Chalk
Chalk is a calcareous, soft and porous sedimentary rock characterized by a high calcium carbonate (CaCO3) content and a very fine-grained structure. It is used mainly i.a.: rubber, paper, chemical, pharmaceutical, cosmetic, ceramic and cement industries; for the production of paints and lacquers, plastic, building materials, in the agriculture as a fertilizer chalk for the soil liming and as a fodder chalk for the animals breeding. The natural raw material is being increasingly replaced by lime meals doming from the processing of limestones and marbles and by a raw material gained from the process of solutions precipitation.
In Poland, chalk is the name traditionally given to two different mineral raw materials: proper chalk rock (still often called as ”writing chalk” in Polish literature) and lacustrine chalk (calcareous tufa). The raw materials differ in an origin, a chemical composition and use.
Proper chalk is an organogenic marine sediment of a white or creamy color constituted mainly from planktonic organism remains: coccoliths and crusts of forams. In Poland, it occurs in Cretaceous sediments in the Lubelszczyzna area and in the area of north-eastern Poland where Cretaceous deposits occur in the form of ice floats within Quaternary sediments. In the vicinities of Kornica and Mielnik on the Bug river on the border of Mazowieckie and Podlaskie Voivodeships there have been 21 deposits of “writing chalk” documented, from which 9 is exploited at the moment. In the Lubelszczyzna area, in the vicinities of Chełm. “writing chalk” is exploited for the cement production. The deposits occurring in this region are presented in the chapter Limestones and marls for cement and lime industries.
Lacustrine chalk is usually of white, white-yellow or grey color and is a very humid, clammy mass. It originates from the biochemical precipitation and the accumulations of a carbonate sediment on the lake bottoms. The significant role in this process play plants which pick up a dissolved calcium dioxide (CO2) from water. This results in solution saturation changes and a calcite crystallization. Except for carbonates, lacustrine sediments contain the organic matter and the material brought from the land. Lacustrine chalk and gyttja usually contain minimum 80% of calcium carbonate (CaCO3), whereas the sediment containing 50-80% of calcium carbonate is called as calcerous gyttja. Very often the lacustrine chalk and gyttja beds occur below the peat beds. It results from the shallowing and encroachment of a sedimentary reservoir (lake). Lacustrine chalk deposits in Poland are usually of the Quaternary age and occur mainly in northern and north-western Poland. The Neogene chalk accumulations are known in the Bełchatów vicinities where they occur within the overburden of the exploited brown coal beds.
The chalk deposits occurrence is presented on the map.
According to the Regulation of the Minster of the Environment of the 1st of July 2015 on the geological documentation of a raw material deposit, excluding a hydrocarbon field (number of Polish act: Dz. U. 2015, poz. 987) the limit values of the parameters that defines the deposit and its boundaries (Appendix 8) are:
- lacustrine chalk and calcareous gyttja (table 38) are documented with the minimum deposit thickness of 1 m, the maximum ratio of overburden to the deposit thickness of 0.3 and the minimum general alkalinity expressed per CaO in dry mass of 40% (71.2% CaCO3);
- proper (“writing”) chalk (table 39) is being documented to the maximum depth of 70 m, with the maximum overburden of 15 m, the maximum ratio of overburden to deposit thickness of 0.2 and the minimum weighted average of the CaCO3 content in a deposit profile of 80% (44.8% CaCO3).
Table 1 shows resources and the current state of the exploration and development of chalk.
Anticipated economic resources of chalk and calcareous gyttja in 2018 amounted to 207.145 million tonnes. They decreased by 0.114 million tonnes (0.6%) in comparison with the previous year.
In “The balance..” there were 2 newly documented deposits of lacustrine chalk included: Górzna (0.011 million tonnes of lacustrine chalk accompanying peat) in Lubuskie Voivodeship and Rańsko 1 (0.020 million tonnes) in Wielkopolskie Voivodeship. The latter was allocated from Rańsko deposit as a result of additional exploration works carried out on the deposit. At the same time, there was a new documentation with updated resources elaborated for Rańsko deposit (-0.054 million tonnes). In turn, for the proper chalk deposit Rudka II located in Mazowieckie Voivodeship, there was a new documentation with recalculated resources prepared as a result of the deposit area and the resources enlargement (+0.199 million tonnes).
The output of proper chalk and lacustrine chalk amounted in 2018 to 0.289 million tonnes in total, increasing in comparison with 2017 by 0.091 million tonnes (46.0%). The exploitation of proper chalk was being carried out from 9 deposits. The output was equal 0.266 million tonnes (92% of the total chalk output) – by 0.091 million tonnes (51.6%) more than in 2017. Lacustrine chalk was recovered from 2 deposits. The exploitation amounted to 0.023 million tonnes (8% of the total domestic output). It was slightly bigger than in 2017 – at the level similar to the previous years (except for the 2016). Lacustrine chalk is also temporarily recovered from the overburden of brown coal beds in the vicinities of Bełchatów. In 2018 from Bełchatów-pole Szczerców deposit there were 0.042 million tonnes of lacustrine chalk exploited (the amount is not included in the output tonnage given above and in Table 2).
Economic resources of chalk are documented for 9 deposits and amount to 14.225 million tonnes which accounts for 86.5% of the total anticipated economic resources of these deposits. In comparison with the previous year they decreased by 0.223 million tonnes due to the exploitation and losses.
The figure given below shows changes in domestic resources and production of chalk in Poland in the years 1989-2018.
Prepared by: Wojciech Szczygielski
Table 1. Chalk - million tonnes