Saprolite Zone Research Articles

Mineralogy and Geochemical Characteristics of Lateritic Nickel Deposit in Wiwirano District, North Konawe, SE Sulawesi, Indonesia

This research aims to understand the mineralogical and geochemical characteristics of the nickel laterite deposit in the East Sulawesi Ophiolite Belt in Wiwirano District, North Konawe, Southeast Sulawesi, Indonesia. The deposit is analyzed and described to determine the laterization process and supergene enrichment. The geochemical data was obtained from X-ray fluorescence analysis, and mineralogical data from petrography and X-ray diffraction analysis. The minerals in the limonite zone are dominated by goethite and hematite. Minerals found in the saprolite zone include quartz, orthopyroxene, and lizardite, whereas the bedrock is made up of olivine, orthopyroxene, serpentine, and chromite. Fe2O3, Al2O3, and Co contents are high in the limonite zone, SiO2 and MgO have high content in the saprolite zone, and Ni is enriched in the saprolite zone. The distribution of enriched Ni is controlled by bedrock or parent lithology with an average content of 1.3% - 2.4% in saprolite, while in the limonite zone, Ni content is lower with an average content of 0.8% - 1.2%.

Analysis of Cobalt Distribution and Co-Ni Correlation in Nickel Laterite Zonation in Tropical Region

Cobalt is a key metallic element required in the manufacture of lithium-ion batteries in the electric car industry, which has led to increased demand for cobalt globally. Cobalt is found associated with laterite nickel deposits but generally at lower levels. This study aims to analyze the distribution of cobalt in the laterite zone, determine cobalt-rich zones, determine cobalt-forming minerals in the limonite, saprolite and bedrock zones. As well as determining the average cobalt content in each nickel laterite zone, and determining the correlation between Co and Ni in the laterite zone. The research methodology was carried out by conducting petrographic analysis on bedrock samples to determine cobalt-forming minerals. Furthermore, X-Ray Diffraction analysis was carried out on limonite and saprolite zone samples to determine the mineral content and cobalt-forming minerals. Furthermore, conduct X-Ray Fluorescence analysis at 12 drill points to determine the percentage of cobalt elements in each laterite zone. Based on the research results, it is known that the distribution of cobalt at 12 drill points has levels in the limonite zone ranging from 0.05-0.12% Co, saprolite zone 0.02-0.05% Co, and the bedrock zone ranges from 0.01-0.04% Co. So it can be concluded that the highest cobalt distribution is in the limonite zone and the average cobalt content in the limonite zone is 0.082%; saprolite zone is 0.029%; and bedrock zone is 0.02%. The mineral identified as the cobalt-forming mineral in the bedrock samples in the study area is the mineral antigorite. The Co-Ni correlation coefficient values range from 0.01 to 0.22.

Co, Sc, and Ni enrichment in the Cagdianao nickel laterite deposit, Dinagat Islands, Philippines

Abstract Nickel laterites are soils that are derived from the weathering of mafic and ultramafic rocks. These deposits are being extracted mostly for their economic Ni and Fe content. However, in recent studies, the potential of nickel laterites to hold significant amounts of critical metals such as Sc and Co are already being investigated. In the Philippines, nickel laterite deposits form through the weathering of ophiolitic units. One of these is the Cagdianao nickel laterite deposit which was derived from the weathering of the ultramafic units of the Dinagat Ophiolite Complex in Dinagat Island, Surigao Del Norte, Philippines. The bedrock of the Dinagat Ophiolite Complex is dominantly comprised of harzburgite. This harzburgite bedrock is overlain by a nickel laterite profile consisting of horizons of Mg- and Si-rich rocky saprolite, earthy saprolite, Fe-rich limonite, and an Al-rich topsoil. Drillcores and field exposures of the nickel laterite profile were observed, sampled, and subjected to petrography, whole rock geochemistry (XRF and ICPMS), and mineral chemistry (LA-ICPMS) analyses. In terms of major elements, Fe is dominant in the limonite zone (up to 59.76 wt.%). Mg and Si are more enriched in the rocky saprolite layer (up to 28.41 and 37.41 wt.%, respectively). In terms of the critical minerals, Ni is more enriched in the saprolite zone (up to 29936 ppm) while Co and Sc are more enriched in the limonite zone (up to 1080 and 86 ppm, respectively). Elemental mapping of the bedrock samples reveals the strong affinity of Ni to olivine and serpentine. Sc was revealed to have a greater affinity with orthopyroxenes. Lastly, Co is observed to have a slight affinity with olivine. These results show a relative enrichment of Co in the profile, particularly in the limonite. Co within the laterite profile also has a very strong affinity with MnO. Similarly, the highest concentration values for Sc were also observed in the limonite. It also exhibits an affinity for Fe2O3 and Al2O3. Lastly, Ni was observed to have a strong affinity with olivine and serpentine minerals in the bedrock and the rocky saprolite horizons. Within the deposit, Ni is the main commodity while Co, Sc, and REEs can be considered as by-products.

Geostatistical Models and Estimation of Laterite Nickel Ore Reserves, Marombo Block, South Sulawesi

Abstract Geostatistical modeling in this study requires a distribution of drill points that have a fixed dimension so that they can produce a reserve accuracy match that is the same as the variograph. The choice of reserve estimation method is prioritized by determining the geological domains of limonite, saprolite and bedrock through a geostatistical approach, namely ordinary krigging (OK) and inverse distance weight (IDW) with the JORC standard (2012), for the accuracy of the limonite and saprolite zone boundaries. The reserve model has shown a definite model of the limonite and saprolite zones and can be used further. By using simulations on cut-off grade (COG) to calculate resources and classify mineral resources, the estimation results obtained mean nickel levels above 1.40% so that the CoG to be used must be greater than Ni 0.90% for limonite, and Ni 1.10% for saprolite. The results of modeling the geometry of laterite nickel ore obtained that the total tonnage shown in limonite was 0.36 wmt (wet metric ton), inferred 0.10 wmt, and indicated in saprolite was 0.58 wmt, inferred was 0.40 wmt.

Using Soil Magnetic Susceptibility Proxies to Estimate Overburden Thickness Overlying Ore of Lateritic Soils in Sulawesi Island Indonesia

Sulawesi Island is one of the largest Ni ore producers in Indonesia. It is also expected to be a significant potential source of some critical metals (e.g., Co, Sc, rare-earth elements, and platinum-group elements). However, few studies show the post-mining impact on some heavy metal elements concentrated in this area. Therefore, improving the efficiency and effectiveness of soil organization and its effect on soil reclamation after mining is helpful. This study aimed to determine the accuracy in estimating the thickness of the overburden covering the nickel ore body profile from lateritic nickel post-mining areas by magnetic susceptibility measurements to discrepancy the overall laterite horizon, whereas χLF and χFD are used to distinguish the overburden zona and limonite and saprolite zone. The lateritic profile studied consists of soil formation of Fe-rich material in the Morowali, and Pomalaa block. We also evaluated the chemical element content of the soil and understood the relationship between the magnetic and geochemical properties of the soil. This study reveals the superparamagnetic (SP)-enriched soils indicated with the increase of the FD% values into the upward horizon, where the maximum values of FD are generally found at ranges 1 to 4m, indicating the overburden layers. Meanwhile, in the depth of 4m to 6m, the values of FD vary only slightly in the lower part initiated by the limonite layers, and then > 6m decreases sharply to the bottom, indicating the saprolite layers. The chemical element mobility trends indicate that Fe, Co, Cr, Mn, and Ti increase toward the layers, which is the same pattern as in FD. Due to this, parameters magnetics may also be a new geophysical approach for estimating the distribution of economically valued minerals on lateritic soils. The strong correlation of Co with Fe, Mn, and Cr in all layers indicates the influence of weathering o n these ultramafic rocks. This suggests an increasing trend toward prolonged pedogenesis.

Porosity and pore structure evolution during the weathering of black shale

Pore type and pore structure evolves systematically across continuous black shale weathering profile. However, the extend and process of pore structure change is still an enigma. In this study, we try to unveil the pore structure evolution during weathering process through studying Cambrian Hetang shales in southern China. Fourteen shale samples, from protolith zone (PZ), fractured and weathered shale zone (FWZ), and saprolite zone (SZ), were collected to elucidate how porosity and pore structure develop during black shale weathering under subtropical condition. Through low pressure argon (Ar) gas adsorption (LP-ArGA), high pressure mercury intrusion (HPMI), nuclear magnetic resonance(NMR) and field emission scanning electron microscope (FESEM) observation, the results reveal significant differences in physical properties and pore structures among the PZ, FWZ, and SZ samples. Specifically, compared to PZ, FWZ and SZ samples are characterized by higher clay mineral content, lower organic matter (OM), and the absence of carbonates and pyrite. Total porosity, determined through HPMI and NMR, exhibits a gradual increase from PZ (6.70 % and 6.41 %) to FWZ (20.47 % and 13.45 %) and SZ (23.22 % and 12.48 %). Ar adsorption isotherms indicate a change in pore type from predominantly ink-bottle and slit-shaped in the PZ to mainly slit-shaped in FWZ and SZ. Integrated analysis of LP-ArGA, HPMI, NMR and SEM observation suggests a substantial decrease in the contribution of micropores to total pore volume (PV) and a concurrent increase in larger pores (meso-macropores) with the increase of weathering intensity. This results in smoother surfaces of micro-transition pores but rougher surfaces of macropores. Changes in mineralogy composition during weathering play a crucial role in influencing pore structure of shales and further accelerating the release and migration of toxic elements in black shale. Our study provides the essential theoretical foundation for the remediation of soil and water environmental pollution caused by black shale weathering.

Identification of Lateritic Nickel Deposits Potential in the Kokoe Area, Kabaena Island, Central Buton Regency, Southeast Sulawesi Province, Indonesia

The study is situated in the Kokoe Region of Central Buton Regency, Southeast Sulawesi, specifically in the southern part of Kabaena Island. Its primary objective is to assess the potential of nickel laterite in the designated area. The research methodology involved microscopic analysis of bedrock using a polarizing microscope, examining the drilling data, including logging descriptions, and utilizing XRF geochemical analysis (Ni, Fe, Al2O3, Co, Mg, and SiO2) from 32 drilling sites. Both elementary grade and laterite profiles were visualized using Strater 5 software to simplify the representation of laterite profiles. Petrographic analysis divided the bedrock into two lithological units: serpentinized lherzolite and serpentinite. The laterite profiles in the study area were classified into four types: type A, type B, type C, and type D. Type A profiles consist of bedrock, saprolite, and limonite layers covered by clay and colluvium. Type B profiles lack limonite and instead exhibit saprolitic rock and rocky saprolite layers on top of the bedrock. Type C profiles comprise bedrock, saprolitic rock, rocky saprolite, limonite, and topsoil layers. Type D profiles contain three zones, namely bedrock, colluvium, and clay, but lack limonite and saprolite layers. Among the four profile types, type A and type C profiles show promising potential due to higher average grades of Ni and thicker saprolite zones compared to the type B and type D profiles.

Estimation of Laterite Nickel Resources Using Ordinary Krigging Method at PT Vale Indonesia Nuha District East Luwu South Sulawesi Province

Resources have an economic value, form, quality, quantity rate, geological characteristics, and endurance to be economically extracted. Mineral resources are grouped according to their degree of geological certainty into the categories of assumed, indicated, and measured. The research aims to assess the potential resource potential of nickel laterite and the spread of the rate of mineralization of nickel in the research area using the geostatistical method of Ordinary Kriging. The research methodology is based on conducting statistical and geostatic analysis, starting with univariate statistical analysis, spatial statistics, bivariate statistics, and resource estimates. The results of the statistical calculation using the Ordinary Kriging for limonite and saprolite zones with an average gap of 25 meters and an average depth of 20 meters with their parallel directions to the west, north-northeast, south-east, southeast, and west-southwest obtained a total volume of 119,920,468 m3 with a tonnage of 201,798,081 tons and a mean rate of nickel laterite of 1.56% Ni. Based on the results of an evaluation, it can be concluded that the number of nickel laterite deposits with a cut-off grade of 1.4% is 89,804,733 tons and the average rate is 1.83% Ni.

Petrographic Studies of a Part of East Coast Bauxite Deposits, Odisha, Eastern India and Implication on their Genesis

Abstract The East coast bauxite deposits of Odisha are well known in the mineral map of India. Some such deposits exposed at Nunapaimali, Sasubohumali and Baphlimali overlying khondalite of the Precambrian Eastern Ghats belt have been studied in respect of petrology, mineralogy and microstructure with a view to find out their genetic evolution. Bore hole samples from two former deposits and mine profile samples from Baphlimali revealed a good profile differentiation, in terms of three horizontal zones of variable thickness, which in descending order are: 1 to 29m laterite zone, 2 to 28m bauxite zone, 9 to 36m saprolite zone, comprising of lithomarge and partially lateritised khondalite [PLK] developed over host khondalite. Petrographic and mineralogical difference between these three zones, brought out through optical microscopy and XRD studies, further confirms the differentiation. Genetic evolution of bauxite is interpreted from the study of a large number of samples and results are collated from the photomicrographs appended in the paper. The authigenic bauxitisation was brought about by gradual dissociation of Al-silicate to Al-hydroxide minerals through different weathering cycles as indicated from their microstructural manifestations and mineral assemblages. Primary gibbsite is formed in the initial stage of weathering directly from Al-silicate minerals. Advanced stage of prolonged weathering converts the Al-silicate to kaolinite and then to secondary gibbsite. Grain size enlargement and recrystallisation showing mosaic habit, grain boundary migration and grain orientation are the outcome of digenesis. The weathering / lateritisation process continues, resulting in colloidal precipitation of gibbsite from pore water of lateritic residuum and is in progress even in recent period The Fe-oxide phases, represented by goethite and hematite are youngest in the paragenesis, and formed due to solution, precipitation and dehydration. Iron is mostly contributed by almandine garnet present in the host khohdalite. During chemical leaching, Fe gets released from garnet and occur either as FeOOH along its fractures or fill the weak planes / inter-granular space as secondary goethite. The goethite dehydrates to hematite during digenesis. Goethitisation and limonitisation particularly in the laterite zone are the results of supergene alteration.

Calculation of Laterite Nickel Resources Using the Inverse Distance Weighting Method at PT Genba Multi Mineral in Morowali Regency

Resource estimation plays a significant role in determining the quantity and quality of a deposit. In nickel laterite mining, estimation is needed to be able to calculate resources before the mining process takes place. This research was conducted to determine the nickel laterite resources at PT Genba Multi Mineral. In this research, the determination of nickel laterite resource estimation using the Inverse Distance Weighting (IDW) method. Based on the estimation of nickel laterite resources using the IDW method. The estimation of nickel laterite resources was carried out in the saprolite zone with the Cut of Grade (COG) used, namely Ni content ≥ 1.6% with a density of 1.5 tons/m3 obtained a resource tonnage of 233,738 tons with an average Ni content of 1.81%.

Mineralogy and geochemistry of the Morro do Engenho lateritic nickel deposit, Goiás Alkaline Province, Brazil

The Morro do Engenho lateritic nickel deposit results from the action of weathering processes on the alkaline mafic-ultramafic rocks that make up the Cretaceous zoned intrusive body belonging to the Goiás Alkaline Province. Historically, the deposit is classified as a silicate one, and mineralization is present especially in phyllosilicates such as serpentine and chlorite. By identifying Ni-bearing phases and providing the lithogeochemical characterization of weathering profiles, this study aims to provide further insights into the metallogenetic processes and controls acting on the mineralization of the Morro do Engenho lateritic Ni deposit. The following methods were used: petrographic studies, SEM-EDS, XRD and lithogeochemical characterization of the weathering profiles developed on each of the parent rocks that make up the body. The Morro do Engenho intrusive massif is formed by a dunite core, surrounded by a peridotite/pyroxenite zone, an alkaline gabbro zone and more externally by a syenite-nepheline zone. The lateritic profile constitutes eight weathering horizons, stacked one upon another from the bedrock namely: (i) saprock, (ii) lower saprolite, (iii) ferruginous saprolite, (iv) ocher saprolite, (v) plasma zone, (vi) lateritic duriccrust, (vii) silcrete and (viii) topsoil. Most Ni mineralization occurs in the lower saprolite, ferruginous saprolite and ocher saprolite zones. The findings pointed to the presence of Ni in silicate mineral phases, represented by serpentine, chlorite, smectite, as well as in Fe and Mn oxyhydroxides. The depressed area, located between the two major topographic elevations, has the highest Ni enrichments, which according to mass balance calculations can account for up to 40%. Hydrodynamic factors, by dissolution/precipitation of silicates in saprolite horizons of dunite core, are suggested as possible agents in the remobilization of Ni, among other mobile elements, to topographically flat zones. The geometry of the Morro do Engenho deposit show that lateral redistribution by hydrodynamic factors could also account for the mineralization of areas peripheral to the dunite core, composed of pyroxenite and gabbro-derived lateritic profiles. The direction of regional groundwater flow, strongly influenced by topography, would also be an important factor in the remobilization of Ni, as well as the mechanical transport of lateritic materials. Silicate mineralization predominates in the Morro do Engenho deposit, concentrated in Mg hydrosilicates and clay minerals; oxide mineralization also occurs, mostly in Fe and Mn oxyhydroxides. The findings discussed in this paper can broaden the understanding of metallogenetic processes involved in the genesis of lateritic nickel deposits. .

Pengaruh Relief Topografi Terhadap Daerah Prospek Nikel Laterit Kecamatan Bahodopi Kabupaten Morowali Provinsi Sulawesi Tengah

Nickel laterite deposit is a result of weathering processes of ultramafic rocks which carry Ni-Silicate. Generally the deposit is found from tropical to subtropical climates. The aim of this research was to find out the influence of the ground slope to the thickness zone of the nickel laterite based on the cross-section of the drill hole. The research method was to create the cross-section nickel laterite. The data ware obtained from assay data, coordinate, drilling points distribution, and cross-section of the drill hole. From cross-section of the drill hole, the data regarding the level of Ni and Fe were obtained. From the hole id 5A_0171, the lowest Ni level for limonite was 0.19%, and the highest level was 1.17% and for the Fe level, the lowest was 32.13% and the highest was 49.84% with the depth ranging from 0 to 18 metres. The lowest Ni level for the saprolite was 0.79% and the highest was 2.04% whereas for the Fe level, the lowest was 9.97% and the highest was 15.77% with the depth ranging from 18 to 25 metres. The lowest Ni level for the bedrock was 0.29% and the highest was 0.56% whereas for its Fe level, the lowest was 6.91% and the highest was 8.67% with the depth ranging from 25 to 27 metres. The concluding data for the sloppy areas from the steep to slightslopes was that the limonite zone tended to follow the surface morphology pattern with the thickening occurrence in the steep slopes however the saprolite zone did not follow the surface morphology but it became thick in the steep slopes.

Analysis of Empirical Bayesian Kriging Methods for Optimization of Measured Resources Estimation of Laterite Nickel

Laterite nickel deposits are formed from the intense weathering of ultramafic igneous rocks. The distribution of Ni content in an area does not always have a stationary data. One method of resource estimation and precise geological modeling is the Empirical Bayesian Kriging (EBK) method which is known to be able to perform precise estimates for stationary and non-stationary data. The results of this study were found that thickness of the limonite layer will increase as the slope decreases, while in the saprolite zone the thickness will increase with increasing the degree of slope up to the limit of 16°-25° then the thickness will decrease when crossing that limit. In the limonite zone, the concentration of Ni is maximally concentrated at a high degree of slope (>16°), while in the saprolite zone, Ni content is maximally concentrated on a slope of 16°-25° and then decreases in Ni content when passing through a slope of 25°. Validation of the estimation results and geological modeling using RMSE, MAE, MAPE, and linear regression in the limonite and saprolite zones indicate that the EBK method is a precise method for resource estimation and geological modeling.

Mineralogical Transformation and Mass Balance Model at a Nickel Laterite Profile in Malili District, South Sulawesi, Indonesia

The purpose of this study is to determine the mineralogy transformation and mass balance model to understand the mobility of laterite elements using Microscopy, X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF). The bedrock of the profile is a serpentinized peridotite consisting mainly of lizardite with minor magnetite. The saprolite zone of profile is dominated by the mineral lizardite, while in the limonite zone due to the perfect weathering process, the lizardite mineral has already transforms into goethite. The results of mass balance calculation analysis using Ti as the immobile element showed that Mg and Si were reduced along all layers of profile. Meanwhile, Fe, Al, Mn, and Cr increased towards the upper zone of the laterite nickel profile. Meanwhile, Ni was concentrated in the saprolite zone with an addition of ~386.42%.

Spread Of Laterite Nickel Based on Drill Data at PT Manunggal Sarana Surya Pratama, Southeast Sulawesi Province

Modeling of nickel laterite resources is intended to determine the distribution of resources represented in the form of block models. The results of resource modeling indicate the shape and distribution of mineral deposits which can facilitate the mining process and can predict mining boundaries referring to the results of resource modeling. The purpose of this study was to determine the thickness of the saprolite zone layer and the distribution direction of nickel laterite based on drill point data. The data used in the laterite nickel resource modeling are exploration drill data, drill coordinates, and exploration grade classification. Data processing and analysis methods apply block modeling and the variogram method to determine the distribution direction of nickel resources. Based on the results of the cross-section profiles in Section 1 to Section 7, the average thickness of saprolite is 6,605 m, and the block model layer of saprolite which shows high levels of red color (Ni 1.9 - so on) is the most in the north, pink color (Ni 1.5-1.89) is in the north direction before the Ni 1.9 level above, the green color (Ni 1.3-1.49) is in the east and south.

GEOMORPHOLOGY AND CHARACTERISTICS OF NICKEL LATERITE IN BAINGKETE VILLAGE, MAKBON DISTRICT, SORONG REGENCY WEST PAPUA PROVINCE

Nickel deposits geologically came from weathering of abducted ultrabasic igneous rock. The rock is exposed during removal, followed by a geomorphological process that develops laterazation. Geologically the Makbon area is on the path of the Sorong horizontal fault field which has been active since the beginning of the Miocene. The dominant Sorong fault movement to the west exposed ocean floor rocks including blocks of ultrabasic rock. To determine the mineralization of nickel laterite in the Makbon area, this study combines mapping and surface geological observation methods with XRF analysis in the laboratory. The results of the study are known that the research area is composed of six land formations, namely the Makbon Fault Block Ridge, Baingkete Fault Block Ridge, Bancuh Baingkete Hills, Baingkete Bald Mountain Bancuh Hills, Makbon Fault Structure Denudation Plain, and Dore Bay Hills. Geomorphological control of the distribution of laterite nickel on steep slopes produces a thin, thickened laterite layer on the topography of the ramps. The characteristics of laterite nickel deposits in Baingkete Village are Type A deposits (Mg-Ni Silicate), on serpentinite bedrock, which consist of laterite profiles of limonite zone, saprolite zone, and bedrock zone

Analisis Karakteristik Mineralogi dan Geokimia Berdasarkan Zona Profil Endapan Nikel Laterit (Studi Kasus: Blok X PT Ang and Fang Brother, Site Lalampu, Kecamatan Bahodopi, Kabupaten Morowali, Provinsi Sulawesi Tengah

Regionally, the study area is located in the Ophiolite Belt of East Sulawesi, particularly in the Tomata Formation (Tmpt), and is composed of igneous rock distribution in the Ultramafic Complex (Ku). The exposed of ultramafic rocks, caused the study area to contain elements of economic value such as nickel. The study aims to identify the constituent minerals, determine the abundance of elements and compounds, as well the correlation of major and minor elements and compounds based on the profile zone of laterite nickel deposits. Study data were in the form of soil and rock samples, and drilling data as many as 59 points. The mineral content of the study results was obtained based on the analysis of X-ray Diffraction and Petrography, while the univariate and bivariate statistical analysis was carried out on the drilling data. The results of the analysis obtained assemblages of minerals in the form of goethite, hematite, chlorite, and quartz in the limonite zone; antigorite, enstatite, chlorite, quartz, and magnetite in the saprolite zone; and lizardite, enstatite, spinel, and magnetite in the bedrock zone, with the bedrock type being serpentinized harzburgite. The results of the descriptive analysis showed the grade of major elements and compounds, which are Fe, SiO2, MgO, and Al, as well as minor elements, which are Ni, Cr, Co, Ca, and Mn which varied in each zone, where grade of SiO2, MgO, and Ca increased to the bottom of the profile, and the grade of Fe, Al, Cr, Mn, and Co decreased towards the bottom of the profile, while Ni increased to the saprolite zone. The results of the correlation of elements and compounds in the limonite zone are Cr vs Mn; SiO2 vs MgO and Ca; Ni vs Co and Cr; Fe vs Co positive is very strong to strong correlation, while Fe vs SiO2, MgO vs Al; Al vs Ni is strong negative correlation. Saprolite zone Fe vs Al, Cr, and Co; Cr vs Mn and Co; Mn vs Co; SiO2 vs MgO; Fe vs Mn; Al vs Cr, Mn, and Co were very strong to strong positive correlation, while Fe vs SiO2 and MgO; SiO2 vs Co; MgO vs Cr and Co; SiO2 vs Al, Cr, and Mn; MgO vs Al and Mn were very strong to strong negative correlation. Bedrock zones of Fe vs Cr, Mn, and Co; Cr vs Mn; Fe vs Al; Co vs Al, Cr, and Mn were very strong to strong positive correlation, while MgO vs Fe and Cr were strongly negative correlation.

The Relationship of Grain Size to Nickel Grade at Saprolite Zone of Lateritic Nickel Deposite in Moronopo Site, East Halmahera Regency, North Maluku

The research was conducted at the Dinding A and Dinding B, Moronopo Site PT Antam Tbk, East Halmahera, North Maluku which is a block that has been opened for the mining process. Generally the stratigraphy of laterite nickel deposits, from top (young) to bottom (old) consists of overburden, limonite, saprolite and bedrock. The saprolite zone is an economical ore layer for Ni content. This research aims to determine the relationship between grain size of ore and the mineralogy and economical Ni content. The research methods used include the grain size fractionation method with sizes of -5 cm, +5 cm, +10 cm, +15 cm, +20 cm and +25 cm, and XRF analysis to determine the Ni content. The result of this study shows the rocks in the saprolite zone containing minerals such as olivine, serpentine, garnierite and chrysoprase. The XRF analysis result shows the highest Ni content is found in the finest grain fraction (-5 cm) i.e. 2.4% and the lowest Ni content found in the coarsest grain fraction (+25 cm) i.e. 1.87 % but is still classified as economic.

THE PERFORMANCE OF ESTIMATION TECHNIQUES FOR NICKEL LATERITE RESOURCE MODELING

The choice of estimation technique according to geological conditions and mineralization character is the main problem in estimating block grade of nickel laterite. CV (coefficient of variance) and variogram determine the choice of estimation technique for nickel laterite resource classification. This study aims to evaluate various techniques for estimating block grades and to select the appropriate method for the classification of nickel laterite resources. The basic statistical analysis is to find out the description of the data, while the variography is to find out the spatial correlation between the data. Nickel grade estimation results are based on Near Neighbor Polygon (NNP), Inverse Distance Weighting (IDW), and Ordinary Kriging (OK) techniques to determine the classification of nickel resources. Accuracy levels are based on cross-sectional visualization comparisons, plan views, probability plots and linear regression analysis. The OK technique were not superior in grade estimation, especially in nickel laterite deposits. The results showed that the IDW technique was suitable to be applied to the limonite zone, while the NNP technique was suitable to be applied to the saprolite zone. Based on the performance of the estimation technique, the weighted average method can be applied for the classification of inferred, indicated, and measurable resources. The grade-tonnage curve shows the nickel laterite resource potential in the study area.

Mineralogical and Geochemical Characterization of the Sta. Cruz Nickel Laterite Deposit, Zambales, Philippines

In this study, we present mineralogical and geochemical characterization of samples systematically collected from a nickel laterite profile at the Sta. Cruz nickel laterite deposit, Zambales, Philippines. Wavelength-dispersive X-ray fluorescence spectroscopy (WDSXRF), mass-balance element mobility calculations, transmitted and reflected light microscopy, and previously reported results from coupled X-ray diffraction (XRD) and Rietveld refinement analyses reveal that the laterite profile investigated is composed of two main horizons—the limonite and saprolite zones—separated by a thin transitional zone. Based primarily on the mineral assemblage and major element chemistry, the main zones are further subdivided into subzones: upper limonite, lower limonite, transitional zone, upper saprolite, and lower saprolite. Garnierite veins were observed cutting the upper and lower saprolite subzones. Investigation of the structure of goethite within the limonite zone via Rietveld refinement shows that the crystallinity of goethite decreases with increasing Ni content and increasing crystallite size. This suggests that upwards through the limonite zone, as goethite ages, its crystallinity increases, which possibly results in the removal of Ni from its crystal structure and eventual remobilization to the lower laterite zones.