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Comments on Gigapan: Anorthosite Roadcut (Wide)

Gigapan Comments (2)

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  1. Ron Schott

    Ron Schott (September 10, 2011, 10:30AM )

    Anorthosite is a specialized member of the gabbro family, and I wouldn't be too surprised to find that in some situations it may even be marketed as granite. It's certainly not rare in the Adirondacks (holding up the High Peaks region), or in the Saint Lawrence Valley - Labrador region of Canada, but globally it isn't that common a rock type. What's even more interesting is that massif-type anorthosites common in these areas are remarkably restricted in occurrence in the geologic time scale. Most massif-type anorthosites around the world were emplaced during the mid- to late-Proterozoic. They are much rarer outside this relatively narrow slice of geologic time.

  2. Chris Fastie

    Chris Fastie (September 10, 2011, 04:26AM )

    Poor anorthosite. Everybody has heard of granite, and many know that it forms when magma cools deep underground. Some also know that diorite and gabbro form the same way. But NOBODY has ever heard of anorthosite which is also a plutonic rock. Is that because it is rare, or because it makes a lousy building material, or is there a big conspiracy to keep it quiet?