Geochemistry of extrusive rocks at Khun Dan Prakan Chon Dam site, Nakhon Nayok Province, Thailand

Abstract

The extrusive rock samples were collected from outcrops at Khun Dan Prakarn Chon Dam site, Nakhon Nayok Province. They are parts of the Pre-Cretaceous Khao Yai Volcanics located at the southern end of the western Loei-Petchabun-Nakhon Nayok Volcanic Subbelt. Petrological study found that the extrusive rock samples can be classified into four groups: felsic pyroclastic rocks, felsic volcanic lava flows, mafic pyroclastic rocks, and mafic-to-intermediate volcanic/hypabyssal rocks. Geochemical characteristics of the extrusive rock samples, however, can be divided into two groups which are mafic-to-intermediate extrusive rocks and felsic extrusive rocks. Although the major and some trace element signatures of these extrusive rocks are identical to those of typical calc-alkalic magmas, the tectonic discrimination diagrams for least-altered rocks showed that they were different in the magmatic suite and erupting episode; and discriminant diagrams can be successfully used to identify the tectonic environments of extrusive rocks and to evaluate the tectonic setting of a region. Incompatible trace element plot on the tectonic discrimination diagrams for the mafic-to-intermediate extrusive rock samples indicated high affinity with a within-plate tectonic setting, while felsic extrusive rock samples had high affinity with continental volcanic arc tectonic setting. In addition, the tectonic setting of these mafic-to-intermediate extrusive rock samples could be correlated to the Khiao Andesite located in the east of studied area. Dykes could be associated with multiple arc magmatism in Loei Fold Belt and resulted in the subduction in the Late Permian.

Tectonic Implication of the Permo-Triassic Khao Yai Mafic Volcanic Rocks in Nakhon Nayok Province, Thailand: Evidence from Geochemistry and Rare Earth Elements (REEs)

“…These volcanic rocks and the adjacent Late Permian hornblende granite were intruded by andesite dikes, a consequence of the Late Permian Palaeo-Tethys subducted beneath the Indochina Terrane. Although the petrochemistry of volcanic and pyroclastic rocks in this research area was previously reported to be comagmatic by Jundee et al [19], in terms of least-mobile elements. the carefully selected least-altered mafic volcanic rocks for REEs, incompatible elements, and modern analogue analyses from this research can confidently depict the tectonic model of Khao Yai Volcanics.…”

“…These imply the multiple continental arc magmatism along the LPN volcanic belt. The distribution of arc-related volcanic rocks and dikes in the area of Khun Dan Prakarn Chon Dam site [19] implies that arc magmatism has been extensively operated in the study area. The tectonic model of the Khao Yai area was not previously presented and has been done in this study.…”

“…The REEs signature is precision evidence for tectonic interpretation. The schematic tectonic model and arc magmatism in the Khao Yai Volcanics in this study, the Khun Dan Prakan Chon Dam site [19], and the Wang Nam Khiao area [21] are illustrated in Figure 7. In the Late Permian, the east-west cross-section was used described the magmatism of LPN volcanic belt.…”

“…Felsic volcanic rocks exposed along the Khlong Tha Dan Dam site include reddish purple, pink, and light grey rhyolites, with local flow bands. Jundee et al [19] reported that the rocks at Khao Yai volcanics at Khun Dan Prakan Chon Dam site, Nakhon Nayok Province are classified as rhyolite, dacite, andesite, and andesitic dikes. In addition, the rocks are indicated as calc-alkalic affinity and have formed in a volcanic-arc setting based on oxide and trace elements.…”