On the Relationship Between Components in Iron Ore Skarns of the Tashtagol Deposit
Abstract Generated abstract
This paper examines chemical relationships among major components of iron ore skarns at the Tashtagol deposit, where ore bodies grade into enclosing skarns and mining dilution affects ore quality. Using chemical analyses, correlation coefficients, graphs, and empirical formulas, it evaluates how SiO2, CaO, Al2O3, and MgO vary with Fe and Fe2O3 and with one another. The study finds inverse relationships of SiO2 and Al2O3 with iron content, direct relationships of CaO and MgO with iron content, and reliable correlations among the oxides themselves. These relationships are proposed as practical tools for estimating skarn and mined ore composition, assessing basicity changes during dilution, and planning ore blending to obtain more uniform raw material for metallurgical processing.
Full Text
On the Relationship Between Components in Iron-Ore Skarns of the Tashtagol Deposit
P. I. Raiskii
(Presented by the scientific seminar of the Departments of Mine Surveying and Geodesy)
The study of the question of the relationship between components in iron-ore skarns is of great practical importance. The ore bodies of the deposit, in terms of the metal content in the ore, do not have clearly expressed contacts. Toward the boundaries of the ore bodies the iron content in the ore, as a rule, decreases, and at the contacts of the ore bodies with the enclosing rocks the ores pass into ore skarns.
During the mining of ore bodies, the ore is diluted by enclosing rocks and, consequently, its qualitative composition changes. Therefore, in order to determine the quality of the mined ore raw material, it is necessary to know not only the material composition of the ore in place, but also to know well the chemical-mineralogical composition of the ore skarns that dilute the ore during mining.
The material composition of ore skarns can also be disclosed more fully if the regular relationships between the various components included in their composition are studied.
In the present work, results are presented of investigations of the relationship
Fig. 1. Graph of the dependence of the CaO content in ore skarn on the Fe content in it.
Fig. 2. Graph of the dependence of the Al₂O₃ content in ore skarn on the Fe₂O₃ content in it.
between the components making up the ore skarns of the Tashtagol deposit.
Relationship of SiO₂, CaO, Al₂O₃, and MgO with Fe and Fe₂O₃
To study the type and strength of the relationship of the oxides SiO₂, CaO, Al₂O₃, and MgO with Fe in the ore and with Fe₂O₃, we constructed plots of the dependence of the contents of SiO₂, CaO, Al₂O₃, and MgO in the ore skarns on the contents of Fe and Fe₂O₃ in them. As examples, two of the above-mentioned plots are shown in Figs. 1 and 2. An assessment was also made of the relationship of the components SiO₂, CaO, Al₂O₃, and MgO with Fe and Fe₂O₃ by determining the magnitude of the correlation coefficient (Table 1).
Table 1
Assessment of the strength of the relationship of the oxides SiO₂, CaO, Al₂O₃, and MgO with Fe and Fe₂O₃
| Name of relationship | Number of analyses | Correlation coefficient | Error of the correlation coefficient |
|---|---|---|---|
| Fe—SiO₂ | 30 | −0,76 | ±0,074 |
| Fe—CaO | 35 | +0,79 | ±0,064 |
| Fe—Al₂O₃ | 41 | −0,67 | ±0,097 |
| Fe—MgO | 30 | +0,66 | ±0,096 |
| Fe₂O₃—SiO₂ | 37 | −0,89 | ±0,041 |
| Fe₂O₃—CaO | 36 | +0,73 | ±0,080 |
| Fe₂O₃—Al₂O₃ | 35 | −0,74 | ±0,077 |
| Fe₂O₃—MgO | 29 | +0,67 | ±0,103 |
The strength of the relationship of the oxides SiO₂, CaO, Al₂O₃, and MgO with Fe and Fe₂O₃ in the ore skarns is somewhat less than the strength of the relationship between the above-mentioned components in the ores themselves [1], but it is quite sufficient for using these relationships for practical purposes, i.e., for determining the quality of the mined ore raw material during the period of its averaging (the correlation coefficients are 0,67–0,89).
Studies have established that, in the ore skarns, the contents of the oxides SiO₂ and Al₂O₃ are in inverse dependence, while the contents of the oxides CaO and MgO are in direct dependence, on the content in them of Fe₂O₃ and Fe. With a decrease in the iron content in the ore skarns, the content in them of SiO₂ and Al₂O₃ increases, while CaO and MgO decreases.
Knowledge of the question of direct and inverse correlation relationships between components in ore skarns is of important practical significance, since it is possible, without chemical analyses, to determine the quality and basicity of the ore raw material during its mining. As a result of dilution of ores by ore skarns, the basicity of the ore raw material (the ratio \(\frac{\mathrm{CaO}+\mathrm{MgO}}{\mathrm{SiO}_2+\mathrm{Al}_2\mathrm{O}_3}\)) will always be lower than the basicity of the ores in the massif. This is explained by the fact that dilution of ores by ore skarns leads to an increase in their content of SiO₂ and Al₂O₃ and a decrease in the content of CaO and MgO.
The decrease in the basicity of the ores is well confirmed in the course of operation of the deposit: the basicity of the ore mass is always 0,1–0,15 less than the basicity of the ore in the massif.
For the solution of many practical problems, it is required that the interrelationship between components both in the ore and in the ore skarn
was presented in analytical form. The studies showed that, for the ore skarns of the Tashtagol deposit, the relationship of SiO$_2$, CaO, and MgO with Fe in analytical form can be expressed by the following empirical formulas:
$$ \mathrm{SiO}_2,\% = A^{1-(0.345+0.149A)\mathrm{Fe}} - 26; \tag{1} $$
$$ \mathrm{CaO},\% = 3.2e^{B\mathrm{Fe}} - 3.2; \tag{2} $$
$$ \mathrm{MgO},\% = 2.35e^{B\mathrm{Fe}} - 2.35, \tag{3} $$
where 26, 3.2, and 2.35 are coefficients numerically equal to the average content in the earth’s crust of SiO$_2$, CaO, and MgO, %;
$A$ and $B$ are undetermined coefficients;
Fe is the iron content in the ore skarn, in relative units.
Interrelationship between the oxides SiO$_2$, CaO, Al$_2$O$_3$, and MgO
The interrelationship between the oxides SiO$_2$, CaO, Al$_2$O$_3$, and MgO in the ore skarns was established by us using the method of correlation theory and by constructing graphs. To study the question of the interrelationship between the components in the ore skarns, the following graphs were constructed:
a) a graph of the dependence of the content in the skarns of Al$_2$O$_3$, CaO, and MgO on their SiO$_2$ content;
b) graphs of the dependence of the content in the skarns of Al$_2$O$_3$ and MgO on their CaO content;
c) a graph of the dependence of the MgO content in the skarns on their Al$_2$O$_3$ content.
Of the above-listed graphs, two graphs are presented as examples in Figs. 3 and 4.
Fig. 3. Graph of the dependence of the CaO content in skarns on their SiO$_2$ content.
Fig. 4. Graph of the dependence of the MgO content in skarn on its CaO content.
The construction of graphs of the relationships between the components comprising the ore skarns, and an evaluation of the strength of the relationships between them, showed that:
a) in the ore skarns, the oxides SiO$_2$, CaO, Al$_2$O$_3$, and MgO are related not only to Fe and Fe$_2$O$_3$, but the oxides of silicon, calcium, aluminum, and magnesium themselves are also interrelated with one another;
b) the oxides SiO$_2$, CaO, Al$_2$O$_3$, and MgO are in a rectilinear dependence on one another; between the oxides SiO$_2$ and CaO, SiO$_2$ and MgO,
between CaO and Al₂O₃ there is an inverse relationship, while between the oxides SiO₂ and Al₂O₃, CaO and MgO there is a direct relationship (Table 2).
Table 2
Assessment of the strength of the relationship between the oxides SiO₂, CaO, Al₂O₃, MgO
| Name of relationship | Number of analyses | Correlation coefficient | Error of the correlation coefficient |
|---|---|---|---|
| SiO₂ — CaO | 33 | −0.82 | ±0.052 |
| SiO₂ — Al₂O₃ | 43 | +0.68 | ±0.083 |
| SiO₂ — MgO | 30 | −0.66 | ±0.101 |
| CaO — Al₂O₃ | 39 | −0.67 | ±0.089 |
| CaO — MgO | 28 | +0.81 | ±0.055 |
| Al₂O₃—MgO | 32 | −0.67 | ±0.095 |
An assessment, by means of the correlation coefficient, of the strength of the relationship between the oxides SiO₂, CaO, Al₂O₃, and MgO showed that there is a sufficiently reliable degree of interrelationship between these components (the correlation coefficients are 0.66–0.84), Table 2. Such a magnitude of the strength of the relationship between the oxides SiO₂, CaO, MgO, and Al₂O₃ is quite sufficient for using these interrelationships for practical purposes, i.e., for determining the material composition of the ore raw material during its averaging.
Conclusions
The results of the investigations allow us to draw the following conclusions.
- In the ore skarns of the Tashtagol deposit, the content of the oxides SiO₂, CaO, Al₂O₃, and MgO depends substantially on the content in them of Fe and Fe₂O₃. In addition, the above-mentioned oxides themselves are interrelated with one another.
The strength of the relationship of the oxides SiO₂, CaO, Al₂O₃, and MgO with Fe and Fe₂O₃, as well as between the oxides themselves, is sufficiently reliable for using these relationships for practical purposes, i.e., for determining the material composition both of the ore skarns themselves and of the mined ore raw material to which skarns are admixed during mining.
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The interrelationships between components in iron-ore skarns reveal with sufficient completeness the picture of changes in the content of the various components making up their composition, depending on changes in their iron content. It is impossible to present such a picture from individual samples. Knowledge of this question facilitates the solution of the problem of determining the qualitative composition of iron ores in those ore bodies that contain inclusions of ore skarns.
-
The interrelationships we have studied between components in ore skarns can be used to solve the following practical problems:
a) without making analyses for the oxides SiO₂, CaO, Al₂O₃, and MgO, their amount in the skarn can be determined from previously prepared graphs of the dependence of the above-mentioned oxides on the content of ore iron in the ore skarn;
b) to plan in advance the mining of ore from different blocks in such a way as to obtain qualitatively homogeneous ore raw material during its averaging, which is very important for the metallurgical process, since the smelting process is improved.
LITERATURE
- Raiskii P. I. On the correlation relationship between components in magnetite ores of deposits of Mountain Shoria. Izvestiya vuzov, Gornyi zhurnal, No. 9, 1959.