This document provides an overview of dolomite petrography and geochemistry. It describes various dolomite rock textures including stoichiometric and non-stoichiometric dolomite, zoned dolomite, fabric-retentive and destructive dolomite, and more. Diagrams show examples of these textures. The document also discusses dolomite geochemistry including trace elements, stable isotopes, and radiogenic isotopes. Graphs illustrate isotopic trends in dolomite over geologic time. In summary, the document categorizes and describes different dolomite rock textures and geochemical signatures.

1. Omar A. Radwan
o.a.radwan@gmail.com
PhD Student – Geosciences Dept. - KFUPM
GEOL533 - Carbonates and Evaporites
Dolomite
Petrography & Geochemistry

2. 2
Dolomite: Petrography
• Stoichiometric dolomite
• Non-stoichiometric dolomite
• Zoned dolomite
• Fabric-retentive dolomite
• Fabric-destructive dolomite
• Fabric-specific dolomite
• Limpid dolomite
• Saddle dolomite
• Xenotopic dolomite
• Idiotopic dolomite
• Hypidiotopic dolomite
• syntaxial dolomite
• Hollow dolomite
• Inside-out dolomite
• Dedolomite
• Detrital dolomite
Dolomite: Geochemistry
• Trace elements
• Stable isotopes
• Radiogenic isotopes

3. Stoichiometric dolomite/Non-stoichiometric dolomite
Stoichiometric dolomite
• A.K.A. True dolomite
• A.K.A. Ordered dolomite
Non-stoichiometric dolomite
• A.K.A. Protodolomite
• A.K.A. Calcian dolomite
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James & Jones, 2015 Schole & Ulmer-Schole, 2003

4. Zoned dolomite
Euhedral dolomite crystals with cloudy cores and clear rims.
Note ghosts of fossil fragments in some of the cloudy cores. Brac
Formation (Oligocene), Cayman Brac. Image width 0.25 mm.
James & Jones, 2015
Euhedral to subhedral dolomite, Lo. Ordovician St. George
Gp., western Newfoundland, Canada.
Zoning is not readily visible because it consists mainly of
slight elemental variations. In such cases, staining,
cathodoluminescence, backscattered electron imaging or
other techniques can be used to accentuate zonation.
PPL/CL, HA = 0.75 mm each
Schole & Ulmer-Schole, 2003 4

5. Fabric-retentive dolomite
• A.K.A. Mimitic dolomite & Fabric-preserving dolomite
Mimetic dolomite, Miocene, Gulf of Suez, Egypt.
(a) Well-preserved but dolomitized scleractinian coral (Montastraea sp.), centimeter scale.
(b) Thin-section (PPL) of mimetically replaced corals. Image width 5 mm.
(c) Thin-section (PPL) of perfectly replaced coralline algae where the cells are clearly visible.
Image width 3 mm.
James & Jones, 2015
5

6. Fabric-destructive dolomite
Fabric-destructive medium crystalline
dolomite, Oligocene, South Australia.
(a) Outcrop image illustrating lower
limestone (Lst) and upper dolomite (Dol).
(b) Limestone, bryozoan floatstone to
wackestone. Scale bar: 1 mm.
(c) Dolomite has replaced limestone in (b),
where the rock is composed of numerous
euhedral planar crystals with no vestige of
the original limestone. Image width 4.4 mm.
(d) CL image illustrating strong crystal
zonation. Image width 4.4 mm.
James & Jones, 2015
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7. Fabric-specific dolomite
(a) Bedding plane view of Lower Ordovician
limestone where burrows, gastropods, and
sponges are preferentially replaced by
dolomite. Lens cap 50 mm.
(b) Thin-section (PPL) calcite stained red
where ooids were replaced by dolomite but
all the other components are calcite, Upper
Cambrian, Utah, USA. Image width 6 mm.
(c) Thin-section (PPL) in which the peloids
and peloid cores to ooids are dolomite
(turquoise) but all the other components are
calcite, lower Cambrian, Labrador, Canada.
Image width 4.4 mm.
(d) Outcrop surface of same unit as (a) but
where the former limestone matrix is
replaced by a later-stage dolomite (a true
multistage dolostone). Sledgehammer head
10 cm long.
7James & Jones, 2015

8. Limpid dolomite
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Pleistocene Coral Rock Fm. Golden Grove, Barbados
An example of mixing zone dolomite cements in a Pleistocene wackestone. Calcite is stained red and dolomite remains unstained. Note
the limpid (very clear, nearly inclusion-free) character of the cements and the thin, interlayered bands of low-Mg calcite cements
growing in continuity with the dolomite. Clear pore space remains at the center of the pore. Photograph courtesy of John D. Humphrey.
PPL, AS, HA = 1.2 mm
Schole & Ulmer-Schole, 2003

9. Saddle dolomite
• A.K.A. Baroque dolomite
Saddle dolomite.
(a) ‘Zebra’ saddle dolomite resulting from
hydrofracturing and white sparry saddle dolomite
in the pores, Upper Cambrian, Alberta, Canada.
Centimetre scale.
(b) Close-up of coarse crystals with conspicuous
curved faces, Devonian subsurface core. Image
width 3 cm.
(c) Thin-section (PPL) impregnated with blue epoxy
showing the curved crystal faces, Devonian
subsurface core. Image width 2 cm.
(d) Same thin-section (XPL) illustrating sweeping
extinction of the saddle dolomite crystals.
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James & Jones, 2015

10. Xenotopic dolomite/Idiotopic dolomite/Hypidiotopic dolomite
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Adapted from Sibley and Gregg (1987)
James & Jones, 2015

11. Syntaxial dolomite
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Mid. Cretaceous Edwards Fm., Bell Co., Texas
This standard light microscope view (that should be compared with the
subsequent CL image) shows a finely crystalline dolostone in which
syntaxial dolomite cement is prominent, forming 24% of the rock and
lining molds in somewhat patchy fashion. The total porosity in this
rock is 25% and the brown pore fillings are epoxy impregnation
medium that has been “burned” by the electron beam. Photograph
courtesy of Philip W. Choquette.
PPL, HA = 1.5 mm
A CL view of the previous sample. Note the clear distinction of
dolomite-overgrowth cements and their patchy distribution as linings
of molds. One cement zone has been dissolved
during subaerial weathering, perhaps because it contained more Mg
than other zones. Photograph courtesy of Philip W. Choquette.
CL, HA = 1.5 mm
James & Jones, 2015

12. Hollow dolomite
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SEM image of hollow dolomite crystal showing
etched crystal interior, Cayman Formation
(Miocene), Grand Cayman. Image width 70 μm.
James & Jones, 2015

13. Inside-out dolomite
SEM image of polished surface etched with HCl showing inside-out dolomite (center of image) showing irregular core
surrounded by rim. Zoning is evident because of differential etching due to varying mole % CaCO3 content of the dolomite.
Cayman Formation (Miocene), Grand Cayman, image width 14 μm.
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James & Jones, 2015

14. Dedolomite
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Thin-section images (PPL and stained with Alizarin red S) of
Oligocene Limestone, Southern Australia.
(a) Numerous dolomite crystals that have been dissolved and their
hollow cores are the site of later calcite precipitation (red). Image
width 1.4 mm.
(b) Close-up of a single crystal, image width 200 μm.
James & Jones, 2015

15. Detrital dolomite
Detrital dolomite.
(a) Thin-section image of a compound Pleistocene dolostone clast incorporated in Holocene sediment, Lacepede Shelf,
southern Australia. Image width 0.7 mm.
(b) CL image of individual Pleistocene dolomite crystals and clusters from Holocene sediment, Lacepede Shelf, southern
Australia. Image width 0.8 mm.
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James & Jones, 2015

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Dolomite: Geochemistry
• Stoichiometric dolomite
• Non-stoichiometric dolomite
• Zoned dolomite
• Fabric-retentive dolomite
• Fabric-destructive dolomite
• Fabric-specific dolomite
• Limpid dolomite
• Saddle dolomite
• Xenotopic dolomite
• Idiotopic dolomite
• Hypidiotopic dolomite
• syntaxial dolomite
• Hollow dolomite
• Inside-out dolomite
• Dedolomite
• Detrital dolomite
Dolomite: Geochemistry
• Trace elements
• Stable isotopes
• Radiogenic isotopes

17. Trace elements
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James & Jones, 2015

18. Stable isotopes
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Adapted from Veizer and MacKenzie (2005)
James & Jones, 2015
Adapted from Veizer and MacKenzie (2005)
James & Jones, 2015
Phanerozoic trend of δ13C for LMC shells. Shaded areas
around running mean include 68% ± 1σ and 95% ± 2σ of all
data.
Phanerozoic δ18O trend for LMC shells. Shaded areas around
running mean include 68% ± 1σ and 95% ± 2σ of all data.

19. Radiogenic isotopes
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Adapted from Koepnick et al. (1985) and Veizer et al. (1999).
James & Jones, 2015
The variation of 87Sr:86Sr ratio as recorded in
brachiopods through Phanerozoic time.
The main sources of Sr. The 87Sr:86Sr values from continental
lithosphere versus oceanic lithosphere are demonstrably different,
whereas most limestones have contributions from both sources.
James & Jones, 2015