APPLICATION OF MAGNETIC SURVEY TO EXPLORE THE IRON ORE DEPOSITS IN THE NUSAWUNGU COASTAL REGENCY OF CILACAP CENTRAL JAVA

The research aiming to explore the iron ore deposits in the Nusawungu coastal Regency of Cilacap has been conducted using the magnetic survey. The acquisition of magnetic data was conducted in April – Mei 2017, covering the area in the ranges of 109.314° – 109.345°E and 7.691° – 7.709°S. The obtained magnetic field strength data were corrected, reduced, and mapped to obtain the contour map of local magnetic anomaly. The modeling process was carried out along the path extending over the map from the positions of 109.314°E and 7.695°S to 109.335°E and 7.699°S, so that some subsurface anomalous objects are obtained. The lithological interpretation was performed to identify the types of subsurface rocks and their formations based on the magnetic susceptibility value of each anomalous objects and supported by the geological information of the research area. Based on the interpretation results, three rocks deposits of alluvium formations were obtained, which are estimated to contain iron ore. The first deposit has a length of 164.85 m, a depth of 0.57 – 8.43 m, and a magnetic susceptibility value of 0.0097 cgs. The second deposit has a length of 376.28 m, a depth of 2.56 – 19.66 m, and a magnetic susceptibility value of 0.0108 cgs. The third deposit has a length of 1,306.26 m, a depth of 3.70 – 58.69 m, and a magnetic susceptibility value of 0.0235 cgs. Out of the whole rocks deposits, the third rock deposit is interpreted to have the most prospective iron ore. This interpretation based on its high magnetic susceptibility value, which indicates the presence of many magnetic minerals (i.e. iron ores) in the rock.

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A Geophysical Survey with Magnetic Method for Interpretation of Iron Ore Deposits in the Eastern Nusawungu Coastal, Cilacap Regency, Central Java, Indonesia

Journal of Geoscience Engineering Environment and Technology ◽

10.25299/jgeet.2020.5.1.2934 ◽

2020 ◽

Vol 5 (1) ◽

pp. 47-55

Author(s):

Muhammad Sehah ◽

Sukmaji Anom Raharjo ◽

Azmi Risyad

Keyword(s):

Magnetic Anomaly ◽

Iron Ore ◽

Magnetic Anomalies ◽

Research Area ◽

Ore Deposits ◽

Magnetic Method ◽

Contour Map ◽

Strength Data ◽

Central Java ◽

Iron Ore Deposits

Geophysical survey with magnetic method to interpret the iron ore deposits in the Eastern Nusawungu Coastal, Cilacap Regency, Central Java, Indonesia was carried out during six month, i.e. March –August 2017, covering the area in the geographical position of 109.3462° – 109.3718° E and 7.6958° – 7.7098° S. This survey has produced total magnetic field strength data at each measuring point in the research area. The magnetic field strength data which have been obtained, then be processed, corrected, and mapped so that the local magnetic anomaly contour map can be obtained. The local magnetic anomaly contour map shows the distribution of magnetic anomalous sources in the subsurface of research area. The 2D-modeling of magnetic anomalies data has been carried out along the AB trajectory extending on the local magnetic anomaly contour map from the position of A(109.3463°E and 7.7023°S) to B (109.3688°E and 7.7053°S), so that some subsurface anomalous objects is obtained. The modelling results of magnetic anomalies data show that the research area is estimated to have the potential of iron ore deposits. The subsurface rocks deposits containing iron ore are estimated to be located below the AB trajectory with a length about of 164.85 meters, a depth ranging of 1.709 – 31.909 meters, and a magnetic susceptibility value of 0.0122 cgs unit. These rocks are interpreted as sand deposits which coexists with silt and clay containing iron ore grains from the alluvium formation. Further, iron ore is also estimated to be present in the rocks deposits below the AB trajectory which have a depth of 24.405 – 49.809 meters and 3.989 – 11.111 meters, with the magnetic susceptibility values of 0.0093 and 0.0073 cgs units.

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Exploration of Iron Sand at The Eastern Coast Area of Binangun in Cilacap Regency Using Magnetic Survey

INDONESIAN JOURNAL OF APPLIED PHYSICS ◽

10.13057/ijap.v7i2.13700 ◽

2017 ◽

Vol 7 (2) ◽

pp. 71 ◽

Cited By ~ 1

Author(s):

Sehah Allasimy ◽

Sukmaji Anom Raharjo ◽

Iska Andriyanto

Keyword(s):

Magnetic Susceptibility ◽

Magnetic Anomaly ◽

Data Interpretation ◽

Research Area ◽

Eastern Coast ◽

Magnetic Data ◽

Magnetic Survey ◽

Magnetic Field Data ◽

Geological Information ◽

Geoelectric Data

<p class="AbstractText">Exploration of the spread of iron sand on the eastern coastal of Binangun District in Cilacap Regency has been conducted using the magnetic surveys. The magnetic data acquisition was conducted in April 2017. The total magnetic field data obtained is processed, so that can be obtained the local magnetic anomaly data. The modeling of the local magnetic anomaly data is performed on the trajectory of AB that extending from the position point of 109,274698° E and 7.686620° S to 109.2296195° E and 7.689099° S so that obtained various model of the subsurface anomalous objects. Interpretation on the subsurface anomalous objects is done to estimate the types of rocks and their formations based on the magnetic susceptibility value of each object which supported by the geological information of the research area. Based on the interpretation results to be obtained two layers of subsurface rocks that can be estimated as the iron sand that coexists with silt dan clay derived from the alluvium formation. The first rock has a length of 1238.2 meters, a depth of 1.709 – 20.513 meters, and a magnetic susceptibility value of 0.0183 cgs unit. The second rock has a length of 643.055 meters, a depth of 16.524 – 34.188 meters, and a magnetic susceptibility value of 0.0174 cgs unit. The results of this research are also supported by the results of geoelectric data interpretation, where the iron sand that coexists with silt and clay is found at a depth of 9.42 – 19.48 meters with a resistivity value of 52.99 Ωm at Geo-1 point; and a depth of 10.56 – 22.20 meters with resistivity value of 49,03 Ωm at Geo-2 point. Based on the results of of this research, the eastern coastal area of Binangun District is estimated to contain potentially iron ore and economically is a prospect for exploitation.</p>

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Results of Geophysical Investigations Related to the Excavated Remains of the Late Antique and Early Mediaeval Iron Production Sites in the Podravina Region, Croatia

10.32028/9781803271026-3 ◽

2021 ◽

pp. 18-42

Author(s):

Branko Mušič ◽

Barbara Horn

Keyword(s):

Magnetic Susceptibility ◽

Iron Ore ◽

Ore Deposits ◽

Magnetic Method ◽

Iron Production ◽

Late Antique ◽

Magnetic Minerals ◽

Iron Mineral ◽

Production Activity ◽

Geophysical Investigations

Several sites containing relatively high quantities of waste products from the bloomery iron production collected during archaeological field surveys in the Podravina region as part of the TransFER project were subsequently investigated by magnetic prospecting and topsoil apparent magnetic susceptibility mapping. The magnetic method proved to be very effective in identifying various archaeological remains of iron production activity in situ due to the high magnetic susceptibility of materials present in iron production workshops, which was confirmed in relation to the results of archaeological excavations at Sušine near Virje as well as Velike Hlebine and Dedanovice near the Hlebine sites. Reasons for the higher magnetic susceptibility include, in addition to the strongly magnetic minerals in iron production waste, fragments of fired clay from furnace construction and features such as shallow pits with burnt bottoms, as well as any other materials that have been exposed to high temperatures (burnt house plaster, etc.). The sites with remains of bloomery iron production were therefore reliably identified on the basis of their magnetic properties and the results were evaluated in relation to the excavated features. This study has also demonstrated that the sites with iron production activity present can also be reliably identified on the basis of changes in the apparent magnetic susceptibility of the topsoil to a depth of only 5 cm, after partial destruction of the archaeological layers by deep ploughing. These anomalies generally have a wider spatial distribution than those detected by magnetometers, due to a wide dispersion of material by ploughing mechanisms. With the aim of identifying layers with major enrichments of bog iron ore, electrical resistivity tomography (ERT) measurements were carried out at the site Novigrad Podravski–Milakov Berek, where pieces of bog iron ore appeared on the surface. Based on these results, we have not been able to reliably identify ore deposits, but it has been shown that it is possible to identify layers of relatively low resistivity on ERT profiles that have increased iron mineral content, as confirmed by X-ray analysis of core samples from shallow drillings at several other locations in the Podravina region.

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Particle swarm optimization inversion of magnetic data: Field examples from iron ore deposits in China

Geophysics ◽

10.1190/geo2017-0456.1 ◽

2018 ◽

Vol 83 (4) ◽

pp. J43-J59 ◽

Cited By ~ 3

Author(s):

Shuang Liu ◽

Miao Liang ◽

Xiangyun Hu

Keyword(s):

Particle Swarm Optimization ◽

Iron Ore ◽

Particle Swarm ◽

Physical Property ◽

Pso Algorithm ◽

Ore Deposits ◽

Source Distribution ◽

Magnetic Data ◽

Swarm Optimization ◽

Iron Ore Deposits

Inspired by the social behavior of birds or fish swarms, particle swarm optimization (PSO) is used to solve many engineering optimization problems. The PSO algorithm is mostly applied to the geophysical parametric inversion based on specific models, and it is rarely used to implement the physical property inversion of geophysical data. We have applied the standard PSO algorithm to the 2D inversion of magnetic data to recover the distribution of subsurface magnetization intensity. To manage the over-stochastic problem of a standard PSO inversion, the velocities of particle swarms are smoothed, and the [Formula: see text]-means clustering model constraint to the objective function is implemented to distinguish the multiple magnetic sources in the case of the complicated magnetic anomaly. The PSO inversion of magnetic data is tested using synthetic models. In the field examples of Galinge and Weigang iron ore deposits in China, concealed iron orebodies were detected, and the reconstructed magnetic source distribution yielded good agreement with the orebodies inferred from drillhole information. The uncertainty analysis results demonstrated that the recovered models using the PSO algorithm had lower reliability for the bottom and boundary areas of target sources because of the influence of observation noise and the weak magnetic response of deep-buried sources. The PSO algorithm obtained a sharp physical property distribution and demonstrated strong global optimization ability.

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