Premium
Hydrothermal Quartz Vein Formation, Revealed by Coupled SEM‐CL Imaging and Fluid Inclusion Microthermometry: Shuteen Complex, South Gobi, Mongolia
Author(s) -
Batkhishig Bayaraa,
Bignall Greg,
Tsuchiya Noriyoshi
Publication year - 2005
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2005.tb00223.x
Subject(s) - quartz , fluid inclusions , hydrothermal circulation , scanning electron microscope , geology , vein , dissolution , mineralogy , geochemistry , materials science , chemistry , composite material , paleontology , psychology , psychiatry
. Scanning electron microscopy‐cathodoluminescence (SEM‐CL) imaging of vein quartz in the Cu‐mineralised, Shuteen Complex (South Gobi, Mongolia) has revealed a complex history of crystal growth, dissolution and microfracture healing, associated with several hydrothermal events that could not be detected using other observational techniques (e.g. transmitted/reflected light microscopy, back‐scattered electron imaging, or secondary electron imaging). The quartz initially grew as CL‐bright/grey crystals in a 345±30d̀C liquid reservoir, as inferred by the analysis of primary liquid fluid inclusions (average Th of 343d̀C; 6.6∼7.7 wt% NaCl eq ). Quartz precipitation occurred at the edge of the crystals as reservoir fluids cooled to 260±25d̀C, as indicated by micron‐scale CL‐dark/CL‐bright quartz growth bands containing abundant fluid inclusions (with an average T h values of 261d̀C). Pressure fluctuations were the likely cause of dissolution, as SEM‐CL imaging reveals the quartz have corroded or rounded crystal edges, and precipitation of later quartz into open space. SEM‐CL imaging shows the quartz contains healed microfractures that trapped low salinity fluids (3.9 wt% NaC1 eq ) with Th values of 173±15d̀C. SEM‐CL imaging provides a means of deciphering the thermal and chemical evolution of the fossil Shuteen hydrothermal system, and the nature of hydrothermal quartz vein‐forming processes, by facilitating the correlation of distinct fluid inclusion populations and their relative chronology, with specific hydrothermal events.