HATIOKAL Pavoubabilkpr STUDIES NETHERLANDS

International Atomic Energy Agency IUREP N.F.S. No. 79 August 1977 Distr. LIMITED Original: ENGLISH

IHTERHATIOBAL URABITJM RESOURCES EYALUATION PROJECT

IUREP

HATIOKAL PAVOUBABILKPr STUDIES

NETHERLANDS ANTILLES

77-7721

INTERNATIONAL URANIUM RESOURCES EVALUATION PROJECT

I U R E P

NATIONAL FAVORABILITY STUDY

NETHERLANDS ANTILLES

CONTENTS

PAGE

1. INTRODUCTION

2. GEOLOGY IN RELATION TO POTENTIALLY FAVORABLE URANIUM-BEARING AREAS

3. PAST EXPLORATION

4. URANIUM OCCURRENCES AND RESOURCES

5. PRESENT STATUS OF EXPLORATION

6. AREAS FAVORABLE FOR URANIUM MINERALIZATION AND POTENTIAL FOR NEW DISCOVERY

7. BIBLIOGRAPHY

MAP OF NETHERLANDS ANTILLES

1. INTRODUCTION (a) Geography The Netherlands Antilles comprises a group of six volcanic islands with an area of 1,018 square kilometers* Its capital is Willemstad on Curacao. Aruha, Bonaire and Curacao lie north of Venezuela. Curacao has 461 sq. km.,.Bonaire has 290 sq. km. and Aruba has 181 sq. km. About 885 kilometerrs to the northeast are St. Maarten, Saba and St. Eustatius, France controls the northern portion of St. Maarten. The islands are generally rocky. The northern group is more mountainous than the southern islands and subject to some hurricane danger. Saba is an extinct volcano, while Bonaire and St. Maarten contain salt pans.

(b) Climate The islands have warm to hot temperatures with high humidity. The southern group has temperatures averaging 27 C. with variable but slight rainfall. The northern group has a similar climate though it receives more rain.

All the islands have good roads but no railroads or rivers. There are 1,150 km. of surfaced highways on Curasao;, Aruba, Bonaire and St. Maarten. The rugged terrain of Saba makes road construction diffi- cult. International airports are found on Curacao (Dr. Albert Plesman), Aruba (Princess Beatrix) and St. Maarten (Juliana). Additional airfields are available on the other islands.

2. GEOLOGY IN RELATION TO POTENTIALLY FAVORABLE URANIUM-BEARING AREAS St. Maarten contains Eocene bedded tuffs and volcanic conglomerates cut by Oligocene quartz diorite, andesite, and basalt* The western part of the island exposes nearly horizontal Miocene limestones and marls* No sinkholes or caves are reported from this arid island. St. Eustatius is composed of a recently extinct volcano, the Quill, formed mainly of agglomerate and tuff, underlain on the north by an older (Pliocene or early Pleistocene) volcanic complex formed of agglomerate, breccia, tuff, and lava cut by andesite dikes. A steeply dipping slab of Pleistocene limestone, 335 by 760 meters in area and 150 meters thick, called The White Wall, rests on the south edge of the Quill volcano. Saba is a single composite volcano formed of agglomerates, tuffs, and andesite lava flows cut by domes, plugs, and dikes of andesite and basaltic andesite. Young nuee ardente ash deposits fill valleys and mantle older rocks on the south aide of the island. The volcano probably began as a submarine eruption in the Middle or late Pleistocene and continued as a subaeriai vent until a few thousand years ago.

Curacao, Aruba, and Bonaire expose a basement of diabase and basalt lava and intrusive rocks, radiolarites, andesitic tuffs, minor limestone, and conglomerates about 120 million years old (Early Cretaceous). These rocks are overlain by Upper Cretaceous and earliest Tertiary shale, conglomerate, and limestone. Welded tuff from six stratigraphic levels in the basal volcanic unit indicates that at least part of the unit was formed above sea level. Granodiorite and diorite intrusions cut these rocks, and all are unconformably overlain by Late Miocene or Pliocene reef limestone and Quaternary reef limestone and eolianite. The Miocene and younger rocks form about 40 percent of the land surface. Sinkhole karst and cave topography is extensively developed in the carbonate rocks, many of which contain phosphate deposits.

3. PAST EXPLORATION

No past exploration has been reported.

*• URANIUM OCCURRENCES AND RESOURCES

No uranium occurrences have been reported.

5. PRESENT STATUS OF EXPLORATION

No current exploration has been reported.

6. AREAS FAVORABLE FOR URANIUM MINERALIZATION AND ' POTENTIAL FOR NEW DISCOVERY

Possible source rocks are sparse. Granitic intrusions are exposed on St. Maarten and the islands near Venezuela, but they are closer in composition to diorite than to granite. Acidic tuffs are rare, probably occurring only on St. Maarten and Bonaire. No pegmatites or alkalic igneous rocks have been reported. Possible host rocks are rare—perhaps only phosphate deposits in caves and sinkholes on Aruba, Bonaire, and Curacao.

The uranium potential is estimated at less than 1,000 tonnes. B 7. BIBLIOGRAPHY

Beets, D. J., 1972, Lithology and stratigraphy of the Cretaceous and Danian succession of Curacao? Natuur. Stud. Suriname Ned. Antillen, no. 70, 153 p., Utrecht.

Beets, D.J*. and Lodder, W., 1967, Indications for the presence of ignimbrites in the Cretaceous Washikemba formation of the Isle of Bonaire, Netherlands Antilles: Koninkl. Nederl. Akadamie v. Wetensch., Amsterdam, Proc. ser. B, v. 70, no. 1, p. 6p-67.

Bui3onje, P. H. de, 1974, Neogene and Quaternary geology of Aruba, Curacao, and Bonaire; Natuur. Stud. Suriname Ned. Antillen, no. 78, 293 pf, Utrecht.

Butterlin, J., 1956, La constitution geologique et la structure des Antilles: Paris, Centre Nat. de la Recherche Scientifique, 453 p.

Christraan, R. A., 1953, Geology of St. Bartholomew, St. Martin, and Anguilla; Geol. Soc America Bull., v. 64, p. 65-96.

Westermann, J. H. and H. Kiel, 1961, The geology of Saba and St. Eustatius: Natuur. Stud. Suriname Ned» Antillen, no. 24, 175 p., Utrecht.

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