Magma Genesis and Arc Evolution at the Indochina Terrane Subduction: Petrological and Geochemical Constraints From the Volcanic Rocks in Wang Nam Khiao Area, Nakhon Ratchasima, Thailand

Vanachawan Hunyek,Alongkot Fanka,Chakkaphan Sutthirat

doi:10.3389/feart.2020.00271

Abstract

Volcanic rocks and associated dikes have been exposed in Wang Nam Khiao area, Nakhon Ratchasima Province, northeastern Thailand where complex tectonic setting was reported. These volcanic rocks are classified as rhyolite, dacite, and andesite while dikes are also characterized by andesitic composition. These dikes clearly cut into the volcanic rocks and Late Permian hornblende granite in the adjacent area. Rhyolite and dacite are composed of abundant plagioclase and quartz whereas andesite and andesitic dike contain mainly plagioclase and hornblende with minor quartz. The volcanic rocks typically show plagioclase and hornblende phenocrysts embedded in fine-grained quartz and glass groundmass whereas dike rocks contain less glass matrix with more albitic laths. P-T conditions of crystallization are estimated, on the basis of Al-in-hornblende geobarometry and hornblende geothermometry, at about 4.5 – 5.5 kbar, 861 – 927 oC and 4.8 – 5.5 kbar, 873 – 890 oC for the magma intrusions that fed volcanic rocks and andesitic dikes, respectively. Whole-rock geochemistry indicates that these rock suites are related to calc-alkaline hydrous magma. The enriched LILE (e.g. Rb, Sr) and depleted HFSE (e.g. Nb, Ce, Ti), with similar REE patterns indicate arc magmatism. The results of this study are comparable to the continental arc magmatism along the Loei Fold Belt as a consequence of the Late Permian Palaeo-Tethys subducted beneath Indochina Terrane.

Highlights

IntroductionThailand and SE Asia are assembled from several tectonic terranes across from east to west (Bunopas, 1981; Charusiri et al, 2002; Sone and Metcalfe, 2008) including Indochina Terrane (Bunopas, 1981; Charusiri et al, 2002; Sone and Metcalfe, 2008), Loei Fold Belt (LFB; Bunopas, 1981), Sukhothai Terrane (Sone and Metcalfe, 2008), and Sibumasu (Sone and Metcalfe, 2008) or Shan-Thai Terrane (Bunopas, 1981; Charusiri et al, 2002), respectively (Figure 1)
The study area, Wang Nam Khiao in Nakhon Ratchasima province, Central Thailand, is located in the critical junction of several tectonic terranes (Figure 1A) where volcanic rocks and related dikes are exposed. Detailed investigation of these rocks has never been reported; this study provides the results coming from petrology, mineral chemistry, and whole-rock geochemistry of these rocks before reconstruction of magmatic process and tectonic model of the area
Volcanic rocks cover an area of about 10 × 12 km2 in the vicinity of Wang Nam Khiao (Figure 3A)

Summary

Introduction

Thailand and SE Asia are assembled from several tectonic terranes across from east to west (Bunopas, 1981; Charusiri et al, 2002; Sone and Metcalfe, 2008) including Indochina Terrane (Bunopas, 1981; Charusiri et al, 2002; Sone and Metcalfe, 2008), Loei Fold Belt (LFB; Bunopas, 1981), Sukhothai Terrane (Sone and Metcalfe, 2008), and Sibumasu (Sone and Metcalfe, 2008) or Shan-Thai Terrane (Bunopas, 1981; Charusiri et al, 2002), respectively (Figure 1). The main Late Permian–Triassic, Devonian–Carboniferous, and Silurian volcanic rocks have been reported (Intasopa and Dunn, 1994; Panjasawatwong et al, 2006; Zaw et al, 2007; Boonsoong et al, 2011) These rocks resulted from amalgamation of tectonic terranes containing multiple generations of successive arc-related magmatic events (Charusiri et al, 2002; Zaw et al, 2014). The magmatic rocks through the LFB, especially in the central and southern parts lacking of geological study (Figure 2), are very important to understand magmatism and tectonic evolution of the western Indochina Terrane

Methods

Results

Discussion

Conclusion