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Geological setting, nature of mineralisation, and fluid characteristics of the Wang Yai prospects, central Thailand

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de Little, JV (2005) Geological setting, nature of mineralisation, and fluid characteristics of the Wang Yai prospects, central Thailand. Honours thesis, University of Tasmania.

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Abstract

The Wang Yai prospects are located along the Loei Foldbelt, central Thailand. They
are a newly discovered resource and up until now have not been the subject of any
scientific research. Eleven vein systems at Wang Yai were investigated in terms of
vein textures, mineralogy, fluid inclusions and stable isotopes. The vein systems
occur as either well-preserved outcrop or sparse sporadic float. The vein systems can
be divided into two types. They include: (1.) mineralised veins which are
characterised by quartz - chalcedony - calcite ± adularia and (2.) poorly mineralised
veins characterised by chalcedony and opaline quartz. The vein systems are hosted in
volcanic and volcanosedimentary units intruded by andesite and diorite. LA-ICP-MS
U-Pb zircon geochronological studies have revealed the age of host rocks as Late
Permian to Early Triassic.
Volcanology studies of the host rocks indicate that the depositional environment was
a submarine below wave base setting. Zr/Y vs Zr plot of least altered volcanic rocks
have identified the andesitic sandstone and andesitic lithic breccia as having island arc
affinities. The younger andesite and diorite intrusives were found to have continental
arc affinities. These findings are consistent with interpretations of the volcanic setting
at the nearby low-sulphidation Chatree deposit.
Vein texture, mineralogy, alteration and paragenesis studies have identified zonation
between gold-bearing vein systems and barren vein systems. Gold-bearing systems
yield crystalline quartz, lattice-bladed quartz, pseudo-acicular quartz and
pseudomorphs after adularia. Ore mineralogy in these systems is hosted in ginguro
bands which comprise of electrum ± argentite ± pyrite assemblages. Barren vein
systems yield chalcedony and opaline quartz assemblages with associated
recrystallisation textures. Based on quartz textural analysis and ore mineralogy
assemblages the gold-bearing veins are interpreted to have formed at levels deeper in
the system than the barren vein systems.
Fluid inclusion studies of quartz indicate salinities are between 1 to 5 wt % NaCl
equiv. Fluid inclusion homogenisation data yields three different ranges. Crystalline
gold-bearing quartz yields temperatures of 187 – 218 C°, comb quartz yields
temperatures of 260 - 290 C°.and crustiform-colloform veins yield temperatures of
140 – 200 C°.Stable sulphur isotope studies of pyrite range between +3.82 and -0.04 per mil. These
values indicate a magmatic source. Stable oxygen isotope values of quartz range from
+11 to +17.5 per mil. Low oxygen isotope values range from +11.0 to +13.0 per mil
and are associated with crystalline quartz gold bearing systems. High oxygen isotope
values (+15.0 to +17.5 per mil) are associated with barren quartz chalcedony
dominated systems.
The volcanic setting, vein textures, mineralogy and alteration assemblages of the
Wang Yai prospects are comparable with the nearby low-sulphidation epithermal
Chatree deposit. The Wang Yai prospects appear to be at the top of the broader
epithermal system and therefore potential for high grade mineralisation at depth
exists.

Item Type: Thesis (Honours)
Additional Information:

Copyright 2005 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Date Deposited: 02 May 2012 05:55
Last Modified: 16 Mar 2016 22:17
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