Bulletin of the Geological Society of Malaysia, Volume 81, May 2026, pp. 31 – 41
Physico-chemical condition and origin of Au mineralisation at Me Xi deposit, Central Truong Son Belt, Vietnam: Insight from fluid inclusion studies
Truong Xuan Le1,2,3,*, Khin Zaw4, Hai Thanh Tran1, Khang Quang Luong1,3, Du Khac Nguyen1,2,3, Ban Xuan To1
1 Faculty of Geosciences and Geoengineering / Economic Geology and Sustainable Development Research Team (EGSD), Hanoi University of Mining and Geology, Hanoi, Vietnam
2 Centre for Excellence in Analysis and Experiment, Hanoi University of Mining and Geology, Hanoi, Vietnam
3 Economic Geology and Sustainable Development Research Team (EGSD), Hanoi University of Mining and Geology, Hanoi, Vietnam
4 CODES Centre Ore Deposit and Earth Sciences, University of Tasmania, Private Bag 126, Hobart, Tasmania 7001, Australia
* Corresponding author email address: lexuantruong@humg.edu.vn
Abstract: The Me Xi gold deposit is an underexplored hydrothermal gold system in the central Truong Son Belt, Vietnam. This study investigates the physico-chemical condition and origin of the ore-bearing fluids at Me Xi based on fluid inclusion analyses. Only primary fluid inclusions are studied, and they are two-phase (i.e., vapor and liquid) inclusions and predominantly less than 10 μm in size, with liquid occupying approximately 70-90% of the inclusion volume. They display homogenization temperatures ranging from 181°C to 394°C (n=77), with a dominant population clustering between 180°C and 260°C (n=56). Fluid salinities range from 0.3 to 16.9 wt.% NaCl (n=57) with the majority comprising moderate to high-salinity inclusions (5-17 wt.%; n=47), which suggests a significant magmatic contribution. The subordinate low-salinity inclusions (<5 wt.%; n=10) are possibly indicative of locally diluted hydrothermal fluids caused by meteoric water and fluid-carbonaceous host rocks interaction. The combined thermometric and salinity data support an isothermal mixing model between magmatic and meteoric fluids, which appears to be a key mechanism for gold precipitation. The magmatic-sourced fluids in the deposit are spatially associated with the nearby dolerite intrusions.
Keywords: Me Xi, Quang Tri, Truong Son Belt, Au mineralisation, fluid inclusion, economic geology, Vietnam
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Manuscript received 15 March 2025;
Received in revised form 31 May 2025;
Accepted 15 July 2025
Available online 29 May 2026
https://doi.org/10.7186/bgsm81202604
0126-6187; 2637-109X / Published by the Geological Society of Malaysia.
© 2026 by the Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC-BY) License 4.0.
