The Wood Lake, Ontario, H4 ordinary chondrite, a new Canadian meteorite

Abstract

The Wood Lake meteorite was found in the Muskoka region of Ontario in July 2003. We examine the mineralogy, physical properties, shock, and weathering state of this recently reported Canadian meteorite. Bulk physical properties for Wood Lake (bulk density 3.57 ± 0.10 g/cm3, grain density 3.64 ± 0.01 g/cm3, and magnetic susceptibility log χ = 5.17) are typical of slightly weathered H chondrite falls and consistent with visual observations of its observed low weathering state (W1). Reconnaissance X-ray micro computed tomography of a Wood Lake fragment yields a similar bulk density (3.56 g/cm3) and allows for a three-dimensional description of the meteorite. Petrographic and electron probe microanalysis examination of the Wood Lake meteorite reveal sharp definition of chondrule margins, occasional mesostasis chondrule glass, only minor development of recrystallized matrix feldspar, and little variation in silicate chemical compositions, indicating Wood Lake to be an H4 ordinary chondrite. Mineral chemistry for Wood Lake olivine (Fa18.6 ± 0.7, n = 26) and low-Ca pyroxene (Fs17.5 ± 2.6, n = 16) agrees well with H chondrite averages for these minerals. The bulk of the stone has undergone a low to moderate level of shock (S3), as indicated in thin section by undulose optical extinction and the presence of planar dislocations in olivine and pyroxene grains. Moderate distortion of olivine crystal structures observed using in situ micro X-ray diffraction quantifies the shock deformation as a full width half maximum (FWHMχ) of 3.38° ± 1.13° (16 reflections from seven olivine grains), consistent with shock stage S3 ordinary chondrites. Wood Lake is confirmed as a new Canadian meteorite find that likely arrived on Earth not long before it was recovered.