Karya
Judul/Title From magma ascent to lava extrusion: Cooling history of the Watuadeg pillow lava, Berbah, Yogyakarta, Indonesia
Penulis/Author Dr. Indranova Suhendro, S.T., M.Sc. (1) ; Dr. Ir. Agung Harijoko, S.T., M.Eng., IPM. (2); Ir. Nugroho Imam Setiawan, S.T., M.T., D.Sc., IPM. (3); Dr. Ir. Haryo Edi Wibowo, S.T., M.Sc. (4)
Tanggal/Date 21 2023
Kata Kunci/Keyword
Abstrak/Abstract The Watuadeg pillow lava (WPL) is known as one of the most well-studied pillow lava outcrops in Yogyakarta, Indonesia, and its origin has been attributed to rapid-cooling process of subaqueous lava extrusion. This study provides a quantitative evidence of rapid cooling process of WPL by comparing the size distribution (CSD) and number density (MND) . of plagioclase microlites from the core, medial, and marginal (rim) domains of WPL, as microlites represent syn-eruptive product. We found that the CSD slope significantly increases towards marginal zones, namely 30.4ᵒ for the core, 53.4ᵒ for the medial, and 228.1ᵒ for the rim. CSD slope is inversely proportional to cooling time (slope= -1/Gt); thus, by assuming a typical plagioclase microlite growth rate (G) of 1×107 mm/s, it is therefore inferred that the rim experienced the fastest cooling time (±12.1 hours), followed by the medial and core ((±52.0 and 91.4 hours, respectively). The increase of MNDs value toward the marginal zones further supports this notion (0.3×1016 m-3 for the core, 1.4×1016 m-3 for the medial, and 2.4×1016 m-3 for the rim), as higher MND with the dominant acicular-spherulitic habit represents a higher degree of undercooling. Our estimation represents the cooling time of magma since it migrated from the reservoir to the surface.
Bahasa Asli/Original Language English
Level Nasional
Status
Dokumen Karya
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