Yuanming Pan

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The White River exploration property of LAC Minerals Ltd. is located approximately 5 km east of the Hemlo gold deposit in the Hemlo-Heron Bay greenstone belt of the Superior Province of the Canadian Shield, and is composed mainly of metamorphosed, metasomatized, and intensively deformed volcano-sedimentary rocks of late Archean age. The supracrustal rocks are bounded by crystalline basement (Pukaskwa Gneissic Complex) to the south and a granodioritic intrusion (Cedar Lake Pluton) to the north. The clastic metasedimentary rocks were mainly derived from intermediate volcanic sources, admixed with minor ultramafic and mafic volcanic materials and continental weathering products, and deposited as turbidites in a large volcanoclastic-sedimentary basin.;All supracrustal rocks in the study area have been subjected to at least two episodes of regional metamorphism. A Barrovian-type metamorphism (6-6.5 kbar and 455-520{dollar}\sp\circ{dollar}C) occurred earlier and followed by a peak thermal metamorphism. The peak thermal metamorphism was generally low in grade at a greenschist-amphibolite transition facies (3.2 kbar and 475-500{dollar}\sp\circ{dollar}C) and climaxed at middle amphibolite facies (4.2-4.5 kbar and 580 {dollar}\pm{dollar} 20{dollar}\sp\circ{dollar}C) in two narrow zones with maximum shear deformation.;Three prominent ore-mineral-calc-silicate occurrences (Cr-rich, Fe-rich and REE-enriched) are located within major structural failures and their salient mineralogical and geochemical characteristics and metallogenic associations strongly correlate with host lithologies. All three calc-silicate occurrences belong to a protracted phase of skarn development, which began during the peak regional metamorphism, continued with a pervasive epidote-prehnite alteration, and concluded with sulfidation, carbonization and gold deposition.;Gold mineralization in the Local Shear Zone is associated with REE-enriched skarn. This auriferous skarn is clearly differentiated from typical Archean lode gold deposits by fluid inclusions of moderate salinity and from Phanerozoic counterparts by its structural setting in a brittle-ductile shear zone and carbonate-free host rocks. Although the dilatant Local Shear Zone most likely acted as a fluid conduit during skarn formation, the precise localization of gold deposition was controlled by a pre-existing pyritic zone. There are remarkable similarities and some discrepancies between this auriferous skarn and the Hemlo gold deposit.



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