AUTHOR=Burrett Clive , Udchachon Mongkol , Thassanapak Hathaithip 

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

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2021.603565

DOI=10.3389/feart.2021.603565

ISSN=2296-6463

ABSTRACT=The three main regions of Indochina have distinctive pre-Visean geological histories and are defined as the Truong Son, Loei-Phetchabun and Kontum terranes.  The Kontum Terrane is characterised 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.  Carbonate platforms are preceded and succeeded by widespread siliciclastic deposition.
The Truong Son has Silurian granites and a Late Ordovician to Silurian magmatic arc along its southern and western borders caused by eastward and northward 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. Widespread siliciclastics become more terrestrially influenced in the Early Devonian and contain distinctive South China fish. 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 widespread until the Late Triassic.
 In the Loei-Phetchabun Terrane Devonian siliciclastics, volcanics and volcaniclastics are overlain by Givetian limestones and patch reefs and in turn overlain by Late Devonian to earliest Tournaisian radiolarian cherts and siliciclastics. Siliciclastic influx in the Tournaisian to early Visean is characterised by turbidites coincident with initial uplift and deformation and later with Visean terrestrial evaporites and coal. 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 into southern Vietnam 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 - early Visean.