Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
GEO PHYSICS
Topic
ISOSTASY
DENSITY,SUSCEPTIBILITY AND RESISTIVITY
INSTITUTE OF GEOLOGY
UNIVERSITY OF AZAD JAMMU & KASHMIR ...
WE PLACED FIRMLY EMBEDDED MOUNTAINS ON
THE EARTH, SO IT WOULD NOT MOVE UNDER THEM
(QUR'AN, 21:31)
ISOSTASY
ISOSTASY
It refers to the state of
gravitational
equilibrium between
the earth's lithosphere
and asthenosphere
such that t...
WORD ATTRIBUTION
• Isostasy is derived
from two Greek words
ISO and STASIS
• ISO means “same”
and
• STASIS mean
“standstil...
HISTORY
• In 1735, expeditions over the
Andes led by Pierre Bouguer,
a French photometrist studied
the isostasy for the fi...
ISOSTASTAIC MODELS
• There are three principal models of isostasy:
 THE AIRY MODEL
 THE PRATT MODEL
 THE VENING OR FLEX...
• THE AIRY MODEL
Different topographic heights are accommodated by changes
in crustal thickness, in which the crust has a ...
The main types of isostatic models. Each model
implies a state of hydrostatic equilibrium such
that the Earth’s outermost ...
Airy isostasy, in which a constant-density crust floats on a higher-density
mantle, and topography is determined by the th...
Airy was mostly correct about what supports large
(wide) mountains, but it took until the 1970’s to
prove this with seismi...
THE VENING MEINESZ OR FLEXURAL MODEL
• This hypothesis was suggested to explain how large topographic loads
such as seamou...
Regional Or Vening Isostasy - The Lithosphere Flexes Under Its Own Weight And Shields
The Asthenosphere From The Differenc...
WHICH DO YOU THINK WOULD HAVE THE GREATER VOLUME
AND MASS?
WHY?
• 1 kg of feathers
• 1 kg of rock
DENSITY
• Density is defined as mass per unit volume. It is a measure of how
tightly packed and how heavy the molecules are in an ...
UNITS FOR DENSITY
The SI unit of density is kg/m3 , g/cm3.
FORMULA
 M = D x V
 V = M / D
 D = M / V
TABLE SHOWING AVERAGE GRAVITY OF VARIOUS
SEDIMENTARY, METAMORPHIC AND IGNEOUS ROCKS
• Density is a property that is propor...
DENSITIES OF TYPICAL ROCK TYPES AND MINERALS
PUMICE
Environment of formation =Extrusive
(Volcanic)
Texture = Glassy, Vesicular
Grain size = Non-Crystalline
Color = Lig...
VESICULAR BASALT
Environment of formation =extrusive
(volcanic)
Texture = Glassy, vesicular
Grain size = non-crystalline
C...
RHYOLITE
Environment of formation =extrusive (volcanic)
Texture = fine
Grain size = less than 1 mm
Color = light
Density =...
ANDESITE
Environment of formation =extrusive
(volcanic)
Texture = fine
Grain size = less than 1 mm
Color = light
Density =...
BASALT
Environment of formation =extrusive
(volcanic)
Texture = fine
Grain size = less than 1 mm
Color = dark
Density = hi...
GRANITE
Environment of formation =intrusive
(plutonic)
Texture = coarse
Grain size = 1 mm to 10mm
Color = light
Density = ...
GABBRO
Environment of formation =intrusive
(plutonic)
Texture = coarse
Grain size = 1 mm to 10mm
Color = dark
Density = hi...
METAMORPHIC ROCKS
SLATE (2.79 g/m3) PHYLLITE (2.18 and 3.3 g/m3)
SCHIST (2.64 g/cm3)
GNEISS (2.80 g/cm3)
MARBLE (2.75 g/cm3) QUARTZITE (2.60 g/cm3)
SEDIMENTARY ROCKS
SANDSTONE (2.35 g/cm3)
ROCK SALT
(2.17 g/cm3)
SHALE (2.40 g/cm3)
GYPSUM (2.31 g/cm3)
LIMESTONE (2.55 g/cm3)
IGNEOUS ROCKS
Igneous rocks form when molten rock (magma) cools
and solidifies, with or without crystallization, either
be...
REASON OF HIGH DENSITY OF IGNEOUS
ROCKS THEN METAMORPHIC AND
SEDIMENTARY ROCKS
 Lack of pore pressure
 Due to mafic mine...
SUSCEPTIBILITY
SUSCEPTIBILITY (K)
• The degree of magnetization in response to the external magnetic field is
known as susceptibility.
Or...
THE VALUES GIVEN HERE ARE FOR SI,
INTERNATIONAL SYSTEM UNITS.
VALUE OF THE MAGNETIC SUSCEPTIBILITY
The value of the magnetic susceptibility can either be
 POSITIVE
 NEGATIVE.
POSITIVE VALUE
• Positive value means that the
induced magnetic field, I, is in
the same direction as the
inducing field, ...
NEGATIVE VALUE
• Negative value means that the
induced magnetic field is in
the opposite direction as the
inducing field.
REMNANT MAGNETIZATION
• If the magnetic material has relatively
large susceptibilities, or if the inducing
field is strong...
MAGNETIC PROPERTIES OF ROCKS
• All rocks contain magnetic properties. Sedimentary and metamorphic
rocks have less magnetic...
KINDS OF MAGNETIC MATERIAL
• Magnetic material are of different kinds. Three main types are as
follows:
1. Paramagnetic ma...
PARAMAGNETIC MATERIALS
• The magnetic material which have weak positive susceptibility is called
paramagnetic material. Gr...
Examples of paramagnetic minerals
Olivine (Fe,Mg)2SiO4 1.6 · 10-3
Montmorillonite (clay) 0.34 ·10-3
Siderite (FeCO3) 1.3-1...
DIAMAGNETIC MATERIALS
• The magnetic material which have weak negative susceptibility is known
as diamagnetic material. Gr...
Quartz (SiO2) - (13-17) · 10-6
Calcite (CaCO3) - (8-39) · 10-6
Graphite (C) - (80-200) · 10-6
Halite (NaCl) - (10-16) · 10...
FERROMAGNETIC MATERIALS
• Such material which have high susceptibility is called ferromagnetic material.
Electron coupling...
MAIN REASON OF MAGNETIZATION OF
ROCKS
• The liquid portion in the outer core consist of iron, nickel and cobalt which are
...
SUSCEPTIBILITY OF VARIOUS ROCKS
TABLE SHOWING SUSCEPTIBILITY OF FEW MATERIALS
REASON OF HIGH SUSCEPTIBILITY OF IGNEOUS
ROCKS
• Susceptibility is higher in rocks having magnetic minerals and in igneous...
IGNEOUS ROCK’S SUSCEPTIBILITY > METAMORPHIC ROCK’S SUSCEPTIBILITY >
SEDIMENTARY ROCK’S SUSCEPTIBILITY
Volcanic rocks, part...
RESISTIVITY
RESISTIVITY
DEFINITION
• Resistivity is an intrinsic property that quantifies how strongly a given
material opposes the fl...
BASIC PHYSICS OF ELECTRIC CURRENT
FLOW
 SIMPLE RESISTOR IN CIRCUIT
Ohm’s Law states that for a resistor, the resistance (...
where ρ is the electrical resistivity of the material (ohm-m). This is the resistance per
unit volume and is an inherent p...
HOW TO CALCULATE RESISTIVITY OF ROCKS
• Pure materials are rarely found in the Earth and most rocks are a
mixture of two o...
FACTORS THAT WILL INCREASE THE
RESISTIVITY OF A ROCK
Factors that will INCREASE the resistivity of a rock
(a) Minimum pore...
FACTORS THAT WILL DECREASE THE
RESISTIVITY OF A ROCK
Factors that will DECREASE the resistivity of a rock:
(a) More pore f...
REASON OF HIGH RESISTIVITY OF IGNEOUS
ROCKS
• Compacted rocks
• No pore spaces
• Presence of Magnetic minerals
• No fluids...
IGNEOUS ROCK’S RESISTIVITY >
METAMORPHIC ROCK’S RESISTIVITY >
SEDIMENTARY ROCK’S RESISTIVITY
 Igneous rocks have highest ...
RESISTIVITY LEVELS OF VARIOUS ROCKS
TABLE SHOWING RESISTIVITY OF FEW
ROCKS
 Groundwater exploration.
 Mineral exploration,
detection of cavities.
 Waste site exploration.
 Oil exploration
APPLI...
REFERENCES
• Archie, G.E., 1942: The electrical resistivity log as an aid in
determining some reservoir characteristics. T...
Isostasy
Isostasy
Isostasy
Isostasy
Isostasy
Isostasy
Upcoming SlideShare
Loading in …5
×

Isostasy

3,628 views

Published on

isotacy

Published in: Science
  • Be the first to comment

Isostasy

  1. 1. GEO PHYSICS Topic ISOSTASY DENSITY,SUSCEPTIBILITY AND RESISTIVITY INSTITUTE OF GEOLOGY UNIVERSITY OF AZAD JAMMU & KASHMIR MUZAFFARABAD
  2. 2. WE PLACED FIRMLY EMBEDDED MOUNTAINS ON THE EARTH, SO IT WOULD NOT MOVE UNDER THEM (QUR'AN, 21:31)
  3. 3. ISOSTASY
  4. 4. ISOSTASY It refers to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density.
  5. 5. WORD ATTRIBUTION • Isostasy is derived from two Greek words ISO and STASIS • ISO means “same” and • STASIS mean “standstill”.
  6. 6. HISTORY • In 1735, expeditions over the Andes led by Pierre Bouguer, a French photometrist studied the isostasy for the first time. About a century later, similar discrepancies were observed by Sir George Everest, surveyor general of India, in surveys south of the Himalayas, indicating a lack of compensating mass beneath the visible mountain ranges. The general term 'isostasy' was coined in the year 1889 by the American geologist Clarence Dutton.
  7. 7. ISOSTASTAIC MODELS • There are three principal models of isostasy:  THE AIRY MODEL  THE PRATT MODEL  THE VENING OR FLEXURAL ISOSTASY MODEL
  8. 8. • THE AIRY MODEL Different topographic heights are accommodated by changes in crustal thickness, in which the crust has a constant density. • THE PRATT MODEL Different topographic heights are accommodated by lateral changes in rock density. • THE VENING OR FLEXURAL ISOSTASY MODEL Where the lithosphere acts as an elastic plate and its inherent rigidity distributes local topographic loads over a broad region by bending. Airy and Pratt isostasy are statements of buoyancy, while flexural isostasy is a statement of buoyancy while deflecting a sheet of finite elastic strength.
  9. 9. The main types of isostatic models. Each model implies a state of hydrostatic equilibrium such that the Earth’s outermost layers are in a state of flotation on their more fluid substrate. (a / 1) The Airy-Heiskanen Model (b / 2) - The Pratt-Hayford Model. (c) Vening Meinesz model.
  10. 10. Airy isostasy, in which a constant-density crust floats on a higher-density mantle, and topography is determined by the thickness of the crust.
  11. 11. Airy was mostly correct about what supports large (wide) mountains, but it took until the 1970’s to prove this with seismic work that measured the thickness of the crust and lithosphere beneath mountains. Pratt was correct in that the difference between the low standing ocean basins and the high standing continents is partially due to the fact that oceans have dense gabbroic composition crust whereas continents have lighter less dense ‘Andesitic’ composition crust.
  12. 12. THE VENING MEINESZ OR FLEXURAL MODEL • This hypothesis was suggested to explain how large topographic loads such as seamounts. A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface (sea level), and thus is not an island.(e.g. Hawaiian Islands) could be compensated by regional rather than local displacement of the lithosphere. This is the more general solution for lithospheric flexure as it approaches the locally-compensated models above as the load becomes much larger than a flexural wavelength or the flexural rigidity of the lithosphere approaches 0.
  13. 13. Regional Or Vening Isostasy - The Lithosphere Flexes Under Its Own Weight And Shields The Asthenosphere From The Difference In Pressures.
  14. 14. WHICH DO YOU THINK WOULD HAVE THE GREATER VOLUME AND MASS? WHY? • 1 kg of feathers • 1 kg of rock DENSITY
  15. 15. • Density is defined as mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object. Density is the amount of matter within a certain volume.
  16. 16. UNITS FOR DENSITY The SI unit of density is kg/m3 , g/cm3. FORMULA  M = D x V  V = M / D  D = M / V
  17. 17. TABLE SHOWING AVERAGE GRAVITY OF VARIOUS SEDIMENTARY, METAMORPHIC AND IGNEOUS ROCKS • Density is a property that is proportional to the composition of the rock. The higher the amount of silica (felsic) the less dense the rock will be. The less amount of silica in the rock the more dense the rock will be.
  18. 18. DENSITIES OF TYPICAL ROCK TYPES AND MINERALS
  19. 19. PUMICE Environment of formation =Extrusive (Volcanic) Texture = Glassy, Vesicular Grain size = Non-Crystalline Color = Light Density = Low (1.00 g/cm3 ) Composition = Felsic
  20. 20. VESICULAR BASALT Environment of formation =extrusive (volcanic) Texture = Glassy, vesicular Grain size = non-crystalline Color = dark Density = medium (2.74 g/cm3) Composition = mafic
  21. 21. RHYOLITE Environment of formation =extrusive (volcanic) Texture = fine Grain size = less than 1 mm Color = light Density = low (2.51 g/cm3) Composition = felsic
  22. 22. ANDESITE Environment of formation =extrusive (volcanic) Texture = fine Grain size = less than 1 mm Color = light Density = medium (2.64 g/cm3) Composition = intermediate
  23. 23. BASALT Environment of formation =extrusive (volcanic) Texture = fine Grain size = less than 1 mm Color = dark Density = high (2.99 g/cm3) Composition = mafic
  24. 24. GRANITE Environment of formation =intrusive (plutonic) Texture = coarse Grain size = 1 mm to 10mm Color = light Density = low (2.667 g/cm3) Composition = felsic
  25. 25. GABBRO Environment of formation =intrusive (plutonic) Texture = coarse Grain size = 1 mm to 10mm Color = dark Density = high ( 3.03 g/cm3) Composition = mafic
  26. 26. METAMORPHIC ROCKS SLATE (2.79 g/m3) PHYLLITE (2.18 and 3.3 g/m3)
  27. 27. SCHIST (2.64 g/cm3) GNEISS (2.80 g/cm3)
  28. 28. MARBLE (2.75 g/cm3) QUARTZITE (2.60 g/cm3)
  29. 29. SEDIMENTARY ROCKS SANDSTONE (2.35 g/cm3)
  30. 30. ROCK SALT (2.17 g/cm3) SHALE (2.40 g/cm3)
  31. 31. GYPSUM (2.31 g/cm3) LIMESTONE (2.55 g/cm3)
  32. 32. IGNEOUS ROCKS Igneous rocks form when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on The surface as extrusive (volcanic) rocks. IGNEOUS ROCK’S DENSITY > METAMORPHIC ROCK’S DENSITY > SEDIMENTARY ROCK’S DENSITY
  33. 33. REASON OF HIGH DENSITY OF IGNEOUS ROCKS THEN METAMORPHIC AND SEDIMENTARY ROCKS  Lack of pore pressure  Due to mafic minerals  Due to slow cooling  Due to close packing or compaction  Due to impermeable nature  Number of atoms  Impurities or Neighboring minerals involvement.  Due to slow crystallization  More pressure in the subsurface.
  34. 34. SUSCEPTIBILITY
  35. 35. SUSCEPTIBILITY (K) • The degree of magnetization in response to the external magnetic field is known as susceptibility. Or • It is a measure of the ease with which the material can be magnetized. Mathematically K= I / H I= intensity of magnetization H = Magnetic Field Strength Definition
  36. 36. THE VALUES GIVEN HERE ARE FOR SI, INTERNATIONAL SYSTEM UNITS.
  37. 37. VALUE OF THE MAGNETIC SUSCEPTIBILITY The value of the magnetic susceptibility can either be  POSITIVE  NEGATIVE.
  38. 38. POSITIVE VALUE • Positive value means that the induced magnetic field, I, is in the same direction as the inducing field, H.
  39. 39. NEGATIVE VALUE • Negative value means that the induced magnetic field is in the opposite direction as the inducing field.
  40. 40. REMNANT MAGNETIZATION • If the magnetic material has relatively large susceptibilities, or if the inducing field is strong, the magnetic material will retain a portion of its induced magnetization even after the induced field disappears. This remaining magnetization is called remnant magnetization. • The total magnetic field is a sum of the main magnetic field produced in the Earth's core, and the remnant field within the material.
  41. 41. MAGNETIC PROPERTIES OF ROCKS • All rocks contain magnetic properties. Sedimentary and metamorphic rocks have less magnetic properties as compared to igneous rocks. Because sedimentary and metamorphic rocks have low susceptibility and igneous rocks have high susceptibility. • IGNEOUS ROCK’S SUSCEPTIBILITY > METAMORPHIC ROCK’S SUSCEPTIBILITY > SEDIMENTARY ROCK’S SUSCEPTIBILITY
  42. 42. KINDS OF MAGNETIC MATERIAL • Magnetic material are of different kinds. Three main types are as follows: 1. Paramagnetic materials 2. Diamagnetic materials 3. Ferromagnetic materials
  43. 43. PARAMAGNETIC MATERIALS • The magnetic material which have weak positive susceptibility is called paramagnetic material. Grains of such material tends to line up with their long dimension in the direction of magnetic field. EXAMPLE 1. Iron compounds 2. Mica 3. Biotite 4. Garnet 5. Amphibole
  44. 44. Examples of paramagnetic minerals Olivine (Fe,Mg)2SiO4 1.6 · 10-3 Montmorillonite (clay) 0.34 ·10-3 Siderite (FeCO3) 1.3-11.0 · 10-3 Serpentinite 3.1-75.0 · 10-3 (Mg3Si2O5(OH)4) κ (SI)Mineral
  45. 45. DIAMAGNETIC MATERIALS • The magnetic material which have weak negative susceptibility is known as diamagnetic material. Grains of such material tends to line up with their long dimension across the direction of magnetic field. • EXAMPLE 1. Rock salt 2. Gypsum 3. Anhydrite 4. Quartz
  46. 46. Quartz (SiO2) - (13-17) · 10-6 Calcite (CaCO3) - (8-39) · 10-6 Graphite (C) - (80-200) · 10-6 Halite (NaCl) - (10-16) · 10-6 Examples of diamagnetic minerals κ (SI)Mineral
  47. 47. FERROMAGNETIC MATERIALS • Such material which have high susceptibility is called ferromagnetic material. Electron coupling is more stronger in these materials. Grains are aligned in the direction of magnetic field. • EXAMPLE 1. Iron 2. Cobalt 3. Nickel 4. Hematite 5. Magnetite
  48. 48. MAIN REASON OF MAGNETIZATION OF ROCKS • The liquid portion in the outer core consist of iron, nickel and cobalt which are in continues motion because it is high density material and it wants to move from high density to low density, as a result convectional currents are produced in the outer core. These convectional currents are also produce in the upper mantle due to which plate moves. Due to these currents iron, nickel and cobalt are magnetized and earth behaves as a magnet as a whole. • Lightening is another factor that magnetized the rocks when it pass through magnetosphere when the electron pass through magnetosphere current is produced which results in the magnetization of the earth and this is a rare case.
  49. 49. SUSCEPTIBILITY OF VARIOUS ROCKS
  50. 50. TABLE SHOWING SUSCEPTIBILITY OF FEW MATERIALS
  51. 51. REASON OF HIGH SUSCEPTIBILITY OF IGNEOUS ROCKS • Susceptibility is higher in rocks having magnetic minerals and in igneous rocks ( mainly mafic and ultramafic ) have more ferromagnetic minerals, so they have more susceptibility then metamorphic and sedimentary rocks. • Igneous rocks have high susceptibility because grains of igneous rocks align in the direction of external field, also electron coupling is stronger in these rocks. • Magnetic susceptibility of rocks is principally controlled by the type and amount of magnetic minerals contained in a rock. • The magnetic susceptibility depends also on temperature. • Outer core’s material.
  52. 52. IGNEOUS ROCK’S SUSCEPTIBILITY > METAMORPHIC ROCK’S SUSCEPTIBILITY > SEDIMENTARY ROCK’S SUSCEPTIBILITY Volcanic rocks, particularly the young ones (called neo-volcanics ), are often strongly magnetic.
  53. 53. RESISTIVITY
  54. 54. RESISTIVITY DEFINITION • Resistivity is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. It Is also called electrical resistivity, specific electrical resistance, or volume resistivity. A low resistivity indicates a material that readily allows the movement of electric charge. • Resistivity is commonly represented by the Greek letter ρ (rho). • The SI unit of electrical resistivity is the ohm meter (Ω⋅m)
  55. 55. BASIC PHYSICS OF ELECTRIC CURRENT FLOW  SIMPLE RESISTOR IN CIRCUIT Ohm’s Law states that for a resistor, the resistance (in ohms), R is defined as R = IV V = voltage (volts); I = current flow (amps)  ELECTRIC CURRENT FLOW IN A FINITE VOLUME Ohm’s Law as written above describes a resistor, which has no dimensions. In considering the flow of electric current in the Earth, we must consider the flow of electric current in a finite volume. Consider a cylinder of length L and cross section A that carries a current I .
  56. 56. where ρ is the electrical resistivity of the material (ohm-m). This is the resistance per unit volume and is an inherent property of the material. Resistivity is basically opposition to the flow of electron. R is the electrical resistance of a uniform specimen of the material (measured in ohms, Ω) L is the length of the piece of material (measured in meters, m) A is the cross-sectional area of the specimen (measured in square meters, m2).
  57. 57. HOW TO CALCULATE RESISTIVITY OF ROCKS • Pure materials are rarely found in the Earth and most rocks are a mixture of two or more phases (solid, liquid or gas). Thus to calculate the overall electrical resistivity of a rock, we must consider the individual resistivities and then compute the overall electrical resistivity.
  58. 58. FACTORS THAT WILL INCREASE THE RESISTIVITY OF A ROCK Factors that will INCREASE the resistivity of a rock (a) Minimum pore fluid. (b) Lower salinity of pore fluid (c) Compaction - less pathways for electric current flow. (d) Lithification - block pores by deposition of minerals. (e)Fluid content constant, but decrease connection between pores.
  59. 59. FACTORS THAT WILL DECREASE THE RESISTIVITY OF A ROCK Factors that will DECREASE the resistivity of a rock: (a) More pore fluid (b) Increase the salinity of the pore fluid - more ions to conduct electricity (c) Fracture rock to create extra pathways for current flow (d) Add clay minerals (e) Fluid content constant, but improve interconnection between pores.
  60. 60. REASON OF HIGH RESISTIVITY OF IGNEOUS ROCKS • Compacted rocks • No pore spaces • Presence of Magnetic minerals • No fluids • Pressure • Temperature • Fractures • Composition
  61. 61. IGNEOUS ROCK’S RESISTIVITY > METAMORPHIC ROCK’S RESISTIVITY > SEDIMENTARY ROCK’S RESISTIVITY  Igneous rocks have highest resistivity.  Sedimentary rocks tend to be the most conductive due to their high fluid content  Metamorphic rocks have intermediate but overlapping resistivity. Age of the rock is also important for the resistivity. For example: Young volcanic rock (Quaternary) ≈10−200Ωm Old volcanic rock (Precambrian) ≈100−2000Ωm
  62. 62. RESISTIVITY LEVELS OF VARIOUS ROCKS
  63. 63. TABLE SHOWING RESISTIVITY OF FEW ROCKS
  64. 64.  Groundwater exploration.  Mineral exploration, detection of cavities.  Waste site exploration.  Oil exploration APPLICATION OF RESISTIVITY
  65. 65. REFERENCES • Archie, G.E., 1942: The electrical resistivity log as an aid in determining some reservoir characteristics. Tran. AIME, 146, 54-67. • Lowrie. Fundamentals of Geophysics. Cambridge University Press. pp. 254–.ISBN 978-1-139-46595-3 • A.B. Watts, Isostasy and flexure of the lithosphere, Cambridge Univ. Press., 2001 • Altschaeffel, A. G., and Harrison, W., 1959, Estimation of a minimum depth of burial for a Pennsylvanian under clay: Jour. Sed. Petrology, v. 29, p.178-185 • Hrouda, F. & Rejl, L., 1982. Small-scale magnetic susceptibility distribution in some plutonic rocks and its geological implications. Věst. Ústř. Úst.geol., 57-69. Prague. • Smirnov, V., 1982. Geology of mineral deposits. Nedra. Moscow.

×