Preliminary Evaluation of Trace Hydrocarbon Speciation and Abundance as an Exploration Tool for Footwall-Style Sulfide Ores Associated with the Sudbury Igneous Complex, Ontario, Canada

Research Article| March 01, 2015 Preliminary Evaluation of Trace Hydrocarbon Speciation and Abundance as an Exploration Tool for Footwall-Style Sulfide Ores Associated with the Sudbury Igneous Complex, Ontario, Canada* Mitchell Kerr; Mitchell Kerr † 1Department of Geology, Saint Mary's University, Halifax, Nova Scotia, Canada †Corresponding author: e-mail, mitchjkerr@gmail.com Search for other works by this author on: GSW Google Scholar Jacob Hanley; Jacob Hanley 1Department of Geology, Saint Mary's University, Halifax, Nova Scotia, Canada Search for other works by this author on: GSW Google Scholar Gordon Morrison; Gordon Morrison 2TMAC Resources, Toronto, Ontario, Canada Search for other works by this author on: GSW Google Scholar John Everest; John Everest 3KGHM International Ltd., Sudbury, Ontario, Canada Search for other works by this author on: GSW Google Scholar Colin Bray Colin Bray 4Department of Earth Science, University of Toronto, Toronto, Ontario, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Mitchell Kerr † 1Department of Geology, Saint Mary's University, Halifax, Nova Scotia, Canada Jacob Hanley 1Department of Geology, Saint Mary's University, Halifax, Nova Scotia, Canada Gordon Morrison 2TMAC Resources, Toronto, Ontario, Canada John Everest 3KGHM International Ltd., Sudbury, Ontario, Canada Colin Bray 4Department of Earth Science, University of Toronto, Toronto, Ontario, Canada †Corresponding author: e-mail, mitchjkerr@gmail.com Publisher: Society of Economic Geologists Received: 23 May 2013 Accepted: 08 Jul 2014 First Online: 09 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 © 2015 Society of Economic Geologists. Economic Geology (2015) 110 (2): 531–556. https://doi.org/10.2113/econgeo.110.2.531 Article history Received: 23 May 2013 Accepted: 08 Jul 2014 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mitchell Kerr, Jacob Hanley, Gordon Morrison, John Everest, Colin Bray; Preliminary Evaluation of Trace Hydrocarbon Speciation and Abundance as an Exploration Tool for Footwall-Style Sulfide Ores Associated with the Sudbury Igneous Complex, Ontario, Canada. Economic Geology 2015;; 110 (2): 531–556. doi: https://doi.org/10.2113/econgeo.110.2.531 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract Deposits of Cu-Ni-platinum group elements (PGE)–rich sulfides occur along the North Range footwall of the Sudbury Igneous Complex, Ontario, Canada. The deposits have been modified chemically, mineralogically, and texturally by multiple syn- to postmagmatic hydrothermal events and are hosted mainly within Sudbury breccia, a contact metamorphosed and hydrothermally altered impact breccia. The composition of C1 to C6 unsaturated and saturated hydrocarbons in bulk fluid inclusion volatiles in the matrix of the Sudbury breccia was investigated using in-line rock-crushing gas chromatography (GC) in order to compare the hydrocarbon composition of this rock type in breccia zones containing economic footwall sulfide deposits at the Morrison deposit (Levack mine, North Range, Sudbury, Ontario) with barren breccia zones.Trace hydrocarbons, possibly abiogenic in origin, occur throughout the Sudbury Igneous Complex footwall and country rocks investigated. However, there are differences in the composition and abundance of bulk hydrocarbons released from mineralized and barren Sudbury breccia when fluid inclusions are opened. Volatiles released from samples of Sudbury breccia from sulfide-mineralized and sulfide-barren environments showed the following: (1) higher average abundances of light saturated hydrocarbons (C1–C4) and an approximately 2× higher total abundance of hydrocarbons (mol/g of rock basis) associated with samples from the mineralized study area, and (2) comparable average unsaturated hydrocarbon abundances in both settings, but a larger range in unsaturated hydrocarbon abundances in the mineralized study area. Differences in bulk hydrocarbon abundance and composition reflect differences in the abundance and hydrocarbon content of fluid inclusions trapped in the barren and mineralized Sudbury breccia zones. In addition, the compositional modification of circulating fluids by processes and conditions unique to the mineralized Sudbury breccia environment may have occurred prior to inclusion entrapment (e.g., modification by mineral catalysts, differences in temperature and oxygen fugacity).Preliminary spatial analysis of the hydrocarbon distribution within and surrounding the Morrison deposit shows that the total hydrocarbon abundance in the Sudbury breccia does not change with orebody proximity within a single host breccia zone. However, volatiles trapped in the Sudbury breccia matrix near the top of the footwall deposit, where it is physically connected to contact-style (Ni-Cu-PGE) ores, have elevated unsaturated hydrocarbon abundances (e.g., propene) compared to other parts of the same breccia zone distal to this zone of physical connection. Samples of the PGE-enriched Sudbury breccia and mineralized veins containing alteration assemblages characteristic of the footwall ore styles have higher unsaturated hydrocarbon abundances and unsaturated/saturated ratios compared to Sudbury breccia and vein samples that are PGE poor. Localized enrichments in unsaturated hydrocarbons in Sudbury breccia zones may be the result of specific ore minerals and metal complexes (involving the PGE and group VIII metals) that acted as catalytic agents, modifying the composition of initially light saturated hydrocarbon species prior to entrapment in fluid inclusions.To apply the analysis of hydrocarbon compositions in trapped fluid inclusions to discriminating mineralized from barren zones of Sudbury breccia, samples from targeted areas were compared to samples of barren Sudbury breccia ("background"). Although a large data set is presented here to establish these compositional fields, analysis of smaller sample subsets from each environment yields a statistically significant separation between the two environments. Total hydrocarbon abundance, C3/C1 ratios, and unsaturated/saturated hydrocarbon ratios are useful indicators of sulfide ore proximity and may help delineate regions enriched in PGE. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.