific, about 300 miles to the southwest. At the end of 1951 the estimated population of 838,084 was distrib- uted among seven provinces -- San Jose, 293,891, Alajuela, 155,384; Cartago, 105,259; Guanacaste, 94,186; Puntarenas, 92,205; Heredia, 53,725; and Limon, 43,434. During 1949-1951 immigration and emigration almost balanced. In descending order of population the chief cities are San JosE (the capital), Alajuela, Puntarenas, Cartago, Ileredia, Lim6n and Liberia (of Guanacaste). Most of the people are European (mainly Spanish) descendants; about 15,000 West Indians are largely in Lim6n; native 'Indians are few. The chief seaports are Lim6n on the Caribbean and Puntarenas on the Pacific side. The United Fruit Co. also maintains ports at Quepos and Golfito on the Pacific. Transportation, communication and industry An intercoastal railway from Lim~n to Puntarenas passes through Cartago, San JosE, Heredia and Alajuela. Another railway to connect Limnon with Almirante (Panama) lacks only a middle section now under construction. The Costa Rican segment of the Inter-American highway, passing through San JosE, has 204 kilometers completed with 300 to follow. Motor roads generally are in good condition and total about 350 miles. There is no road into Panama and only one (passable just in dry weather) into Nicaragua. Passenger traffic into and out of the country is mostly by air. The international Pan American, Taca and Royal Dutch lines use a landing field at La Sabana near San Jos6, and their subsidiaries give daily service to important other towns. - 4- .5C S . ~ . - * 1- 1- - &1rj ---- - - 5t - t- T 6 u6M 4CASTE~ Las Qoas~ ;-.. -- ; -. ~'- . \ ' - C 0 O.tsoo -w, ~ n eYeo Lmi p O -4- V /Ai e . ge -. .4 - -g*. 1 ,' . *- g ci I 0o eCs7-A R.MiC A PCJIAL A 0 41gu6 0 41 0 - 5.- Commercial wireless telegraph stations are located at Cartago (international service), Limon (service to Almirante), Puntarenas, Quepos and Golfito. The government also has 19 wireless stations serving San Jose to Nicaragua, Honduras, San Salvador and Mexico. It further has 202 official telegraph stations and 88 for telephones. (3). Agriculture is the main industry, with some dairy farming and cattle raising. About 1,877,000 acres is under cultivation, 543,000 acres in pasture, while 9,855,000 acres of forest, much of it in the public domain, contains several varieties of valuable timber, cut mostly on the western side. The chief products are coffee, bananas, cocoa, sugarcane and tobacco. A few factories in the larger cities are engaged mainly in the processing of primary produce. Nationalized hydroelectric power is extensively developed. Although gold mining has been practiced in the Guanacaste and Aguacate mountains, known deposits of other ores are but slightly explored. Physiography and climate The main mountain ranges of Mexico and'Central America continue southward and traverse the whole length of Costa Rica from the northwest to southeast with only one important interruption, the valley occupied by the Rio Grande flowing to the Pacific and the Rio Reventazon the the Caribbean. Both rivers have their headwaters near Cartago, and their valleys afford a convenient route for the intercoastal railway. The two principal ranges north of this narrow depression, "lMeseta Central," are the Cordillera del Guanacaste (with high points at volcanoes Mira- valles and Canaste) and Cordillera Central (with several active vol- canoes -- IrazEi, Turrialba, Barba and Pogd. South of lMeseta Central are the short Bustamante Mountains and the mugh longer Cordillera de Talamanca. The latter reaches almost to the Panama boundary and rises to the highest elevation in the country, 3837 meters, at Chirrip6 Grande. The Meseta Central is covered by fertile volcanic ash and supports about three-quarters of the country's population; four of the largest cities are situated here. The region, however, has often been afflicted by disastrous earthquakes. The marshy Caribbean coast is about 130 miles long. It is fairly straight, characteristic of a rising shore, and bordered by lagoons. The Pacific coast, about 630 miles, is much more irregular with many small and two large indentations -- the Gulf of Nicoya on the north, a shallow bay between Nicoya peninsula and the mainland; and the Golfo Dulce on the south, having Osa peninsula at its west side. This shore topog- raphy indicates a sinking coast. Contras-ting with the mountainous interior of Costa Rica are large areas of lowland (below 100-meter elevation) and narrow strips along both coasts. The largest of these lies north of the mountains. It extends northward into Nicaragua and occupies the whole width of the Central American isthmus. The boundary Rio San Juan, draining Lake Nicaragua, flows easterly through this Nicaraguan depression" and was to have facilitated construction of the projected Nicaraguan canal. There is another large expanse of lowland to the north and west of the. head of Nicoya Gulf, a major part of Guanacaste Province. A third area borders Golfo Dulce and Osa peninsula near the Panama boundary. Costa Rica has many short but steep rivers, extensively utilized for power, as well as several longer ones with gentler gradients. The largest tributaries to the Rio San Juan from the Costa Rican side are the rios Sabogal and San Carlos, in Alajuela Province, and the Rio Chiripi, bounding Heredia and Limon provinces. The Rio Tempisque drains the lowlands north of Nicoya Gulf. The interinontane San Jose basin originates the rios Grande and Reventazon. Headwaters of both rivers probably are fairly swift, but both cross lowlands at their mouths. Similarly the Rio Diquis in Puntarenas Province has steep headwater tributaries and traverses a considerable width of lowland. The climate of Costa Rica is diversified according to altitude. In the humid jungles along the Caribbean coast the average annual rain- fall of 120 inches is distributed over all seasons. The narrower Pacific lowland is somewhat drier. The highlands west of the mountains have two seasons, the dry season occurring from December to April. San Jose city is renowned for its equable springlike climate (4). Most of the mines of Guanacaste Province are in this highland belt at elevations of 200 to 500 meters. GENERAL GEOLOGY A striking feature of Costa Rica's geology is the contrast in com- ponents and structure between the mountain ranges north and south of the rios Grande-Reventazon valleys, traversed by the intercoastal railway. So far as now known, those to the north -- cordilleras Guanacaste and Central -- consist entirely of extrusive and volcanic igneous rocks. The southern ranges -- Candelaria, Bustamante and Talamanca -- have a more complex structure involving sedimentaries, metamorphics, and intru- sives of two or more epochs (P1. I). According to Sapper (5), neither Precambrian nor Paleozoic strata had been identified in Costa Rica up to 1937. Schists and altered limestones do occur, but their originals were strata of much later date. The earliest definitely identifiable measures are late Eocene limestones that are exposed in a small area in the Rio Reventazon valley just east of the Turrialba Railway station. While certain breccias, conglomerates, sandstones, shales and limestones along the northwestern coast possibly may be older Eocene, their ages have not been thus proved. They are - 7- unconformably overlain by other shales and silicified limestone (age uncertain), and all are largely buried under Tertiary volcanics. On Nicoya peninsula Romanes (6) found no trace of old metamorphic rocks such as had been mentioned by previous visitors. Pittier's suggestion that such rocks occur on some high ridges of south-central Costa Rica has not yet been confirmed. The Oligocene is extensively developed on both sides of the central range of southern Costa Rica. It occupies large areas in the Candelaria highlands and on Cerro Bustamante; along the southwestern foothills of the Cordillera de Talamanca between longitudes 840 and 830; among the headwaters of the Rio Estrella on the Caribbean slope; and in patches at about the middle of Nicoya peninsula.