Residual Mineral Deposits

Topic 8: Residual (eluvial or laterite) Mineral Deposits
Hassan Z. Harraz
hharraz2006@yahoo.com
2012- 2013
22 November 2015
Prof. Dr. H.Z. Harraz Presentation
Residual (or laterite) Mineral Deposits
1

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Outline of Topic 8:
We will explore all of the above in Topic 8
 RESIDUAL CONCENTRATION
 Definition of Residual mineral deposits
 Definition of Laterites
 Laterite/Bauxite Conditions
 Laterite Profile
 Laterisation system
1) Laterite-type Bauxite
 Characteristics
 Constitution of Bauxite
 Types of deposits
 Origin and Mode of formation
 World bauxite reserves 2010
 Clay (Kaolinite) Deposits
 Source Materials
 Mode of Formation
2) Nickel Laterite Deposits
 Definition
 Mineralogy and Types of lateritic nickel ore deposits
 World Nickel Laterite Deposits
 Processing of Ni Laterites
 Example: Ni-laterites, Ni in soils in east Albania

RESIDUAL CONCENTRATION:
 Result in the accumulation of valuable minerals when
undesired constituents of rocks or mineral deposits are
removed during weathering.
 The concentration is due largely to a decrease in volume
effected almost entirely by surficial chemical weathering.
 The residues may continue to accumulate until their purity and
volume make them of commercial importance.
Process of Formation
The requirement for residual concentration of economic
mineral deposits:
1) The presence of rocks or lodes containing valuable
minerals, of which the undesired, substances are soluble
and desired substances are generally insoluble under
surface conditions.
2) The climatic conditions must favour chemical decay.
3) The relief must not be too great, or the valuable residue
will be washed away as rapidly as formed.
4) Long-continued crustal stability is essential in order that
residues may accumulate in quantity and the deposits
may not be destroyed by erosion.
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The concentration of ore deposits by
weathering processes occurs as soluble rock,
such as limestone, is removed in solution,
leaving insoluble minerals concentrated as a
residue.

Definition of Residual mineral deposits
 Residual mineral deposits formed and concentrated by chemical weathering
reactions at the earth’s surface.
During chemical weathering and original body of rock is greatly reduced in
volume by the process of leaching, which removes ions from the original rock.
Elements that are not leached form the rock thus occur in higher concentration
in the residual rock.
 leaching of rock leaves residual materials behind (i.e., Form by the removal
of soluble minerals (leaching)
 Insoluble minerals (residues) get concentrated at the weathering site
 These deposits often form as a result of intense chemical weathering in warm
tropical climates that receive high temperatures and high amounts of rainfall which
produces highly leached soils rich in both iron and aluminium.
 Resource from residual mineral deposits: Al (Bauxite), Ni (Nickeliferous-laterite),
Fe and kaolinite.
The most important ore of Aluminum, bauxite, forms in tropical climates where
high temperatures and high water throughput during chemical weathering
produces highly leached lateritic soils rich in both iron and aluminum. Most
bauxite deposits are relatively young because they form near the surface of the
Earth and are easily removed by erosion acting over long periods of time.
 In addition, an existing mineral deposit can be turned in to a more highly
concentrated mineral deposit by weathering in a process called secondary
enrichment.
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 Laterite - the resulting soil layer, typically red in color due to the
presence of iron oxides and hydroxides.
 Nodular, red to yellow or brown hematite and goethite with as
much as 20% Al2O3.
 Laterites are formed mostly in the sub-tropical and tropical
regions between 25° North and 25° South latitude.
 Laterites also occur in temperate zones, but were formed when
those regions were tropical millions of years ago.
 Laterite deposits can be thick, up to 20 m.
 It is precipitated into laterite with concentrations ~1-3% by
weight.
 Laterites deposits of aluminum, iron, nickel, cobalt, chromium,
titanium, copper are also formed.
 In the case of a nickel laterite, nickel would be 0.25% by weight
in peridotite: 6 – 20 m thick on top of mafic and ultramafic
rocks.
 Examples: Guinea, Guyana, Indonesia, Australian, Jamaica, Cuba
and the Philippines.
 Laterites are source of metals:
 Ni, Co, Cr, Fe (from laterites derived from ultramafic rocks)
 Al (from laterites derived from aluminous rocks)
Definition of Laterites
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Schematic soil profile in a laterite showing
the progression of weathering effects on
rock. Some commodities, such as aluminum
and nickel, are enriched by weathering.
Modified slightly from Elias (2002).

Laterite/Bauxite Conditions
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 Climate
 Parent Rock Composition
 Subtle Eh-pH Controls
 [1],[2]: Al and Fe leached
 [3],[4]: low solubility so need Fe, Al rich
parent material
 [5]: enough Fe mobility to form Fe-laterites
 [6]: optimal for bauxites
1
2
3
4
5
6

Example:
Formed by the removal of non-ore material from proto-ore.
 e.g. leaching of silica and alkalis from a nepheline syenite may leave behind a
surface capping of hydrous aluminum oxides, called bauxite.
 e.g. weathering granite  kaolinite.
 e.g. laterite can enrich nickel from peridotites.
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Residual (or laterite) Mineral Deposits 7
Australian Laterites. Very large areas are covered by laterite. It is amenable to open pit mining with
only truck and shovel, no blasting required.

LATERITE PROFILE
On Un-serpentinised Peridotite, Sorowako
Red Laterite (Hematite)
Yellow Laterite (Limonite)
Saprolite zone
Bedrock pinnacle
Typical laterite profile in a road cut: dark
limonite overburden above the red line;
limonite low grade to medium grade
between the red and the green lines;
and saprolite below the green line. At
the road level some signs of possible
bedrock pinnacles are exposed.
Imaginary drill holes A,B,C at about 25
meter spacing in this photo would
return completely different profile
interpretations in terms of quantity and
position of each of the three main
layers. This high degree of variability of
the laterite adds risk to exploration in
the early stage that grade and tonnage
estimates will not be representative for
economic studies. Only detailed
exploration will provide the sampling to
reduce this risk.
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Laterisation System
MgO
SiO2
FeO or F2O3
Bedrock
Soft
Saprolite
Hard
Saprolite
All compositions are shown
in terms of the three oxides
PATH OF
LATERISATION
Limonite
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Laterite-type bauxite
Bauxite
(the principal ore of aluminum)
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Definition:
Name: Laterite-type bauxite (simply: Bauxite).
Bauxites are:
 The source of the world’s aluminum.
 Is an aluminum ore and is not actually a mineral.
 Gibbsite Al(OH)3 is the main mineral in Bauxite ore.
 is formed in residual deposits; at or near the surface under tropical or Subtropical
conditions of weathering.
 Concentrated in the tropics because that is where lateritic weathering occurs.
 Occurs in many countries of the tropical belt.
 Found in present-day temperate conditions, such as France, China, Hungary, and
Arkansas, where the climate was tropical when the bauxites formed.
 Not found in glacial regions.
 Glaciers scrape off the soft surface materials.
1) Laterite-type Bauxite
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 Although aluminium is the most abundant metal in the earth's crust and the third most abundant
element, it occurs mainly in combinations that so far have defined commercial extraction.
 It is an important constituent of all clays and soil and of the silicates of common rocks.

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Bauxite – associated with tropical climates
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Bauxite
Aluminum ore, called bauxite, is most
commonly formed in deeply weathered
volcano.oregonstate.edu
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 Shape and Form:
1) Pocket Deposit : pocket; hole (ex. Jamaica & South Europe}
2) Blanket deposits: Irregular blankets several meters to tens of meters
thick on top of their parent rock (usually but not always){ ex.
Australia, Guyana, Surinam}.
3) Detrital Deposits : Accumulate in high slope land and inclined bed
4) Mixed 1, 2 and 3 (ex.Blanket & Detrital Deposits ; Arkansas}
 Age: mostly post-Mesozoic.
 More than 90 % of all known bauxite deposits formed during the
last 60 million years,
 All of the very large bauxite deposits formed less than 25 million
years ago.
 Mined by open pit method.
 Main producers: Australia, Guinea, Jamaica, Brazil, India, Surinam and
Balkan Republics.
 Largest producers are Australia, Jamaica and Guinea.
Characteristics:
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Bauxite in Jamaica
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Pocket Deposit
Jamaica & South Europe
Blanket Deposit
Australia, Guyana, Surinam
Blanket & Detrital Deposits
Arkansas
Shape and Form

Constitution of Bauxite
Mineralogy:
 Bauxite is an aluminum ore and is not actually a mineral.
 The present usage of the term, both minerlogically and in
commerce is to designate a commonly occurring substance
that is a mixture of several hydrated aluminium oxides with
considerable variation in alumina content.
 It is a hardened and partly crystallised hydrogel that
consists of variable proportions of the minerals gibbsite
(Al(OH)3) or hydrargillite, and boehmite {AlO(OH)} and its
dimorphous form {i.e. diaspore AlO(OH)}, together with
hematite, the clay mineral kaolinite and small amounts of
anatase (TiO2).
 Impurities are invariably present in the form of halloysite,
kaolinite, nontronite, and iron oxides; rarely, bauxite
contains octahedrite.
 Typical bauxite contains:
 35 to 65% Al2O3
 2 to 10 % SiO2
 2 to 20% Fe2O3
 1 to 3 % TiO2
 10 to 30% combined water.
 For aluminium ore: bauxite should contain preferably
at least 35% Al2O3 and less than 5% SiO2, 6% Fe2O3
and 3% TiO2.
 For the chemical industry: the percentage of silica is
less important, but iron and titanium oxides should
not exceed 3% each; and
 For abrasive use: SiO2 and Fe2O3 should be less than
6% each.
 Commercial bauxite occurs in three forms:
 Pisolitic or oolitic, in which the kernels are
much as a centimeter in diameter and consist
principally of amorphous trihydrate;
 Sponge ore (Arkansas), which is porous, commonly
retains the texture of the source rock, and is
composed, mainly of gibbsite; and amorphous or clay
ore. All three may be intermingled
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 Gibbsite: Al(OH)3
 Diaspore : AlO(OH)
 Boehmite: AlO(OH)
 Kaolinite: Al2Si2O5(OH)4
 Halloysite: Al2Si2O5(OH)4•2H2O
 Montmorillonite: (Na,Ca)0.33(Al,Mg)2Si4O10(OH)2•nH2O

Gibbsite Al(OH)3
Diaspore AlO(OH)
Bauxite Al-hydroxide*
*hybrid mix of diaspore, gibbsite, and boehmite
(AlO(OH))
Gibbsite-type – dioctahedral
sheets (only two of three
octahedral sites are filled).
(OH)- main anionic group
forming octahedrally
coordinated sheets with weak
bonds between
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Residual (or laterite) Mineral
Deposits 18

Types of deposits:
1) High level or upland
bauxites
2) Low level peneplain
bauxites
3) Karst Bauxites
 Directly on volcanic or
plutonic rocks, no clay
body in between.
 < 30 m in thickness
 In tropical and
subtropical climates
 Porous and friable, often
with relict textures
 Predominated by Gibbsite
 Weathering controlled by
structures in parent rocks
 Examples: Ghana and
Guinea
 Somewhat transported,
separated from their
parent rock by kaolinitic
under clay.
 ~ 9 m thick.
 Along tropical coastlines
 Pisolitic textures.
 Associated with detrital
bauxites produced by
fluvial and marine activity.
 Examples: South America,
Australia, and Malaysia.
 Oldest known.
 In Eastern Europe.
 On top of karst surfaces in
limestone and dolomite.
 Structureless, earthy,
concretions, …. variable
textures!
 Predominated by
Boehemite.
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Fig. 6. Photomicrographs of
selected samples from the Mandan
bauxite deposit. A. Spheroidal ooids
with core filled by other ooids. B.
Porous matrix filled with calcite and
fracture filled by kaolinite. C.
Aggregation of pisolites with light-
color matrix, which is interpreted as
due to deferrification process in the
bauxite deposit. D. Pisolite with a
core of boehmite surrounded by a
cortex of alternating hematite. E.
Euhedral pyrite in gray bauxite. F.
Euhedral and framboidal pyrite in
gray bauxite.
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Origin and Mode of formation
Conditions necessary for formation of bauxites: Mode of formation:
1) favorable parent rock.
2) porosity.
3) high rainfall with intermittent dry spells.
4) good drainage.
5) tropical warm climate.
6) low relief.
7) long period of exposure.
8) vegetation.
9) Low Fe, Ti, alkalis, and alkali earths
1) Weathering.
2) In situ leaching of elements and
enrichment of residue in Al.
3) Possible erosion and
redeposition?
4) Addition of eolian dust.
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Formation of Bauxite deposit is formed by lateritization (intense chemical weathering
in hot, wet, tropical areas) of various silicate rocks such as granite, gneiss, basalt, and
shale.

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Includes Bauxite enrichment from
Laterites
In situ leaching of elements and enrichment
of residue in Al.
Mode of Formation (Cont.)

Steps:
 Al is abundant in earth (after O and Si). But, binds very strongly to O, poorly soluble = difficult to process.
 Bauxite is an accumulated product of peculiar weathering of aluminium silicate rocks lacking in much free quartz,
lie silicates are broken down; silica is removed; iron is partly removed; water is added; and alumina, along with
titanium and ferric oxide (and perhaps manganese oxide), becomes concentrated in the residuum.
 leaching in tropical/subtropical where abundant rainfall (leaching), near neutral pH where Al least soluble.
 Highly soluble materials like Na, K, Ca leach first.
 Then Mg and others.
 Formation of kaolinite from K-feldspar, also production of gibbsite (bauxite) as H2SiO4 drops as SiO2 is leached (Kaolinite ↔
Gibbsite + Silicic Acid).
4KAlSi3O8 (Orthoclase) + 4H2CO3 (Carbonic acid) + 18H2O (water) ↔
Al4Si4O10 (OH)8 (Kaolinite-Clay) + 4K+ (Potassium ions) + 4HCO3
- (Carbonate ions) + 8H4SiO4
+ (Silicic acid)
Al converted mainly to kaolinite (often from feldspars: see phase diagrams and
reactions, compare phase diagram to le Chatelier principle).
 Formation of kaolinite from K-feldspar, also production of gibbsite (bauxite) as H2SiO4 drops as SiO2 is leached (Kaolinite
↔ Gibbsite + Silicic Acid)
 Progressive dissolution of silica from clays in wet soils will eventually turn the:
Kaolinite {Al4Si4O10(OH)8 }  into Gibbsite {Al(OH)3}
Gibbsite (Al(OH)3) boehemite {AlO(OH))+ diaspore (AlO(OH)}
• Basic reaction:
Al2O3  2Al + 3O
 Cathodic reaction: 2Al3+ + 6e-  2Alo
 Anodic reaction : 3O2-  1.5O2 + 6e-
 Eventually, Si in kaolinite can leach out, leaving Al oxides and hydroxides (gibbsite=Al(OH)3, boehmite=AlO*OH).
 Where conditions are slightly more acidic, Fe may also leach (narrow zone), or, more likely, if rocks are initially low in Fe.
 Can be redeposited
 these soils become bauxite, a major ore of aluminum.
 This produces more pure Al ore.
 low relief = slow erosion compared to rate of chemical leaching common pisolitic texture, consequence of insitu process of
phase transformation.
Note: Bacteria may have played a part in bauxite formation.
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Al(OH)3
Insoluble

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World bauxite reserves 2010

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$5.6B
Data in thousands of metric tons Al metal
Data in thousands of metric tons dry ore – Bauxite
$120B $63B
$8B $2.9B

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Clay (Kaolinite) Deposits
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Clay (Kaolinite) Deposits Formed by Residual Concentration
Residual clays can be classified as follows:
1) Kaolins, white in colour, and usually white burning:
a) Veins, derived from weathering of dikes.
b) Blanket deposits, derived from areas of igneous or
metamorphic rocks.
c) Replacement deposits, such as indianite.
d) Bedded deposits, derived from feldspathic
sandstones.
2) Red-burning residuals derived from different kinds of
rocks.
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Source Materials
The chief source rocks of residual clays are crystalline rocks, more
especially the silicic granular rocks that are rich feldspars and low in
iron minerals, such as granite and gneiss.
 Basic igneous rocks yield much ferric oxide, which stain the clay,
often rendering it useless.
 Feldspar-rich pegmatite yield Dike-like masses of high-grade
white kaolin that is generally very low; in iron and other impurities
deleterious chinaware manufacture.
 Syenites yield excellent clay.
 Limestones, after long-continued solution erosion, leave a mantle
of insoluble clayey impurities that are used for brick clays.
 Shale, which is largely made up of clay minerals, is used as clay
material, but weathering often yield a purer product.
 Sericitized igneous rocks yield clay.
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Mode of Formation
Clay formation results from normal weathering processes.
Vegetation plus the atmosphere supply the necessary CO2, and it is noteworthy that good clays
commonly underlie swamps.
Organic compounds:
 serve to remove coloring materials and produce white clays.
 change iron from the insoluble ferric (Fe3+) to the soluble ferrous (Fe2+) state, permitting its
removal in solution thereby bleaching the clay.
The formation of clay from silicate minerals is essentially a breaking down of the silicates to form
hydrous aluminium silicates and the removal of the soluble silica and alkalis in solution. Some free
quartz will remain and must be extracted to obtain pure clay. The alteration of orthoclase, for
example, yields kaolinite, potassium carbonate, and silica. The last two are removed in solution and
the kaolinite persists.
4KAlSi3O8 (Orthoclase) + 4H2CO3 (Carbonic acid) + 18H2O (water) ↔
Al4Si4O10 (OH)8 (Kaolinite) + 4K+ (Potassium ions) + 4HCO3
- (Carbonate ions) + 8H4SiO4
+
(Silicic acid)
Formation of kaolinite from K-feldspar, also production of gibbsite (bauxite) as H2SiO4 drops as SiO2
is leached (Kaolinite ↔ Gibbsite + Silicic Acid).
Kaolinite deposits also result from hydrothermal action. Kaolinite, dickite, and montmorillonite
occur in the halo of hydrothermal rock alteration tint surrounds many hydrothermal ore deposits,
particularly porphyry copper deposits.
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2) Nickel Laterite Deposits
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Nickel Deposits Formed by Residual Concentration
 Many mafic/ultramafic igneous rocks are known to contain very small
quantities of nickel in some unknown form but presumably held in the
silicate lattices.
 Rocks containing nickel are broken down, decomposed, and lose silica by
intense tropical and Subtropical weathering to form a soil layer.
 Water flowing through the soil layer leaches nickel and other metals from
the soil.
 Nickel, iron and magnesium oxides and silicates precipitate from water into
the soil layer, the laterite.
Nickel laterite ore deposits
 Residual soils
 Developed over mafic/ultramafic rocks through processes of chemical weathering and supergene
enrichment under tropical climatic conditions
 the surficial, deeply weathered residues formed on top of ultramafic rocks that are exposed at
surface in tropical climates.
 Found widely in New Caledonia, Cuba, , Celebes, Borneo, Australia, Papua New Guinea, the
Philippines, Indonesia, Brazil, and Venezuela,.
 Are estimated to comprise about 73% of the world continental nickel resource.
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Nickel laterite deposits
Mg RICH “ULTRAMAFIC”
ROCK
0.3% Ni
Olivine and
pyroxene
(silicate minerals)
SAPROLITE
ZONE
1.5 - 2.5% Ni
Serpentine
(hydrated silicate)
Goethite
(hydrated oxide)
LIMONITE
ZONE
1- 2% Ni
Deep downward
penetration of water
producing weathering
The process of oxidation and
weathering depletes the original mafic
rock of Mg and Si, and concentrates
Fe and Ni in the weathered zone.
Near surface upward
evaporation of water
precipitates Fe, Ni oxide
OREBODY
 Ultramafic rock - igneous rocks formed from magma with very low concentrations of quartz (SiO2).
Peridotite is a common ultramafic rock type which contains olivine, a greenish-gray mineral, with
magnesium and nickel.
 Rocks containing nickel are broken down by intense weathering to form a soil layer :
 Weathering begins on joints and fractures in the rock to form large blocks or boulders
with a thin soil layer.
 Further weathering and biological processes thicken the soil layer.
 Water flowing through the soil leaches nickel, iron, and magnesium (and other metals)
from the soil.
 The metals (nickel, iron, magnesium and other) then precipitate from water as oxides,
hydroxides and silicates in different parts of the soil layer as laterite.
22 November 2015 Prof. Dr. H.Z. Harraz Presentation
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Mineralogy:
• Formerly, several species were thought to exist, such as genthite,
pirnelite, nepouite, connarite, garnierite, and noumeite.
• In several places, "garnierite" derived from serpentinized peridotite, has
undergone sufficient residual concentration on the surface to form
workable deposits of nickel ore.
Types of lateritic nickel ore deposits
Three kinds of lateritic nickel ore can be distinguished:
1) Limonite (oxide) types (or Oxide Ni deposits): Ni as hydroxide in the
ferruginous zone
2) Clay silicate deposits: Ni as clay silicate
3) Saprolite types (or Hydrous silicate deposits): Ni as hydrous-silicate
in saprolite
Mineralogy and Types of lateritic nickel ore deposits
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http://en.wikipedia.org/wiki/File:River_South_
New_Caledonia.JPG.JPG
A Creek in southern New-Caledonia. Red
colours reveal the richness of the ground in
iron oxides, and nickel.
Limonite zone
Idealized cross section of tropical laterite-saprolite nickel profile.
Vertical scale is in terms of meters; horizontal scale is in terms of
kilometers.
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Ni-rich Laterites
Papua New Guinea (PNG)

World Nickel Laterite Deposits
Cuba
Dominican
Republic
Brazil
Columbia
Guatemala
Albania
Greece
Philippines
Indonesia
PNG
New
Caledonia
Australia
Venezuela
BurmaIndia
Madagascar
Producing Countries
Non Producing Countries
Ivory Coast
Zimbabwe
Ethiopia
Burundi
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World Nickel Laterite Resources
(Distribution by Contained Nickel)
Caribbean
25%
New
Caledoni
a
20%
Indonesi
a
16%
Philippine
s
11%
Australia
8%
Africa
8%
America
8%
Other
4%
Mt
Ore
%
Ni
Contained
Nickel
Mt
Relative
%
10,382 1.32 140 69%
WORLD’S LAND-BASED Ni RESOURCES
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Ni Market Drivers
More nuclear power?
Wind farms?
Hybrid/electric cars?
NiMH vs Li-Ion?
Ni: metric tonnes

WORLD Ni PRODUCTION & RESOURCES
PRIMARY Ni PRODUCTION WORLD Ni RESOURCES
SULPHIDE
LATERITE
60%
40%
SULPHIDE
LATERITE
30%
70%
Note:
Sulphide nickel deposits : Nickel as nickel sulphide 
pentlandite, millerite)
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Processing of Ni Laterites
Nickel ores processed through three processes:
1) Pyro-metallurgical (smelting) processing
(Ore is melted)
 Ferro-nickel (Ferro-Nickel Product 20 – 50% Ni)
 Ni-matte ((Nickel-Matte Product 78% Ni)
 Ni Pig Iron
2) Hydro-metallurgical processing (Leaching by acid)
 PAL (Pressure acid leaching) – HPAL
 AL (Atmospheric Leaching)
 Heap Leaching
3) Combined pyro and hydro process (Caron)
(Ore is reduced at high temperature, then leached)
Note:
The selection of processing technology must consider:
• Ore characteristic (Chemistry and Mineralogy)
• Ni/Co grades (include potential upgrading)
• Metal recovery
• Mineability (Ore thickness and continuity)
• Capital and Operating costs (potential hydro-
electric power, Residual Storage Facility, Water
source, Limestone source, Existing infrastructure,
etc)
• Market demand
Good Hydro Hydro
Hydro-
Pyro
Fair Hydro
Hydro-
Pyro
Hydro-
Pyro
Poor Pyro Pyro
Poor Fair Good
LimoniteDevelopment
Saprolite Development
Hydro vs Pyro
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Example: Ni-laterites, Ni in soils in east Albania
Simplified tectonic map of central part of Albania (Hoxha, 2001). B: Distribution of
ophiolites along of the Balkan Peninsula (after Bortolotti et al., 1996).
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Ni-laterites, Ni in soils in east Albania
Geological map of the Prrjenas intramontane basin (from the Geological Map of Albania
1:200,000). Noticeable that the chain of Ni-laterite deposits follows always the boundary
of serpentinite and the cover Cretaceous limestone.
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Panoramic view of the Prrenjas intramontane basin with indication of the position of the
village, the mines and the typical lithologies of the major chines.
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Synoptic profiles of major types of the Ni-laterite deposits of the Balkan Peninsula. Compiled
according to: Ivanov, 1960; Augusthitis (1962); Arkaxhiu and Kici (1990); Skarpelis et al., 1996;
Skarpelis, 1997; Eliopoulos and Economou-Eliopoulos, 2000; Peci and Grazhdani, 2001 and
field observations of ID in 2004. (a)-(d): deposits of Cretaceous age. The first column (a)
represents the most typical profile; the laterite deposited more-or-less autochtonously on the
weathered ultrabsic rock. (b): The lateritic material was redeposited and covers slightly- or
unwathered ultrabasite. (c) & (d): The lateritic material was resedimented on Mesozoic
limestone. (e): the footwall and henging wall of the deposit is bordered by faults, the
stratigraphic age of the cover sequenci is unknown. (f): Paleogene cover with alternating
deposition of lateritic and siliciclastic material. (g): Deposits in the Miocene sequences.
22 November 2015
46

Geological setting of laterite ore deposits of the
Edessa are, Greece a: Messimeri; b: Vrita; c:
Flamuria (from Michaildis, 1990). These profiles
show how different are the stratigraphic
successions even within a small area further
these profiles are representing well the
characteristic tilting and thrusting.
no detectable
overprint
(e.g.Prrenjas)
weak, diagenetic
overprint
(e.g. Bitincka)
low-grade
metamorphism
(e.g. Edessa)
medium-high-grade
metamorphism
(e.g. Samos)
nontronite and
clay minerals,
high porosity,
loose structure
garnierite &
other Ni-hydro-
silicates, veins,
compaction
Ni-alkali amphibole,
stilpnomelane,
epidote, reaction
rims on Cr-spinell
Ni-silicates, Ni-
tourmaline,
corund,staurolite,
gahnite
Diagenetic-metamorphic overprint
Major stages of post-sedimentary overprint of
the laterite deposits of the Balkan Peninsula
and the Greek archipelago.
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47

The base of the Bitincka laterite layer shows a
complex geometry, partly due to the deposition
on the irregular surface of the serpentinite, but a
young faulting has also some role.
The immediate cover sequence in
Bitincka.
22 November 2015
48

Serpentinite pebbles and clasts in
protolaterite – Kurbneshi, northern Albania. Limestone fragments in Ni-laterite – Katjeli.
Ni-silicate veins in the Ni-laterite.
Ni-laterite mines and dumps are throning
above the settlements.
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49

Microscopic reflected light image of a
weathered chromite grain (gray)
which is replaced along cracks by
hematite (white). Width of picture is
ca. 270 µm (from Augustithis, 1962).
from Michailidis et al. (1985)
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50

Sample Problem
Answer:
 Distinguish between weathering and depositional methods of the formation of economic mineral
deposits.
 Distinguish between depositional methods of the formation of economic mineral deposits in arid and
tropical (or subtropical) environments.
 Distinguish between different residual methods of the formation of economic mineral deposits.
 Distinguish between evaporation and depositional methods of the formation of economic mineral
deposits.
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51

2-5 Geophysical Surveying
END OF TOPIC 8

Residual Mineral Deposits

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