Geopic of the week: Xenolith

Xenolith

Freshly exposed igneous rock at 3M quarry near Little Rock, Arkansas.  About 100 million years ago, molten rock from the earth’s hot interior was forcibly injected into the bedrock in this area.  The dark-colored rock you see at the center of the picture is what geologists call a xenolith, or accidental inclusion.  It’s basically a hunk of the bedrock that broke off and got trapped in the magma before it cooled.  The bedrock was originally shale, but the heat and fluids from the igneous rock cooked and altered the shale so it’s now a metamorphic rock called hornfels.  

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s