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2 2023

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The Collision Between Indochina and South China Blocks in Northwestern Vietnam and its Controversy

Hung Khuong The, Golonka Jan, Du Nguyen Khac

Inżynieria Mineralna

2023

no. 2, vol. 1

103--112

The Indosinian orogeny, which was regarded as the collision event between the South China and Indochina blocks that occurred in Southeast Asia, including Vietnam, resulting in the formation of the Indosinian mountain range. However, the question of how many times collision between these blocks occurred in the past and during which period remains unanswered. Furthermore, the closure of the ancient ocean and the evidence of its remnants between the South China and Indochina Blocks are still the subjects of serious debate. The underlying origin of the Indosinian thermo-tectonism is uncertain. The entire region was affected by the thermal-tectonic processes in the west, caused by the collision of the Sibumasu plate and Indochina block. The absence of evidence supporting the Indosinian as a significant mountain-building event is highlighted through an examination of regional paleogeography, as well as palaeontological and thermochronological data. There is no conclusive evidence to suggest that the Indochina and South China blocks collided during the Triassic times. A plate tectonic scenario that describes the Indosinian orogeny as a reactivation event triggered by the accretion of the Sibumasu block to Indochina is favored.

The eastern extension of the Avalonian terranes, the Prototethys and Paleotethys oceans

Golonka Jan, Hung Khuong The, Du Nguyen Khac, Krobicki Michał

Geotourism / Geoturystyka

2023

nr 1-2 (72-73)

23--24

Avalonia was an archipelago of microcontinents divided into West and East Avalonia. West Avalonia included south-eastern parts of Nova Scotia, eastern Newfoundland, New Brunswick, Florida(?), and New England, while East Avalonia included southern Ireland, southern Scotland, England, northern France, the Brabant Massif, Lusatia, northern Germany, and north-western Poland. Several crustal fragments such as the Bruno–Silesia terrane, Moesian terranes, Istanbul/Zonguldak terrane constituted an extension of East Avalonia (Golonka et al., 2023). These microcontinents detached from Gondwana during the Early Paleozoic times. Golonka et al. (2023) also portrayed a chain of microcontinents moving away from Gondwana across the Palaeoasian (Protothetys) Ocean. These chain included Scythian, Turan, South Kazakhstan, Junggar, Tarim and Indochina. The Rheic-Palaeotethys Ocean opened behind these microcontinents. Collision occurred between Avalonia, Laurentia and Baltica during Caledonian Orogeny. This collision also included Bruno–Silesia, Moesia terranes, Istanbul/Zonguldak, Scythian and Turan terranes (Golonka & Gawęda, 2012). The events involving Junggar, South Kazakhstan and Tarim are more speculative. Indochina collided with South China along Song Ma– Truong Song–Ailaoshan suture during latest Silurian–earliest Devonian times. In northwestern Vietnam, the Late Silurian Song Chay complex granitoid is connected to this event. Moreover, the deep-water deposits such as Pa Ham formation were later replaced by shallow-water sedimentary formations, including the continental Lower Devonian red beds and Lower Devonian Nam Pia Formation composed mainly of terrigenous sediments and marl, medium-bedded to massive fine-grained limestone, representing shallow water sediments. The Lower Paleozoic greenschists of deepsea origin were unconformably covered in many localities by Devonian redbeds (Son et al., 1978; Hung, 2010; Hung et al., 2023).