
==== Front
Heliyon
Heliyon
Heliyon
2405-8440
Elsevier

S2405-8440(24)12163-9
10.1016/j.heliyon.2024.e36132
e36132
Research Article
Geology, mineralogy, geochemistry and genesis of volcano-sedimentary hosted Lake Abiyata diatomite in central main Ethiopian Rift
Hunegnaw Yirgalem yirgalemgeol@gmail.com
ab1⁎
Getaneh Worash b
a Geological Institute of Ethiopia, P.O. Box 2302, Addis Ababa, Ethiopia
b School of Earth Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia
⁎ Corresponding author. Geological Institute of Ethiopia, P.O. Box 2302, Addis Ababa, Ethiopia. yirgalemgeol@gmail.com
1 Present address: Geological Institute of Ethiopia, P.O. Box 2302, Addis Ababa, Ethiopia.

14 8 2024
30 8 2024
14 8 2024
10 16 e3613214 2 2024
9 8 2024
9 8 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
The Abiyata Diatomite deposit is located in the Main Ethiopian Rift, which is characterized by strong extensional tectonics. The deposit is mostly made up of diatomaceous earth, which is a sedimentary rock made up of the fossilized remnants of diatoms, which are tiny algae. Diatomite's geological, geochemical, and mineralogical features, as well as its formation, are discussed in this research. To characterize diatomite from Abiyata, chemical, mineralogical, technological, and micro paleontological examinations were conducted on samples collected from outcrops and stream sections. The XRD characteristic peaks of diatomite demonstrate that it is primarily made up of Opal A silica, however certain crystalline phases were discovered in adequate amounts. Quartz and feldspar were the predominant crystalline phases, with lesser amounts of Calcite, Cristobalite, Illite, Mordinite, Wairakite, Halloysite, Clinoaptilolite, Adularia, and Tridymite. From SEM photomicrographs diatomites are primarily formed of benthic freshwater diatom species such as Staurosirella pinnata, Staurosira construens, Pseudostaurosira brevistriata, Epithemia Sorex and surirella pinnata. Diatom species, sedimentary profile sections and mineralogical data suggest that diatomite was deposited in lacustrine-type freshwater shallow lake environment. Chemical data obtained from 10 diatomite samples show that while silica is the bodybuilding material for diatomite. i.e., Silica (SiO2), 76.9 %; Alumina (Al2O3), 3.49 %; Sodium Oxide (Na2O), 1.52 %; Potassium Oxide (K2O), 1.107 %; Iron Oxide (Fe2O3), 1.1 %; Loss on ignition (LOI) 13.7 and other oxides are below 1 %. Studies from technological properties like physical tests, chemistry, and mineralogy and micropaleontology of Abiyata diatomite suggest that calcined diatomite can be used for waste treatment processes in the filter aid industry and as filler material.

Keywords

Amorphous silica
Diatomite
Genesis
Lacustrine
Mineralogy
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pmc1 Introduction

The Main Ethiopian Rift (MER) and its flanks are made of Tertiary to Quaternary volcanics and pyroclastic rocks [1], whereas large areas of the rift floor are covered by upper Quaternary volcano–lacustrine, fluvio–lacustrine, and colluvial deposits.

According to Ref. [2], the MER has a potential for some metallic minerals and many industrial minerals including Potash, Salt, Trona, Gypsum, Limestone, Bentonite, Diatomite, Pumice and Clay. Among the widest range of industrial mineral resources, Diatomite is one of the most important industrial mineral resources in the rift. The silica-bearing material group includes diatomite rock. Diatomite is derived from a siliceous sedimentary rock that formed in the tertiary and quaternary periods. It is primarily composed of fossilized skeletal remnants of diatoms, which are unicellular aquatic plants related to algae.

It is a chalky, sedimentary rock composed of the skeletal remains of single-celled aquatic water plants called diatoms. The siliceous skeletons become an inorganic mineral in a form of sediment on the bottom of whatever body of water they have inhabited [3]. They are frequently associated with volcanic activity, with air-fall ash, run-off waters and spring waters providing a source of dissolved silica to replenish that extracted by diatoms [4].

Diatoms live in a wide variety of environments from the open ocean to nearshore; and in freshwater rivers, lakes and marshes. Based on their diagnostic floral assemblages and sedimentary associations, ancient diatomites are readily classified into marine and freshwater deposits. Many freshwater and marine deposits are closely associated with volcanism which provides a ready supply of dissolved silica which the diatoms need to construct their skeletons ([5,6,4,7]). A rapid expansion in diatom population following the supply of pyroclastic material from an eruption has been recorded in the modern environment [8].

Relatively little research has been done on the characterization and investigation of the diatomite deposits in Abiyata. This work investigates the characterization of Abiyata diatomite in an attempt to close this research gap. Diatomite's physical, chemical, and mineralogical characteristics must be investigated in order to fully characterize it. These characteristics give light on its possible industrial uses in filtration, farming, manufacturing, and other fields. Characterization pertains to the features of a material's composition, structure, and flaws that are critical for a particular procedure, application, or study of the material's attributes.

This study's objectives are also to investigate genesis of diatomite and the material's possible industrial uses and perform a quantitative elemental analysis of the material found in the study region. To do this, a quantitative analysis of the elemental composition of the diatomaceous earth collected in the research area was conducted using different techniques such as (an X-Ray Fluorescence (XRF), X-Ray Diffraction, Scanning Electro-microscope (SEM), Granulometry and etc.

This data serves as the foundation for characterizing a material in order to identify potential processing, development, and application areas. The creation of a mined material accelerates economic growth and generates work for the populace, making the paper extremely important. Additionally, these qualities are analyzed in the study to determine their applicability, quality, and possible industrial uses. For scientists, engineers, and businesses interested in using diatomite as a raw material, it offers useful information.

2 Geology and tectonic setting

The geology of the MER is divided into three primary lithostratigraphic sequences, namely the pre-rift, Syn-rift, and main-rift sequences, according [9]The faulting of the pre-rift volcanic sequence, of Oligocene-Miocene age, occurred around ten million years ago ([9], among others. The floor of the rift Valley is covered in deposits from the Miocene-Pliocene to the Holocene [9] and other eras. According to Ref. [1], the MER and its flanks are composed of Tertiary to Quaternary volcanic and pyroclastic rocks, whereas the rift floor is largely covered with upper Quaternary volcano lacustrine, fluvio-lacustrine, and colluvial deposits.

The research area's tectonic context is found in the MER. As a result, it is a component of the enormous East African Rift. Miocene-Quaternary intra-continental extensional system from Mozambique to Afar made up of several interconnected rift segments ([10,11,12]). Tectonically one of the most active geological regions in the world is the East African Rift Valley. The Rift in Ethiopia comprises an area of roughly 150,000 km2, including the Lakes District, and runs about 1000 km in a NE direction from the Kenyan border [13]. According to Ref. [14], the rifting in the central MER is less than 8 million years old and originated after the development of the northern MER. Apart from modest fluvio-lacustrine sediments, largely of Quaternary age, that were deposited on the rift floor, Tertiary to Quaternary volcanics are the only rocks exposed in the MER [14].

Two volcano tectonic units can be differentiated in the northern half of the MER, according to Ref. [9]. According to them, the Nazareth group is an older stratoid unit that is made up primarily of silicic rocks including alkali and peralkali trachytes, rhyolites, ignimbrites, tuffs, and pumice. They estimate its age to be between 2 and 5 million years old. A significant portion of the rift escarpments in the study area are composed of stratoid silicics, ignimbrites, unwelded tuffs, ash flows, rhyolites, and trachytes, while in the floor they are inconsistently overlain by younger volcanic of the Dino formation (east of lake Shala, where the current study is located).

The three sections of the main Ethiopian rift, known as the Afar rift, are said to have evolved progressively from the north east toward the south west [15]. The Southern Segment is dated 18 Ma, whereas the Central Segment (CMER), which spans the “lakes region,” has questionable age estimations that range from 5 to 9 Ma. The Northern Segment (NMER), which connects the distant and main Ethiopian Rifts with the N50° E trend, is dated 10 to 11 Ma.

The Bulbula River and its tributaries expose a significant thickness of late Quaternary lacustrine and fluvial sediments north of Lake Abiyata. According to Street (1979), who was referenced by Ref. [16], these sediments are known as the Bulbula Formation.

3 Methodology

3.1 Field work

The diatomite occurrence's geology was described, extensive geological mapping was done, and samples were collected for lab testing. The area's geological map, prepared at a scale of 1:10,000 to show the lithologic units, and a geological cross section along a chosen profile were both created. At various heights along the stream, representative samples were taken from several locations.

3.2 Laboratory analysis

The primary laboratory studies used for this work were Petro graphical, mineralogical, micro paleontological, physical tests (color, PH, grain size, bulk density, and specific gravity), and geochemical investigations. Data from powder X-ray diffraction (PXRD) experiments were collected at the X-ray diffraction laboratory of the Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Prague, using a PANalytical X'Pert Pro diffractometer operating at 40 kV and 30 mA with a secondary monochromator producing CuK 1,2 radiation with X'Celerator detector. The search-match algorithm High-Score using PDF-2 (ICDD) database was used to identify the phases.

The chemical analysis of 10 diatomite samples was performed at Geological Survey of Czech Analytical Laboratories (Prague, Czech Republic) using ICP-AES, Classical chemical silicate analysis is used to identify the chemical composition of the raw material. SiO2 content is evaluated gravimetrically, whereas Al2O3, Fe2O3, TiO2, CaO, MgO, and MnO content is assessed by volumetric analysis (by titration). A flame photometer is used to measure the concentrations of the alkaline oxides K2O and Na2O. Thermal treatment of the sample at 1000 °C determines the loss on ignition (LOI).

At the Czech Republic's geological survey in Prague, scanning electron microscopy (SEM) was used to examine the Micro-paleontological characteristics of ten chosen diatomite samples. The 10 samples were also subjected to physical tests (specific gravity, pH, and qualitative color determination). The laser diffraction analyzer HELOS/KF-MAGIC (Sympatec, Germany) was used to determine the grain-size distribution of the samples. Prior to measurements, samples were mixed in an ultrasonic bath with distilled water for 30 s. The tests were carried out using the R3 optical module, which has a measuring range of 0.5–175 μm under constant temperature (25 °C) circumstances.

Bulk density of untreated diatomite was analyzed. In this study bulk density was calculated by measurement of the volume occupied by a known weight of diatomite following a controlled compaction procedure by drying it to remove the moisture content. This was done by placing a sample in oven at a temperature of 1050C until constant weight is achieved. Then measure the mass of dried diatomite using balance, and determine the volume occupied by diatomite in the cylinder recording known volume. Finally calculate the bulk density by dividing mass of the diatomite by volume occupied by diatomite.

4 Results

4.1 Geology of the Abiyata diatomite deposit

The geology of the Abiyata area is comprised of lacustrine sediments that range in age from the Miocene to the Quaternary, the Wonji group (pyroclastic rocks, volcanoclastic material), and the Butajira ignimbrite, according to the chronostratigraphic data of the CMER published by [17].

According to Ref. [18] the research region is composed of volcanic rocks and lacustrine sediments from the Pleistocene and Holocene lacustrine units Qlp and Qlh. The oldest outcropping volcanics in the research region, according to Ref. [19], are pumice beds that are roughly 0.60 Ma old and nearby the WFB ignimbrite (see Fig. 1).Fig. 1 Regional geological map of the central main Ethiopian Rift, after GSE, 2004 (Ql = Lacustrine sediments; silts, clays, diatomites, Qdl = Ignimbrites, tuffs, waterlain pyroclastics, occasional lacustrine beds, Qwa = Ryholite with some Trchyte Lava flows, Qwh = Basaltic hyaloclastites (phreatomagmatic deposite), Nbb = Bofa Basalts: mildly alkaline basalts, Qwbp = Pleistocene basalts, mostly vesicular, NQS=Nazreth group and Dino formation undifferentiated, NT-2n = Stratoid silicics: ignibrites, unwelded tuffs, ash – flows, rhyolites).

Fig. 1

According to Ref. [20] the sediments containing diatomite were deposited in the Lakes Region during the Upper Pleistocene. The fine-grained, light-colored rocks that are demonstrably the by-products of pyroclastic eruptions sit beneath the lake bottoms where the diatomite is found. Along the east-west stream that flows into Lake Abiyata, diatomite is revealed. Starting with the westernmost exposure, the exposures vary in color, texture, and friability (Fig. 2). As can be seen in the stream section, the diatomite deposit in the study region is connected to lacustrine sediments of fine-grained, whitish to grayish-colored siliceous material formed of the remains of diatoms and reworked elements such silts, clays, and fine sand Pumiceous layers (see Fig. 3).Fig. 2 Field exposures of Abiyata diatomite from stream cut section.

Fig. 2

Fig. 3 Geological map of the study area and cross Section.

Fig. 3

4.2 Mineralogy of the Abiyata diatomite deposit

Natural diatomite that hasn't been treated primarily consists of amorphous silica, which has a broad peak in X-ray examination and is similar to Opal-A [21,22,3]). However, small components of other crystalline phases are frequently found. According to several studies [[22], [23], [24]]), these phases may comprise quartz, calcite, kaolinite, feldspar, dolomite, Cristobalite, and mica.

Diffraction data has been used to identify main crystalline phases from the locations and intensities of well-defined peaks. It can also be used to identify amorphous and poorly-ordered materials by looking the shape and location of large scattering humps. Crystalline phases have sharp diffraction peaks, whereas amorphous and poorly ordered phases have wide X-ray scattering patterns. The XRD result of Abiyata diatomite samples indicates the presence of many amorphous phases. However, certain crystalline phases were found in sufficient quantities. The primary crystalline phases were quartz and feldspar, with calcite, cristobalite, illite, mordinite, wairakite, halloysite, clinoaptilolite, adularia, and tridymite as minor components. Crystalline mineral impurities in diatomites that have reasonably sharp peaks (Fig. 4) and a semi-quantitative.Fig. 4 XRD patterns of Abiyata diatomite samples.

Fig. 4

4.3 Micropaleontology of Abiyata diatomite deposit

Micro-paleontological examinations of diatom species can tell whether a deposit developed in freshwater, brackish water, or seawater, as well as whether it happened in deep or shallow water. SEM, or scanning electron microscopy, was used on a few chosen samples. This approach offers a useful visual representation of the skeleton of the diatom. The majority of Abiyata samples are composed primarily of diatom morphologies, with several of the species displaying Pennate forms. In valve view, the frustules of pennate diatoms are typically lengthy and bilaterally symmetrical. The majority of them have polar nodules, which are narrow axial thickenings at each end, and central nodules, which are typically median thickenings in the middle. Benthic species dominated the diatom assemblages in all sections, with few planktonic species present. From the SEM studied samples, Staurosirella pinnata, Staurosira construens, Pseudostaurosira brevistriata, and Epithemia sorex are the major species diatoms. This point to a lacustrine ecosystem that is shallow water, seasonally eutrophic, temperate, and alkaline [25].

4.4 Geochemistry of Abiyata diatomite deposit

In terms of chemical composition, as predicted, the Raw Diatomite (RD) is largely composed of SiO2, with some additional oxides such as Al2O3, Fe2O3 and Na2O. All other oxides are in low quantities, with diatomite rocks are constituted essentially by silica. The contents of the major oxides of the 10 samples of the Abiyata diatomites are presented in Table 1, including the loss on ignition (LOI). The composition of the major element oxide is consistent with that of the whole rock minerals.Table 1 Major oxide result of Abiyata diatomite.

Table 1%wt.	ADM4-S1	ADM-31	ADM14-S3	ADM14-S2	ADM15-S1	ADM20-S1	ADM22-S2	ADM23-S3	ADM-26	ADM-27	
SiO2	82.86	62.58	70.04	66.36	75.58	84.66	84.24	77.56	77.26	82.84	
TiO2	0.12	0.26	0.21	0.21	0.20	0.08	0.12	0.24	0.28	0.02	
Al2O3	2.20	4.66	4.16	5.02	3.80	1.52	2.14	4.07	5.16	2.19	
Fe2O3	1.13	2.94	2.28	2.98	2.08	0.08	1.32	2.91	3.09	1.29	
FeO	0.17	0.20	0.11	0.36	0.07	<0,01	0.13	0.31	0.58	<0,01	
MnO	0.03	0.05	0.03	0.07	0.04	0.10	0.02	0.08	0.09	0.02	
MgO	0.20	0.56	0.45	0.39	0.41	0.10	0.21	0.46	0.42	0.20	
CaO	0.43	1.53	0.33	1.21	0.28	0.28	0.33	1.02	0.87	0.46	
Na2O	1.45	1.95	1.41	2.49	2.50	1.03	1.10	1.53	1.89	0.59	
K2O	0.68	1.37	1.20	1.57	1.37	0.45	0.56	1.41	1.90	0.56	
P2O5	0.02	0.04	0.02	0.03	0.03	0.01	0.01	0.03	0.02	0.02	
LOI	10.32	23.63	19.59	19.13	13.47	11.35	9.55	10.25	8.31	11.43	
Total	99.61	99.77	99.83	99.82	99.83	99.66	99.73	99.87	99.87	99.62	
H2O–1050C	6.05	19.09	15.39	14.27	8.57	6.30	5.27	5.15	3.42	6.72	

The primary element oxide's composition matches the overall composition of the rock's minerals. The body-building component of diatomite is SiO2, which is the most prevalent of all oxides. Its SiO2 content ranges from 62.58 % to 84.66 % (average: 76.4 %), Al2O3 content ranges from 1.52 % to 5.16 % (average: 3.47 %), and CaO content ranges from 0.28 % to 1.52 % (average: 0.67 %).

The concentration of TFe2O3, which stands for total iron, which includes Fe2O3 and FeO, ranges from 0.08 % to 3.67 % (average: 1.1 %). Average MgO concentrations vary from 0.1 % to 0.56 percent, average Na2O concentrations from 0.59 to 2.49 percent, and average K2O concentrations from 0.45 to 1.9 %. Additionally, the average concentrations of the other important oxides, such as TiO2 (0.17 %), P2O5, and MnO (0.05 %), are less than 1 %, and the average LOI is 13.7 %, with a range of 8.31 %–23.63 %.

The Abiyata diatomite's principal oxides were calculated, and the findings show that all samples had high SiO2/Al2O3 ratios, ranging from 13.42 to 55.69 and having an average of 21.88. It has been proposed that if the ratio of SiO2/Al2O3 is larger than 3, the portion of SiO2 surpassing Al2O3 can be regarded as biogenic silica. The ratio of SiO2/Al2O3 in the typical crust is widely thought to be approximately 3 [26]. Additionally, practically all of the Abiyata diatomite samples are positioned above the Si/Al line in the cross-plot of Si vs Al (Fig. 6), indicating that they have excess Si, which is indicative of a substantial fraction of biogenic silica. Siliceous minerals other than those found in terrigenous clastic deposits are referred to as having a “excess siliceous mineral content” (Siex).Fig. 5 SEM photos of diatoms

A= Epithemia sorex, B=Pseudostaurosira brevistriata, C= Staurosira construens, D= Staurosirella pinnata, F = surirella pinnata.

Fig. 5

Fig. 6 Si vs Al showing silica excess and silica deficit zone after [27].

Fig. 6

4.5 Physical properties of Abiyata diatomite

Pure diatomite is white and it is comparable with the white color found in the Munsell Soil Color Chart. The organic matter rich diatomite samples (Table 2) show gray (2.5R 7/4) and pink (2.5 Y 7/3) colors. The particle size distribution of Abiyata diatomite contains high percentage of clay and silt size particles (>75 %) that are passing through 63 μm sieve. From the results it is evident that granulometrically samples strongly differ from each other. Results emphasize that almost all diatomite samples from Abiyata are very fine (practically clayey). This is confirmed by the investigation of finely disperse particles of the initial diatomite samples using a laser analyzer. However, the predominant particle sizes in the sample are between 10 and 50 μm, as is indicated by the strongest peaks (Fig. 7C and D) (see Fig. 8).Table 2 Munsell soil cEM photos of diate samples.

Table 2Samples code	Color	
ADM4-s1	HUE 10 YR Munsell soil color name diagram 7/2 Light gray	
ADM11-s1	HUE 5 Y Munsell soil color name diagram 6/3 pale olive	
ADM14-s3	HUE 2.5 Y Munsell soil color name diagram 7/3 pale yellow	
ADM15-s1	HUE 2.5 Y Munsell soil color name diagram 7/4 pale yellow	
ADM19-s1	HUE 2.5 Y Munsell soil color name diagram 5/3 light olive brown	

Fig. 7 Particle size distribution curve of the Abiyata diatomite (x-axis size in um, left y-axis intensity and right y axis distribution frequency).

Fig. 7

Fig. 8 XRD result of diatomite with less crystalline minerals (A) and XRD result of diatomite with more crystalline minerals (B).

Fig. 8

Calculating bulk density also provided a quick and easy way to evaluate the relative purity of the diatomites. Theoretically, diatomites that are “pure” will have a significantly lower bulk density than those that are more mineral-rich. The sample's bulk density is 0.42 g/cm3 on average. Since deeper layers have less organic substance, aggregation, and root penetration than top layers, bulk density often rises with depth. Because of the weight of the soil above them, subsurface strata are also vulnerable to compacting, which reduces their porosity. As we have seen some differences from laboratory findings, the wetting and drying of diatomite also affects the bulk density of diatomite in the region.

5 Discussions

In this section, we will go over the various analytical data that were acquired. In reality, as previously stated, the analytical techniques attempted to characterize raw diatomite from distinct deposits using various techniques. The physicochemical characterization of diatomites was accomplished using X-ray diffraction to assess the mineralogy of the diatomite and scanning electron microscopy to acquire information on the morphology of the diatomite particles and this could be essential for deposional environments to infer the genesis.

5.1 Genesis of Abiyata diatomite

Diatomite can develop in freshwater and marine environments when there is a significant population of diatoms and an accumulation of their byproducts [28]. Numerous lakes located in silica-rich settings, particularly in volcanic and hydrothermally active locations, have been found to contain enormous accumulations of ancient diatom frustules. The high dissolved silicon concentrations under these conditions encourage the formation of diatoms. However, lakes without a volcanic or hydrothermal effect have also been shown to contain significant diatom numbers in the sediment. The greatest instances of it are Lough Neagh, Ireland, and lakes in northern Sweden [29].

A photic zone rich in nutrients is necessary for a significant portion of these bacteria to exist in the environment. Diatoms are present in all streams, with the exception of the hottest and most hypersaline waters. Regardless of latitude, they are widespread in both marine and freshwater phytoplankton and phytobenthos [30]. [4] was the first to categorize diatomite deposits in 1933. The deposit's genesis was used by the author to divide it into four sorts. These include lacustrine and marine diatomite sediments linked to volcanism, ocean diatomite sediments, marsh diatomite sediments, Pleistocene interglacial diatomaceous lake sediments, and lacustrine and marine diatomite sediments. According to Ref. [31], dissolved silicon availability, phosphate and nitrogen availability, pH, salinity, and light are only a few of the environmental factors that have an impact on diatom formation. PH and temperature are related. Elliptical (pennate), mobile diatoms are often found interbedded with waterlain pyroclastics, fine sands, silts, clays, and peat in freshwater fluvial, lacustrine, and paludal diatomaceous deposits.

According to the results of the XRD analysis, the studied raw material may be categorized as amorphous, and the mineral impurities are represented by a collection peak of low intensity that can be estimated to reflect their quantities. Diatomites from Lake Abiyata contain crystalline mineral impurities with reasonably sharp peaks (Fig. 4) and a semi-quantitative. The large “hump” that appears between 15° and 30° (Fig. 4) is thought to be an indication of the existence of opal A in the sample. The lower values of crystalline minerals and high values of amorphous minerals (diatomite) have been determined from samples (ADM4- S1, ADM20-S1, ADM22-S1, ADM26 and ADM27) Fig. 7 A.

SEM photomicrographs of diatoms in the Abiyata diatomite deposit show that elliptical and elongated diatoms are the most prevalent. With just a few planktonic species, benthic species (Staurosirella pinnata, Staurosira construens, Pseudostaurosira brevistriata, and Epithemia sorex.) dominate the Abiyata diatomite deposit (SEM studies of diatomite (Fig. 5). Benthic species, epiphytic taxa, and minimum planktonic components all point to a shallow, alkaline mesotrophic freshwater lacustrine habitat [[32], [33]].

5.2 Grade and quality of Abiyata diatomite

The grade and quality of diatomites are determined from the mineralogical, chemical and physical test results. Commercial diatomite products are offered in a great variety of grades. In terms of mineralogy, accessory minerals can include clay minerals, quartz, gypsum, calcite, feldspar, mica, and, less commonly, salts, phosphates, pyrite, chert, and volcanic ash. Due to the inclusion of iron, aluminum, magnesium, and calcium, it could potentially include contaminants.

The chemical composition of Abiyata diatomite is compared with diatomites from (Turkey, Egypt, Algeria, Jordan, Mexico, Morocco, Suizhou, China, and Caldiran lake van basin east Anatolia Turkey). The SiO2 percentage of Abiyata diatomite is a quite higher than other deposit. These results suggest that the diatomite deposit of the area is high grade. It matters in this instance since the diatomite will be used as an addition in various industrial goods in the end.

The chemical composition of the raw sample from Abiyata diatomite deposit is only slightly below the standards of filter aid quality. The contents of Al2O3, Fe2O3 and CaO are slightly above the permissible limits. Therefore this deposit needs certain beneficiation to enhance the quality of the deposit. It can be observed that diagram 7A (samples ADM4-S1,ADM20-S1,ADM-26, ADM22-S2 and ADM-27) contains about 90 % diatomite (broad humped peak) with a negligible amount of impurities i.e. crystalline mineral (sharp peaks in XRD), and diagram B contain around 75 % diatoms with 20–25 % quartz and other crystalline minerals which are impurities in the case of diatomite. The composition of bulk sample that was compiled for technological testing from section is also represented by the average of these ten samples. The quality of the diatomite from the sample site (ADM20-S1) is only marginally greater than the deposit's overall quality, as indicated in Table 1. The average silica concentration of 76.9 % is below the filter aid quality standard of 85 percent. The highest SiO2 concentration of 84.66 % in sample ADM20-S1 from section suggests that there is very minor quality fluctuation.

5.3 Possible application of Abiyata diatomite

The diatomite from Abiyata area has favorable qualities for a variety of industrial uses. According to the characterization data it can be used as a raw material to create silica-based products including glass, ceramics, and refractories because of its high silica concentration.

It is a rock that is highly porous, has small particles, and has a low specific gravity. Due to its high porosity and low density, diatomite can be an effective heavy metals absorber, playing a significant role in the environment. It is a superior lead absorber than dolomite or perlite, actually, it is generally inert, has a very tiny particle size, and a high porosity. Because of this, it creates a superior material for filters. Diatomite, for instance, can be utilized to boost lime reactivity toward SO2 abatement [34].

Due of these qualities, it will be used as a filter medium, an absorbent, and a lightweight filler for rubber, paint, and other materials. Grain size, porosity, density, and other characteristics of the researched diatomite, as well as its chemical and mineralogical makeup, enable these materials to be used widely in a variety of industries. It may be used as a filter medium, an absorbent, and a light-weight filler for rubber, paint, and plastics because to these qualities. The investigated diatomites have fine granulometry; they have a high SiO2 content (exceeding 76 %) in Table 1 and are mineralogically composed mostly of quartz and amorphous opal, with minor quantities of feldspar and phyllosilicates.

The aluminum oxide included in the clayey fraction can fill the spaces between the diatomite particles, reducing its ability to filter. But the average content of the aluminum in Abiyata diatomite is 3.49, which is low and may not affect its filtration rate. The mineralogical and chemical examinations of diatomite samples indicates the presence of optimum concentration of SiO2, Al2O3, Fe2O3 and TiO2 and best suit for different industrial applications. Physical tests such as particle size, pH, bulk density, and specific gravity, in addition to those mentioned above, showed its use in the cosmetic, pharmaceutical, and paper sectors as well as in fillers for paper, rubber, plastic, and paint.

Now a days Diatomite nanoparticles, made from powdered diatom shells, are innovative nano-based medication delivery methods. So due to the above informations Abiyata diatomite will be for use in pharmaceutical and animal feed formulations. These biocompatible nanocarriers can carry chemotherapy drugs to specific locations while minimizing off-target effects, including anti-angiogenetic, antimetastatic, and immune checkpoint inhibitors.

6 Conclusions

From detail geological, geochemical, mineralogical, paleontological, morphological and textural.

Works of Abiyata diatomite the following conclusions have given.➢ The geological study of the area indicates the presence of lacustrine sediment, pumice, pyroclastic ash, ignimbrites and unwelded tuff. Rhyolitic glass alteration is prevalent in buried tuff deposits as seen in PXRD (Fig. 4)

➢ The results of the PXRD analysis of the diatomite show that the sample exhibited amorphous behavior as evidenced by the emergence of a single complex “hump” that was broadly distributed between 15 and 30° (2°), with the maximum peaking at about 25° (Fig. 4) Other crystalline phase impurities include low temperature hydrothermal minerals such adularia as well as quartz, cristobalite, feldspar, calcite, illite, and zeolite minerals (clinoaptilolite, mordinite, and wairakite).

➢ The Abiyata diatomite sample underwent microscopic examination (SEM) and XRD analysis, which revealed that it was high quality diatomite made up mostly of diatomaceous skeletons (frustules) with trace quantities of other crystalline minerals (impurities).

➢ The findings of the chemical analysis of diatomite point to a material with excellent purity, with SiO2 (76.9 %) predominating, while the presence of the other oxides is minimal and best suited for various industrial uses.

➢ According to a thorough study of the material, crude diatomite is a weakly diagenesis, soft loose rock with a white to greyish white hue and a low bulk density (0.42g/cm3).

➢ Freshwater, epipelic, mesotrophic, mesosaprophic, and alkaline forms dominate the ancient diatom assemblages. The flora is dominated by benthic species, with planktonic species being few (Fig. 5). These diatom species' properties indicate freshwater, and the genesis of the diatomite is related with volcanic activity in the area, as well as an increase in silica within the water, which supplied the circumstances for the formation of the diatoms.

➢ In general, based on the deposit's taxa and species, the deposit's height of 1600 m above sea level indicates that it is young in age, and the deposit is located among terrestrial volcanic sequences. So diatomites from Abiyata are assumed to be fully lacustrine in origin.

➢ The mineralogical and chemical examinations of diatomite samples indicates the presence of optimum concentration of SiO2, Al2O3, Fe2O3 and TiO2 and best suit for different industrial applications.

➢ Aside from particle size, pH, bulk density, and specific gravity, physical testing indicated its applicability in sectors such as filters, filler (in paper, rubber, plastic, and paint), ceramics, medicines, and cosmetics. (this conclusion was from physical properties and possible field of application)

➢ Using the standard technique (area, thickness, and bulk density), a total of 2,892,240 tons of Diatomite resource have been calculated under the given mineral resource category.

CRediT authorship contribution statement

Yirgalem Hunegnaw: Writing – review & editing, Writing – original draft, Software, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Worash Getaneh: Writing – review & editing, Supervision, Project administration.

Declaration of competing interest

The authors have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this manuscript.

Appendix A Supplementary data

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Acknowledgment

The laboratory analysis (XRD, SEM, ICP-AES, and grain size) is performed in Czech Republic, at Charles University and the Czech Geological Survey. As a result, we would like to express our gratitude to Dr. Karle Martinek for his assistance in facilitating laboratories, Dr. Kristof Verner for financial support for laboratory analysis, Dr. Viktor Goliá for XRD analyses, Assoc. prof. Zbynek Engel for grain size analyses, and Assoc. prof. Ladislav Strnad for geochemistry analyses.

Appendix A Supplementary data to this article can be found online at https://doi.org/10.1016/j.heliyon.2024.e36132.
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