Mesozoic Magmatic History and Metallogeny of the Hotailuh Batholith (NW BC) Bram van Straaten , Jim Logan and Larry Diakow 1 1 1 1. Ministry of Energy and Mines, British Columbia Geological Survey , Victoria, BC For More Information [email protected] +1-250-952-0304 Poster presented at the AME BC Mineral Exploration Roundup (Jan. 23 , 2012) BCGS GeoFile 2012-08 rd Digital version released Feb., 2012 ? ? ? ? Refine temporal Link Identify prospective Provide geological base to & magmatic and geochemical evolution magmatism and mineralization magmatic-hydrothermal systems interpret airborne magnetic survey regional geochemical stream sediment survey Stimulate mineral exploration ? Goals Geological maps ? ? Northern Stikine terrane Large composite batholith within Triassic - Jurassic volcanic and sedimentary rocks Late Triassic plutonic suite Early Jurassic plutonic suite Middle Jurassic plutonic suite Regional geology Implications for exploration ? ? ? Identified several new Cu, Au mineral occurrences Presence of significant Late Triassic magmatic- hydrothermal metallogenic event, similar to elsewhere in N. Stikinia Previously unrecognized Middle Jurassic magmatic-hydrothermal mineralization deserves more attention Intrusion-related mineralization (plotted according to age of intrusive host rock or age of spatially associated intrusion) Airborne magnetics (QUEST-NW block 1) F Z D F F Z 190±2 lJ (l?)mJ 221±3 lmJ mJ Jurassic stratified rocks (northwest area) Jurassic stratified rocks (east area) Triassic Stuhini Group (all areas) Z 217±2 Volcanic rocks (J V) Volcanic rocks (J V) Coarse-grained sedimentary rocks (mJ Sc) Fine-grained sedimentary rocks (mJ Sf) Coarse-grained sedimentary rocks (mJ Sc) Fine-grained sedimentary rocks (mJ Sf) Coarse-grained quartz-bearing sedimentary rocks (lmJ Scq) Volcanic rocks (J V) Fine-grained sedimentary rocks (lJ Sf) Augite-phyric coherent rocks (T STap) Fine-grained sedimentary rocks (T STsf) Volcanic rocks (T STv) Z U-Pb zircon age (this study; Anderson and Bevier, 1992) D Detrital U-Pb zircon age (Iverson et al., 2012) F Fossil location (Gabrielse, 1998) D mJ D mJ Cake Hill pluton (LT CH) + + + + + v v v v v v v v v v v v v v v v v v v v v v – – – – – – – – – – – – – – – – – – – • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • v v v v v v v v v v – – – – – – – – – – – – – – – – – – – – – – – McBride River pluton (EJ MR) + + + Gnat Pass intrusive (LT GP) – – – – – – – – – – – – – – – – – – – – v v v v v v v v v v v v v v v v v v v v + + + 100 110 120 130 140 150 160 170 180 190 200 210 220 230 Age (Ma) Jurassic Cretaceous Triassic Late Late Early Early Middle Ar-Ar Bt Ar-Ar Hbl U-Pb Zrn Closed symbols: This study (preliminary) Open symbols: Zagorevski et al. (2011), Anderson & Bevier (1992), Anderson et al. (1982) Timescale after IUGS International Commission on Stratigraphy (2010) Gnat Lakes ultramafite (LT GL) Cpx hornblendite; Cpx-Hbl gabbro Cake Hill pluton (LT CH) Hbl Qtz monzodiorite/Qtz monzonite Gnat Pass intrusive (LT GP) Hbl (Qtz) diorite/granodiorite, often Pl-Qtz porphyritic Beggerlay Creek pluton (LT BC) Websterite; clinopyroxenite; Cpx-Hbl gabbro McBride River pluton (EJ MR) Hbl monzogranite/granodiorite Fine-grained mafic phase (MJ TSf) Hbl diorite Mafic phase (MJ TSm) Hbl-rich (Qtz?) diorite Central felsic phase (MJ TSc) Bt Qtz monzonite/Qtz monzodiorite Potassic phase (MJ TSp) Bt granite/Qtz syenite/Qtz monzonite Tees Creek intrusive (MJ? TC) Altered Hbl-Fsp porphyry Three Sisters pluton Middle Jurassic suite Early Jurassic suite Late Triassic suite Geological units Stratified rocks Intrusive rocks Mineral occurrences More information BC Ministry of Energy and Mines, by Geological Fieldwork 2011 article van Straaten, Logan and Diakow. Publications Catalogue Available online as a downloadable file at see www.empr.gov.bc.ca/geology References Anderson, Loveridge and Sullivan (1982); Current Research, Part C, Geological Survey of Canada, Paper 82-1C, p.133-137. Anderson and Bevier (1992); Radiogenic Age and Isotope Studies (Report 6); Geological Survey of Canada, Paper 92-2, p.145-152. Gabrielse (1998); Geological Survey of Canada, Bulletin 504, 118pp. International Commission on Stratigraphy (2010); International stratigraphic chart Iverson, Mahoney and Logan (2012); B.C. Ministry of Energy and Mines, Geological Fieldwork 2011, Paper 2012-1. Zagorevski, Joyce, Mihalynuk and Logan (2011); AME BC Mineral Exploration Roundup, January 2011, poster presentation. Acknowledgements We would like to acknowledge financial support from Geoscience BC that covered field, analytical and salary costs associated with the Hotailuh project. Travis McCarron, Catie Young, Meagan Hogg and Olivia Iverson are thanked for their capable assistance during the field season. Thanks to Janet Gabites (UBC PCIGR) for providing Ar-Ar analysis and Ray Donelick, Margaret and Paul O’Sullivan (Apatite to Zircon) for providing U-Pb analysis. Thanks also to Bob Anderson for sharing his knowledge of the Hotailuh batholith during discussions. QUEST-Northwest Airborne magnetic survey Regional geochemical stream sediment survey Bedrock mapping + + Triassic rock-hosted mineral occurrences Gnat Pass (Cu) Indicated reserves : Host rock: Alteration: Ore mineralogy: (non-NI 43- 101) 30.4Mt @ 0.389% Cu Qtz-Pl porphyry , tourmaline veining, Fe- Carb-cemented breccias (LT GP) Silicification Ccp, Py Upper Gnat Creek (Au,Cu,Ag) Size: Host rock: Vein with 20 x 20 cm pod of Hbl Qtz monzodiorite / Qtz monzonite massive-sulphide- cemented breccia (LT CH) Pat West (Cu) Size: Host rock: Vein mineralogy: 1 m wide, Bt Qtz monzonite / Qtz monzodiorite intensely veined zone Qtz, Py, Cu sulph (MJ TSc) [Several 10-100s m gossanous exposures present slightly west] 3 Sisters North (Cu W) ± Size: Host rock: Vein mineralogy: Subvertical, west striking Bt Qtz monzonite / Qtz monzodiorite veins (~5% by volume in several m wide interval) Ep,Act,sulph (MJ TSc) 3 Sisters South (Cu Mo) ± Size: Host rock: Associated minerals: Several 20 m wide, pyritic, subvertical, north striking fault zones Stuhini Group volcanic rocks ≤ (T STv) Act 3 Sisters (Cu) Size: Host rock: Vein mineralogy: Three m-scale Fine-grained Hbl diorite intensely veined / in- situ brecciated exposures with copper sulphides Qtz, Py Ccp, Ep (MJ TSf) ± [A 2 x 0.2 km gossanous zone is exposed towards the north/northeast] Midde Jurassic rock-hosted mineral occurrences Mat North (Cu) Size: Host rock: Associated minerals: Ore minerals: cm/dm-sized pods Hbl Qtz monzodiorite / Qtz monzonite coarse-grained euhedral Bt Py Bn (LT CH) ± Total magnetic intensity First vertical derivative Legend Outline of Mesozoic intrusions MINFILE showings, prospects Other mineral occurrences