MAGMA DYNAMICS BASED ON PLAGIOCLASE MICRO-TEXTURE IN GUMUK JANTAN TALANG VOLCANO, WEST SUMATRA
Talang Volcano is a type A composite volcano formed in the pull-apart zone of the Sumatra Fault. This study focuses on the Gumuk Jantan section, which has 4 lava flow units. The rock product at Talang Volcano is basaltic andesite. This study uses plagioclase micro-texture analysis and average anorth...
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| Format: | Theses |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/82872 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Talang Volcano is a type A composite volcano formed in the pull-apart zone of the Sumatra Fault. This study focuses on the Gumuk Jantan section, which has 4 lava flow units. The rock product at Talang Volcano is basaltic andesite. This study uses plagioclase micro-texture analysis and average anorthite-albite content to determine eruption dynamics and magma chamber activity in the Gumuk Jantan lava unit products. Plagioclase micro-texture analysis involves observations on coarse-sieve (CS), fine-sieve (FS), glomerocryst (GL), resorption surface (RS), fine-scale oscillatory zoning (FOZ), rounded zone corner (RZ), synneusis (SYN), swallow tail (ST) and broken crystal (BC) textures. The results of the analysis show that magma dynamics originated from primitive magma injection, with plagioclase micro-textures of CS (10-23%), FS (3-15%), GL (5-17%) and RS (5-15%). The textures of FOZ (7-15%), RZ (2-8%) and SYN (10-15%) indicate the movement of convection currents in the magma chamber. The ST texture (2-5%) shows the short cooling of magma due to the rapid movement of magma from the shallow magma kitchen to the conduit. The BC texture (24-30%) shows a very strong eruption. Anortite-albite analysis shows crystal fractionation in units Jl1 (39.75%), Jl2 (39.5%) and Jl4 (34.5%), while unit Jl3 has increased by (58.5%). The eruption from Jl2 to Jl3 was caused by massive injection of primitive magma, resulting in a decompression eruption. In conclusion, the magma dynamics at Talang volcano, especially in the Gumuk Jantan section, reflects a complex process involving magma injection, convection currents and rapid cooling, which eventually led to a strong eruption.
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