The Per Geijer iron oxide-apatite deposits are important potential future resources for Luossavaara-Kiirunavaara Aktiebolag (LKAB), which has been continuously mining magnetite/hematite ores in northern Sweden for almost 130 years. The Per Geijer deposits reveal a high phosphorus content and vary from magnetite-dominated to hematite-dominated ores, respectively. The high phosphorus concentration of these ores results from highly elevated content of apatite as gangue mineral. Reliable, robust, and qualitative characterization of the mineralization is required as these ores inherit complex mineralogical and textural features. The precise mineralogical information obtained by optical microscopy, SEM-MLA and Raman improves the characterization of ore types and will benefit future processing strategies for this complex mineralization. The different approaches demonstrate advantages and disadvantages in classification, imaging, discrimination of iron oxides, and time consumption of measurement and processing. A comprehensive mineral-chemical dataset of magnetite, hematite and apatite obtained by electron microprobe analysis (EPMA) and LA-ICP-MS from representative drill core samples is presented. Magnetite, four different types of hematite and five types of apatite constitute the massive orebodies: Primary and pristine magnetite with moderate to high concentrations of Ti (∼61–2180 ppm), Ni (∼11–480 ppm), Co (∼5–300 ppm) and V (∼553–1831 ppm) indicate a magmatic origin for magnetite. The presence of fluorapatite and associated monazite inclusions and disseminated pyrite enclosed by magnetite with high Co:Ni ratios (> 10) in massive magnetite ores are consistent with a high temperature (∼ 800°C) genesis for the deposit. The different and abundant types of hematite, especially hematite type I, state subsequent hydrothermal events.
Chromium, Ni, Co and V in both magnetite and hematite have low concentrations in terms of current product regulations and thus no effect on final products in the future. In terms of a possible future hematite product, titanium seems to be the most critical trace element due to very high concentrations in hematite types I and IV, of which type I is most abundant in zones dominated by hematite. Further interest on other products is generated due to the high variability of hematite and apatite in some of these ores.
Information obtained from comminution test works in the laboratory scale can be utilized to characterize ore types and to predict the behavior of ore during comminution circuit in the industrial scale. Comminution tests with a laboratory rod and ball mill of 13 pre-defined ore types from the Per Geijer iron-oxide apatite deposits were conducted in this study. The highest P80 values were obtained by grinding in the rod mill for 10 minutes only (step A). Grinding steps B (25 min ball mill) and C (35 min ball mill) reveal very narrow P80 values. Ore types dominated by hematite have significantly higher P80 values after the primary grinding step (A), which indicates different hardness of the ore types. P80 values are generally lowest after the secondary grinding step C ranging between 26 µm (ore type M1a) and 80 µm (ore type H2a). Generally, Fe content increases in the finer particle size classes while CaO and P contents decrease. The influence of silica or phosphorus seems to be dependent on the dominant iron oxide. Magnetite-dominated ore types are more likely to be affected in their comminution behavior by the presence of the silicates. Contrary, hematite-dominant ore types are rather influenced by the presence of apatite. The difference in the degree of liberation of magnetite and hematite between ore types depends rather on size fractions than the amount of gangue in the ore. Davis tube data indicates that magnetite can be separated from gangue quite efficiently in the magnetite-dominated ore types. Contrary to magnetite ore, hematite-dominated ore types cannot be processed by DT. It is favored to use strong magnetic separation in order to achieve a desirable hematite concentrate. The magnetic material recovered by DT is most efficiently separated at an intensity current of 0.2 A, whereas above 0.5 A the separation process is neglectable. Based on comminution and magnetic separation tests a consolidation to eight ore types is favored which supports possible future mining of the Per Geijer deposits.:Contents
ABSTRACT ……………………………………………………………………… I
CONTENTS ……………………………………………………………………… II
LIST OF FIGURES AND TABLES ……………………………………………… IV
LIST OF ABBREVIATIONS ……………………………………………… V
1 INTRODUCTION ……………………………………………………… 1
1.1 Background and motivation of study ……………………………… 2
1.2 Previous and current work on the Per Geijer deposits ……………… 3
1.3 The need for mineral processing and in-situ ore description ……………… 4
1.4 General and generic aspects on iron oxide apatite deposits ……………… 5
Chapter A
2 REGIONAL GEOLOGY ………………………………………………. 7
2.1 Local geology of the Kiruna area ……………………………………… 7
2.2 Geology of the Per Geijer deposits ……………………………………… 9
3 METHODOLOGY ……………………………………………………… 12
3.1 Core sampling and preparation ……………………………………… 12
3.2 SEM – MLA in-situ ore ……………………………………………… 14
3.3 Electron Probe Microanalyses (EPMA) ……………………………… 15
3.3.1 Iron oxide measurements ……………………………………… 15
3.3.2 Apatite measurements ……………………………………… 15
3.4 In-situ LA-ICP-MS ……………………………………………………… 16
3.5 Whole-rock geochemistry ……………………………………………… 18
3.5.1 Exploration drill core assays ……………………………… 18
3.5.2 Chemical assays of rock chips ……………………………… 18
4 RESULTS ……………………………………………………………… 19
4.1 Pre-definition of ore types ………………………………...……………. 19
4.2 Mineralogy of in situ ore ……………………………………………… 21
4.2.1 Ore Type M1a ……………………………………………… 21
4.2.2 Ore Type M1b ……………………………………………… 22
4.2.3 Ore Type M2a ……………………………………………… 23
4.2.4 Ore Type M2b ……………………………………………… 25
4.2.5 Ore Type HM1b ……………………………………………… 26
4.2.6 Ore Type HM2a ……………………………………………… 27
4.2.7 Ore Type HM2b ……………………………………………… 28
4.2.8 Ore Type H1a ……………………………………………… 29
4.2.9 Ore Type H1b ……………………………………………… 30
4.2.10 Ore Type H2a ……………………………………………… 31
4.2.11 Ore Type H2b ……………………………………………… 32
4.2.12 Comparison of ore types ……………………………………… 33
4.3 Geochemistry of in situ ore types ……………………………… 36
4.3.1 Whole-rock chemical assays of drill cores ……………………… 36
4.3.2 Whole-rock geochemistry of rock chips ……………………… 39
4.4 Mineral chemistry of iron oxides ……………………………………… 42
4.4.1 Iron oxides and associated minerals ……………………………… 42
4.4.2 Mineral chemistry of magnetite from Per Geijer ……………… 43
4.4.3 Mineral chemistry of hematite from Per Geijer ……………… 47
4.5 Mineral chemistry of apatite ……………………………………… 51
4.5.1 Apatite and associated minerals ……………………………… 51
4.5.2 Mineral chemistry of apatite from Per Geijer ……………… 53
Chapter B
5 COMMINUTION TESTS ……………………………………………… 58
5.1 Methodology of comminution tests ……………………………………… 59
5.1.1 Sampling for comminution tests ……………………………… 59
5.1.2 Comminution circuit ……………………………………………… 61
5.1.3 Energy consumption calculation ……………………………… 62
5.1.4 SEM – MLA ……………………………………………………… 64
6 MAGNETIC SEPARATION TESTS ……………………………… 65
6.1 Methodology of magnetic separation by Davis magnetic tube ……… 66
6.2 Davis magnetic tube tests for characterization of the Per Geijer ore types 66
6.3 Separation analysis based on the Henry-Reinhard charts .……………... 67
7 RESULTS OF COMMINUTION OF ORE TYPES ……………………… 69
7.1 General characteristics of magnetite-dominated ore types ……………… 69
7.2 General characteristics of hematite-dominated ore types ……………… 72
7.3 General characteristics of magnetite/hematite-mixed ore types ……… 75
7.4 General characteristics of low-grade ore types ……………………… 77
7.5 Mineral liberation characteristics of magnetite-dominated ore types 79
7.6 Mineral liberation characteristics of hematite-dominated ore types 83
7.7 Mineral liberation characteristics of magnetite/hematite-mixed ore types 87
7.8 Mineral liberation characteristics of low-grade ore types ……………… 90
7.9 Total energy consumption of ore types from the Per Geijer deposits 94
8 RESULTS OF MAGNETIC SEPARATION OF ORE TYPES ……… 95
8.1 Magnetic separation of magnetite-dominated ore types ……………… 95
8.2 Magnetic separation of hematite-dominated ore types ……………… 96
8.3 Magnetic separation of magnetite/hematite-mixed ore types ……………… 97
8.4 Magnetic separation of low-grade ore types ……………………………… 98
8.5 Henry-Reinhard charts ……………………………………………… 99
9 DISCUSSION ……………………………………………………… 101
9.1 Mineralogy of the in-situ ore types from the Per Geijer deposits ……… 101
9.2 Geochemistry of the in-situ ore types from the Per Geijer deposits ……… 103
9.3 Mineral chemistry of iron oxides from the Per Geijer deposits ……… 105
9.4 Mineral chemistry of apatite from the Per Geijer deposits ……………… 114
9.5 Comminution of ore types from Per Geijer ……………………… 119
9.6 Magnetic separation of ore types from Per Geijer ……………………… 120
9.7 Issues with process mineralogy of in-situ and grinded ore types ……… 121
10 CONCLUSIONS ……………………………………………………… 128
11 IMPLICATIONS FOR FUTURE WORK ……………………………… 131
12 REFERENCES ……………………………………………………………… 134
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:78554 |
| Date | 04 April 2022 |
| Creators | Krolop, Patrick |
| Contributors | Seifert, Thomas, Niiranen, Kari, Schulz, Bernhard, TU Bergakademie Freiberg |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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