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Chen, C.; Zhong, H.; Wang, X.; Ning, M.; Wang, X.; Ge, Y.; Wang, H.; Tang, R.; Hou, M. Dolomite Mineralogy. Encyclopedia. Available online: https://encyclopedia.pub/entry/52279 (accessed on 19 May 2024).
Chen C, Zhong H, Wang X, Ning M, Wang X, Ge Y, et al. Dolomite Mineralogy. Encyclopedia. Available at: https://encyclopedia.pub/entry/52279. Accessed May 19, 2024.
Chen, Chao, Hanting Zhong, Xinyu Wang, Meng Ning, Xia Wang, Yuzhu Ge, Han Wang, Ruifeng Tang, Mingcai Hou. "Dolomite Mineralogy" Encyclopedia, https://encyclopedia.pub/entry/52279 (accessed May 19, 2024).
Chen, C., Zhong, H., Wang, X., Ning, M., Wang, X., Ge, Y., Wang, H., Tang, R., & Hou, M. (2023, December 02). Dolomite Mineralogy. In Encyclopedia. https://encyclopedia.pub/entry/52279
Chen, Chao, et al. "Dolomite Mineralogy." Encyclopedia. Web. 02 December, 2023.
Dolomite Mineralogy
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This entry is adapted from the peer-reviewed paper 10.3390/min13121479

Dolomite [CaMg(CO3)2] is a rhombohedral carbonate mineral. The dolomite structure consists of an ordered arrangement of alternating layers of Ca2+ and Mg2+ cations interspersed with CO32− anion layers normal to the c-axis, which is in contrast to the disordered distribution of Ca2+ and Mg2+ in the (high-Mg) calcite structure.

dolomite problem dolomite mineralogy

1. Calcite and Dolomite

When we study the crystal structure of rhombohedral carbonates, the crystal structure of calcite should be considered first. Because some important carbonate mineral constituents of sedimentary rocks, e.g., magnesium- and iron-bearing carbonates, have structures that are identical to or closely related to the crystal structure of calcite [1]. Accordingly, the structure of calcite can be used as a basis for describing the structure of such minerals. Calcite, a rhombohedral carbonate mineral, is a typical trigonal system. The vast majority of diagenetic calcite in the rock record formed from shallow burial in marine-derived fluids [2]. The calcite crystal structure consists of alternating layers of calcium cations (Ca2+) and carbonate anions (CO2−3CO32−) oriented normal to the c-axis. The calcite crystal structure is of space group R3̲3¯c [1], and the unit cell of calcite is hexagonal [dimension: a = 4.9896 (Å), c = 17.0610 (Å)] [3][4][5]. The (104) reflection peak is the most intense reflection in calcite and dolomite, which corresponds to the cleavage rhombohedron planes [5], but there are no ‘ordering’ reflections of dolomite in the XRD pattern of calcite.
Dolomite (CaMg(CO3)2) is a special rhombohedral carbonate mineral containing Ca and Mg. Very few sedimentary dolomites are truly stoichiometric and are more suitable to be represented by CaxMg1−x(CO3)2. The stoichiometric compositions of natural dolomite vary from Ca1.16Mg0.84(CO3)2~Ca0.96Mg1.04(CO3)2 [6]. Dolomite is a trigonal system mineral whose crystal structure is a derivative of the calcite crystal structure. Dolomite is distinguished from calcite and other rhombohedral carbonates by its stoichiometry [7], and the ideal dolomite crystal structure consists of alternating layers of Mg2+ and Ca2+ interspersed with CO2−3CO32− groups oriented normal to the c-axis [5]. In addition, the dolomite structure violates the c glide plane in the calcite structure, which means that dolomite has R3̲3¯ symmetry [1]. The hexagonal unit cell dimensions of dolomite are a = 4.8069 (Å), c = 16.0034 (Å) [8][9]. Additionally, single-crystal dolomite is often rhombohedral {101̲1¯1} and sometimes columnar {112̲2¯0} [8]. Analysis of the XRD pattern shows that the crystal structure of dolomite is different from that of calcite. The ordered dolomite has superlattice XRD reflections [e.g., (101), (015) and (021)] [10][11][12]. The ratio of the diffraction intensity of the (015) crystal plane to that of the (110) crystal plane is used to calculate the degree of cation ordering in dolomite [δ = r (015)/r (110)] [13]. Ancient sedimentary dolomite tends to have a much more regular lamellar structure than Holocene dolomite. In addition, ancient sedimentary dolomite typically possesses a pervasive modulated microstructure (wavelengths ≈ 200 Å) that is generally parallel to {1014} [6].

2. High-Mg Calcite

Calcites containing > 4 mol% MgCO3 are considered to be high-Mg calcite [5]. Liu et al. [14] pointed out that the MgCO3 content of high-Mg calcite ranges from 4 mol% to 36 mol%, while calcite with a MgCO3 content ranging from 36 mol% to 55 mol% is called disordered dolomite. High-Mg calcite is characterized by a large number of Mg2+ cations randomly substituting for Ca2+ cations in a single cation position in the calcite lattice, and the disordered distribution of Ca2+ and Mg2+ in high-Mg calcite is in contrast to the ordered distribution of cations in dolomite. High-Mg calcite usually does not reproduce the ‘ordering’ reflections seen in the XRD pattern of dolomite, and the (104) diffraction peak position (2θ) of high-Mg calcite is between that of dolomite and calcite [5]. So high-Mg calcite is often rhombohedral [15][16]. At present, it is believed that the genesis of high-Mg calcite is mainly through biological origin [17][18][19][20] and inorganic precipitation in seawater [21]. Biogenic species include red corals [18], red coralline algae [22][23], calcareous sponges [19], sea urchin [24] and so on, and the magnesium contents of these biogenic high-Mg calcites range from 4 mol% to 45 mol% [19]. Moreover, high-Mg calcite is unstable with respect to dolomite and calcite under ambient conditions [25].

3. Protodolomite, Very High-Mg Calcite and Disordered Dolomite

Protodolomite, very high-Mg calcite and disordered dolomite are terms used to describe products that have near-dolomite stoichiometry (ca 40 to 50 mol% MgCO3) in experiments. The discussion of these terms has been documented in detail in the review of Gregg et al. [5]. We endorse their view that a rhombohedral Ca-Mg carbonate mineral is dolomite if its XRD pattern does display evidence of ordering reflections. If the mineral does not show evidence of cation ordering, then it is not dolomite and is very high-Mg calcite. This view is also supported by other authors [26][27]. They think the absence of two out of the three principal ordering reflections (the XRD pattern of ideal dolomite has (101), (015) and (021) ‘ordering’ reflections) indicates the arrangement of Ca2+ and Mg2+ in the mineral crystal is not ordered, and it should belong to the calcite space group (R3¯c) rather than the dolomite space group (R3¯).
Over the two decades, the microbial model of dolomite formation has attracted much attention from geologists. Many scholars have carried out simulation experiments in the laboratory on the dolomite precipitation induced by microorganisms at ambient temperature and pressure [28][29][30][31][32][33][34][35]. However, Gregg et al. [5] and Kaczmarek et al. [26] reevaluated the XRD data of the experimental products of microbial-induced experiments and found that the products precipitated by microbial mediation actually lack cation ordering. Therefore, these minerals are not strictly dolomite, but calcite group minerals. They suggested that these products may be very high-Mg calcite that is close to the ideal stoichiometric composition of dolomite. Qiu et al. [35] also found in their experiment using halophilic archaea to mediate dolomite precipitation that XRD and SAED patterns of the products did not have the ordering characteristics of dolomite, and it was likely that disordered dolomite (very high-Mg calcite) formed. The experimental results of Zhang et al. [36] showed that in the presence of ~113 mg L−1 of non-living biomass, disordered dolomite with ~41 and 45 mol% of MgCO3 was precipitated in solutions with initial Mg:Ca ratios of 5:1 and 8:1, respectively. They believed that non-living biomass of the methanogen Methanosarcina barkeri can enhance the incorporation of Mg into the calcitic structure and induce the crystallization of disordered dolomite. Based on the above facts, the products of most microbially induced experiments are still strictly disordered and are more likely to be very high-Mg calcite in nature.

References

  1. Lippmann, F. Sedimentary Carbonate Minerals; Springer: Berlin/Heidelberg, Germany, 1973; 228p.
  2. Hasiuk, F.J.; Kaczmarek, S.E.; Fullmer, S.M. Diagenetic origins of the calcite microcrystals that host microporosity in limestone reservoirs. J. Sediment. Res. 2016, 86, 1163–1178.
  3. Graf, D.L. Crystallographic tables for the rhombohedral carbonates. Am. Mineral. 1961, 46, 1283–1316.
  4. Liu, J.Y.; Wang, Z.Y. Crystal structure characterization and X-ray study of dolomite. Mineral. Petrol. 1988, 8, 28–33, (In Chinese with English Abstract).
  5. Gregg, J.M.; Bish, D.L.; Kaczmarek, S.E.; Machel, H.G. Mineralogy, nucleation and growth of dolomite in the laboratory and sedimentary environment: A review. Sedimentology 2015, 62, 1749–1769.
  6. Warren, J. Dolomite: Occurrence, evolution and economically important associations. Earth Sci. Rev. 2000, 52, 1–81.
  7. Tribble, J.S.; Arvidson, R.S.; Lane, M., III; Mackenzie, F.T. Crystal chemistry, and thermodynamic and kinetic properties of calcite, dolomite, apatite, and biogenic silica: Applications to petrologic problems. Sediment. Geol. 1995, 95, 11–37.
  8. Yang, S.Y.; Huang, Z.C.; Chen, Z.N. Microstructural Correlation between Primary and Replacement Dolomites. Acta Petrol. Mineral. 1997, 16, 362–366, (In Chinese with English Abstract).
  9. Zhang, J.; Shou, J.F.; Zhang, T.F.; Pan, L.Y.; Zhou, J.G. New Approach on the Study of Dolomite Origin: The crystal structure analysis of dolomite. Acta Sedimentol. Sin. 2014, 32, 550–559, (In Chinese with English Abstract).
  10. Zheng, W.L.; Liu, D.; Yang, S.S.; Fan, Q.G.; Papineau, D.; Wang, H.M.; Qiu, X.; Chang, B.; She, Z.B. Transformation of protodolomite to dolomite proceeds under dry-heating conditions. Earth Planet. Sci. Lett. 2021, 576, 117249.
  11. Riechelmann, S.; Mavromatis, V.; Buhl, D.; Dietzel, M.; Immenhauser, A. Controls on formation and alteration of early diagenetic dolomite: A multi-proxy δ44/40Ca, δ26Mg, δ18O and δ13C approach. Geochim. Cosmochim. Acta 2020, 283, 167–183.
  12. Cai, W.K.; Liu, J.H.; Zhou, C.H.; Keeling, J.; Glasmacher, U.A. Structure, genesis and resources efficiency of dolomite: New insights and remaining enigmas. Chem. Geol. 2021, 573, 120191.
  13. Huang, Z.C.; Yang, S.Y.; Chen, Z.N. Mineralogical study on primary dolomite and Replacement dolomite. Sci. China Ser. D 1996, 26, 544–550, (In Chinese with English Abstract).
  14. Liu, D.; Xu, Y.Y.; Yu, Q.Q.; Yu, N.; Qiu, X.; Wang, H.M.; Papineau, D. Catalytic effect of microbially-derived carboxylic acids on the precipitation of Mg-calcite and disordered dolomite: Implications for sedimentary dolomite formation. J. Asian Earth Sci. 2020, 193, 104301.
  15. Ge, Y.Z.; Pederson, C.L.; Lokier, S.W.; Traas, J.P.; Nehrke, G.; Neuser, R.D.; Goetschl, K.E.; Immenhauser, A. Late Holocene to Recent aragonite-cemented transgressive lag deposits in the Abu Dhabi lagoon and intertidal sabkha. Sedimentology 2020, 67, 2426–2454.
  16. Goetschl, K.E.; Dietzel, M.; Purgstaller, B.; Crengg, C.; Mavromatis, V. Control of MgSO40(aq) on the transformation of amorphous calcium carbonate to high-Mg calcite and long-term reactivity of the crystalline solid. Geochim. Cosmochim. Acta 2021, 312, 357–374.
  17. Boussetta, S.; Bassinot, F.; Sabbatini, A.; Caillon, N.; Nouet, J.; Kallel, N.; Rebaubier, H.; Klinkhammer, G.; Labeyrie, L. Diagenetic Mg-rich calcite in Mediterranean sediments: Quantification and impact on foraminiferal Mg/Ca thermometry. Mar. Geol. 2011, 280, 195–204.
  18. Floquet, N.; Vielzeuf, D. Ordered misorientations and preferential directions of growth in mesocrystalline red coral sclerites. Cryst. Growth Des. 2012, 12, 4805–4820.
  19. Long, X.; Ma, Y.R.; Qi, L.M. Biogenic and synthetic high magnesium calcite—A review. J. Struct Biol. 2014, 185, 1–14.
  20. Al Disi, Z.A.; Zouari, N.; Dittrich, M.; Jaoua, S.; Al-Kuwari, H.A.S.; Bontognali, T.R.R. Characterization of the extracellular polymeric substances (EPS) of Virgibacillus strains capable of mediating the formation of high Mg-calcite and protodolomite. Mar. Chem. 2019, 216, 103693.
  21. Malta, J.V.; Castro, J.W.A.; Cabral, C.L.; Fernandes, D.; Cawthra, H.C. Genesis and age of beachrocks on the Rio de Janeiro coastline, Southeast–Brazil. Mar. Geol. 2021, 442, 106649.
  22. Nash, M.C.; Troitzsch, U.; Opdyke, B.N.; Trafford, J.M.; Russell, B.D.; Kline, D.I. First discovery of dolomite and magnesite in living coralline algae and its geobiological implications. Biogeosciences 2011, 8, 3331–3340.
  23. Nash, M.C.; Adey, W.; Harvey, A.S. High magnesium calcite and dolomite composition carbonate in Amphiroa (Lithophyllaceae, Corallinales, Rhodophyta): Further documentation of elevated Mg in Corallinales with climate change implications. J. Phycol. 2021, 57, 496–509.
  24. Veis, A. Organic matrix-related mineralization of sea urchin spicules, spines, test and teeth. Front. Biosci. 2011, 16, 2540–2560.
  25. Land, L.S. Dolomitization; AAPG: Tulsa, OK, USA, 1982; pp. 1–20.
  26. Kaczmarek, S.E.; Gregg, J.M.; Bish, D.L.; Machel, H.G.; Fouke, B.W. Dolomite, very-high magnesium calcite, and microbes—Implications for the microbial model of dolomitization. In Characterization and Modeling of Carbonates–Mountjoy Symposium 1; SPEM Special Publication: New York, NY, USA, 2017; Volume 109, pp. 7–20.
  27. Zhao, D.F.; Tan, X.C.; Luo, B.; Wang, X.F.; Qiao, Z.F.; Luo, S.Q. A review of Microbial Dolomite: Advances and challenges. Acta Sedimentol. Sin. 2022, 40, 335–349, (In Chinese with English Abstract).
  28. Vasconcelos, C.; Mckenzie, J.A.; Bernasconi, S.; Grujic, D.; Tiens, A.J. Microbial mediation as a possible mechanism for natural dolomite formation at low temperatures. Nature 1995, 377, 220–222.
  29. Vasconcelos, C.; McKenzie, J.A.; Warthmann, R.; Bernasconi, S.M. Calibration of the δ18O paleothermometer for dolomite precipitated in microbial cultures and natural environments. Geology 2005, 33, 317–320.
  30. Wright, D.T.; Wacey, D. Precipitation of dolomite using sulphate-reducing bacteria from the Coorong region, South Australia: Significance and implications. Sedimentology 2005, 52, 987–1008.
  31. Sánchez-Román, M.; Vasconcelos, C.; Schmid, T.; Dittrich, M.; McKenzie, J.A.; Zenobi, R.; Rivadeneyra, M.A. Aerobic microbial dolomite at the nanometer scale: Implications for the geologic record. Geology 2008, 36, 879–882.
  32. Sánchez-Román, M.; McKenzie, J.A.; Wagener, A.D.L.R.; Romanek, C.S.; Sánchez-Navas, A.; Vasconcelos, C. Experimentally determined biomediated Sr partition coefficient for dolomite: Significance and implication for natural dolomite. Geochim. Cosmochim. Acta 2011, 75, 887–904.
  33. Kenward, P.A.; Fowle, D.A.; Goldstein, R.H.; Ueshima, M.; González, L.A.; Roberts, J.A. Ordered low temperature dolomite mediated by carboxyl-group density of microbial cell walls. AAPG Bull. 2013, 97, 2113–2125.
  34. Bontognali, T.R.R.; Mckenzie, J.A.; Warthman, R.J.; Vasconcelos, C. Microbially influenced formation of Mg-calcite and Ca-dolomite in the presence of exopolymeric substances produced by sulphate-reducing bacteria. Terra Nova 2014, 26, 72–77.
  35. Qiu, X.; Wang, H.M.; Yao, Y.C.; Duan, Y. High salinity facilitates dolomite precipitation mediated by Haloferax volcanii DS52. Earth Planet. Sci. Lett. 2017, 472, 197–205.
  36. Zhang, F.F.; Xu, H.F.; Shelobolina, E.S.; Konishi, H.; Roden, E.E. Precipitation of low-temperature disordered dolomite induced by extracellular polymeric substances of methanogenic Archaea Methanosarcina barkeri: Implications for sedimentary dolomite formation. Am. Mineral. 2021, 106, 69–81.
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Subjects: Mineralogy
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Chao Chen
,
Hanting Zhong
,
Xinyu Wang
,
Meng Ning
,
Xia Wang
,
Yuzhu Ge
,
Han Wang
,
Ruifeng Tang
,
Mingcai Hou
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Update Date: 04 Dec 2023
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