Timing and Source of the Hermyingyi W-Sn Deposit in Southern Myanmar, SE Asia: Evidence from Molybdenite Re-Os Age and Sulfur Isotopic Composition

【摘要】 The Hermyingyi W-Sn deposit, situated in southern Myanmar, SE Asia, is a typical quartz-vein type W-Sn deposit. The ore-bearing quartz veins are mainly hosted by the Hermyingyi monzogranite which intruded into the Carboniferous metasedimentary rocks of Mergui Series. According to mineral assemblages and crosscutting relationships, four ore-forming stages are recognized:（1） silicate-oxide stage;（2） quartz-sulfide stage;（3） barren quartz vein stage;（4） supergene stage. Five molybdenite samples from the deposit yield Re-Os model ages ranging from 67.8±1.6 to 69.2±1.6 Ma（weighted mean age of 68.7±1.2 Ma）, and a well-defined isochron age of 68.4±2.5 Ma（MSWD=0.18, 2σ）. This Re-Os age is consistent with the previously published zircon U-Pb age of the Hermyingyi monzogranite（70.0±0.4 Ma）（MSWD=0.9, 2σ） within errors, which indicates a genetic link between the monzogranitic magmatism and W-Sn mineralization. The new high-precision geochronological data reveal that the granitic magmatism and associated W-Sn mineralization in southern Myanmar took place during the Late Cretaceous（70–68 Ma）. The extremely low Re contents（22.9 ppb to 299 ppb） in molybdenite, coupled with sulfide δ³⁴S values in the range of +1.9‰ to +5.6‰ suggest that ore-forming metals were predominately sourced from the crustal-derived granitic magma.更多还原

【Abstract】 The Hermyingyi W-Sn deposit, situated in southern Myanmar, SE Asia, is a typical quartz-vein type W-Sn deposit. The ore-bearing quartz veins are mainly hosted by the Hermyingyi monzogranite which intruded into the Carboniferous metasedimentary rocks of Mergui Series. According to mineral assemblages and crosscutting relationships, four ore-forming stages are recognized:（1） silicate-oxide stage;（2） quartz-sulfide stage;（3） barren quartz vein stage;（4） supergene stage. Five molybdenite samples from the deposit yield Re-Os model ages ranging from 67.8±1.6 to 69.2±1.6 Ma（weighted mean age of 68.7±1.2 Ma）, and a well-defined isochron age of 68.4±2.5 Ma（MSWD=0.18, 2σ）. This Re-Os age is consistent with the previously published zircon U-Pb age of the Hermyingyi monzogranite（70.0±0.4 Ma）（MSWD=0.9, 2σ） within errors, which indicates a genetic link between the monzogranitic magmatism and W-Sn mineralization. The new high-precision geochronological data reveal that the granitic magmatism and associated W-Sn mineralization in southern Myanmar took place during the Late Cretaceous（70–68 Ma）. The extremely low Re contents（22.9 ppb to 299 ppb） in molybdenite, coupled with sulfide δ³⁴S values in the range of +1.9‰ to +5.6‰ suggest that ore-forming metals were predominately sourced from the crustal-derived granitic magma.更多还原