International Refereed Journal of Engineering and Science (IRJES)


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International Refereed Journal of Engineering and Science (IRJES) is a leading international journal for publication of new ideas, the state of the art research results and fundamental advances in all aspects of Engineering and Science. IRJES is a open access, peer reviewed international journal with a primary objective to provide the academic community and industry for the submission of half of original research and applications

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International Refereed Journal of Engineering and Science (IRJES)

  1. 1. International Refereed Journal of Engineering and Science (IRJES)ISSN (Online) 2319-183X, (Print) 2319-1821Volume 2, Issue 4(April 2013), 46 | PageMapping of Iron body or anomaly by using magnetic methods inAceh Jaya Province IndonesiaAdi Susilo1and Walid Mohamed,21Geophysics, Brawijaya University,Malang, Indonesia,2Geophysics, Brawijaya University,Malang, Indonesia,ABSTRACT : In Indonesia, manganese is often found in the shape of sediment mining grain, which is mostlycomposed of oxide. It is usually associated with volcanic activity and alkali rock. Manganese may be presentedin the form of minerals such as Pirolusit and Psilomelan, or sometimes in the form of Rhodokrosit, Rhodonit,Manganit, Brausit, and Nsutit. Manganese reserve of Indonesia is very huge and distributed throughout manylocations. The presence may be in various degrees of small lens shape. The already observed manganesereserve is 5.35 millions tones, while the mining reserve is 490 thousands tones. The mining is operated by theprivate mining company.Manganese rock exploration is looking for the lateritic form or primary rock. Prospect region shall bedetermined before exploration. Nangro Aceh Province is a promising region for exploration due to its geology.During the exploration and the geological mapping, manganese rock deposit is identified based on the previousGeological Mapping Report (Rahmat, 2011) which indicates that manganese rock at Babahlo Nangro AcehRegion (KP Area of PT SURYA TAMBANG PERKASA) is very potential for exploitation.Keywords : geological mapping, magnetic, Aceh Jaya Province IndonesiaI. INTRODUCTIONManganese rock at KP of PT SURYA TAMBANG PERKASA, Aceh Jaya, Nangro Aceh Province hasgreat prospect for exploitation because the result of geological mapping shows that the manganese reserve isabundant. However, in Aceh Jaya, none manganese rock is exploited for industry, export and domestic interests.The development of manganese rock resource, hydrogeology, and the access and mining of manganese are notconsidered, possibly due to community issue in the prospect region.The report of manganese rock sediment exploration shall be submitted as the condition of the miningactivity. Exploration activity must consider the result of preliminary study because it gives a more detaildescription of the sediment condition of excavated material. The result of this study will determine the reliabilityand the prospect of sediment before going toward exploitation stage (the mining process).Exploration survey against manganese rock deposit may involve geophysic, in this case usingGeomagnet method. This method measures magnetic field variation on the earth surface due to the magnetizedthing below earth surface. The measurement data can inform the physic of rock, the geometry of rock belowsurface, and the position of depth. This information will be useful for us to understand the relationship betweenthe physic nature and observation data. This relationship will always include mathematic equation (mathematicmodel). Using this mathematic model, we can obtain the precise information of physic nature below the surfaceand the depth position.II. MINERALOGY OF MAGNESIUMWorldwide manganese mineral is only 0.1 % of earth crust, but being one of 12 substances withgreatest rate within earth crust. There are more than 300 manganese minerals acknowledged, but only 13minerals are often found in the commercial grain deposit. The main grains of manganese are Pirolusit andPsilomelan.III. MAGNETIC PROPERTIES OF ROCKS.The magnetic properties describe the behavior of substance under the effect of magnetic field. Thismagnetic phenomenon occurs from the electric loaded movement in the substance. There are three groups ofmaterial based on its magnetic properties:A- DIAMAGNETIC SUBSTANCE.Electron shell of the substance under the effect of electron magnetic field will rotate and produce magnetizationin the reverse direction against Lenz Law. Rock-forming atoms have paired electron shell. If it obtains magnetic
  2. 2. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 47 | Pagefield from beyond orbit, the electron will produce low magnetic field to challenge against the outer magneticfield. This substance has negative and small k susceptibility, and does not depend on outer magnetic field. Theexample substances are bismuth, graphite, gypsum, marble, quartz, and salt.B- PARAMAGNETIC SUBSTANCE.This substance has less saturated outer most part of electron shell, with not-paired spun electron. If theoutsider magnetic field is presented, the spin is processing to produces magnetic field with parallel direction tothe outside field to strengthen this field. However, magnetic moment is randomly oriented by thermal agitation,and therefore, its k susceptibility is positive and > 1, and also depending on temperature. The examplesubstances are manganese, pyroxene, olivine, garnete, biotite, amphybolite and others.Within magnetic things, the field produced by permanent atomic magnetic moments tends to empower theoutside field, while the field dielectrics from dipoles always challenge against the outside field, whether thesedielectrics have either induced or oriented dipoles. In both cases, the power of induced M (magnetic moment perunit volume) directly relates with H magnetic field:where k is magnetic susceptibility, and thusIn general, susceptibility is two-rank tensor. Indeed, k symbolizes "quasi isotropic" of the susceptibility.Diamagnetic Substance, therefore, has negative susceptibility. This measure is suitable for the rock which makesup the mineral (Tarling and Hrouda, 1993). Diamagnetic susceptibility does not depend on temperature. Thedependability on temperature of paramagnetic susceptibility is explained by Curie Law or Curie-Weiss Law.C- FERROMAGNETIC SUBSTANCE .Many electron shells are only filled by one electron, and therefore, the shell is easily induced by theoutside field. The inducement is further supported by the presence of parallel spun groups with establishingmagnetic dipoles (domain) with similar direction, especially in the outside magnetic field. Its k susceptibility ispositive and >> 1, and depending on temperature. The example substances are iron, nickel and cobalt.D- Anti-Ferromagnetic.Some domains are producing magnetic dipole with reverse direction such that whole magnetic momentis very small. Anti-ferromagnetic material has crystal defect, small magnetic field, and small susceptibility. Itssusceptibility may be similar to paramagnetic field but the price of anti-ferromagnetic will increase until Curiepoint but decrease again based on Curie-Weiss Law. The example substance is hematite (Fe2O3).E- FerrimagneticSome domains are anti-parallel but the number of dipole in each direction is not similar. Therefore, ithas relatively huge magnetization resultant. The susceptibility is high depending on temperature. The examplesubstances are magnetite (Fe3O4), ilmenite (FeTiO3), and pirhotite (FeS).IV. Magnetic Properties of Mineral.Mineral is also classified as:a. Diamagnetic Mineralb. Paramagnetic Mineralc. Ferromagnetic Minerald. Ferrimagnetic Minerale. Anti-ferromagnetic Minerala) Diamagnetic Mineral and Paramagnetic MineralBecause of the presence of non-stoichiometry-Fe or Mn-ion (Manganese), some minerals areparamagnetic (Petersen, 1985). Some degrees of these minerals are shown by Dortman (1976) as positive andrelatively higher, and thus, it is assumed that the sample observed has dirt (Fe, Ti) which produces positivesuperimposed component.
  3. 3. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 48 | PageFigure 1 The Table of Susceptibility Rate of Paramagnetic Mineral (Dortman, 1976).Figure 1. Order tectonic and sedimentary basins in Kalimantan.Iron (Rao and Bhimasnkaram, 1960)
  4. 4. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 49 | PageFigure 2. The Table of Susceptibility Rate of Manganese Mineral Associated with Iron (Rao andBhimasnkaram, 1960).b- Ferro-, Antiferro-, and Ferromagnetic MineralsThe most important mineral which is abundant in the ferromagnetic rocks is titanium oxide. Iron, ironoxyhydroxide and iron sulfide are also presented but not abundant (Beil and Petersen, 1982).Fe-Ti-oxide is "substance" dominated magnet, and it is a magnetic rock which is particularly presented in TernerSystem.FeO (wustite) - Fe2O3 (hematit, maghemite) - TiO2 (Rutile)This system provides “the most fundamental knowledge about the characteristic of generalferromagnetic rocks” (Nagata, 1966). Terner System contains chemical compositions such as:● Mineral oxide in the rock magnetism (Nagata, 1961): FeO (wustite), Fe3O4 (magnetite), γ-Fe2O3(maghemite), α-Fe2O3 (hematite), FeTiO3 (ilmenite), Fe2TiO4 (ulvospinel), Fe2TiO5 (pseudobrookite) andFeTi2O5 (ilmeno-rutil, ferropseudobrookite); and● Four-series (solid solution serial), including titanomagnetit, ilmeno-hematit, pseudobrookite, andtitanomaghemite.Below is the elaboration of some relevant parameters.Figure 3.. The Terner System of Rock Ferromagnetic Characteristic (Nagata, 1966).Serial titanomaghemite: its structure of cubic / inverse spinal. This serial has final member of magnet,ulvospinel, which has equation of Fe3-X TixO4 with 0 ≤ x ≤ 1. It is characterized by saturated magnetization,early susceptibility, and reduction Currie-temperature with increased x, as shown as follows (Bleil and Petersen,1982):
  5. 5. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 50 | PageTc = 851 - 580x-150x2In relative with titanomagnetitues abundance, Bleil and Petersen (1982) explain that: "titanomagnetities ... ... isthe most common magnetic mineral in the rocks.... Magnetite aggregate may occur in some kinds of rocks suchas frozen rock, metamorph, and sediment. This aggregate is found in certain meteorite, but not observed in themoon sample. Usually, it is produced from various subsolidous reactions. Due to its magnetism on rocks, SerialIlmenite-hematite: the structure is hexagonal/rombohedral. This serial has final member of ilmenite andhematite, and the formula isFe2-x TixO4 with 0 ≤ x ≤ 1For the detail of complex relationship between the characteristic and composition, see Bleil and Petersen (1982).The serial produces natural characteristic orientation. Hematite is the carrier of remanent magnetization is thesediment (mainly in the specular grain and pigment). In the frozen rock, the main composition of serial ischemical properties of the rock. Due to the reduction of alkalinity,ilmenit is reduced, but subsolidus reaction increases ilmenite. This serial is also found in various metamorphrocks.Serial Pseudobrookite: The structure is ortorombik. The serial is defined by the final member ofPseudobrookite Fe2TiO5 and FeTi2O5 ferroPseudobrookite. At room temperature, Pseudobrookites isobviously paramagnetic (Bleil and Petersen 1982). It is found in the natural occurrence of frozen andmetamorph rocks.Serial Titanomaghemite: The structure is spinal. Titanimaghemite is produced by oxidation oftitanomagneties at 300°C (Petersen, 1985) with +. change on Fe2 + Fe3. In maghemite, one member and otherare shown by formulation (Fe, Ti, δ) 3O4, where δ shows that the emptiness is variable at metal ion sites incrystal structure. The magnetic properties are controlled by the composition and affected by “ratio of oxidation”,Fe2O3 / (Fe2O3 + FeO). The ratio of oxidation to Currie temperature is increased. Titanonaghemite is the mainmagnet constituent in the basaltic sea basement, but it is also found in the continent frozen rock (Bleol andPeterson 1982). Pyrrotite FeS1-x is a representative from iron sulfide (monoclinier and hexagonal) withferrimagnetik behavior. The representative of iron oxyhydroxides α gutit-FeOOH and lepidocrocite γ-FeOOHare ortorombic.V. Earth Magnetic FieldEarth magnetic field is characterized by physic parameters, which are also called as the element ofearth magnetic field (Figure 1). These are measured by direction and intensity of magnetization.These physic parameters are:a. Declination (D), which is the angle between magnetic north and horizontal component, ascounted from north toward east.b. Inclination (I), which is the angle between total magnetic field and horizontal plane, countedfrom horizontal plane toward vertical plane at the below.c. Horizontal Intensity (H), which is the rate of total magnetic field on the horizontal plane.d. Total Magnetic Field (F), which is the rate of total magnetic field vector.
  6. 6. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 51 | PageFigure 4. There Elements of Earth Magnetic FieldMain magnetic field in the earth is changing with time. To keep the uniformity of earth magnetic field values,the standard is made, which is called International Geomagnetics Reference Field (IGRF), which is revised oncein 5 years. IGRF values are obtained from the measurement of the average of width coverage of 1 million km2in the one year period.Earth magnetic field comprises to three parts:1-Main magnetic field (main field)Main magnetic field is defined as the average field which is the result of measurement at long term and coveringthe width more than 106 km2.2- Outside magnetic field (external field)The effect of outside magnetic field may come from the outside the earth, and it represents the result ofionization in the atmosphere caused by ultraviolet beam from the sun. This external field source associates withthe electric current flown in the ionized layer at atmosphere, and thus, the field change is accelerated with time.3-Anomaly magnetic field (main field)Anomaly magnetic field is also called as local magnetic field (crustal field). This magnetic field is produced byrocks composed of magnetized mineral such as magnetite ( 87 SFe ), titanomagnetite ( 42 OTF ie ) and others inthe earth crustIn the survey on magnetic method, the target of measurement is the variation of magnetic field measured on thesurface (magnetic anomaly). In general, magnetic field anomaly is caused by remanent magnetic field andinduced magnetic field. The remanent magnetic field plays great role in the rocks magnetization because itdetermines the rate and direction of magnetic field. However, it always associates with previous magnetic eventsuch that it is complex for observation. Anomaly found in survey is the result of mixture of ermanent andinduced magnetic fields. If the direction of remanent magnetic field is parallel with induced magnetic field, theanomaly is greater, and so is the reverse. In the magnetic survey, the effect of remanent field is negligible, ifmagnetic field anomaly is less than 25 % of main magnetic field of earth (Telford, 1976), such that themeasurement of magnetic field is as followsALMT HHHHwhere : TH: total magnetic field of the earthMH: main magnetic field of the earthLH: external magnetic fieldAH: anomaly magnetic field .
  7. 7. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 52 | PageVI. Conclusion and ResultsThe measurement of geomagnetic data is conducted by surevy team from University of Brawijaya Malang, EastJava, from 15-21 July of 201 at Babahlo Region, IE Jeureungeh Region, Sampoinet Subdistrict, Aceh JayaDistrict, Nangro Aceh Darussalam Province. The location of survey is at the following coordinates:POINT LONGITUDE (EAST) LATITUDE (NORTH/SOUTH)A 95o3049.74 4o5659.26B 95o3112.53 4o5659.26C 95o3112.53 4o5613.30D 95o3049.76 4o5613.30AREA WIDTH: 100 HaTable 1. The Coordinate Points of The Location of KP.Exploration of PT. Surya Tambang PerkasaFigure 4.1. The Survey Location Map at Babahlo Region, IE Jeureungeh Region, Aceh Jaya DistrictFigure .2. The Survey Location Map at Babahlo Region in 3D
  8. 8. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 53 | PageData are collected using Magnetometer Device, in the Proton Precision Magnetometer (PPM). Data collectionspread includes 1624 data collecting points, as shown in Figure 4.3 as follows.Figure 4.3. The geomagnetic data collecting points which are correlated with the contour of magnetic valuespread at survey location.The result of data measurement correlated with topographic contour at Babahlo region is shown in Figure 4.4and 4.5.Figure 4.4. Topography Contour Map which is overlaid with magnetic value spread from the result ofmeasurement at survey location in 2D.
  9. 9. Mapping of Iron body or anomaly by using magnetic methods in Aceh Jaya Province 54 | PageFigure 4.5. Topography Contour Map which is overlaid with magnetic value spread from the result ofmeasurement at survey location in 2D.Figure 5. Topography Contour Map which is overlaid with magnetic value spread from the result ofmeasurement at survey location in 2D.ACKNOWLEDGEMENTSFirst of all, many thanks to my big family (My mother, my Father, my sisters, my brothers Mostfa,ali,almhde) for their prayer, patience and invaluable support during my long lasting study in a distant country.I would like to say thanks to our Lord Allah Subhanahu wa Ta’ala and to the Messenger Zoher alhdad peace beupon him that guide me to the beautiful path in my live. I dedicated all of my life and work to them totallySecond My special thanks to Adi Susilo, PhD for providing me with the opportunity to work on this paper. Ialso appreciated their guidance, encouragement to make this paper, spending extensive time in the field duringdata processing, and always being available to discuss interpretation of the data. I would like to thank, Dr. Eng.Didik R., for reviewing this paper. Their suggestion improved significantly this manuscript.Finally I would like say thank to all of my friends: Mr. Ramdahan, Mr. Abdulrazak et al. And also my friendNabil in Libya , thank you so much for your friendship.REFERENCES[1]. Akbar, Reza. 2008. Eksplorasi Batu Besi (Iron Ore) Menggunakan Metode Magnetik. Pontianak : UNTAN[2]. Kartasaputra, Kusdinar. 2008. Metode Survei Geofisika (Online), (Karta Corp, 2008)[3]. Lowrie, William. 2007. Fundamental of Geophysics second Edition. Cambrigde : Cambrigde University Press[4]. Meju, A Max. 1994. Analisis Data Geofisika : Memahami Teori Inverse. Diterjemahkan oleh Supriyanto. 2007. Depok :Departemen Fisika FMIPA Universitas Indonesia[5]. Milsom, John. 2003. Field Geophysics : The Geological Field Guide Series Third Edition. England : John Wiley & Sons Ltd[6]. Refrizon. 2004. Interpretasi Data Magnetik Desa Sokoagung Kecamatan Begelen Purworejo Jawa Tengah dengan MetodeTransformasi Reduksi ke Kutub Magnet Bumi. Jurnal Penelitian UNIB, Vol. X, No. 2, Juli 2004 Hlm. 98-104. Bengkulu : UNIB[7]. Santoso, Djoko. 2002. Pengantar Teknik Geofisika. Bandung : ITB[8]. Untung, M. 2003. The Core – Berjalan – Jalan ke Inti Bumi (Online), (, Februari 20011).