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Temporal Variations of Petrological Characteristics of Tangkil and Rajabasa Volcanic Rocks, Indonesia Hasibuan, Reza Firmansyah; Ohba, Tsukasa; Abdurrachman, Mirzam; Hoshide, Takashi
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

DOI:10.17014/ijog.7.2.135-159Tangkil and Rajabasa Volcanoes are neighbouring subduction-zone volcanoes located on the southeast tip of Sumatra Island (Sunda Strait, Indonesia). Stratigraphic correlation of lavas in Tangkil-Rajabasa volcanic area was established from field observations, morphological analysis, and K-Ar dating analysis. Detailed petrography and geochemical data of two and eleven lava units from Tangkil and Rajabasa, respectively, were then integrated with the stratigraphy to show the temporal variations. Early stage (> 4.3 Ma) effusives of Tangkil Volcano are dacitic to rhyolitic (67-71 wt. % SiO2; Tklf), whereas the later (c. 4.3 Ma) rocks are basalt to basaltic andesite (c. 52 wt. % SiO2; Tklm). Tangkil shows bimodal magmatism, of which the felsic endmember is > 71 wt. % SiO2 and < 0.1 wt. % MgO. Lavas of Rajabasa Volcano are comparatively younger (c. 0.3 to 0.1 Ma) with compositions ranging from basalt to andesite (51-62 wt. % SiO2; Rbs). Chemical variations of Rajabasa accounts for the interactions of at least three endmembers: Mg-rich medium-K basalt magma, low-Mg medium-K basalt magma, and high-K andesitic magma. During the long evolution of Rbs magma system, the temporal chemistry shows rising-falling variation in SiO2 and MgO indicating the three magmas were active. The felsic endmember magma of Rajabasa is fixed in composition (at ~62 wt. % SiO2; ~2.2 wt. % MgO). The rocks from the last Tklf and Rbs indicate open system processes by containing plagioclase and pyroxene phenocrysts that show resorption of evolved core and overgrowth of less evolved mantle. The multiple zones of dissolution-overgrowth in plagioclase crystals and the fluctuating trend in temporal whole-rock variation suggest that the changes of magmatic condition in temperature, H2O, or chemical composition were repetitive.

Temporal Variations of Petrological Characteristics of Tangkil and Rajabasa Volcanic Rocks, Indonesia Hasibuan, Reza Firmansyah; Ohba, Tsukasa; Abdurrachman, Mirzam; Hoshide, Takashi
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.135-159

DOI:10.17014/ijog.7.2.135-159Tangkil and Rajabasa Volcanoes are neighbouring subduction-zone volcanoes located on the southeast tip of Sumatra Island (Sunda Strait, Indonesia). Stratigraphic correlation of lavas in Tangkil-Rajabasa volcanic area was established from field observations, morphological analysis, and K-Ar dating analysis. Detailed petrography and geochemical data of two and eleven lava units from Tangkil and Rajabasa, respectively, were then integrated with the stratigraphy to show the temporal variations. Early stage (> 4.3 Ma) effusives of Tangkil Volcano are dacitic to rhyolitic (67-71 wt. % SiO2; Tklf), whereas the later (c. 4.3 Ma) rocks are basalt to basaltic andesite (c. 52 wt. % SiO2; Tklm). Tangkil shows bimodal magmatism, of which the felsic endmember is > 71 wt. % SiO2 and < 0.1 wt. % MgO. Lavas of Rajabasa Volcano are comparatively younger (c. 0.3 to 0.1 Ma) with compositions ranging from basalt to andesite (51-62 wt. % SiO2; Rbs). Chemical variations of Rajabasa accounts for the interactions of at least three endmembers: Mg-rich medium-K basalt magma, low-Mg medium-K basalt magma, and high-K andesitic magma. During the long evolution of Rbs magma system, the temporal chemistry shows rising-falling variation in SiO2 and MgO indicating the three magmas were active. The felsic endmember magma of Rajabasa is fixed in composition (at ~62 wt. % SiO2; ~2.2 wt. % MgO). The rocks from the last Tklf and Rbs indicate open system processes by containing plagioclase and pyroxene phenocrysts that show resorption of evolved core and overgrowth of less evolved mantle. The multiple zones of dissolution-overgrowth in plagioclase crystals and the fluctuating trend in temporal whole-rock variation suggest that the changes of magmatic condition in temperature, H2O, or chemical composition were repetitive.

Studi Petrografi Batuan Beku dan Sinter Silika di Kecamatan Alam Pauh Duo, Kabupaten Solok Selatan Sauri Aulia Putri; Ardian Putra; Mirzam Abdurrachman
Jurnal Fisika Unand Vol 7 No 4 (2018)
Publisher : Universitas Andalas

Telah dilakukan analisis petrografi terhadap batuan beku dan sinter silika di Kecamatan Alam Pauh Duo, Kabupaten Solok Selatan. Penelitian ini bertujuan untuk mengetahui kenampakan mikroskopik batuan meliputi struktur dan tekstur, komposisi mineral penyusun batuan, jenis, dan nama batuan.Â Batuan diambil pada empat titik di Kecamatan Alam Pauh Duo, sedangkan sinter silika diambil di sekitar mata air panas Sapan Maluluang. Batuan dan sinter silika dipreparasi menjadi sayatan tipis. Analisis dilakukan menggunakan mikroskop polarisasi dan X-Ray Diffractometer (XRD). Hasil analisis menunjukkan bahwa batuan pada Kecamatan Alam Pauh Duo didominasi oleh batuan beku basalt. Batuan ini menunjukkan struktur masa batuan yang seragam. Batuan beku basalt ini disusun oleh mineral primer dan sekunder. Mineral primer berupa plagioklas, piroksen, dan hornblen. Mineral sekunder berupa klorit, kalsit, dan kuarsa. Mineral sekunder ini mengindikasikan bahwa temperatur reservoir panas bumi di Kecamatan Alam Pauh Duo berkisar antara 120ÂºC-320ÂºC. Nilai estimasi ini berada dalam kisaran nilai estimasi temperatur reservoir yang diperoleh oleh PT. Supreme Energy yaitu 210ÂºC - 320ÂºC.Kata kunci: batuan beku basalt, petrografi, temperatur reservoir

Heavy Metals Distribution in the Artisanal Gold Mining Area in Wonogiri Mohammad - Nurcholis; Dwi Fitri Yudiantoro; Darban - Haryanto; Abdurrachman - Mirzam
Indonesian Journal of Geography Vol 49, No 2 (2017): Indonesian Journal of Geography
Publisher : Faculty of Geography, Universitas Gadjah Mada

Artisanal and small gold mining activity in Wonogiri Regency has long been done with problems on environmental quality. This study was aimed to analyze the levels and spatial distribution of heavy metals in the mining area. Survey of mining and amalgamation sites, sampling the soil and tailings had been conducted. There were 66 samples of soil and tailing were collected, analysis of heavy Fe, Mn, Pb, Hg, As and Co, using X-ray fluorescence (XRF). Normal distribution test of data was conducted using the Kolmogorov-Smirnov and Shapiro Wilk. The spatial distribution of heavy metals was described using Krigging method. Contents of most heavy metals in the area studied were high, except for Co. According to the distribution pattern of heavy metals indicated that the contamination caused by the mining.

Temporal Variations of Petrological Characteristics of Tangkil and Rajabasa Volcanic Rocks, Indonesia Reza Firmansyah Hasibuan; Tsukasa Ohba; Mirzam Abdurrachman; Takashi Hoshide
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.135-159

DOI:10.17014/ijog.7.2.135-159Tangkil and Rajabasa Volcanoes are neighbouring subduction-zone volcanoes located on the southeast tip of Sumatra Island (Sunda Strait, Indonesia). Stratigraphic correlation of lavas in Tangkil-Rajabasa volcanic area was established from field observations, morphological analysis, and K-Ar dating analysis. Detailed petrography and geochemical data of two and eleven lava units from Tangkil and Rajabasa, respectively, were then integrated with the stratigraphy to show the temporal variations. Early stage (> 4.3 Ma) effusives of Tangkil Volcano are dacitic to rhyolitic (67-71 wt. % SiO2; Tklf), whereas the later (c. 4.3 Ma) rocks are basalt to basaltic andesite (c. 52 wt. % SiO2; Tklm). Tangkil shows bimodal magmatism, of which the felsic endmember is > 71 wt. % SiO2 and < 0.1 wt. % MgO. Lavas of Rajabasa Volcano are comparatively younger (c. 0.3 to 0.1 Ma) with compositions ranging from basalt to andesite (51-62 wt. % SiO2; Rbs). Chemical variations of Rajabasa accounts for the interactions of at least three endmembers: Mg-rich medium-K basalt magma, low-Mg medium-K basalt magma, and high-K andesitic magma. During the long evolution of Rbs magma system, the temporal chemistry shows rising-falling variation in SiO2 and MgO indicating the three magmas were active. The felsic endmember magma of Rajabasa is fixed in composition (at ~62 wt. % SiO2; ~2.2 wt. % MgO). The rocks from the last Tklf and Rbs indicate open system processes by containing plagioclase and pyroxene phenocrysts that show resorption of evolved core and overgrowth of less evolved mantle. The multiple zones of dissolution-overgrowth in plagioclase crystals and the fluctuating trend in temporal whole-rock variation suggest that the changes of magmatic condition in temperature, H2O, or chemical composition were repetitive.

Simple Statistical Testing on Existing Data of Core 39 KL SO189/2 to Reveal its Correlation Towards Sea Surface Temperature Variation Taufan Wiguna; Khoiril Anwar Maryunani; Mirzam Abdurrachman; Yusuf Surachman Djajadihardja
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 2 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.2.2020.682

Several paleotemperature proxies using marine core sediment data have been developed and well-proven, but they need excellent laboratory handling and destructive tools. Spectrophotometer and Multi-Sensor Core Logger (MSCL) is considered rapid and non-destructive tools compared to other climate proxies. This paper enhances the correlation between existing data of spectrophotometer, MSCL, and sea surface temperature (SST) of the sediment core 39 KL from SO189/2 through a statistical test. The dataset is processed using interpolation, Pearson correlation, and K-means clustering. Pearson correlation reveals a strong correlation between spectrophotometer, MSCL, and SST. K-means clustering points out that SST is shifting from relatively colder to warmer. This study also tries to understand the source of four tephra and one terrigenous layer. It can be concluded that the spectrophotometer and MSCL have a positive correlation to SST variation. Keywords: statistical approach, existing data of SO189/2, spectrophotometer, Multi-Sensor Core Logger, sea surface temperatureBeberapa proksi paleotemperature menggunakan sedimen inti laut telah dikambangkan dan terbukti baik, namun membutuhkan penanganan laboratorium yang bagus dan bersifat destruktif. Spektrofotometer dan Multi Sensor Core Logger (MSCL) relatif lebih cepat dan tidak destruktif. Makalah ini membahas hubungan antara spektrofotometer, MSCL, dan temperature muka laut (SST) berdasarkan data sedimen inti 39 KL dari SO189/2 melalui pendekatan statistik. Data diolah menggunakan metode interpolasi, korelasi Pearson, dan kluster K-means. Korelasi Pearson menunjukkan korelasi kuat antara spektrofotometer, MSCL, dan SST. Kluster K-means menunjukkan pergeseran SST dari kondisi yang lebih dingin ke lebih hangat hubungan Stufi ini juga mencoba untuk memahami sumber 4 lapisan tefra dan 1 lapisan mineral terrigenous. Melalui studi ini, dapat disimpulkan bahwa spektrofotometer dan MSCL mempunyai korelasi positif terhadap variasi SST.Kata Kunci: Pendekatan statistik, Data existing SO189/2, spektrofotometer, Multi Sensor Core Logger, Suhu Permukaan Laut

KEANEKARAGAMAN TANAMAN BUAH DAN KANDUNGAN MERKURI KAWASAN PENAMBANGAN EMAS RAKYAT DUSUN MESU DESA BOTO JATIROTOWONOGIRI JAWA TENGAH Arum Suproborini; Sunarto Sunarto; Wiryanto Wiryanto; Dwi Fitri Yudiantoro; Muhammad Nurcholis; Dewi Sri Sayudi; Mirzam Abdurrachman
EnviroScienteae Vol 13, No 1 (2017): EnviroScienteae Volume 13 Nomor 1, April 2017
Publisher : Universitas Lambung Mangkurat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20527/es.v13i1.3508

The processing of gold by means of amalgamation produces mercury wastes. Mercury wastes can pollute the environment. This study aims to determine the diversity of fruit crops and mercury content in the gold mining area of Dusun Mesu. The research method used is survey method, measurement, field observation, and laboratory analysis. The types of plants found are recorded, the number and the diameter. Samples of roots, stems, and leaves of plants were analyzed mercury contents in the laboratory. Based on the results of the analysis, there were 7 types of fruit plants, as many as 32 individuals with the type of vegetation seedling, stake, poles, and trees. The results of calculation of diversity index (H¹), uniformity index (E), and dominance index (C) at all growth rates show low diversity (H = 0.02222 - 0.86648), low uniformity (E = 0.00403-0) , 27959), low dominance (C = 0,0000162 - 0,08). The content of mercury in the soil ranges from 0.001 to 0.044 mg/m³. The content of mercury in fruit crops ranges from <0.0001 - 0.0168%, and soil pH ranges from 4 to 6.8.

Magma Evolution of Ngebel Volcano, Ponorogo, East Java, Indonesia Dwi Fitri Yudiantoro; Dyah Rini Ratnaningsih; Puji Pratiknyo; Mahreni Mahreni; Dewi Sri Sayudi; Intan Paramita Haty; Hafiz Hamdalah; Mirzam Abdurrachman; Isao Takashima; Wisnu Ismunandar; Richzkey Muhammad; Demi Ganjar Sampurno
Indonesian Journal on Geoscience Vol 10, No 1 (2023)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.10.1.51-62

The magma evolution of Ngebel Volcano, both temporally and spatially, is represented by the characteristics of its lava. Ngebel Volcano, located in East Java, is a Quaternary andesitic stratovolcano. This volcano is part of the Wilis Volcanic Complex. The volcanism stage of Ngebel Volcanic Complex can be divided into the Jeding with andesitic basalt (SiO2 49 - 59%), pyroxene andesite Kemlandingan (SiO2 49 - 59%), Manyutan with hornblende andesite (SiO2 49 - 59%), and Ngebel with dacite (SiO2: 49 - 59%). The variation of major elements combined with petrographic features such as plagioclase, pyroxene, hornblende, quartz, and opaque minerals from basaltic andesite to dacite is interesting. The minerals show that the magma differentiation process of Ngebel Volcanic Complex is the results of fractional crystallization of magma. The purpose of this study is to determine the evolution of magma from volcanic rocks of which stratigraphic positions have been determined. The analytical methodology used is petrographic and geochemical analysis. Detailed temporal evolution shows that magma from the Ngebel Volcanic Complex underwent a differentiation process that changed the magma composition from mafic to more felsic.

Crustal Contamination Versus Subducted Components: An Example from The West Java Arc, Indonesia and Its implications in Magma Genesis Mirzam Abdurrachman; Masatsugu Yamamoto
Indonesian Journal on Geoscience Vol 10, No 1 (2023)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.10.1.97-107

New Sr isotope and K2O data are presented for Papandayan and Cikuray Volcanoes in West Java. The data are combined with published Sr isotope and K2O data, and compared with arc that has a similar geological setting, namely Northeast Japan Arc (NJA, N 38° ~ 41°) to constrain the relative importance of crustal assimilation and subducted input of crustal material in magma genesis beneath West Java Arc (WJA). New strontium isotope and K2O data from fifty-four Quaternary volcanic rocks from WJA were collected and compared to forty-six Quaternary volcanic rocks from NJA. The increasing K2O and decreasing of 87Sr/86Sr ratios with distance from trench have been found in NJA, but there are rough and no across arc variation of K2O and Sr isotopic ratios in WJA. This study shows that the across arc variation of magma chemistry on the WJA is attributed to the crustal assimilation and the involvement of subducted sediments and slab fluids from altered oceanic crust.

Crustal Contamination Versus Subducted Components: An Example from The West Java Arc, Indonesia and Its implications in Magma Genesis Mirzam Abdurrachman; Masatsugu Yamamoto
Indonesian Journal on Geoscience Vol. 10 No. 1 (2023)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.10.1.97-107

New Sr isotope and K2O data are presented for Papandayan and Cikuray Volcanoes in West Java. The data are combined with published Sr isotope and K2O data, and compared with arc that has a similar geological setting, namely Northeast Japan Arc (NJA, N 38° ~ 41°) to constrain the relative importance of crustal assimilation and subducted input of crustal material in magma genesis beneath West Java Arc (WJA). New strontium isotope and K2O data from fifty-four Quaternary volcanic rocks from WJA were collected and compared to forty-six Quaternary volcanic rocks from NJA. The increasing K2O and decreasing of 87Sr/86Sr ratios with distance from trench have been found in NJA, but there are rough and no across arc variation of K2O and Sr isotopic ratios in WJA. This study shows that the across arc variation of magma chemistry on the WJA is attributed to the crustal assimilation and the involvement of subducted sediments and slab fluids from altered oceanic crust.

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