Dolomite which is also known as Dolostone is a mineral stone that is one of the sedimentary minerals which is classified under the carbonic minerals group. This mineral is found in sedimentary parts of the earth’s crust on the planet and it’s mostly found in Africa and Europe. Carbonate minerals including calcite, aragonite and dolomite are the outcome of sediment of minerals like magnesium oxide and lime (CaO). This valuable mineral is available in cream, and grayish-white colors but yellow, green and black are also available. Carbonate rocks are very useful because of having many mineral features and materials and amongst these rocks, dolomite is the most useful. There are five different types of dolomites:
Dolomicrite: fine crystals, unformed with equal sizes, laminated, form of evaporative minerals and fenestral fabric. This kind of dolomite has got very tiny crystals the size of 5 to 15 microns and is formed of anhedral and unimodal crystals. Algal filaments, cavities and holes left from evaporative minerals and anhydrous nodules are visible in Dolomicrite. Based on this evidence we can conclude that this dolomite is formed near the surface and under low temperatures. This sort of dolomite is associated with the Mudstone Dolomite facies and is expanded in the higher portions of the hot and dry tidal zone. Usually, these dolomites are dense and without porosity and contain quartz particles. In this dolomite type, maybe the sea water or rich Mg intergranular solutions become the cause of dolomitization.
Dolomicrosparite: Or tiny-crystal to medium-crystal dolomites, dense and even that are formed from Dolomicrite crystallization. The size of this type of dolomites crystals is between 16 to 62 microns and they’re formless and dense and even. This type of dolomite is equivalent to nonplanar A and xenotopic A. This texture looks like limes that are affected by neomorphism. They are produced Possibly by alteration of limestones or recrystallization of dolomicrites and what proves this is the existence of dolomicrites between dolomicrosparites. Dolomicrospars are the most plentiful kind of dolomite in the Asmari Formation. These dolomites are formed as a result of the recrystallization of dolomites that previously have been near the surface of the earth.
Medium Crystalline Dolomites or Granular Sugar Dolomites: The crystal sizes of such dolomites range from 62 to 250 microns. The Dolomites with sugar granules Dolomite atom crystals formed from planar-s to planar-e are intracrystalline crystals. Crystal sizes are larger than 62 microns, sometimes in the range of 200 to 250 microns. These dolomites are formed at temperatures below 50 °C. Dolosparites consist of dense, dart-shaped, semi-crystalline polymorphic mosaics of various sizes (multimodal). Intracrystalline boundaries are flat, equivalent to Friedman’s xenotropic planar-A. Sugar-grained-size dolomites are generally broken down by dolomites (primary dolomites) and dolomicrosparites (primary diagenetic dolomites) and are considered delayed diagenetic dolomites. In general, the transformation of dolomite texture from Dolomicrite to crossparite dolomite in the Asmari (Iran) layer of dolomite indicates an increase in the degree of alteration of dolomite.
Medium-crystalline regular dolomite, cloudy core and clear edges: The dark cloudy state of dolomite crystal cores is due to the concentration of calcite-containing material in the center of the dolomite crystals. This is due to the high saturation factor of dolomite fluid. At first, the calcite could not be completely dissolved. Therefore, the primary Dolomite crystal contains calcite-containing substances in the core and as the saturation coefficient of the Dolomite solution and the calcite dissolution gradually decrease, the peripheral part of the Dolomites becomes transparent and the inclusions disappear. It contains only a small part of the formation and is mainly observed in underground samples.
Saddle dolomites: buried dolomites are baroque dolomites or saddle dolomites characterized by very large crystals, curved crystal surfaces, wavy blacks, dark colors and white. This type of dolomite, in cement form or alternatively is a large crystal with a crystalline surface and curved cleavage, and wavy disappearance. These Dolomites often contain inclusions (liquid or traces of minerals), most of which are iron compounds. Saddle Dolomites are generally associated with sulfide mineralization, hydrothermal activity and hydrocarbons and show regeneration conditions. This is used to show that the Dolomites are formed in the oil window at temperatures between 60 and 150 °C.
In general, the use of dolomite ore can be written as:
- Dolomite is used as building stone material.
- It can be used in the manufacture of glass.
- Dolomite ore is also used in cement production.
- In agricultural applications it is believed to remove soil acidity and promote plant growth.
- The Dolomites are also used in steel mills to smelt and refine iron.
- Dolomite can be turned into stone and used in railways, sewer tunnels and coal mines.
- It can also be used due to the high strength of concrete structures.
- Some dolomite stones are used as decorative stones due to their unique elegance and beauty.
- Dolomite is effective in adjusting the water in aquariums due to its pH feature.
- Dolomite is also used in the pharmaceutical industry.
Dedolomitation Description
It is the process of depleting all or part of magnesium in dolomite or dolomite limestone and enriching calcite.
Dolomitization model
The Dolomites are used in construction (ceramic tile, casting, glass manufacturing, etc.), metal smelting (as a smelter), agriculture (as fertilizer and nutrient regulator in the soil), preparation, etc. importance and widespread use in various industries such as Years of research on manganese seawater production (pH controller), magnesium oxide and hydroxide production, rubber fillers in the fireproof industry (chamotte brick, cement production, etc.), relaxation, dyeing and these carbonates.
The name dolomite refers to both minerals and rocks with the chemical formula CaMg (CO3)2, and the arrangement of calcium and magnesium ions is regular. It was named after the French scientist Deodat Guyde Dolomieu who lived between 1750-1801. Previously, carbonate rocks in this formula were considered dolomite but now they are not. It is necessary to determine whether this carbonate has a certain atomic arrangement. In this case, it is necessary to determine whether it is called perfect grade dolomite or whether it has a certain atomic arrangement. In this case, it is called Protodolomite or unwanted dolomite.
The Dolomites and their formation types:
Regarding the formation of some new Dolomites, the following will be introduced:
1-Similar dolomite
Primary dolomite diagenesis, in which displacement occurs before and after precipitation of cement. These Dolomites are found in evaporation series together with gypsum, anhydrite and salt. Dolomite formation in the marine environment is very rare at first but the amount of magnesium salts in seawater is about three times that of calcium salts but still far from saturation, and only evaporation can push these salts near to their saturation.
2-row dolomite
Delayed dolomite diagenesis in which substitution occurs after sedimentation. These Dolomites are not associated with evaporation lines, mud cracks, moss covers and other limited evidence of occupation. Dolomite mineral isotope values and trace elements, ie the ratio of heat, dolomite ion order, calcium factors such as magnesium, salt, sulfate, appropriate hydraulic regime and primary rocks in secondary dolomite formation Scientific properties These are effective. Evidence such as substituted calcareous fossils, isotopic data, and chemical weathering suggest that most Dolomites are secondary Dolomites and primary Dolomites are rare.
Environment and pattern of dolomite formation:
Dolomites occur in a variety of environments.
1-Ultrasalt coastal turf medium evaporation pumps result
Most of the Dolomites formed today are located in evaporation environments and rocks. In these environments, sediment occupational precipitation is moderate but high. Dolomites are less common on the continental shelf, but are found in the coastal Sabkhas at the top of their fashion range and are usually supplied by seawater (saline) groundwater. This pattern mainly causes dolomitization of the more superficial parts of the sediment (in the form of crust). This type of occupation can be called shoregrass in the southern Persian Gulf, especially in the Abu Dhabi region.
2-Salt Lake:
In some areas there are salt water areas in the form of lagoons or lakes. An example of this environment is the Coulomb Salt Lake in southern Australia. The water in this region dries up in late summer, the pH of the environment rises (in the range of 2.8 to 10.3) and the magnesium to calcium ratio varies between 3 and 20 depending on the location. The amount of negative SO4 ions in the water is also small. In this case, the sediments in this area consist of aragonite, calcite, high magnesium calcite, dolomite calcite, magnesite and hydromenite which increases as the dolomite gets deeper.
3-Marsh environment and tsunami as a result of osmotic reflux:
Behind coral reefs and other sedimentary uplifts, seawater is separated, evaporation is effective and saltwater lagoons and tidal flats can form. It creates gypsum deposits in the lagoon environment and increases the ratio of magnesium to calcium. Magnesium-rich brine returns to the sea and travels to coral reef sediments and sediment ridges, transforming these sediments into dolomite. This pattern is called reflux and results in deeper dolomitic deposits.
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4-Shallow salt water:
In such an environment, gypsum is formed and the ratio of magnesium to calcium increases, and when this ratio exceeds 5.1, dolomite begins to collapse. Salt is also important in this environment and as salt increases, the ratio of magnesium to calcium required to form dolomite also increases.
5- Diluted seawater:
One of the most important theories about how the Secondary Dolomites formed is the mixing of seawater with fresh water, known as the hybrid Dolomites model. Prior to the introduction of this model, it was unclear how the Dolomites and continental shelf Dolomites which lacked evaporative minerals (especially gypsum) were formed. There is no need to increase the ratio of magnesium to calcium in the hybrid model and dolomitization is carried out in a 1: 1 ratio. In this model, the required magnesium is supplied from seawater.
6-Deep seawater:
The ratio of magnesium to calcium in seawater is 3:1. Theoretically, dolomites can accumulate from normal seawater and require sufficient time to form sulfate ions in seawater and in conditions such as low sulfate ions.
7-Burial environment
The main effective mechanism of dolomite formation in buried environments is the outflow of water from the sediment density and the efflux of magnesium by this mechanism. The main sources of magnesium are interparticle water, clay minerals and fossils with a high magnesium calcite composition. The source of carbonate ions is shales in sedimentary basins rich in organic matter. Due to the high temperature of this environment, many problems with the formation of dolomite are solved and the reaction rate is improved. In fact, these Dolomites are of organic origin.
Baroque dolomite
Baroque dolomite is defined as coarse-grained dolomite with regular to irregular curved crystal boundaries and widespread extinction, one of the diagenetic-altered carbonates and sandstones in the hydrocarbon reservoir. It is one. This chapter examines the petrological, geochemical and fluid inclusion data of saddle dolomites from carbonate and sandstone published since 1980 and examines potential high-temperature diagenesis of this type of dolomite. Evaluate the main interpretation as a geothermometer.
This collection shows that saddle dolomites from various sedimentary basins have the following characteristics: (1) Variable Fe + manganese and calcium enrichment of host saddle dolomite in sandstone compared to carbonate saddle dolomite. (2) Carbon isotope compounds from slightly positive amounts (in the case of carbonate rocks) to relatively negative amounts (in the case of sandstone). (3) Relatively negative oxygen isotope values for sandstone and carbonate rocks. (4) The strontium isotope ratio is usually higher than that of Phanerozoic seawater (> 0.708). The liquid in the saddle dolomite homogenizes at temperatures above 60-80 ° C, up to 90-160 ° C. The salinity of palaeofluids is uniformly higher than that of seawater (NaCl equivalent to -2518-25 wt ٪). The low eutectic temperature indicates that the complex aqueous solution is dominated by NaCl + CaCl2 ± MgCl2 ± KCl.
Geochemical and fluid inclusion data, along with mineral paragenetic information, are a reliable indicator of rock salt-water interactions at temperatures where saddle dolomites almost coincide with the “window” of liquid hydrocarbons. It shows that it also expands well in dry gas areas.
Source of magnesium ions
Magnesium is the 11th most abundant element in the human body and is essential for all cells and about 300 enzymes. It reacts with many polyphosphate compounds such as metal ions, ATP, DNA, and RNA. As noted already, magnesium is the eighth, most abundant element in the earth’s crust. This metal is found in major sources of dolomite, magnesite and other minerals and in water (as magnesium ions). Considering that this element is found in more than 60 minerals, only some minerals such as dolomite, magnesite, Brucite, carnallite, talc and olivine are of economic value.
Magnesium hydroxide (brucite) is insoluble in water and is removed by filtration. Finally, concentrated magnesium chloride is produced by reaction with hydrochloric acid and the metal can be obtained by electrolysis.
China’s magnesium production in 1993 was very low and about 20 years later it was about 90% of the world’s magnesium production. Due to the large amount of energy required to produce magnesium, production has been halted in many countries, including in Western Europe.
Magnesium is found in seawater and brackish water solutions. Magnesite and dolomite rocks are other sources of this metal.
Before China increased production, electrolysis was the main production method for magnesium due to the low cost of electricity generation. Most magnesium plants today use advanced methods introduced by Canada in the 1940s to increase production. In this process, dolomite is ground and heated in a furnace to produce a mixture of magnesium oxide and calcium oxide. This process is called “calcination”.
Dolomite is converted into an oxide mixture by heating and is used to treat seawater. The accumulation of magnesium hydroxide makes calcium hydroxide water-soluble. Magnesium hydroxide is separated from the solution by filtration and converted to pure oxide by heating. In some processes, the oxides are converted to magnesium chloride. This involves heating the oxide at high temperatures in a stream of chlorine and mixing it with the carbon. All these processes are done in an electric furnace.
The crystal structure of dolomite is triangular and rhombic, and it can replace magnesium carbonate ion in its molecular formula. Due to the presence of magnesium, the acid dissolution rate of dolomite is slower than that of calcium carbonate. It is found in nature in white, gray, yellow, pink and brown colors. The greater the amount of magnesium contained in the composition of dolomite lime, the more likely it will turn pink, allowing you to check the magnesium concentration. This substance is found in nature along with iron, zinc, cobalt, lead, etc.
Dolomite is similar to lime in nature and often occurs in organically rich rivers, caves, and ocean floors. Organics produce them in the presence of carboxyl groups with magnesium compounds. This process can occur in any environment and is called dolomite. Dolomite formation occurs in large quantities in moist, shallow water environments containing magnesium compounds.
The main sources of magnesium ion source for very fine primary dolomite and other types of dolomites in seawater are suggested as Diagenesis of subsoil clay minerals (red shale layer) and branching brine.
Dolomite cement
This type of dolomite consists of large crystals that are transparent and often formed, with straight borders, filling large and small cavities, and containing cement-shaped crevices. The crystal size of this dolomite cement varies (200-500 microns) and generally depends on the size of the available space. Such Dolomites are formed at temperatures below 60-50 degrees. Sparse dolomite crystals filling the voids are formed in shallow burial which is the late stage of diagenesis. Another type of dolomite cement that fills the void is horse saddle dolomite with wavy vanishing and arcuate cleavage. Horse saddle dolomite usually consists of salt water and a hot liquid at temperatures above 50-60 degrees Celsius during the final stages of diagenesis. This type of dolomite is obtained in a deeply buried state. Although dolomitization in the deep burial phase has been criticized for insufficient magnesium ions, published articles suggest that dolomitization occurs at various depths.
Dolomite cement is an important and common ingredient in the Phanerozoic sucrosic dolomites. Dolomite cement, which is never deeply buried, is transparent has a flat surface (non-saddle shape), has a distinct cathodoluminescence band structure, and often forms syntactic overgrowth in the pores facing the crystal. Five examples of sucrosic dolomite, interpreted as having predominantly lime mudstone or wackestone precursors in the four carbonate aquifers, provide information on the abundance of flat cement in sucrose dolomite. This type of cement contains 11% to 45% (32% on average) tidal to subtidal Dolomites on the surface of the Edwards Aquifer (Early Cretaceous) in central Texas. 19% to 33% (25% on average) of Eocene-Eocene Hawthorn Group (Eocene-Eocene) Lamp Dolomites and 50% to 70% (Eocene) of Avon Park Shelf Dolomites in the Upper Florida Underground Peninsula. Eocene); 18% to 45% (32% +% on average) of the shelves under the tide in the quarry of the Burlington-Keokuk Formation (early Mississippian culture) in southeastern Iowa. 18-76% (50% on average) of shallow cores and outcrops of the outer shelves of the Gambian limestone (oligo-Miocene) in South Australia. The back peeling of the cement phase revealed by the cathode luminescence color micrographs documents the effects of cement on the coarsening of the texture of these dolomites, the reduction of interstitial space, hardening, and the overall “maturation”. Most pre-Holocene Dolomites are polymorphic rocks consisting of (i) seed crystals or “cores”. (ii) A crystalline cortex that expands the nucleus concentrically; (iii) A free-field syntactic deposit of clear cement around the crystal. The remaining CaCO3 particles and miclinite can be replaced with dolomites, but usually, they dissolve between stages (ii) and (iii), and the inter crystal and moldy pores typical of saccharic dolomites. Create a system. A network of excess cement growth supported by a hydrostatic to sub hydrostatic water-filled pore system is determined to slow or prevent compression of the sucrose dolomites. It can be argued that cortical growth involves both displacements of CaCO3 particles and micro cementation of interparticle pores. This interpretation, and the abundance of cement in many dolomites, will resolve the debate about the volume of “replacement dolomites”. Clear, planar and syntactic dolomite cement of early diagenetic origin precipitates from clear porous water at low temperatures (<30-35 ° C) and shallow burial depths (<100 m) of water-saturated dolomite networks. It is interpreted as having done. ‘Silt’ and ‘sand’. Many Dolomites cements in the island and continental aquifer systems appear to be derived from event-driven processes associated with sea-level peaks. Cementation events can follow geologically “momentary” to “displacement dolomite” events at time intervals ranging from tens of millions of years.
Hydrology
Hydrological models are a valued means for examining the effect of changes in land use on water resources. Decentralized physics-based models are commonly applied to the impact studies of land-use changes in hydrology. However, it is difficult to provide a detailed description of the subsurface physics base of the karst system. In contrast, the bulk model is easy to implement and is widely used in karst hydrological studies but it is not applicable to land-use change impact studies. To overcome these limitations, a new quasi-dispersion model LuKARS (Land use change modeling in KARSt systems) that characterizes the uniform hydrological properties of major hydrotopes in different regions (i.e., resulting from similar land use and soil types). Was developed. Individual landscape unit). As an independent non-linear unit within the catchment area. The flow from each hydrotopes represents a specific response of the aeration zone (soil-epikarst infiltration zone) to the defined recharge zone. The saturation region consists of a single linear storage unit that is individually recharged by each hydrotopes. The main goal of this approach is Waidhofen A.D. which investigates the impact of land-use changes in the dolomite karst system used to supply cities. Ybbs (Austria) Change the area covered by each hydrotopes. Here, land-use changes have occurred at the expense of existing forest sites, in the form of more sites used to mine dolomites. Using a parameterized model, we were able to reproduce the flow rate measured by the largest spring (Kershbaum spring) in the Waidhofen karst system. In addition, we succeeded in transferring the parameterized hydrotope to other recharge areas, verifying the transferability of the modeling approach. In conclusion, we succeeded in demonstrating the applicability of the model to land-use change impact studies by validating a model calibrated over a period of nearly doubling the location of the dolomite mine in the Kershbaum recharge area. did. The results of our study suggest that the increase in dolomite mines has a negative impact on the city’s water supply.
Occurrence and origin
The Dolomites are found in vast layers, tens of feet thick. They make up about 15% of the Earth’s crust and are found in large numbers around the world and are known as one of the most common constituents of sedimentary rocks. Stones containing dolomite are also known as dolomite or dolomite limestone. Dolomite is one of the most abundant minerals in sedimentary rocks, most of which is second only to calcium, not calcium itself. It is also initially formed in a sedimentary environment. Small amounts are observed in igneous cavities, especially lodes containing calcite, quartz and barite. The Dolomites are found in many parts of Iran and are being abused in some of them. Among the mines around Isfahan are Islamabad-Gharb, Damavand, and Shahmiazrd, Seman. The mineral dolomite of the chemical formula Ca, mg (co3) 2 is carbonate with a rhombohedral crystal crystallization system. Most Dolomites are formed by replacing them with preformed carbonate minerals. Replacement of calcium carbonate with dolomite or deposition of dolomite cement can occur immediately after deposition and during early diagenesis (synthetic dolomite) or long after deposition (epigenetic dolomite). The term dolomite is sometimes used for direct subsidence of seawater or lakes. Later in diagenesis, dolomites may replace some major particles, reduce limestone matrices, and particles, form limestone tunnels or complete layers or affect only certain species. there is. To give. In some cases, only high magnesium aragonite and calcite particles are initially dolomite (biocrust and iodide), and primary calcite (low magnesium) fossils (brachiopods, asters, etc.) are unaffected.
Chemical composition
The chemical composition of dolomite is CaMg(CO3)2. There are extra oxides in it like iron oxide (FeO) and sodium oxide (Na2O) and potassium oxide (K2O). The formation of dolomite is just like the sedimentary surroundings wherein limestone is formed. These environments are heat and shallow, marine environments wherein calcium carbonate accumulates as dust shale debris, fecal material, coral debris, and carbonate deposits. Dolomite is thought to shape as soon as calcite (CaCO2) in carbonate dust or limestone is substituted with the aid of using magnesium-wealthy groundwater. The current magnesium eases the conversion of calcite to dolomite (CaMg(CO2)3). This chemical transformation is recognized as “Dolomitization.” Dolomitization can both completely convert limestone to dolomite or a part of the rock to “dolomite limestone”.
Physical properties
Most Dolomites are found in creamy brown and greyish-white, while others are found in white, yellow, green and black colors.
This mineral weighs about 2.6 grams per cubic centimeter has a hardness of 3.5-5, and has a glass or pearl luster.
Chinese dolomite
Chinese dolomite is large crystalline dolomite of slow diagenetic origin.
Polycrystal dolomite
This type of dolomite is formed by diagenesis immediately after deposition.
Grabow classification:
- a) Calcium rhodite (most particles exceed 2 mm), gravel grain-sized coarse-grained limestone.
- b) Rolled arnite (most particles are between 2 mm and 62 µm), medium particle limestone whose particle size is approximately sand size.
- c) Calcite luteite (most particles less than 62 µm), fine-grained limestone containing silt and clay particle sizes.
Public classification:
It is primarily structure-based and divides components into two categories: Allochems and orthochems.
The components of limestone are:
Allochems:
Allochems are in-situ, perishable particles, including skeletal and non-skeletal particles.
Non-skeleton particles:
These particles include pizoids, pellets, intraclasts, and aggregates.
Pisoids:
Spherical or oval particles less than 2 mm in size and containing cores of skeletal particles, pellets or other particles such as quartz.
Ovoids are asymmetric and asymmetric. An ellipse with a layer surrounding the nucleus is called a surface. For asymmetric eggs, the bottom layer of the egg is thicker.
In the current sedimentary environment, concentric structures are formed when the long axis of aragonite touches the ring or underlying layer, whereas radial cloth is formed when these axes are perpendicular to the underlying surface.
The current egg shape has a radial cloth and is formed by high salt water and a diagenetic medium. Radial fabric ovoids are formed in a cool, low-energy environment, and tangential ovoids are formed in a high-energy environment. Organic matter and compounds are the means by which an egg-shaped radial cloth is formed. The oval composition is aragonite, calcite, and permagnesium which change over time. This changes as the sea level rise and the sea level expand. On the other hand, crust subduction occurs, this action occurs in metamorphic rocks, CO2 is formed and when the two crusts open, the basalt comes into contact with water and the resulting Mg2 + water is used to form chlorite. In addition, low magnesium calcite predominates because the Mg/Ca ratio is reduced. Eggs, which are aragonite form an oval mold.
