Indicators of gold mineralization in the Yellowknife greenstone belt: a lithogeochemistry and mineralogy study

• Author / Creator

  Langlois, Lauren A

• Geochemical signatures within an economic deposit are an important indicator used in the exploration of high-grade mineralization. In this study, we aim to identify elements that can act as geochemical indicators for orogenic gold within the Yellowknife greenstone belt that allow the discrimination of mineralized structures. The ability of a portable x-ray fluorescence spectrometer (pXRF) to provide a fast and accurate assessment of compositions depends on particle sizes and the degree of chemical homogeneity within various lithologies. Therefore, we have tested the precision and accuracy of pXRF in six drill cores with heterogeneous mineralogy, lithology and grain sizes from various locations across the Yellowknife Greenstone Belt against standard assay data and inductively coupled plasma mass spectrometry (ICP) data from Gold Terra. The six cores come from three drilling locations within Gold Terra’s mineral claims and represent gold mineralization hosted within two different lithologies. The pXRF analysis picks up distinct geochemical trends approaching mineralized structures and surrounding alteration/shear zones; However, the trends vary by location and host rock lithology. The correlation coefficients for elements analyzed with respect to gold were calculated at a belt wide scale for all drilling locations, and at a local scale for each drilling location. The elements with the highest correlation with gold across all drilling locations were As and S and vary at a local scale, dependent on host-rock lithology and alteration. Mineralogical variability as a function of distance from gold-bearing structures has been determined to assess what minerals control the geochemical trends detected. Oxide minerals such as rutile, titanite, and ilmenite are the mineralogical controls for geochemical trends seen in siderophile elements, while chlorite is the mineralogical control for lithophile elements, such as magnesium. Across lithologies, ilmenite (FeTiO3) displays replacement textures as it is altered to rutile (TiO2) and titanite (CaTiSiO5), liberating iron in the process. These iron liberating replacement reactions likely contributed to the iron budget that aided in the sulphidation of the wall rock and destruction of the gold bisulphide complex, triggering gold deposition.

• Subjects / Keywords

  • Gold
  • Geology
  • Yellowknife Greenstone Belt
  • Lithogeochemistry
  • Mineralogy

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-wvp3-zx38

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.