Celeste G. Engel
Thomas W.C. Hilde
1967
<p>Hon<span> </span>Trung<span> </span>Lon<span>, a </span>granite<span> </span>island<span> </span>off<span> the </span>coast<span> of </span>South<span> </span>Vietnam<span>, is composed solely of a unique, extremely differentiated, high-silica alkali </span>granite<span> of Cretaceous </span>age<span>. An adjacent </span>island<span>, </span>Hon<span> </span>Trung<span> Nho, is composed solely of rhyolitic rock of similar </span>composition<span>. The </span>Hon<span> </span>Trung<span> Nho rhyolite may be a fine-grained equivalent of the </span>granite<span>. Whole-rock potassium-argon analysis suggests that the </span>age<span> of the </span>Hon<span> </span>Trung<span> </span>Lon<span> </span>granite<span> is greater than 70 m.y. and less than 100 m.y. This </span>age<span> implies a previously unrecognized period of intrusion for the zone of granitic rocks outcropping along the northeast side of the Gulf of Thailand. Extensive investigation of the Mesozoic and Tertiary igneous rocks of Southeast Asia, particularly Indochina, including reliable geochronological work, is needed to trace the geologic events that produced the complicated structural features and orogenic history of this region. Existing data suggest that Southeast Asia has been the site of active orogeny since the Paleozoic and that the </span>Hon<span> </span>Trung<span> </span>Lon<span> </span>granite<span> was emplaced through a sialic crust which has been evolving in this area for at least the last 400 m.y.</span></p>
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10.1130/0016-7606(1967)78[1289:ACATSO]2.0.CO;2
en
Geological Society of America
Age, composition, and tectonic setting of the granite island, Hon Trung Lon, off the coast of South Vietnam
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