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All Journal Journal of Geoscience, Engineering, Environment, and Technology Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)
Nurahmah, Siti Chusnul Chatimah
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Chemistry Earth & Planetary Sciences Energy Engineering Environmental Science Physics

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Geochemistry of Volcanic Rocks in Ponelo Island, North Gorontalo, Indonesia Nurahmah, Siti Chusnul Chatimah; Rosana, Mega Fatimah; Haryanto, Iyan
Journal of Geoscience, Engineering, Environment, and Technology Vol. 9 No. 3 (2024): JGEET Vol 09 No 03 : September (2024)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2024.9.3.16832

Abstract

Ponelo Island is located in the northern part of Sulawesi, which is still an enigma regarding the genesis of the volcanic rocks found on this island. Therefore, the objective of this study is to understand the petrogenesis and tectonic implication of these volcanic rocks. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) to obtain trace and rare earth elements is the method of this study. The volcanic rocks found on Ponelo Island consist of basalt and basaltic andesite rocks with a calc-alkaline affinity. The transition data suggested a highly fractionated cause of low transition element (Ni=17-38 ppm; Cr=13-47) compared to primary magma concentration, anomalies negative of Ba, Sr, and Ti of spider diagrams, and negative anomaly of Eu (Eu/Eu*=0.88-0.99). Relationship between low concentration between Ce/Y (0.74-0.76) and La/Yb vs Sm/Yb ratio indicated ~5% spinel-lherzolite mantle source partial melting. On the other hand, incompatible element ratios, such as Ba/Nb (39.03-45.28), Ba/Th (75.52-82.67), Rb/Nb (3.93-6.22), K/Nb (1772.22-2703.45), Ba/La=13.67-14.57, Th/La (0.17-0.18), La/Nb (2.91-3.16), depleted Nb/U (6-6.74), and also lack of xenolith or enclaves indicate cryptic crustal contamination.  The slab-derived fluid indicated by ratios of Rb/Y (0/019-0/05), Nb/Y (0.10-0.11), Th/Yb (0.52-0.61), and Ba/La ratio (13.29-14.57). Ponelo volcanic rocks shows typical calc-alkaline island arc tectonic setting particularly with enrichment in ion lithophile element (LILE) and light rare earth elements (LREE) along with depletion in high field strenght elements (HFSE) and heavy rare earth elemets (HREE), as shown by spider diagrams.
Karakteristik Petrografi dan Geokimia Unsur Utama Batuan Vulkanik Pulau Ponelo, Gorontalo Utara Nurahmah, Siti Chusnul Chatimah; Rosana, Mega Fatimah; Haryanto, Iyan
Jurnal Geologi dan Sumberdaya Mineral Vol. 25 No. 4 (2024): JURNAL GEOLOGI DAN SUMBERDAYA MINERAL
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v25i4.892

Abstract

Abstrak-Batuan vulkanik Pulau Ponelo terletak pada Kepulauan Ponelo di bagian utara Busur Utara Sulawesi yang mana asal usul mengenai batuan ini belum diketahui. Maka dari itu, penelitian ini bertujuan untuk mengetahui karakteristik petrografi dan geokimia unsur utama batuan vulkanik Pulau Ponelo yang belum pernah diidentifikasi sebelumnya. Metode penelitian menggunakan analisis mikroskopis (petrografi) dan geokimia (XRF). Batuan vulkanik Pulau Ponelo mrerupakan batuan andesit basaltik dengan beberapa tekstur, seperti porfiritik intergranular, glomeroporfiritik, seriate, serta berbagai tekstur mikro-plagioklas. Afinitas magma batuan vulkanik Pulau Ponelo berupa kalk-alkalin dengan terjadinya proses fraksinasi kristal, pencampuran magma, serta magma pada sistem magma plumbing berupa dekompresi adiabatik, konveksi, injeksi magma, serta degassing atau eksolusi air akibat peristiwa undercooling saat erupsi. Tatanan tektonik pembentukan batuan ini berupa zona subduksi busur kepulauan dengan karakteristik pengayaan fluida akibat adanya dehidrasi lempeng saat subduksi terjadi. Katakunci: Andesit basaltik Ponelo, busur kepulauan, Busur Utara Sulawesi.
Co-Authors Iyan Haryanto, Iyan Mega Fatimah Rosana