Paleomagnetic and mineral magnetic constraints on Zn-Pb ore genesis in the Pend Oreille Mine, Metaline District, Washington, USA
Paleomagnetic and mineral magnetic constraints on Zn-Pb ore genesis in the Pend Oreille Mine, Metaline District, Washington, USA
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (December 2007) 44 (12): 1661-1673
- age
- apparent polar wandering
- Cambrian
- characteristic remanent magnetization
- Cretaceous
- demagnetization
- experimental studies
- isothermal remanent magnetization
- lead ores
- lead-zinc deposits
- magnetization
- Mesozoic
- metal ores
- Metaline Limestone
- Middle Cambrian
- mineral deposits, genesis
- natural remanent magnetization
- Ordovician
- paleomagnetism
- Paleozoic
- Pend Oreille County Washington
- pole positions
- remanent magnetization
- sphalerite
- sulfides
- tailings
- thermal history
- United States
- Washington
- zinc ores
- northeastern Washington
- Metaline mining district
- Pend Oreille Mine
Zinc-lead mineralization in the Metaline mining district of northeastern Washington, USA, is hosted by the Cambrian Metaline Formation and is classified into Yellowhead-type (YO) and Josephine-type (JO) ore based on texture and mineralogy. Paleomagnetic results are reported for four Cambrian Metaline Formation sites, one Ordovician Ledbetter slate site, 12 YO and 13 JO (including two breccia sites) mineralization sites in the Pend Oreille Mine, and eight sites from the nearby Cretaceous Kaniksu granite batholith. Thermal and alternating field step demagnetization, saturation isothermal remanence analysis, and synthetic specimen tests show that the remanence in the host carbonates and Zn-Pb mineralization is carried mostly by pseudosingle (PSD) to single domain (SD) pyrrhotite and mostly by PSD to SD magnetite in the Kaniksu granite. Based on thermomagnetic measurements, sphalerite and galena concentrates and tailings from the mine's mill contain hexagonal and monoclinic pyrrhotite. The postfolding characteristic remanent magnetization (ChRM), known thermal data, and paleoarc method of dating suggest that the Zn-Pb mineralization carries a primary chemical remanent magnetization (CRM), and Metaline Formation carbonates a secondary CRM that were acquired during the Middle Jurassic (166+ or -6 Ma) during the waning stages of the Nevadan orogeny. A paleomagnetic breccia test favours a solution-collapse origin for the Josephine breccia. Finally, the Kaniksu paleopole is concordant with the North American Cretaceous reference paleopole, suggesting the Kootenay terrane has not been rotated since emplacement of the batholith at approximately 94 Ma.