A SEMINAR REPORT ON SKARN DEPOSITS

1. THE FEDERAL UNIVERSITY OF TECHNOLOGY,
AKURE, ONDO STATE, NIGERIA.
SEMINAR PRESENTATION ON
SKARN DEPOSITS
BY:
OBI, VICTOR CHIZOBA
IN PARTIAL FUFILMENT OF THE
REQUIREMENT FOR THE AWARD OF THE
DEGREE OF BACHELOR OF TECHNOLOGY,
APPLIED GEOLOGY
OCTOBER, 2017.
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2. Presentation Outline
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• Aim
• Objectives
INTRODUCTION
• Definition and Composition
• Formation
• Classification
• Profile and speculations in Nigeria
CASE STUDY
• The Geology of Antamina Cu-Zn Skarn deposit, Peru
• Industrial importance of Skarn deposits
CONCLUSION AND RECOMMENDATION

3. 3
AIM
•To Understand and discuss the basic theories and
principles of skarn deposits.
OBJECTIVES
• To define skarn and its classifications;
• To discuss the mineral deposits associated with skarns;
• To highlight possible occurences in Nigeria.

4. INTRODUCTION: DEFINITION AND COMPOSITION
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A METASOMATIC ROCK
SKARN IS
FORMED BY CHEMICAL ALTERATION OF
CARBONATE (DOLOSTONE AND LIMESTONE)SKARN IS
ARE METALLIC DEPOSITS ASSOCIATED WITH
SKARN ROCK FORMING MINERALS.
SKARN
DEPOSITS

5. 5Figure 1: Tungsten (W) Skarn in a marble environment, Meinert (2000).
SKARN

6. MINERAL COMPOSITION
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7. FORMATION OF SKARN
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Isochemical metamorphism:
Metasomatic transfer of components between
adjacent lithologies on a small scale (argillite and
limestone, banded iron formation and limestone)
forming reaction skarns.
Infiltration metasomatism:
Hyrdrothermal fluid interaction
(magmatic/metamorphic origin) with calcareous
rocks forming replacement or infiltration skarns.
(Ray et al. (1997) and Meinert (1992)

8. 8
FORMATION OF SKARN
ISOCHEMICAL METAMORPHISM
 INTRUSION OF MAGMA (900⁰C – 700⁰C
 METAMORPHIC RECRYSTALLIZATION,
FLUID CIRCULATION AND LOCAL
BIMETASOMATISM FORMING
REACTION SKARNS AND SKARNOIDS
FROM IMPURE LITHOLOGIES
Figure 2: Isochemical Metamorphism, Modified after Meinert (1992, 1995).

9. 9
SKARN CLASSIFICATION
Soloviev et al. (2013) and Ray et al. (1997)
BASED ON ALTERATION ASSEMBLAGES
•PROGRADE CALCIC SKARN
•PROGRADE MAGNESIUM SKARN
BASED ON PROTOLITH
•ENDOSKARN
•EXOSKARN

10. EXPLORATION GUIDES FOR SKARN
DEPOSITS
GEOCHEMICAL STUDIES
GEOPHYSICAL STUDIES
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11. Seven (7) major classes of metallic skarn deposits:
Fe Skarn Deposits
Cu Skarn Deposits
Au Skarn Deposits
Pb-Zn Skarn Deposits
Sn Skarn Deposits
Mo Skarn Deposits
W Skarn Deposits
PROFILE OF SKARN DEPOSITS
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12. PROFILE OF SKARN DEPOSITS
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Main Metal
(By-products)
Fe (Cu, Ag, Au)
Tectonic setting Calcic Fe skarns: Oceanic Island arc
Magnesium Fe Skarns: Continental margin
Host/Associated Rock Types Calcic Fe Skarns: Dykes of Gabbro to
syenite intruding limestone
Magnesium Fe Skarns: Granodiorite to
Granite intruding dolomite and dolomitic
sedimentary rocks
Ore Mineralogy Principal Ore: Magnetite. Subordinate Ore:
Chalcopyrite, bornite, pyrite, etc.
Grade and Tonage Grades are typically 40 to 60%
TABLE 1: Characteristics of Fe Skarn

13. 13
CU SKARN DEPOSIT
Main Metal
(By-Products)
Cu (Au, Ag, Mo, W)
Tectonic Setting Andean-type plutons intrude older
continental-margin carbonate sequences
Hosted / Associated Rock
Types
Dykes and Breccia types of quartz diorite,
granodiorite, etc.
Ore Mineralogy (Moderate to high sulphide content) Pyrite,
Chalcopyrite, magnetite, etc.
Grade and Tonage Average 1 to 2 % Cu
Compiled from: Nadoll et al., 2015; Ray et al., 1997 and soloviev, 2015)
TABLE 2: Characteristics of Cu Skarn

14. 14http://www.danieleheon.com/fieldwork-photos-yukon--bc.html
A B
Figure 3:
A. Copper(gold-silver-molybdenum) skarn from Whitehorse Copper Beli, Yukon.
B. Core sample of copper skarn

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Tin (Cassiterite) Deposits in The Younger Granites Complex of
Nigeria.
Schist Belts of Nigeria.
OCCURRENCES (OR SPECULATIONS) OF SKARN
IN NIGERIA

16. 16
Marble occurrences (Schist Belts) in the Precambrian
Basement Complex of Nigeria.
lifeinplanetlight.wordpress.com
Figure 4: Model for Marble formation from Contact Metamorphism

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CASE STUDY
THE GEOLOGY OF THE ANTAMINA COPPER-ZINC SKARN
DEPOSIT, PERU.
 It is located in the eastern part of the Western Cordillera of
north Peru at 9° 32’ south and 77° 03’ west, at an altitude
between 4,200 and 4,800 meters.
Antamina is hosted by Mesozoic carbonates that are within a
fold and thrust belt in the eastern part of the Western
Cordillera.
Antamina is hosted by Cretaceous sedimentary rocks that
comprise carbonates overlying a sandstone-shale-coal sequence.

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DEPOSIT GEOLOGY
Figure 5: Geological sketch map of the Antamina deposit, Peru (After, Stewart D. Redwood)

19. 19
CASE STUDY
Figure 6: Cross Section 20, 200N showing skarn zonation (After, Stewart D. Redwood)

20. 20
MINERALIZATION
 The skarn is dominantly garnet.
The metals are also zoned, with copper in the brown garnet and
copper-zinc in the green garnet.
The core intrusion actually comprises a series of quartz monzonite
porphyry intrusions that can be divided into early, middle, and late
phases.

21. ECONOMIC OR INDUSTRIAL APPLICATION
 Tin has long been used in alloys with lead
as solder.
 Tin in combination with other elements
forms a wide variety of useful alloys
Figure 7 :A coil of lead-free solder wire
Figure 8: A plate of Tin in combination with other elements
forms a wide variety of useful alloys Molybdenum Copper
Alloy 21

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ECONOMIC OR INDUSTRIAL APPLICATIONS
(CONTD)
 Tungsten is mainly used in the production of hard materials based on tungsten carbide
 Lead has been used for bullets since their invention in the middle Ages
 Lead is still used in statues and sculptures (Fig. 10), including for armatures
Figure 9: Tungsten carbide ring (jewelry) Figure 10: A 17th –century gold-plated lead sculpture

23. ECONOMIC OR INDUSTRIAL APPLICATIONS
(CONTD)
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 Gold is usually alloyed with base metals for use in jewelry because of the softness of pure (24k)
 Copper is used to make copper fittings
Figure 12: Moche gold necklaceFigure 11: Copper fittings

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ECONOMIC OR INDUSTRIAL APPLICATIONS
(CONTD)
 Copper wire is used in power generation, power transmission, power distribution,
telecommunications, electronics circuitry, and countless types of electrical equipment
 ARCHITECTURAL PURPOSES
Figure 14: Copper roof on the Minneapolis city hall, with patinaFigure 13: Copper electrical busbars distributing
coated power to a large building

25.  Skarn, as a metasomatic rock is a product of hydrothermal alteration of
calcium- and magnesium-rich carbonate rocks. Its formation is associated
with the concentrations of metallic deposits (skarn deposits).
 The Younger Granites Complex and marble-bearing Schist Belts are the
possible locations of skarn occurrences in Nigeria. The marble-bearing
schist belts in the country are likely to be host to exoskarns rich in Fe, Cu,
Au and Mo skarn deposits.
CONCLUSION
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26. RECOMMENDATION
I employ that more researches be executed as far as exploring and exploiting
skarn deposits is concerned in Nigeria especially in the Younger Granites of
Nigeria which is in a non-rifted extensional environment, is likely to have
been associated with the hydrothermal system in a skarn environment
Secondly, marbles, in the Schist Belts of Nigeria, formed by contact
metamorphism, have been discovered to be sharing similar protoliths and
agents of metamorphism with skarn; hence, the possibility of skarn
occurrences in the marble-bearing schist belts in the country is probable
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27. REFERENCE
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 Meinert L. D., 1992, Skarn and Skarn Deposits: Geoscience Canada 19 (4), 145-162.
 Ray, G.E, Dawson, G.L. and Simpson, R., 1988, Geology, geochemistry and metallogenic zoning
in the Hedley Gold-Skarn camp, 1987, Paper 1988-1, p. 59-80.
 Soloviev, S. G., 2015, Geology, mineralization, and fluid inclusion characteristics of the
Kumbel oxidized W–Cu–Mo skarn and Au–W stockwork deposit in Kyrgyzstan, Tien Shan:
Mineralium Deposita 25 (2), 187-220.
 Nadoll, P., Mauk J. L., Leveile R. A. and Koenig A. E., 2015, Geochemistry of magnetite from
porphyry Cu and skarn deposits in the Southwestern United States: Mineralium Deposita 50 (4), 493-
515.
 Soloviev, S. G., Kryazhev, S. G. and Dvurechenskaya, S. S., 2013, Geology, mineralization, stable
isotope geochemistry, and fluid inclusion characteristics of the Novogodnee–Monto oxidized Au–
(Cu) skarn and porphyry deposit, Polar Ural, Russia: Mineralium Deposita 48 (5), 603-627.
 http://www.danieleheon.com/fieldwork-photos-yukon--bc.html
 Stewart D. Redwood and Shanks: International Geology Review, v. 12, p. 761-858.

28. Thank You!!!