#diabase

Bit of a headscratcher today. When a pyroxene and a pyroxene love each other very much...?

The Karoo LIP: The Destroyer of Gondwana About 500 million years ago, a huge continent was assembled due to collisions between multiple ancient cratons, or cores of continents. This supercontinent, Gondwana (Gondwanaland) contained what we know today as Africa, South America, The Arabian Peninsula, India, Antarctica, Australia, and New Zealand – give or take that’s something like ½ of the planet’s continental landmass. That large continent held together for nearly 400 million years, and was even joined with a few other large landmasses for a time to create Pangaea. It lasted for about 10% of Earth’s history, and here you’re looking at the leftovers of its killer.

Piet van Stuivenberg (Dutch, 1901-1988)

Mother and Child - 33cm high - granite

Mother and Daughter - diabase - 1958

Mother and Child - diabase

title unknown - carrara marble - 32cm high

title unknown - travertine - 38cm high - 1955

title unknown - carrara marble - 40cm high (sans base)

Head - granite - 37cm high - 1961

Grey

Cradle Mountain

This fog-shrouded peak is Cradle Mountain on the island of Tasmania. Although the peak is not the highest on the island at an elevation of 1545 meters above sea level, it is one of the island’s most popular tourist locations in part from the spectacular columnar features that define the mountain’s shape.

Tasmania contains one of the world’s largest outcrops of dolerite, a type of igneous rock related to basalt. Dolerite, also called diabase, forms when basaltic lava gets close to Earth’s surface but doesn’t quite erupt. Dolerite is defined by an “intermediate” grain size – it doesn’t stay hot long enough to form large crystals as in a gabbro, but it doesn’t erupt on the surface where it would cool extremely fast to make a fine-grained basalt. The spectacular vertical columns form perpendicular to the cooling direction due to thermal contracting; the rocks shrink as they cool down, causing fractures to form.

These basalts were produced during the Jurassic, as the large continent Gondwana broke apart, with Australia rifting away from Africa and the other pieces. Tasmania has a long history of rifting, having both spread away from Gondwana during the Jurassic and from Australia itself more recently, leading to an island with large outcrops of igneous rocks.

-JBB

Image credit: https://flic.kr/p/7ht28V