Transcript A BRIEF REVIEW OF INDUSTRIAL MINERAL OF DJIBOUTI REPUBLIC
REPUBLIC OF DJIBOUTI
MINISTRY OF ENERGY,IN CHARGE OF NATURAL RESOURCES Presented By ABDOURAHMAN OMAR HAGA PRESENTED BY ABDOURAHMAN OMAR HAGA
Djibouti
A) INTRODUCTION
Industrial minerals mean any rock or mineral of economic value excluding hydrocarbons and metallic ores. In fact, almost any naturally occurring mineral substance which can be used for the need of industry, whether large scale, small scale or artisanal is considered as industrial mineral.
The Djiboutian economy is mainly based on the tertiary sector. The service sector exceeds the industrial, the agricultural and mining sectors.
The agriculture is mainly subsistence farming with some large farms where products are sold at Djibouti town.
The industrial sector is dominated by small scale manufacturing (water, beverage and other consumable product.
The mining sector is represented by: - Salt extraction - Brick manufacturing - Sand, gravel exploitation - Crushed stone (basalt), cutted stone for building, .
The inventory of industrial minerals was not done properly during the geological mapping of the country (1982 to 1996).
But with the several scientific research publications done by local and foreign scientists, it is possible to give a brief and generalized overview of industrial minerals of Djibouti.
This report attempt to give a brief and generalized overview of the utilization of industrial minerals in RDD.The second part of the report present a summary of the industrial minerals resource of RDD .
B)GENERAL GEOLOGY
Djibouti is at the junction of three rifts (east African, red sea, Gulf of Aden).
Volcanic formations cover a large percent of the country. The oldest rocks (Mesozoic sediments) crops out in the southern part of the country.Endoreic plains, grabben and coastal plains are filled by tertiary to quaternary sediment.
The volcanic rocks of Djibouti are mainly basalt and rhyolite (bimodal volcanism).
The following series are recognized: adolei basalt(22 to26 my) mabla rhyolite(15 to19 my) dalha basalt(4 to 9my) stratoid basalt (1 to 4 my) gulf of tadjoura basalt (1 to 3 my) recent basalt(rifts)
Geological map of Djibouti
.
These basalt and rhyolite are often altered by hydrothermal fluid; they may contain a variety of metallic minerals deposited by geothermal water (gold copper, lead, zinc, manganese….) Mesozoic sedimentary are recristallized by dike intrusion, several mineralization are noted by geologist but not fully explored.
Tertiary to quaternary sediments of lacustrine, marine origin are widespread in endoreic plain, grabben and coastal plain; exploitable clay, gypsum, diatomite, salt, sand, gravel ….are recoverable from those sediments.
C)MINERAL PRODUCTION AND TRADE
The only documented information on export of industrial minerals concern the salt of Lake Assal exportation to ETHIOPIA (1999 to 2003) (fig 1, fig 2)
YEARS
1999 2000 2001 2002 2003 TOTAL(1999 to 2003)
PRODUCTION(tonnes)
127283 135933 173099 162266 128494 727075
Salt production (1999 to 2003)
salt production
180000 160000 140000 120000 100000 80000 60000 40000 20000 0 1999 2000 2001 salt production salt production 2002 2003
The decline of the production of salt from Lake Assal is mainly due to the arrival of new salt product in the Ethiopian market and certainly a reorganisation of several companies.
Others industrial minerals: clay, gravel, crushed basalt, building stones are exploited in the vicinity of the capital
It seems that some cutted bock of basalt and rhyolite are exported. Near Djibouti town a brick making factory use the residual clay from the alteration of the Gulf of Tadjoura basalt .Sand and gravels for aggregate purpose are exploited all over the country from wadi bed .
In 2009, an exploitation license for a perlite deposit was delivered by the MERN to JB JIBOUTI MINING LTD, the exportation of Egerleyta perlite was estimated to be of 50 000 tonnes per years .
The lack of systematic record of mineral production, consumption and trade, overshadow the contribution of mineral sector to the economy.
The republic of Djibouti import several mineral raw materials and products: ceramic products(pipe, tile, cement, clay based refractories) roofing tiles chalk, pigments cement product Abrasives….
The high costs of imported product are likely to encourage development of indigenous resource in the future
D)INDIGENOUS INDUSTRIAL MINERALS 1) Construction raw materials
Basalt, rhyolite, trachyte, sandstone, limestone can lend to the production of a wide variety of cut and polished stones.
Sand and gravel used today are from wadi bed, marine sand have never been exploited.
Abundant sand, gravel can be recovered in graben (HANLE, GAGGADE….)
2) Clay
Several deposit of clay is encountered: clay from alteration of basalt lacustrine clay clay deposited in endoreic plain All these clay must be studied to determine their suitability in different end uses. Bentonitic clay is present in the graben of Hanle (it was used by a drilling company (GENZEL) during gradient wells drilling).
3) Gypsum
Thick and extensive resource of gypsum are found around the LAKE ASSAL.Other deposits of gypsum are noted as intercalation in Jurassic limestone of Ali sabieh.The gypsum deposit of Assal is huge (millions of tons).
4) Limestone
Slightly metamorphosed limestone of Ali sabieh is a potential target for decorative and semi-precious stone.
Travertine deposit (thermal spring calcareous deposit) are seen in Hanle ,lake assal ,lake Abbe,allol… Jurrassic limestone suitable for cement oucrop in the Ali-sabieh area(cement factory project in progress)
5)Pumice, pozzolane, scoria
Abundant resources of scoria are widespread in the stratoid basalt, the gulf of Tadjoura basalt, recent basalt (Assal, Manda inakir).
Volcanic cones composed of scoria and pozzolane are visible at the southern part of Djibouti town.
Pumice flow and fall are sometimes associated to the terminal rhyolitic extrusion of the stratoid series (southern part of Assal rift).
Pumice is also found in the rhyolitic series of mabla.
6)silica sand and quartz
The cretaceous sandstone of Ali sabieh are source of silica sand but proper evaluation must be made to determine their suitability for various end uses.
Quartz gravel and sand cover large area at Assamo and south of Ali adde (suitable may be for ceramic manufacturing or glass manufacturing).
7) Salt
Salt of lake assal is a resource of considerable importance; it is a renewable resource (the lake is fed by the sea from fractures).SALT-INVEST a Djibouti American company have the exclusive permit of exploitation of the salt .
8) Soda ash
Elevated content of sodium carbonate are signalled in Lake Abbe.The quantity and quality of the soda ash deposit of Lake Abbe must be evaluated properly.
9) Diatomite
In gobaad, hanle, gaggade, assal… calcareous and diatomite deposit cover great surface; strata of pure diatomite (1 to 5m) are intercalated in more calcareous levels.
CONCLUSION
Until know, limited effort was expended to explore industrial mineral resource of Djibouti.
The resource already identified suggests that enormous undiscovered mineral potential exist in the republic of Djibouti.
Satellite view of assal Lake
Lake ASSAL salt