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All Journal Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources) Buletin Sumber Daya Geologi
Sendjaja, Purnama
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Education Energy Engineering Environmental Science

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Petrology and Geochemistry of The Volcanic Arc Tarusan Pluton in Comparison to Lolo Pluton, West Sumatra Irzon, Ronaldo; Syafri, Ildrem; Agustiany, Irfani; Prabowo, Arief; Sendjaja, Purnama
Jurnal Geologi dan Sumberdaya Mineral Vol 20, No 4 (2019): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (325.055 KB) | DOI: 10.33332/jgsm.geologi.20.4.199-210

Abstract

The Volcanic Arc Suite is the group of batholiths in the range of the Barisan Mountains and mostly denotes I-type affinity. Previous investigations of the intrusions in West Sumatra emphasized the crystallization age without completing geochemistry characteristics. No former study discussed a pluton which mapped in the Kota XI Tarusan District. This study explains the geochemistry and petrology of the Tarusan Pluton using polarized microscope, XRF, and ICP-MS at the Center for Geology Survey of Indonesia. The microscopic analysis confirms the granite character of the samples. Although both plutons are identified as I-type calc-alkaline series, the Tarusan Pluton is peraluminous granite whilst the Lolo Pluton denotes wider range from metaluminous to peraluminous of granodiorite to granite. Both the plutons are clearly classified as volcanic arc granitoid in the correlation to Volcanic Arc Suite of Sumatra. Negative Ba, Nb, and P anomalies together with positive K, Nd, and Y anomalies are pronounced on the two felsic intrusions. Negative Eu anomaly on the Tarusan Pluton but the positive one at the Lolo Pluton might explain different magma evolution process.Keywords: volcanic arc granite, geochemistry, Tarusan Pluton, Lolo Pluton.
KAOLINITISASI DAN MOBILITAS UNSUR TANAH JARANG PADA PROFIL PELAPUKAN BATUAN GUNUNGAPI DI PUNCAK MANDEH, SUMATRA BARAT: KAOLINITIZATION AND RARE EARTH ELEMENTS MOBILIZATION OF A VOLCANIC ROCK WEATHERING PROFILE IN PUNCAK MANDEH, WEST SUMATRA Irzon, Ronaldo; Kurnia; Sendjaja, Purnama; E. Setiawan, Verry
Buletin Sumber Daya Geologi Vol. 16 No. 1 (2021): Buletin Sumber Daya Geologi
Publisher : Pusat Sumber Daya Mineral Batubara dan Panas Bumi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47599/bsdg.v16i1.312

Abstract

The weathering process occurs on the Earth's surface, especially in tropical climates, and causes the parent rock's mobilization of elements. Weathering is interesting because it is often associated with the enrichment of economic materials such as iron, alumina, and REEs. The weathering profile of Tertiary volcanic rocks is spread across tropical Sumatra. This study aims to describe REEs' kaolinization and mobilization process on the weathering profile of volcanic rocks in the east of Mandeh Peak, West Sumatra. XRF and ICP-MS devices are utilized to measure the abundance of major oxides, trace elements, and REEs. The increase in IOL is proven to occur in the same direction as weathering levels. A triangular diagram of SiO2-Al2O3-Fe2O3T indicates kaolinization on weathering at Mandeh Peak. Feldspar and mica were prone to weathering and instantly turn into kaolinite in the early stages of weathering to explain the main oxide variations in weathering profiles. The weathering process has increased the amount of alumina and iron significantly relative to the parent rock. There is no REEs enrichment on any of the weathering horizons other than its composition on the parent rocks. Part of Ce is oxidized into Ce4+ and left on the saprolite horizon. This condition makes Ce's mobility in the direction of weathering level is different from other REEs.
Co-Authors Agustiany, Irfani E. Setiawan, Verry Ildrem Syafri Kurnia Prabowo, Arief Ronaldo Irzon