Characterisation of fluids from the giant muruntau Au-ore field, Uzbekistan, utilizing fluid inclusion microthermometry, volatile and dissolved anion/cation data

摘要

Fluid inclusions in quartz and scheelite from "central", "flat", and "stockwork-type" veins within the Muruntau Au ore field (>4,000 t Au) have been investigated using fluid inclusion mapping, microthermometry, laser Raman spectroscopy, and the integrated GC/IC method. Muruntau "central" veins are dominated by primary and pseudosecondary CO_2-bearing fluid inclusions; "flat" quartz veins contain mainly low-density pure aqueous fluids occurring on deofrmation relatd microstructures. Fluid phase separation is indicated by data from microthermometry and fluid geochemistry for samples from the Muruntau high-grade mineralized "central" ore veins; however, in "flat" veins and in the Myutenbai deposit no evidence for fluid immiscibility could be found. Fluid inclusion data may suggest formation of the "flat" veins before the main stage of hydrothermal activity and a considerable variation in the geochemical conditions during fluid evolution for the Muruntau and the Myutenbai deposits.