Characterization, evolution and IOCG-potential of the of the Iron Range iron oxide mineralization, Belt-Purcell basin, BC

Transcription

1 Characterization, evolution and IOCG-potential of the of the Iron Range iron oxide mineralization, Belt-Purcell basin, BC Galicki, M. and Marshall, D. (SFU) Anderson, B. and Enkin, R. (GSC) Downie, C. and Gallagher, C. (EPL)

2 Outline Overview of the Iron Range Petrography Petrogenesis Geochronology (Paleomag) Base metal ore deposit potential

3 Overview of the Iron Range iron-oxide mineralization occurs along Proterozoic Iron Range Fault hosted within Proterozoic Aldridge Formation mainly deep-water sediments and turbiditic sequences interbedded with gabbroic sills (Moyie sills)

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5 Overview of the Iron Range iron-oxide mineralization occurs along Proterozoic Iron Range Fault normal, steeply west dipping fault reactivated multiple times hosted within Proterozoic Aldridge Formation mainly deep-water sediments and turbiditic sequences interbedded with gabbroic sills (Moyie sills) ore minerals: hematite, magnetite ± chalcopyrite occur in massive lenses and vein size length: ~ 3 km, width varies (20-50m), depth up to 200m

6 exploration history mineralization: various industry-driven efforts (e.g. CP Rail, Cominco) Eagle Plains Resources acquired Iron Range claims in 2000 (SEDEX/IOCG investigations)

7 Petrography two distinct mineralization types along the Iron Range fault: inner corridor of massive iron-oxides (mfeox) flanked by brecciated iron-oxides (bfeox) host to cpy-mineralization at depth

8 Petrography (mfeox) massive iron-oxide mineralization varies in width between 20-40m best exposed in 7 trenches between the Golden Cap and Rhodesia showing ore minerals are predominantly hematite with lesser magnetite and trace pyrite and ilmenite locally only hematite or predominantly magnetite with lesser hematite euhedral to subhedral grains, large range of grain-sizes multiple generations of hematite and magnetite precipitation (hematite replacing magnetite and vice versa) silica and carbonate alteration

9 Marshall and Downie, 2002

10 Petrography (mfeox) hem Py massive iron-oxide mineralization varies in width between 20-40m best exposed in 7 trenches between the Golden Cap and Rhodesia showing ore hemminerals are predominantly hematite with lesser magnetite and trace pyrite and ilmenite hem locally only hematite or predominantly magnetite with lesser hematite euhedral to subhedral grains, large range of grain-sizes multiple generations of hematite and magnetite precipitation (hematite replacing magnetite and vice versa) silica and carbonate alteration Mag

11 Petrography (bfeox) iron-oxide-albite-quartz breccia, varies in width (m-10 s m) flanking massive iron oxide in gradational contact ore minerals are predominantly hematite with lesser magnetite and trace pyrite and ilmenite clast-supported breccia with anhedral grains of albite and quartz and veins of iron-oxide multiple generations of hematite and magnetite precipitation (hematite replacing magnetite and vice versa) chlorite, silica and carbonate alteration

12 Petrography (bfeox) feox iron-oxide-albite-quartz qtz breccia, varies in width (m-10 s m) flanking massive iron oxide in gradational contact ore minerals are predominantly hematite with lesser magnetite and trace pyrite and ilmenite clast-supported breccia with anhedral grains of albite and quartz and veins of iron-oxide multiple generations of hematite and magnetite precipitation (hematite replacing magnetite and vice versa) chlorite, silica and carbonate alteration alb

13 Petrography (bfeox) iron-oxide-albite-quartz breccia, varies in width (m-10 s m) flanking massive iron oxide in gradational contact ore minerals are predominantly hematite with lesser magnetite and trace pyrite and ilmenite clast-supported breccia with anhedral grains of albite and quartz and veins of iron-oxide multiple generations of hematite and magnetite precipitation (hematite replacing magnetite and vice versa) chlorite, silica and carbonate alteration

14 Petrography (bfeox) Cu-mineralization at about 200m depth below surface associated with chl-alteration discovered at the bottom of the deepest drill-hole in 2008 mag cpy py hem

15 Petrogenesis stable isotopes: quartz and albite from the iron-oxide breccia, coexisting with magnetite yield temperatures in the range of 340 to 400 C

16 Petrogenesis fluid inclusions: fluid inclusions record original fluid composition and PT-conditions quartz from iron-oxide breccia hosts 2 fluid populations carbonic present (CP) and carbonic absent (CA) both fluid populations are very saline eutectic melting temperatures below NaCl-H20 system eutectic (-21 C) other salts than NaCl present KCl or CaCl

17 Petrogenesis combination of stable isotope data with isochores from fluid inclusions constrains mineralization to depth of least 5km ( bars)

18 Petrogenesis IRFZ Aldridge Fm. low P Aldridge Fm. high P fluids

19 Petrogenesis fluid and heat-source: Cretaceous Mt. Skelly Pluton ~10 km Carboniferous? Carbonatites, occur locally Proterozoic Moyie Sills, occur locally basinal derived fluids

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21 Geochronology Paleomag (PM), due to lack of dateable primary minerals PM has been successfully used in dating MVT and SEDEX deposits around the world i.e.: HYC-Sedex, Australia by D.T.A. Symons (2007) Red-Dog MVT, Alaska by M.T. Lewchuk, D.L. Leach, Kelley, K.D. and D.T.A Symons (2004) Navan-MVT, Ireland by D.T.A. Symons, M.T. Smethurst and J.H. Ashton (1997)

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23 Geochronology ~100 collected samples were analyzed at the GSC-PGC (Sidney, BC) PM has limitations, but could point towards one of the known heat sources in the area

24 Geochronology Results: Iron Range FeOx are excellent carriers for remanent magnetization (single domain hematite and magnetite) very stable lightning and other sec. remanent magnetizations have been successfully removed PRM (primary remanent magnetization)

25 Geochronology Results: however data was somewhat scattered because of multiple FeOx-precipitation events which locally created a magnetic field subsequent ferromagnetic hematite and magnetite grains will inherit ambient field when created PLUS the locally created magnetic field of previously formed FeOx

26 Geochronology Results: nonetheless, general trend is observable towards a Cretaceous direction (not all samples demagnetized completely) one site recorded a true reversal of the magnetic field (samples with one 8cm drill-core) ~avg. duration of a reversal is 10,000 years time span between 2 iron-oxide precipitation events ~ 10, 000 yrs

27 Geochronology IR sites

28 Geochronology IR sites Bathozonal Tilt Corrections to Paleomagnetic Data From Mid-Cretaceous Plutonic Rocks: Examples From the Omineca Belt, British Columbia by E. Irving and D.A Archibald (1990)

29 IOCG Potential Although there is broad agreement on what generally constitutes this family of deposits, there is little consensus on the characteristics of the geological systems and the processes that form them (M.D. Barton and D.A. Johnson, 2004)

30 IOCG Potential Iron Range shares many characteristics of iron-oxide-(cu-au) (IOCG) deposits worldwide, which according to Hitzman (2000); Williams et al, (2005); and Barton and Johnson (2004) are: hydrothermal veins, breccia and replacement ore styles in a specific structural site CO2-bearing fluid inclusions associated magmatism with no clear spatial association at the structural level of mineralization abundant magnetite and hematite with a low Ti-content extensive sodic and/or potassic alteration (sub-economic) Cu and/or Au mineralization

31 Acknowledgments SFU Derek Thorkelson Reid Staples Karin Fecova Lara Loughrey GSC (TGI3 Cordillera) Eagle Plains Resources Tim Termuende Mike McCuaig Brad Robinsen Kootenay Gold, Ruby Red Resources Craig, Sean and Mike Kennedy