閃電化石的生成與蝕變—以金門花崗片麻岩上的閃電熔岩為例;The Formation and Alteration of Lightning Fossil—A Case Study of Fulgurite on Granitic Gneiss in Kinmen

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Title:	閃電化石的生成與蝕變—以金門花崗片麻岩上的閃電熔岩為例;The Formation and Alteration of Lightning Fossil—A Case Study of Fulgurite on Granitic Gneiss in Kinmen
Authors:	陳則元;Chen, Tze Yuan
Contributors:	地球科學學系
Keywords:	閃電熔岩;閃電;蝕變;Fulgurite;Lightning;Alteration
Date:	2024-07-16
Issue Date:	2024-10-09 15:37:48 (UTC+8)
Publisher:	國立中央大學
Abstract:	閃電熔岩為閃電雷擊地面後形成的產物。由於閃電可產生具高溫高壓特徵的變質作用，研究閃電熔岩有特殊的科學價值。雲對地閃電發生的頻率約為每秒十次，但相關研究相對稀少，尤其是雷擊於岩石上形成的岩石閃電熔岩。本研究藉由2018年在金門太武山花崗片麻岩上生成的閃電熔岩以及附近大片暴露岩石上的風化閃電熔岩殘跡，利用微觀構造、礦物相、化學成分分析、以及水熱實驗等方法，探討岩石閃電熔岩的生成與蝕變。我們的結果顯示，僅0.03%的閃電傳至地面能量能形成岩石閃電熔岩，暗示能量不大的閃電，難以形成可被觀察的閃電熔岩。另外，閃電熔岩在冷卻過程時若接觸到雨水會快速蝕變，說明閃電熔岩的保存困難。水熱蝕變實驗與模擬顯示，在金門的天氣會在一千年內讓兩百微米的閃電熔岩消失殆盡。本研究深入探討了岩石閃電熔岩的生成和蝕變過程，為閃電熔岩研究的重要性及其潛在應用提供了重要的基礎，還顯示了其在地質高溫高壓變質作用的獨特研究價值。;Fulgurites are formed by lightning strikes on the ground. Due to the lightning-induced high-temperature and high-pressure metamorphism, the study of fulgurites holds significant scientific value. Despite cloud-to-ground lightning occurring at a rate of approximately ten times per second, research on fulgurites, particularly those formed on rocks, is relatively rare. This study investigates the formation and alteration of rock fulgurites using samples from the Tawushan granitic gneiss in Kinmen, including fulgurites formed in 2018 and altered fulgurite remnants on nearby exposed rock surfaces. We employed microstructural characterization, mineralogical investigations, chemical composition analyses, and hydrothermal experiments. Our results indicate that less than 0.03% of the lightning energy that conducted to the ground is utilized in generating rock fulgurites, making it challenging for low-energy lightning to form noticeable fulgurites. Moreover, fulgurites undergo rapid alteration when exposed to rainwater during cooling, posing significant preservation challenges. The hydrothermal alteration experiments and modeling suggest that under Kinmen′s weather conditions, a glassy layer with a thickness of 200 µm would completely dissolve within a thousand years. This study offers a detailed exploration of the formation and alteration processes of rock fulgurites, laying a crucial foundation for understanding the importance and potential applications of fulgurite research and highlighting their unique research value in high-temperature and high-pressure geological metamorphism.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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