Calcite trace element geochemistry of Au deposits in the Singu-Tabeikkyin Gold District, Myanmar: Implications for the sources of ore-forming fluids

Abstract

The Singu-Tabeikkyin gold district is one of the largest gold districts in Myanmar. The gold mineralization is represented by several tens of quartz lodes, which are hosted by a metamorphic sequence of marbles, calc-silicate rocks, gneisses, and migmatites. Trace- and rare earth element (REE) concentrations of successive generations of hydrothermal calcites from gold deposits of the Singu-Tabeikkyin gold district were analyzed in order to determine the origin of the ore fluids. Calcite samples contain variable concentrations of REE (3–1051 ppm) and Y (1–219 ppm). The chondrite-normalized rare earth element and yttrium (REEY) patterns of ore-stage calcites show three different trends which are (1) being strongly enriched in light REE (LREE) with positive Eu anomalies, (2) being enriched in heavy REE (HREE) with negative Eu anomalies, and (3) being enriched in middle REE (MREE) with no distinct Eu anomalies. The first trend, which is representative of the majority of ore-stage calcites, is in agreement with ore fluids originating from a magmatic origin at high temperature (>250 °C). This is consistent with previous geochronological and geochemical data, demonstrating that the ore fluids are primarily associated with the Miocene magmatism. HREE- and MREE-rich REEY patterns of some hydrothermal calcites from Te-rich deposits are interpreted to represent the minor involvement of additional fluids.