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All Journal POSITRON IJOG : Indonesian Journal on Geoscience Jurnal Geofisika
Fajar, Silvia Jannatul
Faculty Of Mining And Petroleum Engineering, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung 40132, Indonesia
Earth & Planetary Sciences Energy Physics

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Thermomagnetic Analysis of the Lake Matano Sediments and the Surrounding Lateritic Soils, South Sulawesi, Indonesia Silvia Jannatul Fajar; Gerald Tamuntuan; Satria Bijaksana; James Russell
Jurnal Geofisika Vol 16 No 2 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1872.654 KB) | DOI: 10.36435/jgf.v16i2.384

Abstract

Thermomagnetic is one of the most commonly used measurements for determining the dominant type of magnetic mineral of samples. The measurement is separated into two distinct processes, heating and cooling. The sample susceptibility is measured for each temperature change, i.e., from room temperature to 700oC and vice-versa. Based on the thermomagnetic measurement results, magnetite is found to be the predominant magnetic minerals in Lake Matano sediments. The present study applied a correlation analysis technique on the results of thermomagnetic measurement of Lake Matano sediments and compared the result to that of lateritic soils to indicate whether a diagenetic process has occurred on the lake sediments.
Karakterisasi Mineral Magnetik Sedimen Sungai Citarum Hilir Melalui Analisa Sifat Magnetik, Mineralogi serta Morfologi Magnetik Kartika Hajar Kirana; Mechdi Ghazali; Luh Ayu Eka Safitri Septiana; Dini Fitriani; Eleonora Agustine; Silvia Jannatul Fajar; Muhamad Gina Nugraha
POSITRON Vol 10, No 2 (2020): Vol. 10 No. 2 Edition
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam, Univetsitas Tanjungpura

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (807.096 KB) | DOI: 10.26418/positron.v10i2.42143

Abstract

Sungai Citarum merupakan sungai utama yang ada di Provinsi Jawa Barat yang sangat penting bagi kehidupan sosial dan ekonomi. Di bagian hilir, Sungai Citarum ini banyak melewati daerah pemukiman padat penduduk, daerah industri, dan bahkan pesawahan. Oleh karena itu, perlu kajian mengenai kondisi Sungai Citarum salah satunya dengan mengidentifikasi parameter electrical conductivity (EC), total dissolve solid (TDS), pH dan suhu serta karakteristik mineral magnetik pada sedimen melalui analisis sifat magnetik, mineralogi dan morfologi magnetiknya. Pengukuran parameter EC, TDS, pH dan suhu dilakukan secara in situ pada sampel air Sungai Citarum, pengukuran sifat magnetik dilakukan pada sampel sedimen yang telah dipreprasi, sedangkan pengukuran mineralogi dan morfologi dilakukan pada sampel sedimen yang telah diekstraksi. Sifat magnetik sedimen diketahui dari nilai suseptibilitas magnetik dual frekuensi yang diukur menggunakan Bartington Magnetik Susceptibilitymeter, sedangkan mineralogi dan morfologi magnetik diketahui berdasarkan hasil pengukuran scanning electron microscope–energy disperdsive x-ray (SEM-EDS) dan x-ray diffractometer (XRD). Hasil pengukuran secara in situ pada sampel air menunjukkan bahwa rentang nilai EC, TDS, pH dan suhu berturut-turut adalah (200–4120) mS/cm, (100–2060) ppt, 7,34–9,22, dan (26,8–32,6) oC. Sedangkan, hasil pengukuran sifat magnetik menunjukkan bahwa sampel sedimen Sungai Citarum bagian hilir memiliki nilai suseptibilitas magnetik frekuensi rendah (cLF) dengan rentang (65,00–173,80) x 10-8 m3/kg, sedangkan rentang nilai suseptibilitas magnetik frekuensi tinggi (cHF) adalah (64,90–165,70) x 10-8 m3/kg. Dari kedua pengukuran cLF dan cHF diperoleh rentang nilai cFD (%) sebesar 0,15–4,66. Selanjutnya, hasil analisis morfologi dari citra SEM-EDS dan analisis mineralogi berdasarkan pengukuran XRD menunjukkan dominasi jenis mineral magnetik pada sampel sedimen adalah magnetit. Mineral magnetit ini memiliki morfologi berbentuk oktahedral sebagai representasi mineral magnetik alami dan ada pula yang berbentuk spherule sebagai representasi mineral magnetik karena adanya proses oksidasi akibat kehadiran material antropogenik pada sedimen Sungai Citarum bagian hilir.
Magnetic Basement Depth from Marine Magnetic Data in Cendrawasih Bay Hydrocarbon Prospect Area, Bird Head, Papua, Indonesia Ibrahim, Khalil; Kawab, Gracia Abigail Paraskah; Bijaksana, Satria; Fajar, Silvia Jannatul; Sapiie, Benyamin; Ngkoimani, La Ode; Suryanata, Putu Billy; Harlianti, Ulvienin; Kurniawan, Syaiful Apri; Wibisono, Salsabila Nadhifa
Indonesian Journal on Geoscience Vol. 12 No. 3 (2025)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.12.3.383-400

Abstract

The magnetic basement and structural segmentation of the eastern Bird Head region, Papua, were investigated using marine magnetic data and frequency-domain inversion (MagB_Inv). The studied area includes The Cendrawasih and Yapen–Biak Basins, both were influenced by the Yapen strike-slip fault and transtensional tectonics. Processing involved reducing to the pole, spectral depth estimation, and 3D magnetic inversion to delineate basement geometry, and to infer the sediment thickness. Three structurally bounded subbasins were identified: (1) between Cendrawasih Bay and Num Island, (2) between Cendrawasih Bay and Yapen Island, and (3) between Yapen and Biak Islands. These subbasins exhibit magnetic basement depths ranging from 0.4 to 7 km and sediment thicknesses exceeding 3 km. Magnetic highs around Yapen Island correlate with Miocene volcanic and ultramafic outcrops, interpreted as shallow high-magnetization crustal blocks. The subbasins are bounded by ridges and faults, including the Yapen Fault Zone and fold-thrust systems, which deform both basement and sedimentary cover. The basement morphology controls sediment distribution, and defines fault-bound sedimentary zones, consistent with regional tectonic trends. Seismic cross-sections and shallow earthquake hypocentres, and further supports this structural segmentation. These results provide a structural framework to understand the basin structure, and to support preliminary hydrocarbon evaluations in this underexplored region. Despite these insights, interpretations are constrained by the non-uniqueness of magnetic inversion prosess and the absence of well and high-resolution seismic data.
Co-Authors Benyamin Sapiie Dini Fitriani Eleonora Agustine Gerald Tamuntuan Harlianti, Ulvienin Ibrahim, Khalil James Russell Kartika Hajar Kirana Kawab, Gracia Abigail Paraskah Kurniawan, Syaiful Apri La Ode Ngkoimani, La Ode Luh Ayu Eka Safitri Septiana Mechdi Ghazali Muhamad Gina Nugraha Satria Bijaksana Satria Bijaksana Suryanata, Putu Billy Wibisono, Salsabila Nadhifa