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Carbonates Earth Materials J.D. Price

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Page 1: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

CarbonatesCarbonates

Earth Materials J.D. Price

Page 2: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Aragonite CaCO3

Calcite CaCO3

Magnesite MgCO3

Rhodochrosite MnCO3

Siderite FeCO3

Dolomite CaMg (CO3)2

Ankerite CaFe(CO3)2

Malachite Cu2CO3(OH)2

Azurite Cu3(CO3)2

CarbonatesCarbonates

Page 3: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Tenorite + H2O

Cuprite + H2O

Copper + H2O

Azurite + H2O

Malachite + H2O

k =aAz

2 aH 2O1

aMal3 pCO2

1

3Cu2 CO3 (OH)2 Mal + CO2 gas = 2Cu3 (CO3)2 (OH)2 Az + H2O liq

GºTP - Gº = RT ln K = 2.303 RT log K

At s.s. GºTP =0 with T=298K,

log kº = -0.1750 Gº = 1/p CO2

Gºf Az = -1429.56 kJ/mol

Gºf Mal = -900.41 kJ/mol

Gºf H2O = -237.23 kJ/mol

Gºf CO2 = -394.37 kJ/mol

Gºrxn = -0.75 kJ/mol

log p CO2 = -0.13

Page 4: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

We discussed this previously. Aragonite and calcite are polymorphs. Aragonite is the higher pressure configuration of CaCO3.

CaCO3CaCO3

Page 5: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Image from Klein and Hurlbut, 1985

CalciteCalcite

Page 6: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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Humbolt College

DolomiteDolomite

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The substitution of Mg for Ca maintains the same structure. As a consequence, dolomite is also rhombohedral, has similar high birefringence and similar density.

Not so much effervescence in dilute, cold HCl

What’s the reaction?

Page 7: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Ca-MgCa-Mg

Solid solution is only permitted at high temperatures. At ambient conditions there is virtually no solid solution in the Ca-Mg carbonate system.

Page 8: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Image from Klein and Hurlbut, 1985

There is much more (but still limited) solid solution in the Ca-Fe carbonate system. And extensive solid solution in both CaMg-CaFe and Mg-Fe space.

Lines - coexisting compositions

Ca-Mg-FeCa-Mg-Fe

Page 9: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

By now you know that minerals can be recorders of the processes that create and sustain them.

Carbonates - some powerful information

•Trace element incorporation (divalent cations, such as Sr in calcite)

•Isotopes of C and O (13C and 18O)

•These are influenced by temperature (directly or indirectly)

Because carbonate materials are incorporated into marine organisms, carbonate minerals may record ocean climate history.

DetailsDetails

Page 10: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

18O is a stable isotope influenced by global ice content.

δO18 =

18O16O

⎛ ⎝ ⎜

⎞ ⎠ ⎟sample

−18O

16O

⎛ ⎝ ⎜

⎞ ⎠ ⎟s tandard

18O16O

⎛ ⎝ ⎜

⎞ ⎠ ⎟s tandard

⎢ ⎢ ⎢ ⎢

⎥ ⎥ ⎥ ⎥

×1000

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Standard for carbonates is a belemenite fossil from the K Peedee formation, SC

18O/16O = 0.0020672

H2O16 vs. H2O18

For a volume of water, more 16O water evaporates relative than water with 18O.

Evaporated water from near the equator is eventually transported toward the poles through repeated evaporation and precipitation.

The 18O/16O ratio will be lower in the snow that falls on a glacier than it is in the ocean from which the water evaporated.

If global ice volume increase, the 18O values of seawater become larger as more 16O stored is locked away in ice.

Page 11: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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Analyzing the 18O/16O ratio of a dated carbonate mineral from a fossil or marine precipitate gives you an estimate of global ice - a proxy for two parameters

1.Global climate trends

2.Sea level

Page 12: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Carbonate originsCarbonate origins

Carbonate is abundant at the earth’s surface, but may be produced deeper in the earth where the activity of CO2 is elevated.

Igneous: Carbonatites - rare magmatic systems that produce carbonate materials

Hydrothermal: Alteration of mantle rocks and dissolution in aqueous fluids

Ground/surface water: Chemogenic precipitation, karst

Metamorphic: Recrystallization and metasomatism

Sedimentary: Biogenic and reworking of biogenic materials, clastic continental materials

Page 13: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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CarbonatitesCarbonatites

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Mt. Erebus, Antarctica - a very active carbonatite volcano

MEVO

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Page 14: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Critters make minerals

Aragonite and calcite

In general the oceans are nearly saturated in CaCO3

Ca2+ + HCO3- = CaCO3 + H+

Temperature is important (latitude, depth)

Biogenic SedimentsBiogenic SedimentsQuickTime™ and a

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Page 15: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Gastropoda and Pelecypoda,Cretaceous, New Jersey

Trilobite Ameura , Upper Pennsylvanian, Kansas

KGS Website

Page 16: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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CoralsCorals

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Corals are great limestone builders. They put a lot of time and energy into building skeletons made from aragonite

The coral polyp only inhabits the outer 1-2 cm of the structure. The rest is just a framework to increase reproduction and feeding

Page 17: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

CoccolithsCoccoliths

Tiny plankton with calcareous shells. Abundant enough to live and die to make massive limestone deposits like Santa Elena Canyon, TX

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Page 18: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Carbonate producing organisms die, but their shells will only be preserved if they are deposited above 4 km depth

Page 19: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Ice cores trap gas and dust. Temperature from concentration of deuterium in ice.

375 CurrentAtmosphereCO2

Vostok, Antarctica Ice CoreVostok, Antarctica Ice Core

Page 20: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Feely et al., 2001 Feely et al., 2001

Increased atmospheric CO2 means big changes in ocean chemistry. This could be detrimental to much of marine life.

Page 21: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Feely et al., 2001 Feely et al., 2001

Carbon isotopes show the location of industrial CO2 in the worlds largest oceans. As we know ocean mixing is a slow process - the most recent excess CO2 remains in the first 1 km of the ocean.

Carbon isotopes show the location of industrial CO2 in the worlds largest oceans. As we know ocean mixing is a slow process - the most recent excess CO2 remains in the first 1 km of the ocean.

Page 22: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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DiagenesisDiagenesis

In sedimentary rocks, the individual particles need to be cemented together. Carbonate minerals precipitate out of water to cement grains.

Thin section under XP shows calcite overgrowth on micrite grains.

Page 23: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

0.3mm©Ryan Hanson

Fragmented or whole aquatic invertebrate hard parts

Origin: Bodies of water with suitable environments

LimestoneLimestone

Page 24: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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Fossiliferous limestone - pore space colored blue

Page 25: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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Oolitic limestoneOolitic limestone

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Ooids form through growth and/or accumulation in dynamic carbonate environments.

Page 26: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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Page 27: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Brucite

Calcite

Dolomite

Magn

Dolomite precipitationDolomite precipitation

Dolomite dominates older rocks and has decreased over time.

It only forms in special chemical environments.

Thermodynamically it should be the dominant phase in sea water.

The dolomite problem.

Page 28: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

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SpeleothemsSpeleothems

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Page 29: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Fault in Wonder CaveFault in Wonder Cave

Pit Cave - Gregg Eckhardt Carbonates easily dissolve into water (rain water is slightly ascidic), Many limestone will dissolve into meteoric waters; and perhaps precipitate out at another location

The Edwards Aquifer is hosted in within an initially low-porosity limestone. Water has worked its way into cracks over last 1 million years

The Edwards Aquifer is hosted in within an initially low-porosity limestone. Water has worked its way into cracks over last 1 million years

Page 30: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Pucek Property, near San Antonio, TX

This is the largest water well in the world.  When tapped, it blew out rocks the size of basketballs 20 feet into the air. Water flowed out at 25000 gallons each minute.

Not potable, but enough water to support about 250,000 people

Page 31: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

So what’s the problem? It’s bad water.

The problem is that the Pucek well was draining the aquifer at a much more rapid rate than water could be replaced. If allowed to persist, the well would eventually tap the sweet water and lower San Antonio’s supplies beyond use.

Page 32: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Reprecipitation of carbonates occurs, particularly if energy conditions, composition, or pH of the water changes.

Travertine

Tuffa

Page 33: Carbonates Earth Materials J.D. Price. Aragonite CaCO 3 Calcite CaCO 3 Magnesite MgCO 3 Rhodochrosite MnCO 3 Siderite FeCO 3 Dolomite CaMg (CO 3 ) 2 Ankerite

Univ. of North Carolina Web atlas of metamorphic textures

Marble

Conditions: low to moderate P & T

Minerals: calcite or dolomite (carbonates)

Origin: biogenic (limestone or dolostone)