The Truong Son, Loei-Phetchabun, and Kontum Terranes in Indochina: Provenance, Rifting, and Collisions

Abstract

The three main regions of Indochina are defined as the Truong Son, Loei-Phetchabun, and Kontum terranes. The aim of this review is to integrate numerous petrological studies with sedimentary, palaeontological, and provenance studies in order to construct a preliminary tectonic model which shows the terranes docked in the earliest Carboniferous (Truong Son with Loei-Phetchabun) and in the Permian (Kontum). The Kontum Terrane is characterized by Proterozoic magmatism, mid-Ordovician to Early Devonian granites, and Permian charnockites. Major carbonate platforms developed in the Givetian to earliest Tournaisian on Truong Son and from the Visean to mid-Permian across Truong Son and Loei-Phetchabun terranes. The Truong Son has Silurian granites and a Late Ordovician to Silurian magmatic arc along its southern and western borders caused by subduction of oceanic lithosphere, the remnants of which are now partially preserved in the Loei and Tamky sutures. A region to the east of the Loei Suture in the Loei Foldbelt has a similar-age volcanic arc extending northwards into Laos and is included in Truong Son. A platform-margin coral-stromatoporoid reef developed on Truong Son in the Frasnian and was coincident with a gap in magmatism until the Pennsylvanian with granite magmatism became widespread until the Late Triassic. In the Loei-Phetchabun Terrane, Devonian siliciclastics, volcanics are overlain by Givetian limestones and patch reefs and in turn overlain by Late Devonian to earliest Tournaisian radiolarian cherts and siliciclastics. Tournaisian to early Visean siliciclastic turbidites were coincidental with initial uplift and deformation and were replaced by Visean terrestrial evaporites and coal and marine limestones. Arc magmatism along the Loei-Phetchabun Terrane indicates intermittent eastward subduction from mid-Devonian to mid-Triassic. Carboniferous-Triassic volcanism extends eastward along the northern margin of Cambodia and is probably an extension of Loei-Phetchabun. Ordovician within-plate basalts in Kontum and the transition from shallow marine Ordovician siliciclastics to Silurian deep-marine sediments and a volcanic arc in Truong Son suggest rifting of both terranes from Gondwana in the Late Ordovician. Initial docking of Truong Son with South China was probably in the late Silurian to Early Devonian and docking of Loei-Phetchabun and Truong Son was in the late Tournaisian to early Visean.

Early Cretaceous volcanic-arc magmatism in the Dalat-Kratie Fold Belt of eastern Cambodia: implications for the lithotectonic evolution of the Indochina terrane

“…The Indochina Block is bounded to the northeast by the Ailaoshan-Song Ma suture and to the west by the Sukhothai-Chanthaburi arc and the Paleo-Tethys suture. The block is generally divided into several tectonic zones: the Truong Son Fold Belt (Laos and western Vietnam) and Kontum massif (central Vietnam) along its eastern margin, the Loei Fold Belt (western Cambodia, Thailand and eastern Myanmar) along the western margin and the Dalat-Kratie Fold Belt (eastern Cambodia and southern Vietnam) in the south (Hutchinson, 2014;Metcalfe, 2017;Burrett et al, 2021).…”

“…Subsequent deformation and metamorphic overprinting on the Truong Son and Kontum rocks suggests that the accretion of the Indochina Block to the Eurasia margin occurred during the Early Triassic (260-240 Ma;Carter et al, 2001;Lepvrier et al, 2004;Roger et al, 2007). The Loei Fold Belt is composed of a succession of carbonates and metamorphosed tuffaceous rocks, intruded or overlain by Silurian to Late Cenozoic igneous rock (Wang et al, 2018;Burrett et al, 2021;Shi et al, 2021).…”

“…Of particular interest is the evolution of the Indochina terrane as it was affected by multiple collisional and accretionary events related to the subduction of the Paleotethys Ocean (Sone and Metcalfe, 2008;Hutchinson, 2014;Metcalfe, 2017;Faure et al, 2018;Wang et al, 2018;Tran et al, 2020;Waight et al, 2021). During the Early Triassic, the Indochina terrane collided and accreted to the South China Block whereas during the Late Triassic it was affected by collision and accretion of the Sukhothai and Sibumasu terranes (Lepvrier et al, 2008;Burrett et al, 2021;Jiang et al, 2021). Furthermore, the Paleo-Pacific plate subducted beneath the Indochina terrane beginning in the Early Cretaceous and was responsible for the generation of widespread Cordilleran Batholiths throughout the Dalat-Kratie Fold Belt of southern Vietnam and eastern Cambodia (Nguyen et al, 2004a;Nguyen et al, 2004b;Shellnutt et al, 2013;Cheng et al, 2019;Hennig-Breitfeld et al, 2021;Nong et al, 2021;Nong et al, 2022).…”

P–T–t conditions of Early Palaeozoic low‐P high‐T granulite facies metamorphism in the southern Truong Son Belt, Central Vietnam

“…Geochronological data from the Truong Son Belt and Kontum Massif reveal two major tectonothermal events during the Ordovician-Silurian and Permian-Triassic periods. Different interpretations have been proposed for the Ordovician-Silurian tectonothermal events, including (1) extension within the Gondwana supercontinent (Burrett et al, 2021;Carter et al, 2001); (2) collision between the Indochina and South China blocks (Usuki et al, 2009); (3) subduction and subsequent collision between the Truong Son Belt and Kontum Massif along the TKPS suture zone (Faure et al, 2018;Gardner et al, 2017;Jiang et al, 2020;Tran et al, 2014;Wang et al, 2020); (4) arc-related magmatism (Nagy et al, 2001;Nakano et al, 2013Nakano et al, , 2021Vuong et al, 2022); and (5) an intra-continental thermal event (Maluski et al, 2005). The Permian-Triassic event is generally considered to have resulted from the subduction of the Song Ma Palaeo-Tethys Ocean beneath the Indochina Block or South China Block and the consequent collision of the Indochina and South China blocks, namely, the Indosinian Orogeny (Faure et al, 2014;Liu et al, 2013;Nakano et al, 2010;Zhang et al, 2013Zhang et al, , 2014.…”

A new orogenic gold belt in Southeast Asia: Geology, mineralogy and genesis of the Vangtat gold deposit, Southeastern Laos

“…The Indochina Terrane is a major tectonic unit of mainland Southeast Asia and is made up of several tectonic domains, volcanic arcs, and suture zones (Charusiri et al, 2002;Metcalfe, 2002;Lepvrier et al, 2004;Burrett et al, 2021). The Tam Ky-Phuoc Son and Poko suture zones mark the tectonic collision between the main part of the Indochina Terrane and the Kontum Massif in central Vietnam and southeastern Laos, respectively (Figure 1; Lepvrier et al, 2004Lepvrier et al, , 2008Tran et al, 2014).…”