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You are browsing the archive for igneous Archives - Page 3 of 12 - Mountain Beltway.

11 January 2017

More Messengers from the Mantle

Since I showed off the 3D kimberlite intrusion breccias yesterday, I feel as if I owe you some other photos from that lovely exhibit at the IGC. I apologize for the poor quality of these photos – the gorgeous samples were behind glass and brightly lit, which made photography difficult. But the rocks are sooooooooo pretty, I think you’ll enjoy viewing them just the same. Let’s start with a gargantuan …

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10 January 2017

Two kimberlite intrusion samples presented in 3D model format

While in Cape Town for the 35th meeting of the International Geological Congress in August/September, I was delighted at the “Messengers from the Mantle: Craton Roots and Diamonds” exhibit on kimberlites. It was a world-class collection of excellent specimens that traveled to the Congress from across the city at the University of Cape Town. I took some photos of two specimens to make 3D models from, and my student Marissa …

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22 December 2016

Dikes at Bunnahabhain

Yesterday I blogged the stromatolites to be seen in northeastern Islay, south along the shore from the distillery at Bunnahabhain. The sharp-eyed among you may have noticed that in this GigaPan, there’s more going on than merely Neoproterozoic carbonates: Link 1.46 Gpx GigaPan by Callan Bentley There’s also a prominent dolerite dike, weathering out recessively. A photo, centered on the GigaPanned dike: This is but one of several to be …

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29 October 2016

New digital media of Shenandoah National Park feeder dikes

In Shenandoah National Park, astride Virginia’s Blue Ridge, feeder dikes of Catoctin Formation (meta-)basalt cut across the Grenvillian-aged granitoid basement. Due to their mafic composition and columnar jointing, these feeder dikes generally weather more rapidly than their host rocks. I led a field trip in the park on Thursday for my son’s school, and my student Marissa was there the weekend prior, checking out the autumn leaves and geology with …

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24 October 2016

GIGAmacro views of komatiite

Erik Klemetti posted today at Eruptions about komatiite, which is apropos, considering I just finished imaging some samples of that ultramafic volcanic rock. Have a look at three samples from Barberton Greenstone Belt here, each from the 3.27 Ga Weltevreden Formation: Link GigaPan by Callan Bentley Link GigaPan by Callan Bentley Link GigaPan by Callan Bentley And, while we’re at it, here’s one from the Red Lake Greenstone Belt (~3.0 …

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11 October 2016

A virtual field trip to Portrush, Northern Ireland

One of my favorite places in Northern Ireland is the east side of the peninsula that hosts the tourist town of Portrush. There, two early schools of geological thought engaged in a battle. The opposing sides were: the Neptunists, who thought all stratified rocks, and in particular basalt, must form from precipitation from the sea, and the Plutonists, who thought some rocks, including basalt, formed through intrusion of molten rock …

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10 October 2016

Oddball Icelandic rocks, part II: granite!?!?

Silly Iceland! Don’t you know you’re not a continent?

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6 October 2016

Oddball Icelandic rocks, part I: A green ignimbrite

Iceland does basalt really, really well. But there are a few non-basaltic igneous rocks to be found there, too. One of them is a green ignimbrite (pyroclastic conglomerate) that crops out in coastal Berufjörður, eastern Iceland. Check it out!

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3 September 2016

Viewing the Sea Point migmatite through the lens of GigaPan

It was five years ago when I first visited Sea Point, the outcrop on the coast of the Cape Peninsula where the Cape Granite (~540 Ma) intrudes the (meta-)sedimentary rocks of the Malmesbury Group. The outcrop is (a) beautiful and evocative, and (b) of historical importance, as Charles Darwin visited it while on the voyage of the Beagle, contemplating and confirming Lyell’s assertions of the validity of plutonism as he …

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21 June 2016

Porphyritic rhyolite dike seen on the beach at Cushendun

At the opposite end of the beach at Cushendun, Northern Ireland, we found some outcrops of schist – I’ll be featuring some of them as Friday folds later this week. But cutting across the schist was a pink porphyry, with big well-formed potassium feldspars. I splashed some water from the Irish Sea onto it to increase the contrast: Here’s a handheld GigaPan image, so you can explore it for yourself. …

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