The Late Devonian to Early Mississippian Sicker Group of Vancouver Island, British Columbia, Canada, is host to the Myra Falls polymetallic, volcanic-hosted massive sulfide (VHMS) deposits (production has exceeded 30 Mt at average grades of 5.5% Zn, 1.6% Cu, 0.6% Pb, 2.0 g/t Au, and 54.0 g/t Ag), along with numerous historic VHMS workings and occurrences. Two cycles of bimodal volcanism and marine sedimentation at Myra Falls are prospective for VHMS deposits. These cycles are defined as the lower and upper subdivisions of the Myra Formation. The lower Myra Formation consists of the H-W member, Hanging-Wall Andesite, and Lower Mixed Volcanics units. Rhyolitic rocks of the H-W member host the HW, Battle, Trumpeter Zone, Extension Zone, Gap, Ridge, and Marshall Zone orebodies. The upper Myra Formation includes the L-M-P member, Upper Mixed Volcanics and the Upper Mafic units. Rhyolitic rocks of the L-M-P member host the Lynx, Myra, and Price orebodies. Prior to this study, geological observations suggested that the H-W and L-M-P VHMS mineral deposits were likely coeval based on similar volcanic host rocks, base metal sulfide mineralization zoning, and only 200 vertical meters of stratigraphic separation. Previous attempts to date the duration of felsic volcanism at Myra Falls have resulted in relatively imprecise crystallization ages and were unable to resolve the temporal relationship between the L-M-P and H-W members and the VHMS deposits they host. New chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) U–Pb zircon geochronology yielded crystallization and maximum deposition ages of volcanic rock units from Myra Falls. This new data temporally constrains the felsic volcanic history at Myra Falls by a precise CA-ID-TIMS age of 362 ± 1 Ma for coherent rhyolite of the H-W member and a LA-ICPMS maximum depositional age of 356 ± 3 Ma for volcaniclastic rhyolite of the L-M-P member. This new geochronological data suggests there is a 3.5–11 myr time interval between the H-W and L-M-P members and therefore, a previously unrecognized unconformity exists between the lower and upper subdivisions of the Myra Formation and that the VHMS deposits of the H-W and L-M-P members were not coeval, but likely formed from temporally, distinct hydrothermal events. The results of this study, together with published age constraints from across Vancouver Island, provide a revised geochronological and lithological framework for volcanism and VHMS deposit formation within the Sicker Group. At least three Paleozoic felsic volcanic events (~ 362 Ma; ~ 355 Ma; and 310–300 Ma) host VHMS mineralization on Vancouver Island. Recognizing the specific chronostratigraphic intervals, and the lithostratigraphic setting, of VHMS deposits is important for genetic and mineral exploration models, and will aid explorers in identifying key stratigraphic units that are most prospective for VHMS mineralization.

加拿大不列颠哥伦比亚省温哥华岛晚泥盆纪至密西西比纪早期 Sicker 群是 Myra Falls 多金属火山岩块状硫化物 (VHMS) 矿床的所在地（产量已超过 30 Mt，平均品位为 5.5% Zn，1.6% Cu、0.6% Pb、2.0 g/t Au 和 54.0 g/t Ag），以及众多历史悠久的 VHMS 工作和事件。Myra Falls 的两个双峰火山作用和海洋沉积循环是 VHMS 矿床的前景。这些旋回被定义为迈拉组的下部和上部。下迈拉组由 HW 段、挂壁安山岩和下混合火山单元组成。HW 成员的流纹岩包含 HW、Battle、Trumpeter 带、延伸带、Gap、Ridge 和 Marshall 带矿体。上迈拉组包括 LMP 成员，上混合火山和上镁铁质单位。LMP 成员的流纹岩拥有 Lynx、Myra 和 Price 矿体。在这项研究之前，地质观察表明，HW 和 LMP VHMS 矿床可能是基于相似的火山主岩、贱金属硫化物矿化带和只有 200 米垂直距离的地层分离而同时形成的。以前对迈拉瀑布长英质火山活动持续时间的尝试导致结晶年龄相对不准确，并且无法解决 LMP 和 HW 成员与它们所在的 VHMS 沉积物之间的时间关系。新的化学磨损同位素稀释热电离质谱 (CA-ID-TIMS) 和激光烧蚀-电感耦合等离子体质谱 (LA-ICPMS) U-Pb 锆石年代学产生了来自迈拉瀑布的火山岩单元的结晶和最大沉积年龄。这一新数据在时间上将迈拉瀑布的长英质火山历史限制为 HW 成员的连贯流纹岩的精确 CA-ID-TIMS 年龄为 362 ± 1 Ma，而火山碎屑流纹岩的 LA-ICPMS 最大沉积年龄为 356 ± 3 Ma LMP 成员。这一新的地质年代学数据表明，HW 和 LMP 成员之间存在 3.5-11 myr 的时间间隔，因此，在 Myra 组的下部和上部细分之间存在以前未被识别的不整合，并且 HW 和 LMP 成员的 VHMS 沉积物是不是同时代的，但很可能是由时间上不同的热液事件形成的。这项研究的结果，连同温哥华岛各地公布的年龄限制，为 Sicker Group 内的火山活动和 VHMS 矿床形成提供了一个修订的年代学和岩性框架。温哥华岛至少有三个古生代长英质火山事件（~ 362 Ma；~ 355 Ma；和 310-300 Ma）在 VHMS 矿化。识别 VHMS 矿床的特定年代地层间隔和岩石地层环境对于成因和矿产勘探模型很重要，并将帮助勘探者确定最有可能进行 VHMS 矿化的关键地层单元。为 Sicker Group 内的火山活动和 VHMS 矿床形成提供修订的年代学和岩性框架。温哥华岛至少有三个古生代长英质火山事件（~ 362 Ma；~ 355 Ma；和 310-300 Ma）在 VHMS 矿化。识别 VHMS 矿床的特定年代地层间隔和岩石地层环境对于成因和矿产勘探模型很重要，并将帮助勘探者确定最有可能进行 VHMS 矿化的关键地层单元。为 Sicker Group 内的火山活动和 VHMS 矿床形成提供修订的年代学和岩性框架。温哥华岛至少有三个古生代长英质火山事件（~ 362 Ma；~ 355 Ma；和 310-300 Ma）在 VHMS 矿化。识别 VHMS 矿床的特定年代地层间隔和岩石地层环境对于成因和矿产勘探模型很重要，并将帮助勘探者确定最有可能进行 VHMS 矿化的关键地层单元。