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Ordo-silurian assemblage in the Indochina interior: geochronological, elemental, and Sr-Nd-Pb-Hf-O isotopic constraints of early Paleozoic granitoids in South Laos


Wang, Y and Zhang, Y and Qian, X and Senebouttalath, V and Wang, Y and Wang, Y and Gan, C and Zaw, K, Ordo-silurian assemblage in the Indochina interior: geochronological, elemental, and Sr-Nd-Pb-Hf-O isotopic constraints of early Paleozoic granitoids in South Laos, Bulletin of the Geological Society of America, 133 pp. 325-346. ISSN 0016-7606 (2020) [Refereed Article]

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Copyright 2020 Geological Society of America

DOI: doi:10.1130/B35605.1


In order to verify the early Paleozoic accretionary assemblage in the Indochina interior and constrain the Prototethyan tectonic evolution in Southeast Asia, this study presents a set of new U-Pb geochronological, elemental, and Sr-Nd-Pb-Hf-O isotopic data for the fifty-two representative granitoids in South Laos. The granitoids from the Kontum terrane, Tam Ky-Phuoc Son tectonic zone, and southern Truong Son igneous zone in South Laos yield the crystallization ages of 464-485 Ma, 455-471 Ma, and 427-446 Ma, respectively, with a northerly younging trend within the Indochina interior. They are mainly monzogranite with A/CNK = 0.96-1.99 and K2O > Na2O, which are marked by enrichment in largeion lithophile elements and depletion in high field strength elements with remarkable NbTa, Sr-P, and Ti negative anomalies. Their initial Sr-87/Sr-86 ratios range from 0.70510 to 0.71559, epsilon(Nd)(t) from -9.5 to -3.0(Pb-206/Pb-204) from 18.65 to 19.72, (Pb-207/Pb-204) from 15.66 to 15.80, and (Pb-208/Pb-204), from 38.84 to 39.79. The corresponding zircon epsilon(Hf)(t) and delta O-18 values are in the range of -10.6 to +1.0 and 6.88 parts per thousand to 8.94 parts per thousand, respectively. In addition, their Sr-Nd-Pb and Hf-O isotopic compositions are generally similar with those of time-equivalent granitoids in South Tibet and SW Yunnan, China, and synchronous mafic-intermediate igneous rocks in South Laos, but distinctive from those of the supracrustal sedimentary-derived South China Paleozoic granite and Lincang-Sukhothai S-type granite. The early Paleozoic granitoids in South Laos might have originated from a mixed source of the wedge-derived juvenile crust coupled with supracrustal materials. All these data synthetically suggest the southward subduction of the Tam Ky-Phuoc Son Ocean and the northerly on-growing Ordo-Silurian accretionary orogenesis within the previously defined "single-ancient" Indochina block. The assemblage of the Indochina block might initiate at ca. 430 Ma in the Silurian and terminate in the Early-Middle Devonian.

Item Details

Item Type:Refereed Article
Keywords:truong son terrane, kon-tum-massif, menglian suture zone, central vietnami-type, indosinian orogeny, yunnan implications, tectonic evolution, crustal evolution,volcanic-rocks
Research Division:Earth Sciences
Research Group:Geology
Research Field:Resource geoscience
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Other mineral resources (excl. energy resources)
Objective Field:Other mineral resources (excl. energy resources) not elsewhere classified
UTAS Author:Zaw, K (Professor Khin Zaw)
ID Code:152680
Year Published:2020
Web of Science® Times Cited:14
Deposited By:CODES ARC
Deposited On:2022-08-23
Last Modified:2022-09-16

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