Mineralogy of the Mudeungsan Tuff (Republic of Korea) Using Synchrotron X-ray Powder Diffraction and Rietveld Quantitative Analysis

Donghoon Seoung,Hyeonsu Kim,Min Huh,Pyosang Kim,Hyun–Woo Lee ,Hyunseung Lee ,Yong Jae Lee

doi:10.3390/app112210796

Abstract

Mudeungsan (Mount Mudeung) is an extinct volcano located in the southwestern part of South Korea that was formed in the Late Cretaceous period. This mountain, 1187 m above sea level, is adjacent to Gwangju Metropolitan City, which has a large population (about 1.4 million) and volcanic rocks, including columnar joints, which form various types of outcrops. Although this mountain was listed as a national geopark in 2014 and a UNESCO Global Geopark in 2018, much basic research has yet to be carried out. In particular, there are no mineralogical studies of volcanic rock samples despite the well-preserved variety of volcanic rocks. For this study, X-ray diffraction analysis was conducted using rock samples from Mudeungsan columnar joints known as tuff. We report that the rocks are mostly dacite, mainly composed of quartz, plagioclase, and sanidine through Rietveld quantitative analysis. In particular, α-cristobalite, a crystalline polymorph of silica, appears in the columnar joint rocks, indicating that Mudeungsan experienced an explosive eruption during the formation of the mountain.

Highlights

Mudeungsan (1187 m above sea level) is a UNESCO Global Geopark located in the southwest of the Korean Peninsula (Figure 1)
At the top of the mountain, the dacitic tuff consists of columnar joints, which allowed Mudeungsan to be registered as a national geopark and a UNESCO Global
A synchrotron X‐ray diffraction (XRD) analysis was conducted for the Mudeungsan columnar joint samples, and quantitative information on major minerals was provided through Rietveld refinement

Summary

Introduction

Mudeungsan (1187 m above sea level) is a UNESCO Global Geopark located in the southwest of the Korean Peninsula (Figure 1). During the Cretaceous period of the Korean Peninsula and East Asia, the Izanagi plate was subducted into the Eurasian plate, and the Korean Peninsula, as a continental arc, had numerous volcanic activities. Cretaceous volcanic rocks are abundant in the southeastern and southwestern regions of the Korean Peninsula [1]. In this regard, many columnar joints formed in the Cretaceous period have been reported in the southwestern part of the Korean Peninsula, showing traces of volcanic eruptions [2]. Jung et al (2014) suggested that Cheonwangbong and Anyangsan in the Mudeungsan region were formed from calc-alkaline magma in the continental subduction zone [4]

Methods

Findings

Discussion

Conclusion