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- Title
Pervasive Crustal Volcanic Mush in the Highly Stretched Sunda Plate Margin of Northern Sumatra.
- Authors
Feng, Mingye; Wei, Shengji; Chen, Ling; Muksin, Umar; Lythgoe, Karen; Wang, Tuo; Wu, Zimu
- Abstract
Arc volcanism, crustal deformation, and their interplay are poorly understood in northwestern Sumatra. Traditional receiver function H‐κ stacking studies constrain the variations in crustal thickness and Vp/Vs ratio in volcanic zones but rarely estimate the melt fractions. Here, we propose a H‐Φ stacking method, a variant of the H‐κ stacking method, and apply it to the dense nodal array data from Aceh, northern Sumatra, to estimate crustal thickness, Vp/Vs ratio, and melt fraction. Most results show considerably high Vp/Vs ratios (∼1.98) and melt fractions (up to 19%), indicating pervasive crustal magmatic mush. The northwestern edge of the Aceh crust is much thinner (∼22 km) than extended crust globally, reflecting a highly stretched crust due to tectonic processes governing the opening of the Andaman Sea. This thin crust and high melt fractions explain the Bouguer gravity anomaly, and partly explain the northward migration of Quaternary volcanics. Plain Language Summary: Crustal thickness and melt fraction are important indicators of crustal magmatism and deformation. Situated between the Sumatran and Andaman subduction zones, Aceh, in northwestern Sumatra, is distinguished by strong crustal deformation, resulting in active crustal seismicity, and Quaternary volcanics that have migrated northward over time. However, the abnormal arc volcanism, crustal deformation, and their interplay, remain unclear because of poor understanding of the crustal structure. To fill this knowledge gap, we deployed 155 nodal seismic stations in Aceh for 18 months. In this work, we develop a new receiver function method that takes advantage of converted seismic energy from the base of the crust to constrain the crustal thickness and melt fraction beneath the stations in Aceh. We find that: (a) the average crustal melt fraction is as high as 19%, indicating a considerable volume of partially molten rock in the crust and (b) the crust in northern Aceh is as thin as ∼22 km, suggesting high stretching of the crust associated with the opening of the Andaman Sea. The stretched crust with a high melt fraction partly explains the northward migration of Quaternary volcanics and active seismicity/crustal deformation, but the migration mechanism of other volcanics requires further investigation. Key Points: A new receiver function method is developed to constrain crustal thickness and melt fractionApplications to dense nodal array data in northwestern Sumatra show a thin (∼22 km) crust and high crustal melt fraction (up to 19%)The new constraints partly explain abnormal volcanic migration and crustal stretching
- Subjects
ACEH (Indonesia); SUMATRA (Indonesia); SUBDUCTION zones; GRAVITY anomalies; VOLCANOLOGY; VOLCANISM; MAGMATISM
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 21, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL104391