Yellow Dog peridotite - clinopyroxene interstitial to olivine

Click on image to enlarge.          Photo © Daniel R. Snyder

The dark areas are olivine (partially serpentinized with stringers of magnetite), the magenta and violet shapes are clinopyroxene, and a few gray plagioclase laths show at the upper left. There appear to be several varieties of pyroxene in the Yellow Dog peridotite. One of the most noticeable is anhedral clinopyroxene occupying the interstices between fractured olivine crystals, as in this image. Apparently the pyroxene was the last major mineral to solidify from the melt (In his M.S. thesis, Morris (1977)* refers to these occurrences in the Yellow Dog peridotite as poikilitic texture). Also notice the dark rims around the olivine crystals, and the smooth interface between olivine and pyroxene, suggesting a reaction between the early-crystallizing olivine and the melt.  XPL. Imaged area 2.7 mm x 4 mm.

In the PPL enlargement (below) of the right center of the XPL image, the dark rims around the olivine appear to contain an iron-rich alteration product. The olivine fragments remaining in the core of the crystal are transparent in PPL. Imaged area of enlargement 1.3 mm x 2 mm.

Click on image to enlarge.          Photo © Daniel R. Snyder

Marquette County, northern Michigan.

*Morris, William J., (1977) Geochemistry and Origin of the Yellow Dog Plains Peridotite, Marquette County, Northern Michigan, unpublished master's thesis, Michigan state University.