Diabase

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Diabase
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Diabase (/ˈdaɪ.əˌbeɪs/), also called dolerite (/ˈdɒl.əˌraɪt/) or microgabbro,[1] is a

aphanitic chilled margins which may contain tachylite
(dark mafic glass).

Diabase is the preferred name in North America, while dolerite is the preferred name in the rest of the English-speaking world, where sometimes the name diabase refers to altered dolerites and basalts. Some geologists prefer to avoid confusion by using the name microgabbro.

The name diabase comes from the French diabase, and ultimately from the Greek διάβασις – meaning "act of crossing over, transition".[2]

Petrography

Fair Head, Northern Ireland

Diabase normally has a fine but visible

serpentine, chlorite, and calcite. The texture is termed diabasic and is typical of diabases. This diabasic texture is also termed interstitial.[4] The feldspar is high in anorthite (as opposed to albite), the calcium endmember of the plagioclase anorthite-albite solid solution series, most commonly labradorite
.

Locations

A diabase dike crosscutting horizontal limestone beds in Arizona
Diabase boulders at Devil's Den on the Gettysburg Battlefield, Pennsylvania, US
Quiver trees near Keetmanshoop
(Namibia)
Dolerite forms tall vertical columns throughout Tasmania. These columns form steep vertical features through its alpine areas.

Diabase is usually found in smaller, relatively shallow intrusive bodies such as

volcanic
center.

The

Guéra Massif of Chad in Central Africa.[6]

In the Death Valley region of California, Precambrian diabase intrusions metamorphosed pre-existing dolomite into economically important talc deposits.[7]

In the Thuringian-Franconian-Vogtland Slate Mountains of central Germany the diabase is entirely of Devonian age.[8] They form typical domed landscapes, especially in the Vogtland. One geotourist attraction is the Steinerne Rose near Saalburg, a natural monument, whose present shape is due to the typical weathering of lava pillows.

Gondwanaland and Australia

A

Aboriginal name for Elcho Island, occurs on the Gove Peninsula and continues under the Arafura Sea and on Wessel Islands, including Elcho and Milingimbi Islands.[11]

In the Yilgarn Craton of Western Australia, a Proterozoic 200-kilometre (120 mi) long dolerite dike, the Norseman-Wiluna greenstone belt[12] is associated with the non-alluvial gold mining area between Norseman and Kalgoorlie, which includes the largest gold mine in Australia,[13] the Super Pit gold mine. West of the Norseman–Wiluna Belt is the Yalgoo-Singleton greenstone belt, where complex dolerite dike swarms obscure the volcaniclastic sediments.[14] Large dolerite sills such as the Golden Mile Dolerite can exhibit coarse-grained texture, and show a large diversity in petrography and geochemistry across the width of the sill.[15]

The vast areas of mafic volcanism/plutonism associated with the Jurassic breakup of the Gondwana supercontinent in the Southern Hemisphere include many large diabase/dolerite sills and dike swarms. These include the Karoo dolerites of South Africa, the Ferrar Dolerites of Antarctica, and the largest of these, the most extensive of all dolerite formations worldwide, are found in Tasmania. Here, the volume of magma which intruded into a thin veneer of Permian and Triassic rocks from multiple feeder sites, over a period of perhaps a million years, may have exceeded 40,000 cubic kilometres.[16] In Tasmania, dolerite dominates much of the landscape, particularly alpine areas, with many examples of columnar jointing.

roadstone and other building materials has been an important activity there for over 180 years.[18][19]

Use

Diabase is crushed and used as a construction aggregate for road beds, buildings, railroad beds (rail ballast), and within dams and levees.[20][21]

Diabase can be cut for use as headstones and memorials; the base of the Marine Corps War Memorial is made of black diabase "granite" (a commercial term, not actual granite). Diabase can also be cut for use as ornamental stone for countertops, facing stone on buildings, and paving.[21] A form of dolerite, known as bluestone, is one of the materials used in the construction of Stonehenge.[22]

Diabase also serves as local building stone. In Tasmania, where it is one of the most common rocks found,[23] it is used for building, for landscaping and to erect dry-stone farm walls. In northern County Down, Northern Ireland, "dolerite" is used in buildings such as Mount Stewart together with Scrabo Sandstone as both are quarried at Scrabo Hill.

Balls of diabase were used by the ancient Egyptians as pounding tools for working softer (but still hard) stones.[24]

See also

References

  1. ^ "BGS Rock Classification Scheme - Dolerite (Synonymous with Microgabbro)". British Geological Survey. Retrieved 24 August 2015.
  2. ^ "diabase". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ISBN 0-471-80580-7
  4. ^ Morehouse, W. W. (1959) The Study of Rocks in Thin Section, Harper & Row, p. 160
  5. ^ Continental Flood Basalts (and Layered Intrusions)
  6. ISSN 2391-5447
    .
  7. ^ Miller, MB, and Wright, LA. 2007, "Geology of Death Valley National Park (Third Edition)", Kendall Hunt Publishing, p 19.
  8. ISBN 3-8274-1586-1
    .
  9. ^ Ranford, Cath; Melville, Paul; Bentley, Craig (August 2008). "Wellington Range Project Northern Territory EL 5893 Relinquishment Report" (PDF). Report No.: WR08-02. Cameco Australia Pty Lt. Retrieved 5 Oct 2020.
  10. ^ "Definition card for: Oenpelli Dolerite". Australian Stratigraphic Units Database. Australian Government. Geoscience Australia. Retrieved 5 October 2020. Text was copied from this source, which is available under a Attribution 3.0 Australia (CC BY 3.0 AU) licence.
  11. ^ "Definition card for: Galiwinku Dolerite". Australian Stratigraphic Units Database. Australian Government. Geoscience Australia. Retrieved 5 October 2020. Text was copied from this source, which is available under a Attribution 3.0 Australia (CC BY 3.0 AU) licence.
  12. ISBN 0-909869-55-3
  13. S2CID 140677224
    .
  14. doi:10.1080/08120099808728413
    .
  15. ^ Travis, G.A.; Woodall, R.; Bartram, G.D. (1971), "The Geology of the Kalgoorlie Goldfield", in Glover, J.E. (ed.), Symposium on Archaean Rocks, Geological Society of Australia (Special Publication 3), pp. 175–190
  16. ISBN 0-9581199-0-2
    p. 117.
  17. ^ Jones, I., and Verdel, C. (2015). Basalt distribution and volume estimates of Cenozoic volcanism in the Bowen Basin region of eastern Australia: Implications for a waning mantle plume. Australian Journal of Earth Sciences, 62(2), 255–263.
  18. ISBN 978-0-521-38083-6
    .
  19. ^ Wilshire, H.G. (1967) The Prospect Alkaline Diabase-Picrite Intrusion New South Wales, Australia. Journal of Petrology 8(1) pp.97-163.
  20. ^ Allen, George (Spring 2004). "Clayton Quarry". Mount Diablo Interpretive Association. Archived from the original on 2017-11-16. Retrieved 2017-03-30.
  21. ^ a b "Diabase Rock". comparerocks.com. Archived from the original on 2017-03-31. Retrieved 2017-03-30.
  22. ^ John, Brian S.; Jackson Jr., Lionel E. (31 December 2008). "Stonehenge's Mysterious Stones". Earth magazine. American Geosciences Institute. Retrieved 8 November 2019.
  23. ^ "Tasmanian Viticultural Soils and Geology" (PDF). Tasmania Department of Primary Industries, Water and Environment / University of Tasmania / Tasmanian Institute of Agricultural Research. Retrieved 8 November 2019.
  24. S2CID 127942498
    . Dolerite pounders are hand-held stone tools that were widely used in Egypt from the third to late first millennium BCE for quarrying and dressing granite and other hard rocks.

External links

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