Geology and Chemistry of the Low Ti Magnetite-bearing Heff Cu-Au Skarn and its Associated Plutonic Rocks, Heffley Lake, South-Central British Columbia

Abstract

Research Article| July 01, 2007 Geology and Chemistry of the Low Ti Magnetite-bearing Heff Cu-Au Skarn and its Associated Plutonic Rocks, Heffley Lake, South-Central British Columbia G.E. Ray; G.E. Ray † 12234 McNeill Avenue, Victoria, British Columbia, V8S 2Y7. †Corresponding Author: E-mail: geray@shaw.ca Search for other works by this author on: GSW Google Scholar I.C.L. Webster I.C.L. Webster 2B.C. Geological Survey, P.O. Box 9320, Victoria,British Columbia, V8W 9N3. Search for other works by this author on: GSW Google Scholar Exploration and Mining Geology (2007) 16 (3-4): 159–186. https://doi.org/10.2113/gsemg.16.3-4.159 Article history received: 02 Nov 2006 accepted: 29 Apr 2007 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation G.E. Ray, I.C.L. Webster; Geology and Chemistry of the Low Ti Magnetite-bearing Heff Cu-Au Skarn and its Associated Plutonic Rocks, Heffley Lake, South-Central British Columbia. Exploration and Mining Geology 2007;; 16 (3-4): 159–186. doi: https://doi.org/10.2113/gsemg.16.3-4.159 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyExploration and Mining Geology Search Advanced Search Abstract The magnetite-rich Heff Cu-Au skarn lies in the Quesnel Terrane of south-central British Columbia, approximately 26 km northeast of Kamloops. The skarn formed close to the northern margin of the Heffley Creek pluton, and is hosted by Carnian (Late Triassic) Nicola Group limestone. The Late Triassic pluton (208.1 ± 6.1 Ma, U-Pb zircon) is a composite body of alkaline affinity that includes dioritic, gabbroic, and magnetite-rich clinopyroxene ± olivine ultramafic phases.The skarn has been discontinuously traced along strike for more than 1 km, and individual skarn layers are up to 40 m thick. The most common non-opaque minerals are garnet, clinopyroxene, and carbonate, with lesser epidote, biotite, amphibole, and chlorite. Apatite locally forms more than 3 vol.% of the rock. Compositionally the garnet is a low Mn grandite averaging Pyr3–Grs41–Adr56 mol.%.Mineralization consists of lenses, up to 10 m thick, containing massive low Ti-V magnetite (avg. 0.03 wt.% TiO2 and 0.01 wt.% V2O3). Magnetite is associated with up to 20 vol.% pyrrhotite, lesser pyrite, and trace chalcopyrite and gold. There is a moderate enrichment in rare earth elements with assays up to 570 ppm La and 490 ppm Ce.The Heffley Creek pluton belongs to a suite of Late Triassic–Early Jurassic alkalic and Fe-rich intrusions that are widely developed throughout the Quesnel Terrane. Some host Cu-Au porphyry mineralization, but less commonly they are associated with magnetite-apatite veins such as at the Glen Iron mine and Magnet occurrence, or with magnetite-rich Cu-Au skarns such as the Heff occurrence.Although abundant low Ti magnetite is present in the Heff skarn, it does not appear to represent iron oxide copper-gold (IOCG) type mineralization. Microprobe analyses completed during this study show that low Ti magnetite is not a unique feature of IOCG deposits, but also characterizes some other types of hydrothermal mineralization. In British Columbia these include some alkalic porphyry-related magnetite-apatite veins in the Quesnel Terrane, as well as the well-known Wrangellia-hosted Fe skarn deposits. Thus, low Ti magnetite appears to be a common signature of many magmatic hydrothermal deposits in contrast to the high Ti primary magnetite found in most igneous rocks. You do not currently have access to this article.