U.S. GEOLOGICAL SURVEY CIRCULAR 962 

Und-iscovered Phosphate Resources in the 

Caribbean Region and Their Potential 

Value for Agricultural Development 

Prepared as a cooperative eHort between 

the U.S. Geological Survey, East Carolina 

University, Greenville, North Carolina, and 

the International Geological Correlation 

Program Project 156 

Undiscovered Phosphate Resources in the 

Caribbean Region and Their Potential 

Value for Agricultural Development 

By R. P-. Sheldon, D. F. Davidson, 

5. R. Riggs, and W. C. Burnett 

U.S. GEOLOGICAL SURVEY CIRCULAR 962 

Prepared as a cooperative effort between 

the U.S. Geological Survey, East Carolina 

University, Greenville, North Carolina, and 

the International Geological COITtllation 

Program Project 156 

1985 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Free on application to Distribution Branch, Text Products Section, 

U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page 

Abstract . • . • • . . • • • • . . . • • • • . . . • • . . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1 

Introduction . . . . . . . . . . . • . • • • . . . • . • . • . • • . • . . . . . . • • . . . . . . • • • • • • • • • • . 1 

World phosphate situation • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 

History of demand and production • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 

History of discovery • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3 

Phosphate rock quality requirements for fertilizer 

production . • . . . . . . • • . . • . . • . . . . . . . . • • . . • • • . . . . • . • . • • . • • . • . 3 

Present world phosphate production and trade • • • • • • • • • • • • • • • • • • • • • • • • • 6 

Present application rates • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 9 

Need for phosphate fertilizer in the Caribbean region •••••••••••••••••••••••• 10 

Economic implications of phosphate rock resource development ••••••••••••••••• 16 

Phosphate exportation • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 16 

Substitution for phosphate imports •••••••••••••••••••••••••••••••••• 16 

Agricultural product exportation .•••••••••••••••••••••••••••••••••• 17 

Increased food production • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 17 

Benefits of successful development of phosphate rock 

resources • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 17 

Undiscovered phosphate rock resource potential of the 

Caribbean region • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 17 

Comparative analysis of the phosphate resource potential 

of the tropics • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 17 

Origin of marine phosphate rock • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 19 

Geology of the Caribbean region ••••••••••••••••••••••••••••••••••• 19 

Phosphate resource potential of the Caribbean region •••••••••••••••••••• 21 

Discovery and development program for undiscovered phosphate 

rock resources of the Caribbean region •••• _ •••••••••••••••••••••••• 22 

Cost of a phosphate resource development program ••••••••••••••••••••••••• 23 

Glossary of phosphate resource terms ••••••••••••••••••••••••••••••••••• 24 

References cited •••••••••••••••••••••••••••••••••••••••••••••••••• 25 

ILLUSTRATIONS 

Page 

Figure 1. Graph showing world phosphate rock production, 

1900 to 1980 • . • . • • • • • • • . . . • • • • • • • • • • • • • • • • • • • • • • • • 3 

2. Map showing major phosphate rock mining districts 

of the world in 1980 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 4 

3. Time lines showing history of discovery of phosphorite 

mining provinces and province extensions, age of 

deposition, and location • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 5 

III 
Table 

4. Map and pie diagrams showing import-export trade of 

phosphate rock • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 8 

5. Graph showing phosphate fertilizer use on arable lands 

in relation to per capita gross national product. • • • • • • • • • • • • • 9 

6. Graph showing phosphate fertilizer use on arable lands 

in relation to income and geographical area • • • • • • • • • • • • • • • • 10 

7. Map showing countries of the world with application 

rates Jess than 15 kilograms of P2o5 per hectare of 

arable land • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 11 

8. Graph showing relation between rice yields of the 

INPUTS experimental sites and latitude ••••••••••••••••••• 13 

9. Chart showing geologic episodes of phosphate 

1. 

2. 

3. 

4. 

rock deposition • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 20 

TABLES 

Page 

Phosphate rock production and estimated reserve base 

by country • • . • • • • • • • • • • • . • . • • • • • • . . • • . . . • • • . • • • . • . 7 

1981-82 grain production in Caribbean Basin countries 

and other countries and regions • • • • • • • • • • • • • • • • • • • • • • • • • 12 

1982 cereal production statistics and projected cereal 

production statistics for new agricultural 

technology in the Caribbean Basin countries •••••••••••••••• 14 

1982 phosphate fertilizer consumption in the Caribbean 

Basin countries, Amazon Basin, and Japan 

and projected consumption and cost for new 

agricultural technology in the Caribbean Basin 

countries • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 15 

5. Programs for developing a phosphate rock mining and 

phosphate fertilizer production industry ••••••••••••••••••• 23 

IV 
Undiscovered Phosphate Resources in the 

Caribbean Region and Their Potential 

Value for Agricultural Development 

By R. P. Sheldon, D. F. Davidson, 5. R. Riggs, and W. c. BurneH 

ABSTRACT 

The countries of the world's humid 

tropical regions lack the soil fertility necessary for high agricultural productivity. A 

rece~tly developed agricultural technology 

~hat 1nc~eases soi! fertility can make tropIcal agnculture highly productive, but the 

technique requires large inputs into the soil 

of phosphorus and other fertilizers and soil 

amendments. 

Use of fertilizers derived from phosphate rock is increasing greatly throughout 

the world, and fertilizer raw materials are 

being produced more and more frequently 

from phosphate rock deposits close to the 

areas ?f. use. An increased understanding of 

the ongin of phosphate rock in ancient 

oceans has enabled exploration geologists to 

target areas of potential mineral resource 

value and to search directly for deposits. 

However, because of the difficulty of prospecting for mineral deposits in forested 

tropical regions, phosphate rock deposits 

are not being explored for in the countries 

of the humid tropics, including most countries of the Caribbean region. As a result 

the countries of the Caribbean must impo;t 

phosphate rock or phosphorus fertilizer 

products. In the present trade market . ' Imports of phosphate are too low for the 

initiati~n of new agricultural technology in 

the Canbbean and Central American 

region. 

A newly proposed program of discovery and development of undiscovered 

1 

phosphate rock deposits revolves around 

reconnaissance studies, prospecting by core 

drilling, and analysis of bulk samples. The 

program should increase the chance of dis-

~overing economic phosphate rock deposIts. The search for and evaluation of phosphate rock resources in the countries of the 

Caribbean region would take about 5 years 

and cost an average of $15 million per 

country. The program is designed to begin 

with high risk-low cost steps and end with 

low risk-high cost steps. 

A successful program could improve 

the foreign exchange positions of countries 

in the Caribbean region by adding earnings 

from agricultural product exports and by 

substituting domestically produced phosphate rock and fertilizer products for imported phosphate fertilizers. A successful 

program also could provide enough domestically produced phosphorus fertilizer products to allow initiation of new agricultural 

technology in the region and thus increase 

domestic food production. Finally, a new 

phosphorus fertilizer industry would create 

new jobs in the mining, chemical, and 

transportation industries of the Caribbean 

region. 

INTRODUCTION 

The countries of the humid tropical 

areas of the world, including the countries 

of the Caribbean region, have two of the 

three essentials for productive agriculture--

water and sunlight--but lack the third 
essential, fertile soil. In fact, the abundance of water and sunlight in the tropics 

has caused ( 1) the leaching of vital nutrients from soil and ( 2) the breakdown, leaching, and oxidation of the soil minerals. As a 

result of these processes, the soil is acidic 

and infertile. Modern agricultural science 

has developed and demonstrated a technology to give high fertility to such soils by 

applications of fertilizer and soil amendments and by development of new strains of 

food plants and rotational crop systems that 

give high yields under the new soil conditions. 

The full potential of tropical agriculture is high but unrealized. Technology 

that could effectively increase production 

in the area is not in place, partly because of 

the newness of the technology and partly 

because of the lack of raw materials to 

carry the technology out. Phosphate fertilizers are among the important inputs for 

this new technology. Because of the difficulty of discovering mineral deposits in 

forested tropical regions, phosphate rock 

resources in the tropics often go undiscovered and undeveloped, and, as a result, 

phosphate in one form or another must be 

imported. 

The agricultural problems of humid 

tropical countries are compounded by the 

large populations of the countries and the 

resulting domestic food needs. The economies of the tropical countries, however, 

rely substantially, if not primarily, on the 

export of cereals, sugar, coffee, tea, cocoa, 

fruits, and other agricultural products. The 

agricultural land resources must be apportioned between these two uses--production 

of food for domestic consumption and production of agricultural export products. 

National policymakers, given the low productivity of the agricultural lands, must 

make difficult choices between stimulating 

their national economies and meeting the 

food requirements of their people. With a 

growing population, this dilem rna becomes 

increasingly difficult. Improving soil fertility and using new agricultural technology 

are critical needs. 

Availability of phosphate materials is 

basic to increasing agricultural productivity 

2 

of the Caribbean region. This report 

reviews the current world phosphate production and trade situation and the problem 

of phosphate fertilizer needs versus present 

levels of consumption. The report discusses 

the economic implications of phosphate 

rock resource development and presents 

data on the phosphate resource potential of 

the Caribbean region. Finally, the report 

outlines the essential elements of a phosphate rock resource development program. 

WORLD PHOSPHATE SITUATION 

HISTORY OF DEMAND AND PRODUCTION 

To be fully understood, the phosphate 

situation of the Caribbean region must be 

seen in a world context. The world exploitation of phosphate rock has been rising for 

decades; this increase has been exponential 

during the last 40 years (fig. 1). Most of 

this phosphate is used as fertilizer, and the 

consumption curve is approximately the 

same as the production curve. The consumption curve, however, demonstrates the 

cyclic economic nature of the phosphate 

business more accurately than does the production curve. Over the decades, the 

increase in demand has caused the exhaustion of smaller deposits, the abandonment 

of higher cost deposits, and the development of large, low-cost deposits that benefited from the economies-of-scale in mining 

techniques. As a result, from World War II 

until a few years ago, three areas dominated world supply and set prices. These 

areas were ( 1) Florida and North Carolina, 

U.S.A., ( 2) Morocco and Western Sahara, 

and ( 3) Khibini in the Kola Peninsula of the 

U.S.S.R. (fig. 2). The Khibini deposit supplies mainly the U.S.S.R. and eastern 

Europe; the U.S. and Moroccan deposits 

supply phosphate rock or fertilizer to the 

rest of the world. Many other smaller 

deposits exist (see fig. 2). Because of small 

size, low grade, remote location, or 

governmental policies, these other deposits 

have not contributed greatly to world phosphate trade, although they may be important locally. 
130 

en 

c 120 B 

J 

v u 

·s 

(!) 100 E 

c 

.9 

j_ 

v 

.E 80 

c i/ .:Jt!.- 60 u 

e 

2 40 co 

.c 

a. 

en 

0 

.c 20 a... 

0 

1/ 

/ v 

_v ~ ......- r--.,.- 1>-- ,_....... 

1900 1920 1940 1960 1980 

Figure 1.--World ·phosphate rock production, 

1900 to 1980. Data from W. F. 

Stowasser (written commun., 1981). 

HISTORY OF DISCOVERY 

Exploration for phosphate rock deposits has increased continually as the demand 

for fertilizer has increased. No comprehensive history of phosphate rock exploration 

and discovery has been written. However, 

an important trend is evident from available information. Most of the early discoveries of marine-origin phosphate rock 

deposits (the commercially most important 

type) were made in the process of regional 

geologic mapping (fig. 3). This mapping was 

carried out not to explore for phosphate 

rock but to understand the regional geologic 

structure and distribution of different rock 

types. Phosphate rock deposits were found 

by chance. Occurrence of most of these 

early-found deposits where rocks are well 

exposed in desert, glaciated, or mountainous countries is highly significant. Phosphate is still being discovered in this manner, 

as improved geochemical and geophysical 

surveying techniques make regional 

mapping more efficient. 

The origin of phosphate rock was the 

subject of great debate until 1937, when the 

Russian sedimentary petrologist A. V. 

Kazakov ( 1937) developed a hypothesis of 

3 

the origin of marine phosphorite through 

upwelling deeper ocean water onto shallow 

water continental shelf areas. His hypothesis evolved into a generally accepted 

theory (McKelvey, 1967; Sheldon, 1981). 

Perhaps more than any other factor, 

Kazakov's theory allowed exploration geologists to develop theoretical targets and 

search directly for phosphate deposits. As a 

result, an era of discovery began in the 

mid-20th century and continues today (fig. 

3). At the same time, recognition of the 

likely geologic environment in which to find 

marine phosphate has allowed significant 

extensions of previously known phosphorite 

provinces (fig. 3). 

Exploration for phosphate rocks, however, has been remarkably unsuccessful in 

the tropical regions of the world, primarily 

because of the poor exposure of the rocks. 

This climate-biased exploration history is a 

major factor in the present distribution of 

phosphate mining districts of the world. 

PHOSPHATE ROCK QUALITY REQUIREMENTS 

FOR FERTILIZER PRODUCTION 

Once a phosphate rock deposit has 

been discovered and measured, the quality 

of the deposit must be evaluated for its 

potential as a raw material for agricultural 

use. The quality of the phosphate rock is as 

important a factor as the minability, size, 

and accessibility of a deposit in evaluating 

the deposit. The quality evaluation requires 

extensive physical and chemical testing to 

( 1) determine the best method for beneficiating the rock and removing detrimental 

minerals and ( 2) select the best process for 

fertilizer manufacture. 

The present technology for manufacturing phosphorus fertilizer uses dissolution 

of phosphate rock in sulfuric acid. The 

products are then processed in several ways 

to produce one of a number of phosphorus 

fertilizers. 

A number of contaminants in phosphate rock can interfere with fertilizer 

production processes and make the processes more costly or less efficient. Perhaps 

the most damaging contaminants are calcium and magnesium carbonates, which are 

also dissolved by sulfuric acid. The pres-
-1=" 

w 140 

o~---+----~----4 

• Equatorial phosphate rocks 

• Trade-wind-belt phosphate rocks 

A lgneousphosphaterocks ~----~--~----~---+--~~--+---+----r--~· 

0 

Figure 2.--Major phosphate rock mining districts of the world in 1980. See text ( p. 19-22) for explanation of phosphate 

rock types. Data from Stowasser ( 1981) and Sheldon ( 1982). 
1850 

® 

0 

1900 

@ @ @@ 

0 ®G)@@@@ 

1950 1980 

Phosphorite provinces found by regional geologic studies 

1850 1900 1950 

@ 

@@@ 

@@@@ @ 

1980 

Phosphorite provinces found by prospecting based on geologic theory 

1850 1900 1950 1980 

Major province extensions based on geologic projection 

Phosphate rock deposits 

Regional geologic studies 13. Precambrian, Surinam Province extensions 

14. Lower Proterozoic, India 

1. Miocene, North Carolina 

2. Miocene, California 

15. Lower Proterozoic, Michigan 22. Miocene, offshore North Carolina 

23. Cretaceous-Eocene, Israel 

3. Cretaceous-Eocene, North Africa Geologic theory 24. Cretaceous, Turkey 

4. Cretaceous-Eocene, Middle East 16. Holocene, Baja California 25. Cretaceous- Eocene, Saudi Arabia 

5. Jurassic, Mexico 17. Miocene, Peru 28. Cretaceous, Colombia 

6. Triassic, Alaska 18. Jurassic, Peru 29. Cretaceous, Ecuador 

7. Permian, Utah 19. Devonian, Iran 30. Cambrian, China 

8. Precambrian, Liberia 20. Cambrian, India 31. Precambrian, Nepal 

9. Pliocene, Florida 

10. Cambrian, China 

21. Upper Proterozoic, India. 

12. Cambrian, Australia* *Australian phosphorite found 

simultaneously by two different 

techniques. 

11. Cambrian, Mongolia 26. Cambrian, Spain 

12. Cambrian, Australia* 27. Precambrian, Benin 

Figure 3.--History of discovery of phosphorite mining provinces and province extensions, 

age of deposition, and location. 

ence of calcium and magnesium carbonates 

increases the amount of acid required to 

dissolve the total rock and thereby 

increases the processing cost. Iron and 

aluminum oxides and magnesium carbonates 

or silicates interfere with the manufacturing of phosphorus fertilizer by forming 

sludges that clog filters and form scale on 

phosphoric acid production equipment. 

Excessive amounts of chlorine, fluorine, and 

some minor elements are also deleterious to 

fertilizer manufacturing processes and the 

resulting fertilizer. McClellan { 1980) has 

5 

given an excellent account of these problems. 

For the acid soils of the humid tropics, adding crushed raw phosphate rock to 

the soil commonly improves agricultural 

productivity; therefore, in some conditions 

and for some crops, processing phosphate 

requires nothing more than crushing the 

rock. When using crushed raw phosphate 

rock as an additive, the presence of calcium 

and magnesium carbonates is not as serious 

a problem as when using rock processed by 

the sulfuric acid procedure. In fact, the 
carbonates in crushed phosphate rock help 

to reduce the acidity of the soil, and the 

magnesium in the rock is a valuable nutrient. 

Discerning the quality of undiscovered 

phosphate rock is impossible. With the deep 

leaching typical of rocks in the humid tropics, phosphate rock originally rich in calcium and magnesium carbonates may be 

leached free of these contaminants in some 

parts of the deposit, thus increasing the 

deposit's value (Altschuler, 1973). Conversely, leaching can spoil a phosphate rock 

deposit by forming calcium aluminum phosphate or aluminum phosphate minerals in 

the leached zone from the original phosphate rock (calcium phosphate). The resulting aluminum-bearing phosphate minerals 

are more insoluble than the original calcium 

phosphate and are more difficult and expensive to process into phosphorous fertilizer. 

After the quality of a discovered 

phosphate rock deposit is ascertained, the 

best process to use in beneficiating and in 

making phosphorus fertilizer from the concentrate can be determined, and the deposit 

can be fully evaluated. Even the lowest 

grade phosphate deposit sometimes can be 

used if a suitable process is selected. 

PRESENT WORLD PHOSPHATE PRODUCTION AND TRADE 

World production of phosphate by 

country is shown in table 1. The top six 

producers of phosphate rock in 1980 produced 85 percent of the phosphate rock, and 

the bottom 16 produced 15 percent. Table 

1 lists the reserve base of each of these . 

producer countries and indicates a potential 

for increased production, particularly in 

South Africa, Brazil, Syria, Algeria, 

Mexico, and Finland (see Glossary for definition of resource terms). Phosphate rock 

mines in India, Syria, Brazil, Australia, 

Finland, Turkey, Peru, and Mexico have 

opened up in the last decade, and additional 

mines in Iraq, Egypt, and Mongolia are reported to be opening soon. In contrast, in 

the last 10 years, the mines on Ocean Island 

and Curacao have closed because of exhaustion of the resource. 

6 

The phosphate rock from the new deposits is commonly less pure or more difficult to mine or beneficiate than is the 

phosphate rock of the southeastern United 

States and of Morocco and Western Sahara, 

but the new deposits have the economic 

advantage of shorter distances to local 

markets. The increasing cost of ocean 

transportation, as well as a shortage of hard 

currency in many countries, increasingly 

has caused the world phosphate market to 

take into account the numerous smaller and 

poorer deposits of the world. The general 

trade patterns generated by this situation 

are shown in figure 4. The dominance of 

the southeastern United States and Morocco 

and Western Sahara is clearly illustrated in 

the pie diagram (fig. 4) that shows the 

major phosphate rock exporters. Phosphate 

rock is often shipped halfway around the 

globe from these two areas to ports in 

western Europe, South America, and Asia. 

Other trade occurs from the Soviet Union 

to eastern Europe and from Christmas 

Island and Nauru to Australia and New 

Zealand. As can be seen in figure 4, economically developed countries form the 

majority of importers of phosphate rock. 

The map in figure 4 shows that phosphate rock trade is a major international 

enterprise. The major phosphate rock and 

fertilizer sales are by large companies 

(which, outside the U.S., are primarily 

national companies) to the major cash crop 

farming areas. Moreover, developing countries have received relatively little international assistance with respect to phosphate imports. The trade barriers around 

the centrally planned economies are apparent also on this map; that is, the region that 

includes the Eastern Europe Bloc countries 

and northern Asia is isolated from the rest 

of the world as far as phosphate trade is 

concerned, except for minor phosphate rock 

imports from Jordan. A vigorous phosphate 

trade is going on within the bloc of countries with centrally planned economies, and, 

generally speaking, the phosphate resources 

are more fully developed in these countries. 
Table I.--Phosphate rock production and estimated reserve base by country 

[In millions of metric tons of phosphate rock] 

Country 1980 production Reserve base1 

U.S.A •••• •• 54.4 8,000 

U.S.S.R ••• • 26.1 6,300 

Morocco and Western Sahara. • .18.8 44,000 

China . 6.7 10,000 

Tunisia 4.6 500 

Jordan. 4.2 1,100 

South Africa . . . . . 3.3 700 

Togo •• . . . . . . . . . . 2.9 110 

Brazil . . . 2.9 800 

Israel. 2.6 150 

Nauru ••• . . . . . . 2.1 20 

Christmas Island. 1.7 62 

Senegal . . . . . . . . . . . 1.4 75 

Syria •• . . . . . . . . . . . 1.3 883 

Algeria 1.0 1,000 

North Korea. .5 90 

India •••• . . . . . . . . . .4 108 

Vietnam •• .4 100 

Mexico . . .3 1,034 

Zimbabwe .1 50 

Finland •••• . . . . . . . .1 565 

1Reserve base is phosphate rock in the ground that can be mined under 

existing economic conditions. Data from Stowasser ( 1981). 

7 
00 

Figure 4.--Import-export trade of phosphate rock. Trade routes are shown on map, and market shares of major 

exporters and major importers are shown ·in pie diagrams. Data from Stowasser ( 1979). 
PRESENT APPLICATION RATES LOW INCOME MIDDLE INCOME HIGH INCOME 

COUNTRIES COUNTRIES COUNTRIES Ill Application rates of phosphate fertil- ~ 

izer to arable land correlates with the per ~ 

capita gross national product (GNP) in many 

countries (fig. 5). The higher the per capita 

GNP, the larger the application per hectare 

of phosphorus pentoxide ( P 2o 5). One probable cause for this relation is the richer 

countries' ability to buy needed phosphate 

fertilizer. Another cause may be the 

dependence of the productivity of the agricultural sector of the economy on efficient 

agricultural technology and, by implication, 

effective fertilization programs. The resulting increase in productivity tends to 

raise the per capita GNP of a country. 

Phosphate fertilizer application rates, however, are only one part, although an essential part, of agricultural productivity. 

Other factors include application rates of 

other fertilizers, the type of crop and crop 

varieties raised, water availability, length 

of growing seasons, and agricultural technolo~y. 

If the relation between per capita 

GNP and P2o5 per hectare is examined in 

more detaif for the higher application rate 

countries, an interesting phenomenon surfaces (fig. 6). Geographically related 

groups of countries show unique ranges of 

these combined values. Most clear is the 

relation in the western Europe group (Belgium and Luxembourg, Switzerland, Netherlands, West Germany, and France), with 

high per capita GNP and high phosphate 

application rates. The poorer central and 

southern European countries (East 

Germany, Hungary, Poland, Bulgaria, 

Czechoslovakia, Romania, Italy, Greece, 

Spain, Portugal, and Yugoslavia) use less 

phosphate; this suggests that perhaps with 

more money they would consume more 

phosphate. Consumption of phosphate, 

however, is dictated by more than economic 

conditions. Climate, soil conditions, and 

different crops influence phosphate use. 

Because cold, temperate soils tend to have 

relatively high mineral contents, Scandinavian countries (Sweden, Norway, Denmark, 

and Finland) use less phosphate than do the 

western European countries just to the 

9 

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8 

.... 1000 c 

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~ 100 

c 

0 

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.... 

10 

.. 

100 

. . . . 

. . 

. . 

. . 

. . 

. 

. 

·. . 

.... 

1000 

.. ... . .... . . 

.. 

10,000 

1979 per capita GNP, in U.S. dollars 

Figure 5.--Phosphate fertilizer use on 

arable lands in relation to per capita 

gross national product. Data from Food 

and Agricultural Organization ( 1980) and 

World Bank ( 1980). Note logarithmic 

scale. 

south, although they have similar per capita 

GNP's. Soils in desert areas also have high 

mineral contents; therefore, in desert countries such as Australia, Libya, and Saudi 

Arabia, the rate or use of phosphate is relatively low, although these countries have 

few financial constraints. The United 

States, Canada, and the Soviet Union also 

use relatively small amounts of phosphate 

per hectare, possibly because of their wide 

variety of soils and climate. 
1500 

0 

.Q ! 1250 

«; 0 (.J 

:.= Cl 

~ 8 1000 co ,.... 

.... c 

.~ ·-- :="0 

~ ~ 750 ..... - Q)~ 

~~ 

~ ~ 500 

..c. co C.t) 

en OJ 

G; :: 250 ,.... Q) 

c. 

JAPAN 

• 

SCANDINAVIA 

U.S.A. 

• DESERT 

COUNTRIES 

0 2500 5000 7500 10,000 12,500 15,000 

1979 per capita GNP, in U.S. dollars 

WESTERN EUROPE 10. Bulgaria 18. Greece 

1. Switzerland 11. Romania 19. Yugoslavia 

2. West Germany 20. Portugal 

3. Benelux SCANDINAVIA 

4. Netherlands 12. Sweden OTHER 

5. France 13. Denmark 21. Israel 

14. Norway 22. Ireland 

CENTRAL EUROPE 15. Finland 

6. East Germany DESERT COUNTRIES 

7. Czechoslovakia SOUTHERN EUROPE 23. Australia 

8. Poland 16. Italy 24. Libya 

9. Hungary 17. Spain 25. Saudi Arabia 

Figure 6.-Phosphate fertilizer use on 

arable lands in relation to income and 

geographical area. Data from Food and 

Agricultural Organization ( 1980) and 

World Bank ( 1980). Note arithmetic 

scale. 

The countries that use Jess than 15 

kilograms of phosphate per hectare have a 

combined population of 2.75 billion people65 percent of the world's population (fig. 

7). These low-use countries are largely in 

the humid or arid tropics, where the soils 

not dedicated to plantation crops for export 

are too wet, too leached, too dry, or too 

salty to allow anything other than subsistence-level farming. The subsistence-level 

farmer generally does not grow sufficient 

cash crops to allow him to buy fertilizer. 

As a result, except for plantation farming, 

no significant economic demand for phosphate arises from these countries. 

NEED FOR PHOSPHATE FERTILIZER 

IN THE CARIBBEAN REGION 

Except for the mountainous areas, the 

Caribbean region has low-latitude, humid or 

wet-and-dry climates and low agricultural 

productivity. Production of cereal, sugarcane, and paddy rice in the Caribbean 

region and, for comparison, production of 

the same crops in Asia, Africa, South 

America, Europe, the United States, and 

Japan are shown in table 2. The productivity of arable land for any given crop varies 

according to many factors, only one of 

which is soil fertility. The latitude factor, 

which influences the length of the day during the growing season, is fundamental (fig. 

8 and table 2). In the humid tropics, however, year long multiple cropping is possible 

and can overcome the latitude factor if satisfactory agricultural technology is used. 

Soil studies at the School of Tropical 

Agriculture of the University of Hawaii 

show that soils of humid and wet-and-dry 

tropical climates are broken down by leaching and oxidation to form low-productivity 

soils called uitisols and oxisols (Fox and 

Yost, 1980; Uehara, 1980). As a result of 

this leaching and oxidation process, the fixation of phosphorous in the soil is greatly 

increased because phosphate from fertilizer 

is absorbed or fixed by the degraded clay 

minerals of the soil and is not available as 

plant nutrient. Sanchez and others ( 1982) 

of the Department of Soil Science, North 

Carolina State University, studied the soils 

of the Amazon Basin and found that 75 percent of the soils are acidic, infertile oxisols 

and ultisois, 90 percent are phosphorous 

deficient, and 16 percent have a high phosphorus fixation. 

Fox and Yost ( 1980) calculated that 

540 million metric tons of P2o5, the equivalent of about 1.7 billion metric tons of 

high-grade phosphate rock, would have to 

be added to the currently cui tivated soils of 

the world (mostly in the tropical regions) to 

bring the soils up to a moderate level of 

fertility. Thereafter, the fertility level 

could be maintained with annual applications of 20 million metric tons of P2o5, or 

about half of the 1980 world consumption. 

10 
--

Figure 7.-Countries of the world with application rates of less than 1' kilograms of P2o, per hectare of arable land. 

Data from Food and Agricultural Organization ( 1980). 
Table 2.-1981-82 grain production in Caribbean Basin countries and other 

countries and regions 

[Production figures in kilograms per hectare. Data from Food and 

Agricultural Organization ( 1982a)] 

Country Cereals Sugarcane Paddy rice 

Belize •••••••••••••••••• 2,01.5 

Costa Rica ••••••••••••••• 2,250 

Cuba •••••••••••••••••• 2,.531 

Dominican Republic •••••••• 3,.559 

EI Salvador •••••••••••••• 1,713 

Guatemala ••••••••••••••• 1,395 

Haiti • • • • • • • • • • • • • • • • • • • 902 

Honduras •••••••••••••••• 1,107 

Jamaica ••••••••••••••••• 1,633 

Nicaragua ••••••••••••••• 1,414 

Panama ••••••••••••••••• 1 ,291 

Asia •••••••••••••••••• 2,199 

Africa • • • • • • • • • • • • • • • • • • 970 

South America • • • • • • • • • • • • 1, 906 

Europe • • • • • • • • • • • • • • • • • • 3, 796 

U.S.A ••••••••••••••••••• 4,409 

Japan •••••••••••••••••• 5,308 

Amazon Basin •••••••••••• 7,800 

12 

37,096 

49,020 

48,387 

56,084 

76,014 

76,398 

37,.500 

33,684 

.52,858 

76,923 

.54,902 

.54,707 

71,499 

60,.594 

62,407 

88,.595 

63,333 

2,364 

2,.571 

3,200 

3,840 

3,166 

3,200 

2,100 

1,9.57 

2,000 

3,191 

1,667 

2,923 

1,752 

2,022 

4,928 

5,315 

.5,688 
The field studies of Sanchez and 

others ( 1982) in the Amazon Basin region of 

Yurimaguas, Peru, showed that an annual 

application of 172 kilograms of P 2o 5 per 

hectare to fields of a test project of continuous cropping allowed annual yields of 7.8 

metric tons of grain (rice, corn, soybeans, 

and peanuts) per hectare (table 2). Applications of lime, nitrogen, potassium, magnesium, and trace metals also were required. 

These tests were carried out over 9 years 

on 3 fields with 88 harvests; however, the 

yield from test plots in agricultural experiments are generally higher than those of 

farmer-operated fields. To evaluate this 

factor, eight farmers of the region planted 

three crop rotations on a number of demonstration plots and increased their yields sixto tenfold over slash and burn agricultural 

yields. The economic analysis by Sanchez 

and others ( 1982) shows that continuous 

cropping technology is viable over a wide 

range of crop and fertilizer prices, capital 

levels, and labor force composition. 

Sanchez and others carefully state 

* * *It would be unwise to assume that 

continuous cultivation technology is 

directly applicable to the millions of 

hectares of ul tisols and oxisols in the 

humid tropics. Our work has concentrated on nearly level soils, thereby 

avoiding the erosion hazard of cultivating sloping lands. Landscape adaptations, including terracing such as is 

practiced in parts of humid tropical 

Asia, would be needed for continuous 

cui tivation on sloping lands. 

Sanchez and others ( 1982) also point out 

that weed, insect, and disease attacks are 

likely to increase above the levels reached 

in their 9-year study. Also, variability in 

socioeconomic conditions is a limitation. 

Finally, they believe that the new technology must be tested locally to determine any 

necessary modifications. 

Despite the early stage of development of the continuous cropping technology, appropriate variations adapted to local 

conditions clearly can have a major impact 

on tropical agricultural productivity. If the 

8 

Q) 

s 6 (.) 

Q) 

£. 

(i) 

a. 

(/) 

c 

9 

-~ 4 

2 • 

• 

• 

o~------~------~~------~-----

0 10 20 30 

Latitude, in degrees N. 

Figure 8.--Relation between rice yields of 

the INPUTS (Increased Production Under 

Tight Supplies) experimental sites and 

latitude. From Uehara ( 1979). 

area presently under cereal cui tivation in 

the Caribbean region were farmed under 

the new continuous cropping technology and 

yielded only 5 metric tons of cereal per 

hectare (instead of the 7.8 metric tons in 

the experiment), the region's cereal production would more than double (table 3 ). 

Applying this technology to agricultural production in the Caribbean region at 

present unsubsidized, free-market prices 

for phosphate fertilizer (about $650 per 

metric ton of Pto5 in 1980) would cost 

about $978 mill1on per year (table 4). The 

total cost of the technology also will include expenditures for other inputs. The 

value added of the projected additional 8.6 

million metric tons of cereals produced 

(table 3) (not including increased production 

of other crops), at $350 per metric ton, 

would be more than $3 billion. These figures are based on current international 

prices and, as such, are unrealistic in that 

13 
Table .3.-1982 cereal production statistics and projected cereal production 

statistics for new agricultural technology in the Caribbean Basin countries 

[Data from Food and Agricultural Organization ( 1982a)] 

Country 

1982 

yield, 

in kg/ha 

Belize ••••••••• 2,01.5 

Cuba •••••••••• 2,.5.31 

Dominican 

Republic •••••• .3,559 

El Salvador •••• 1,71.3 

Guatemala •••••• 1,.395 

Haiti ••••••••••• 902 

Honduras ••••••• 1,107 

Jamaica •••••••• 1,6.3.3 

Nicaragua •••••• 1,414 

Panama •••••••• 1,291 

Total •••••• 19,810 

1982 

production, 

in 1,000 t 

29 

577 

484 

651 

1,.397 

415 

466 

8 

499 

21.3 

7,89.3 

Value,1 

in million 

dollars 

10 

202 

170 

228 

489 

145 

16.3 

.3 

175 

75 

2,764 

Projected 

production, 

in 1,000 t 

70 

1,140 

680 

1,900 

5,00.5 

2,.300 

2,10.5 

2.5 

1,765 

825 

16,515 

Value, 

in million 

dollars 

~4 

.399 

2.38 

66.5 

1,751 

80.5 

7.37 

9 

618 

289 

.5,780· 

1cereal average value taken as $.350 per metric ton. 

great increases of cereal supply inevitably 

would affect the world market price of 

cereals. Despite this effect, the new cropping technology could greatly increase agricultural supply at cost-benefit ratios that 

would support use of the technology. 

Annual application of 172 kilograms of phosphate per hectare, as used in the Sanchez 

field test, is 5 to 10 times the application 

rates in countries of the Caribbean region 

but only slightly higher than the 1979 P 2o 5 application rate of Japan (table 4). 

Such application rates require large 

amounts of phosphate. For example, the 

rate of yearly application of 172 kilograms 

of phosphate per hectare to all of the 

arable land in the Caribbean region ( 9.7 

million hectares as of 1982) would require 

14 
-\.11 

Table 4.-1982 phosphate fertilizer consumption in the Caribbean Basin countries, Amazon Basin, 

and Japan and projected consumption and cost for new agricultural technology in the 

Caribbean Basin countries 

Country 

Arable land, 

in 1,000 ha 

Belize ••••••••••••• lf.6 

Costa Rica. • • • • • • • • 283 

Cuba •••••••••••• 2,.53.5 

Dominican 

Republic • • • • • • • • • 88.5 

El Salvador • • • • • • • • .560 

Guatemala •••••••• 1,48.5 

Haiti ••••••••••••• .548 

Honduras • • • • • • • • • 1 ,.563 

Jamaica. • • • • • • • • • • 20.5 

Nicaragua •••••••• 1,08.5 

Panama ••••••••••• lf.62 

Amazon Basin 

experiment • • • • • • • • -

Japan ( 1979). • • • • • • • • -

Total ••••••••• 9,6.57 

[Data from Food and Agricultural Organization ( 1982b)] 

1982 P 2o .5 consumption 

per 1,000 ha of 

arable land, 

in kg/ha 

12.0 

42.4 

31.6 

12.1f. 

3.5.9 

18.7 

2.6 

2.7 

14.2 

6.9 

13.6 

171.8 

169.0 

.533.1 

1982 P2o, 

consumption, 

in 1,000 t 

0 • .5.56 

1.200 

8.010 

11.000 

20.086 

27.800 

1.400 

•• 200 

2.910 

7 • .500 

6.300 

90.962 

Projected P2o, 

requirements, 

in 1,000 t 

a 

49 

436 

1.52 

96 

22.5 

94 

269 

32 

187 

79 

1,627 

Projected P~o, cost 

at $6.5 It, 

in millions 

of dollars 

32 ' 

283 

99 

62 

146 

61 

17.5 

21 

121 

.51 

1.01f. billion 
1.63 million metric tons P2o5 per year at a 

cost of $1.06 billion, assuming a price of 

$650 per metric ton of P 20 5 (table 4 ). 

In summary, if the agricultural potential of the Caribbean region is to be realized, substantial amounts of phosphate fertilizer will be needed, along with other fertilizers and soil amendments. The value of 

the increase in agricultural products is expected to readily exceed the cost of phosphate fertilizer and other agricultural 

inputs. 

ECONOMIC IMPLICATIONS OF PHOSPHATE 

ROCK RESOURCE DEVELOPMENT 

The successful development of minable phosphate rock deposits could impact 

the economies of the Caribbean countries in 

four ways: ( 1) Foreign exchange earnings 

could be increased by the export of either 

raw phosphate rock or manufactured phosphate fertilizer. (2) Domestically produced 

phosphate rock could be a direct substitute 

for current phosphate rock imports into the 

region. ( 3) Application of optimal quantities of phosphate fertilizer to lands used for 

production of export crops could result in 

greater agricultural exports and higher foreign exchange earnings. ( 4) Application of 

phosphate to lands used for production of 

food crops for domestic consumption could 

increase the domestic supply of food crops 

for the region and reduce food imports into 

the region. These possible impacts are discussed below. 

PHOSPHATE EXPORTATION 

The discovery and development in the 

Caribbean Basin of a large phosphate rock 

deposit that could be mined and beneficiated competitively with the deposits of the 

southeastern United States would allow 

entry of the Caribbean Basin countries into 

the international phosphate market. Such a 

discovery, however, is unlikely. 

The deposits of Florida and North 

Carolina are large, uniform, flat lying, and 

16 

close to the surface, all of which allow intensive surface mining by large pieces of 

equipment at low cost. The deposits are 

beneficiated easily and provide a high--

grade, high-quality concentrate. Because 

the deposits are close to ports, transportation costs are low. These deposits are 

nearly unique, matched only by the deposits 

of Morocco. As a result of these deposits, 

the United States and Morocco set the 

competitive price floor for the world phosphate rock market. These two countries 

supply over 60 percent of the world's phosphate exports. 

AI though unlike I y, another such deposit may exist in the Caribbean region. If 

such a deposit were found, it would have to 

compete in the same local market area as 

the southeastern United States deposits. 

Although the discovery of a world-class deposit in the Caribbean region is remote, the 

chance of such a discovery should not be 

totally discounted. 

SUBSTITUTION FOR PHOSPHATE IMPORTS 

In 1982, imports of phosphate rock to 

the Caribbean Basin countries amounted to 

90,000 metric tons of P205 in the form of 

phosphorus fertilizer.. The total value was 

about $60 million. The resulting trade deficit could be avoided by substituting domestically produced phosphorus fertilizer for 

that now imported. Savings could be large 

and would be determined largely by the increase in phosphorus fertilizer use, as well 

as by future energy prices. For example, 

transportation costs, which are a part of 

the import cost of phosphate rock, are sensitive to bunker fuel costs. Also, a significant percentage of mining and processing 

costs is sensitive to energy costs. Thus, the 

future prices of imported phosphorus fertilizer will increase as energy costs increase, 

and the savings created by substituting domestic phosphorus fertilizer for imported 

fertilizer products will increase accordingly. 
AGRICULTURAL PRODUCT EXPORTATION 

The economies of the tropical countries of the Caribbean region rely substantially, if not primarily, on the export of 

cereals, sugar, coffee, tea, cocoa, fruits, 

and other agricultural products. The field 

studies of Sanchez and others ( 1982) (see p. 

13) demonstrated that an annual application 

of phosphate fertilizer to fields increased 

agricultural productivity in a continuous 

cropping test project in Peru. Despite the 

early stage of development of this technique, appropriate variations adapted to 

local conditions clearly can have a positive 

impact on tropical agriculture. Applying 

phosphate fertilizer to lands used for production of export crops, along with other 

soil amendments, can result in increased 

agricultural exports and higher foreign exchange earnings. 

INCREASED FOOD PRODUCTION 

Finally, applying phosphate to agricultural land would increase production of food 

crops for domestic consumption. Because 

of anticipated population growth, additional 

food supplies must be produced to avoid a 

decrease of food supplies for per capita 

consumption. Food shortages can be prevented by an increased application of phosphorus and other fertilizers to the lands 

currently used for production of food crops 

and by the adoption of new agricultural 

technologies to improve and sustain the soil 

fertility. If domestic food production is not 

increased, food imports must increase--with 

a resulting increase in trade deficits. 

BENEFITS OF SUCCESSFUL DEVELOPMENT OF 

PHOSPHATE ROCK RESOURCES 

In summary, the implication of successful development of phosphate rock 

resources in the Caribbean region is an 

improved foreign exchange position for the 

countries of the region because of foreign 

exchange earnings from exports and savings 

from import substitution. The availability 

of Caribbean-region-produced phosphorus 

fertilizer would facilitate adopting new 

agricultural techniques for tropical soils 

and result in new lands being brought into 

productive cultivation. An additional benefit of a new phosphorus fertilizer industry 

would be the creation of jobs in the mining, 

chemical, and transportation sectors associated with the industry. 

UNDISCOVERED PHOSPHATE ROCK RESOURCE 

POTENTIAL OF THE CARIBBEAN REGION 

The undiscovered phosphate rock resource potential of the Caribbean region 

has never been assessed systematically. As 

a result, areas for prospecting cannot be 

targeted systematically, and the resource 

potential cannot be estimated. Indications 

are, however, that a considerable potential 

exists in the Caribbean region. 

COMPARATIVE ANALYSIS OF THE PHOSPHATE 

RESOURCE POTENTIAL OF THE TROPICS 

The humid tropical areas of the world 

constitute 22 percent of the total land area, 

yet they contain only 2 percent of the presently known phosphate rock reserve base 

(shown by country in table 1 ). The combined cold, temperate, and arid climate 

regions of the world have a phosphate rock 

reserve base of about 7 metric tons per 

hectare, whereas the humid tropics contain 

only 0.4 metric tons per hectare. If the 

tropical regions had the same phosphaterock-per-hectare reserve base as the rest of 

the world has, the tropics would contain 

about 20 billion tons, rather than the present estimate of 1.25 billion tons, of phosphate rock reserve base. Even this estimate is inaccurate, however, because the 

reserve base of countries now producing 

phosphate rock excludes many of the 

world's known phosphate deposits that are 

not currently being mined but have commercial potential. 

17 
Another factor contributing to the 

underestimate of phosphate resources by 

the reserve base comparison is that many of 

the present commercial deposits are not 

well defined, and reserve base estimates 

predicted on these deposits commonly represent minimum estimates. Even more 

important, these estimates exclude undiscovered phosphate rock deposits. For 

example, recent estimates of the identified 

recoverable phosphate rock resources of the 

United States are placed at 45 billion 

metric tons (Cathcart, Sheldon, and 

Gulbrandsen, in press). The undiscovered 

phosphate rock resources of the United 

States are estimated to be an additional 13 

billion tons. Thus, the total resource is 

estimated as 58 billion tons. Earlier estimates had prospected only 8 biJlion tons of 

reserve base for the United States (see 

table 1). 

FinaJly, the area used in the calculation of reserve base for areas of the world 

other than the humid tropics includes much 

cold-climate land that has not been prospected for phosphate rock. Thus, we consider the 7 metric tons of phosphate rock 

per hectare figure used as a basis for comparison with the humid tropics to be too 

low. 

Despite its limitations, this type of 

comparative analysis can be used with some 

degree of validity for very large regions of 

the world. When large areas are considered, their geologic histories can be assumed to have been comparable. As a 

result, their average mineral contents can 

be assumed to be comparable. In general, 

the geologic history of the tropics does not 

seem to differ greatly from that of the rest 

of the world. The primary reason for this 

similarity is the movement of the continental masses over the globe throughout 

geologic time. In the past, continental 

areas that are now in the tropics were in 

other climate zones, and present nontropical areas have at times been in the tropics. Consequently, the distribution of different rock types is not geologically biased 

by the present climate areas of the world. 

A bias does exist, however, between 

the humid tropics and the rest of the world 

for the amount of rock outcrop. The presence of dense tropical forests and thick soil 

cover over deeply weathered rocks makes 

direct observation of underlying fresh rocks 

very difficult, particularly for the more 

soluble rocks such as phosphate rock and 

carbonate rock. Alirio Bellizzia, SecretaryGeneral of the Association of Geoscientists 

for International Development, in 1977 

wrote in the foreword to "Hidden Wealth: 

Mineral Exploration Techniques in Tropical 

Forest Areas" (Laming and Gibbs, 1982): 

The vast areas of the world covered 

by tropical rain forests, consisting 

largely of Precambrian rocks, include 

geological environments whose mineral and energy potential is very great; 

but, due to cJimatic and geographic 

conditions, most of the countries 

which form part of this belt are not 

capable of undertaking discovery of 

these resources utilizing modern 

methods. Modern exploration techniques have largely been developed in 

temperate regions and these, especially geochemical and geophysical 

techniques, which can give excellent 

results in temperate areas, present 

problems of application and interpretation when used in tropical rain forests. 

In the same book, Vicente Mendoza (p. 6) 

summarized technical papers presented on 

the topic "Mineral Exploration Strategies in 

Tropical Forest Areas," as follows: 

18 

Faced with an area covered with tropical rain forest, the exploration geologist requires a coherent exploration 

strategy, more than in any other type 

of terrain. The difficulties, both the 

obvious ones and those revealed only 

by experience, make such exploration 

more expensive and less fruitful. 

However, we must suppose that the 

rocks beneath tropical forests are as 
well mineralized as comparable geological terrains that are well exposed. The problems of exploration in 

the jungle cannot be solved by reading 

books or using powerful geophysical 

formulae: The practical experience of 

geologists long familiar with the terrain must be combined with appropriate technical methods in an exploration strategy, a properly managed 

sequence of operations, if an efficient 

and effective mineral search is to be 

undertaken. 

The lack of rock outcrops in the humid 

tropics probably is the controlling factor in 

the scarcity of known phosphate rock de-

'losits. Phosphate rock deposits in the 

tropics are covered and therefore difficult 

to find and so have not been efficiently and 

~ffectively prospected. 

The present-day approach to assessing 

the phosphate rock resource potential of 

the Caribbean region is to apply knowledge 

of the origin of marine phosphorite to 

Caribbean geology and then determine 

whether reason to suspect the occurrence 

of undiscovered phosphate rock deposits 

exists. When such an assessment is made 

for the Caribbean tropics, reason to suspect 

undiscovered phosphate deposits clearly 

exists. Exploration for suspected phosphate 

deposits must take into account both the 

area's complex geology and the deep soil 

weathering, and prospecting strategies used 

must be both cost and production effective. 

ORIGIN OF MARINE PHOSPHATE ROCK 

Marine phosphorite is formed within 

narrowly defined environments. Its formation requires phosphorus deposition in 

shallow water (Burnett, 1980; Sheldon, 

1981). Second, the deposition must take 

place at low latitudes where the shallow 

seas are warm enough to provide a physicalchemical environment in which phosphorite 

can form (Sheldon, 1964; Cook and 

McElhinny, 1979). Deposition of phosphorus 

is theorized to occur by upwelling of phosphorus-rich deep-ocean waters onto shallow 

continental shelf areas that causes high surface-water productivity and subsequent 

settling of phosphorus-bearing oceanic plant 

and animal remains on the shallow ocean 

floor. 

The formation of large phosphorite 

deposits has not been continuous over geologic time but has occurred at 11 different 

intervals (fig. 9). During each of these 

intervals, deposits were formed in shallow 

seas at low latitudes in many sites around 

the world. At times other than these 11 

intervals, deposition was limited, rare, or 

nonexistent. AI though the phosphorite 

formed during these 11 intervals is similar, 

the global distribution is not similar, and 

two major families of phosphorite deposits 

can be discerned (Sheldon, 1980, 1982) (figs. 

2 and 9). The first occurs along the western 

coasts of the continents on shallow marine 

shelves in the trade wind belt zone, where 

deeper phosphate-rich ocean water is 

brought to the surface by upwelling currents. The best understood example of this 

family is the young deposits that are about 

5 to 15 million years old (of Neogene age; 

fig. 9). This type of phosphorite deposition 

is ongoing, although the amount of phosphorite being deposited is very small 

( Baturin, 1982). This and other examples of 

the family are indicated by the notation 

"TW" (for trade wind) in figure 9. The 

second family of phosphate rock deposits is 

distributed around the ancient shallow seas 

of the Earth in a circumglobal, low latitude 

belt centered around the equator and in 

figure 9 is noted "E" (for equatorial). The 

oceanographic conditions that cause the 

formation of deposits of the equatorial 

family are not well understood and continue 

to be the subject of discussion and research, 

but the existence of the family is clear. 

GEOLOGY OF THE CARIBBEAN REGION 

The continents have been in constant 

motion over the Earth through geologic 

time, due to the process of plate tectonics. As the result of this movement, 

ancient continental shelf areas are now 

19 
0 

MILLIONS PHOSPHATE DEPOSITION OF YEARS GEOLOGIC AGE EXAMPLES BEFORE EPISODE FAMILY PRESENT 

NEOGENE ~ TW U.S. (Southeast), Mexico, Peru 

t--24 

PALEOGENE t0 

1---65 t://; E North Africa, Middle East, Senegal, 

~ Togo, Colombia, Venezuela 

- CRETACEOUS 100 

~140 

~ TW Mexico 

JURASSIC 

200 -~200 ~ TW Peru 

TRIASSIC 

f----250 

PERMIAN ~ TW U.S. (Rocky Mountains) 

~290 

300 -

CARBONIFEROUS 

f---365 17/?1 TW U.S. (Rocky Mountains) 

DEVONIAN 

-,____405 

SILURIAN 

400 

f---425 

~ TW U.S. (Tennessee), Australia 

ORDOVICIAN 

-f---500 ~ E? India (Mussoorie), U.S.S.R. 

"'""""" (Baltic Basin) 500 

CAMBRIAN 

~ Australia, Benin, China, India, 

f---570 '/ Mongolia, U.S.S.R. (Siberia 

~ E and Kazakhstan), Vietnam 

- ~ ~ ~ 

~ 

600 

LATE 

PROTEROZOIC 

700 -

~ ' E 

' 

Figure 9.--Geologic episodes of pho~phate rock deposition. An additional episode of 

phosphate rock deposition occurred in the Middle Proterozoic but is not shown. TW, 

trade wind family; E, equatorial family. 

20 
found at latitudes different from those at 

which they formed. Also, because plate 

tectonic processes have both split ancient 

continents into pieces and welded the 

pieces together in different combinations to 

form new continents, ancient continental 

shelves commonly are found in the middle 

of the present continents (for example, the 

Mongolian and Siberian Continental Shelf 

phosphorites of Precambrian age in cent~al 

Asia). These processes make understanding 

the Caribbean region's geologic history 

quite difficult (Case and Holcombe, 1980). 

For land areas that have been formed 

by the welding together of pieces of ancient 

continents, unraveling geologic history is 

especially difficult because the rocks tend 

to be deformed and metamorphosed by the 

welding process and because volcanoes are 

common in such areas. Another complicating factor is that continental shelves ten~ 

to be short lived in areas where such active 

plate tectonic processes are ongoing. Although the geologic environments of such 

areas may not appear favorable for the 

formation of phosphorites because of deposition of volcanic rocks and the short life of 

continental shelves, many important phosphate deposits of the world have formed in 

this environment. Areas of major deposits 

include northwestern South America, western North America, Turkey and Iran, and 

Kazakhstan, Siberia, and Mongolia. 

PHOSPHATE RESOURCE POTENTIAL OF THE 

CARIBBEAN REGION 

Two major phosphate rock provinces 

occur in the Caribbean region, one of Miocene age and the other of Late Cretaceous 

age. Both provinces are being mined, and 

the Miocene phosphate deposits of the 

southeastern United States are a major 

world source of phosphate rock. Neither of 

these provinces has been explored to its 

original sedimentary edges. 

The Miocene phosphate province in 

the southeastern United States was the subject of much research during the early 20th 

century; recent research by S.R. Riggs and 

his colleagues in North Carolina has greatly 

advanced the understanding ?f the origin of 

the area's phosphate rock (Riggs, 1984). 

The Caribbean region also contains 

Miocene deposits. A Miocene phosphate 

deposit occurs in Cuba (Pokrishkin, 1967). 

On Mona Island, between Puerto Rico and 

the Dominican Republic, a Miocene-Pliocene phosphate rock, which possibly is a 

marine phosphorite, occurs above an unconformity (Kaye, 1959). A Miocene phosphate 

deposit, which has been in part altered, 

exists in Falcon State in northern Venezuela 

(Rodriguez, 1984). These deposits indicate 

that the Miocene age province extends over 

the eastern Caribbean region. Phosphorite 

sedimentation in this province was controlled by the ancestral Gulf Stream (Riggs, 

1984 ), which flowed from south to north 

from the northeastern South American Continental Shelf, through the Caribbean Sea, 

and along the eastern U.S. Continental 

Shelf. Many parts of the province have not 

been explored for phosphate, particularly 

the larger Caribbean islands and the eastern 

parts of Central America and northern 

South America. Miocene rocks have been 

mapped on the coastal plains of Puerto 

Rico, the Dominican Republic, Haiti, 

Jamaica, Venezuela, and the eastern Continental Shelves of Central American countries. Miocene marine sediments probably 

occur extensively offshore of these areas 

and possibly are phosphatic. 

The second province is made up of 

late Cretaceous age phosphorites of Venezuela, Colombia, and Ecuador. A recently 

discovered potentially minable phosphate 

deposit in Tachira, Venezuela (Rodriguez, 

1984 ), enhances the potential of this province. The resource potential of the area is 

already being exploited on a small scale in 

Colombia (Cathcart and Zambrano, 1967). 

The Cretaceous phosphorite beds occur in 

cyclic, laminated sequences deposited on 

the northern Continental Shelf of South 

America. Much postdepositional tectonic 

movement has disturbed these phosphate 

rock beds, so that exploration and exploitation are difficult, but the potential of the 

deposits is significant. Other Continental 

21 
Shelf areas of the Caribbean region, some 

of which were rifted off the South American craton and now form parts of the 

Caribbean islands, also may contain phosphate deposits. Descriptions of the Late 

Cretaceous age rocks of these areas indicate that sedimentary environments possibly suitable for phosphorite deposition occurred. 

The extension of the Late Cretaceous 

age episode of phosphate sedimentation into 

early Tertiary time in other parts of the 

world, particularly North Africa and the 

Middle East, suggests that rocks of these 

ages in the Caribbean region may be prospective. Geologic mapping of the Caribbean region has shown that Upper Cretaceous and early Tertiary age rocks are 

widespread in both the Caribbean island 

countries and Central American countries. 

In general, this region has been underexplored for phosphate deposits. Modern 

geologic knowledge and tools should be 

applied to further investigate possible extensions of the known phosphate provinces 

of the region. 

DISCOVERY AND DEVELOPMENT PROGRAM 

FOR UNDISCOVERED PHOSPHATE ROCK 

RESOURCES OF THE CARIBBEAN REGION 

Discovery and development of undiscovered resources of phosphate rock will 

require two main programs, a prefeasibility 

program and a feasibility program. The objective of the prefeasibility program is to 

discover phosphate rock deposits and measure the inferred reserve base; the feasibility program assesses the possibility of economically producing the phosphate rock. 

The relation of these two programs is shown 

in table 5, and the definitions of phosphate 

resource terms are given in the Glossary (p. 

24). 

The prefeasibility project consists of 

two phases. The first is a reconnaissance 

study. Previously collected data on the 

geologic structur:e and distribution of rock 

types are assembled by the project team 

from libraries and government files and 

analyzed with respect to the geology of 

phosphate rock. On the basis of this analysis, a field reconnaissance project is 

planned and carried out by geologists in 

each country, guided by phosphate resource 

specialists. This reconnaissance includes 

examination of outcrops and soil geochemical sampling. Resource assessment reports 

are prepared jointly by the resource specialists and the geologists of each country. 

Target areas that may contain phosphate 

deposits are identified by additional reconnaissance geologic mapping and by stratigraphic studies to determine the areal distribution and depth of potential phosphatebearing rocks and their relations to surrounding rocks. 

The second phase of a prefeasibili ty 

program is initiated when positive results of 

the reconnaissance phase are obtained. 

This phase consists of prospecting by reconnaissance core drilling and estimating the 

inferred reserve base by detailed core drilling to collect samples of phosphate rock to 

measure its thickness, quality, depth, and 

lateral extent. This part of the program is 

undertaken by geologists of each country 

under the guidance of phosphate resource 

specialists. 

If a significant inferred reserve base 

of phosphate rock is established, bulk samples are collected for chemical and mineralogical analysis to determine the quality of 

the rocks for making phosphate fertilizer. 

A study of the rocks to establish appropriate mineral technology is necessary. 

This study ends the prefeasibility phase. 

At this point, the feasibility program 

begins. The phosphate inferred reserve 

base of the participating countries of the 

Caribbean region is established, and studies 

initiated to establish the feasibility of economic development. The studies should 

include a detailed analysis of mining and 

beneficiation of the most promising phosphate rock deposits and should require the 

delineation of demonstrated reserves. 

Phosphate fertilizer manufacture and 

market studies also must be designed, and 

corresponding cost analyses performed. 

22 
Table 5.--Programs for developing a phosphate rock mining and 

phosphate fertilizer production indt~stry 

Prefeasibility program 

First phase--Reconnaissance study 

A. Collection and review of available data relevant to geologic 

environment of phosphate rock. Identification of target areas. 

B. Field reconnaissance. Evaluation of target areas. 

Second phase-Discovery 

A. Prospecting by core drilling. 

B. Measurement of inferred reserves of phosphate rock by development 

core drilling. 

Feasibility program 

A. Design and cost analysis of mining and beneficiation of phosphate 

rock deposit. 

B. Design and cost analysis of phosphate fertilizer manufacture. 

COST OF A PHOSPHATE RESOURCE 

DEVELOPMENT PROGRAM 

Whether a country should invest 

money in the high-risk venture of mineral 

exploration depends on the cost of the program weighed against the value of the resource gained if the venture is successful. 

To take geologic uncertainty and cost into 

account, the development program can be 

designed in steps that start as low cost-high 

risk and escalate at each stage in cost but 

decrease in risk. The risk of economic loss 

is thereby reduced in each step. 

23 

The first phase, the identification of 

target areas, has a low geologic certainty 

but is quite inexpensive because it consists 

of a phosphate resource assessment that 

lasts only a few months and primarily uses 

data already collected. The cost is projected to be less than $100,000 for each 

country. The more expensive field reconnaissance phase should be undertaken only 

if the results of the target area identification are encouraging. The field reconnaissance to evaluate target areas should 

include established geochemical prospecting 

techniques, stratigraphic studies of sedimentary rocks, and geologic structural 
studies. The program would cost between 

$0.5 million and S1 million (U.S.) and last 1 

to 3 years. Most of the work would be carried on by geologists of each country. 

Phosphate rock deposits may be discovered 

in the field reconnaissance phase, but, because of the deep weathering of rocks and 

dense vegetation cover, probably only 

promising areas would be located. 

If field reconnaissance shows that one 

or more of the target areas is highly promising, the second phase, prospecting by core 

drilling and hand and bulldozer trenching, is 

started. This discovery phase would cost $1 

million to $4 million per country and last 2 

or 3 years. The goal of this phase of exploration is the discovery of phosphate deposits. Development exploration, to delineate 

the deposit after discovery by core drilling 

and trenching, would cost $4 million to $8 

million and should define inferred reserves 

of phosphate rock in terms of quality, quantity, and minability. 

At the conclusion of the second phase 

of the prefeasibility program, the feasibility studies begin. Each country should be 

able to complete a successful program of 

discov~ry and prefeasibility development of 

phosphate resources in 5 years at a cost of 

less than $15 million. Because of the 

staged approach, less than $2 million of this 

total would be at high economic risk, with 

subsequent expenditures at decreasing economic risk. 

GLOSSARY OF PHOSPHATE RESOURCE TERMS 

Taken from the sedimentary resource 

classification system of the U.S. Bureau of 

Mines and the U.S. Geological Survey (U.S. 

Geological Survey, 1982). 

Identified resources. Phosphate resources 

whose location, grade, quality, and quantity 

are known or estimated from specific geologic evidence. To reflect varying degrees 

of geologic certainty, identified phosphate 

resources can be subdivided into demonstrated and inferred resources. 

Demonstrated resources. A term for the 

sum of measured plus indicated resources. 

24 

Measured resources. Quantity is computed 

from dimensions revealed by outcrops, trenches, workings, or drill holes; grade and (or) 

quality are computed from the results of 

detailed sampling. The sites for inspection, 

sampling, and measurement are spaced so 

closely and the geologic character is so well 

defined that size, shape, depth, and phosphate content of the resource are well 

established. 

Indicated resources. Quantity and grade 

and (or) quality are computed from information similar to that used for measured 

resources, but the sites for inspection, 

sampling, and measurement are farther 

apart or are otherwise less usefully 

spaced. The degree of assurance, although 

lower than that for measured resources, is 

high enough to assume continuity between 

points of observation. 

Inferred resources. Estimates are based on 

an assumed continuity beyond measured and 

(or) indicated resources for which there is 

geologic evidence. Inferred resources may 

or may not be supported by samples or 

measurements. 

Undiscovered resources. Phosphate resources whose existence is only postulated. 

Economic resources. Those phosphate resources for which profitable extraction or 

production under defined investment 

assumptions has been established, analytically demonstrated, or assumed with reasonable certainty. Economic resources 

include reserves, inferred reserves, and 

economic undiscovered resources. 

Reserves. That part of the demonstrated 

resources that can be economically extracted or produced at the time of determination. Reserves include only recoverable materials. 

Inferred reserves. That part of the inferred 

resources that can be economically extracted or produced at the time of determination; otherwise similar to phosphate 

reserves. 
Marginally economic resources. Those 

phosphate resources that, at the time of 

determination, border on being economically producible. Their essential characteristic is economic uncertainty. 

Reserve base. That part of an identified 

phosphate resource that meets specified 

minimum physical and chemical criteria 

related to current mining and production 

practices, including those for grade, quality, thickness, and depth. The reserve base 

is the in-place demonstrated (measured plus 

indicated) resource from which reserves are 

estimated. 

Inferred reserve base. The in-place part of 

an identified resource from which inferred 

reserves are estimated. 

Subeconomic resources. That part of identified resources that does not meet the 

economic criteria of reserves and marginal 

reserves. 

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26 

*U.S. GOVERNMENT PRINTING OFFICE: 1985-491-405:20060