Typically it is found in volcanic plugs which channeled the basalt to the surface. Geochemistry and petrology of dolerite sills in the Huab 7. of diabase Ref: AGI As nouns the difference between basalt and dolerite is that basalt is (mineral) a hard mafic igneous rock of varied mineral content; volcanic in origin, it makes up much of the earth's oceanic crust while dolerite is (geology) a fine-grained basaltic rock. Diabase is the preferred name in North America, while dolerite is the preferred name in the rest of English-speaking world, where sometimes the name diabase is applied to altered dolerites and basalts. For example, Slemish in County Antrim is a dolerite plug. 0000192896 00000 n A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. There are also an area with a lot of dolerite in County Tyrone. Because extrusive rocks make contact with the atmosphere they cool quickly, so the minerals do not have time to form large crystals. Gabbro vs Diabase Information. Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. 0000004959 00000 n These are photomicrographs - very thin slices of rock, seen in plane-polarised light, or between crossed polarisers, when the colours seen are produced by interference of light. 0000004169 00000 n Earth’s outer layer is covered by rocks and these rocks have different physical and chemical properties. Greenschist contains clots and lenses of blue quartz and abundant sulfide. This coarse grain makes granite a favorite of rock climbers. 0000000956 00000 n 0000154188 00000 n 0000004441 00000 n Basalt Igneous rock Composition Mafic: plagioclase, amphibole, and pyroxene, sometimes feldspathoids, or olivine. Metabasalt - Sequence of conformably layered volcanic rocks of fine-grained to aphanitic, greenish-gray, retrogressively metamorphosed greenstone, greenschist, and basalt. 61 33 %%EOF Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphanitic chilled margins which may contain tachylite (dark mafic glass). xref Dolerite and the synonym diabase are not root names but usually defined as medium grained mafic intrusive rocks. endstream endobj 62 0 obj<>/Metadata 59 0 R/Pages 56 0 R/Type/Catalog/PageLabels 54 0 R>> endobj 63 0 obj<>/ColorSpace<>/Font<>/ProcSet[/PDF/Text/ImageB]/ExtGState<>>>/Type/Page>> endobj 64 0 obj<> endobj 65 0 obj<> endobj 66 0 obj[/ICCBased 81 0 R] endobj 67 0 obj<> endobj 68 0 obj<>stream 0000004059 00000 n It typically forms slabs and blocks and the varying crystal size and exact chemical make-up determines its roughness. Temperatures of approximately 400 to. The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. i. Diabase or Dolerite. Dolerite is an igneous rock type, similar in origin to rhyolite but with a composition closer to basalt as it contains a higher proportion of iron and magnesium, giving it a darker colouring. The Healing Properties Of Lava Stone Sivana East. Unit does not crop out and is known only from subsurface borings and artificial exposures. Though some rocks look identical, they have certain characteristics which distinguish them from others. 0000154714 00000 n Up through the thick cake of Karoo sediments it came – long after the Ecca shale through which it cuts had been deposited – to flow over the surface as sheet after sheet of lava; where it didn’t make it to the surface, it squeezed be… basalt: fine grained extrusive (cools above ground) mafic rock. Comparative testing of basalt and dolerite indicates that dolerite has better properties for road seals. Some common rock types as seen under the microscope. See more. While granite often takes the form of monoliths or boulders, basalt is often found in roughly hexago… Dolerite is an igneous rock formed below the Earth's surface, a form of basalt, containing relatively little silica (mafic in composition). Diabase, also called Dolerite, fine- to medium-grained, dark gray to black intrusive igneous rock.It is extremely hard and tough and is commonly quarried for crushed stone, under the name of trap. The grain size of diabase is on the smaller side. Some geologists … Ophitic texture (randomly oriented plagioclase laths enclosed by pyroxene grains) is a characteristic feature of … Diabase and gabbro have the same general mineral composition as basalt, but they have a larger grain size. Basalt, on the other hand, has a smooth texture from rapid cooling, usually by water. This allows for the growth of constituent minerals to the point where the groundmass crystals may be easily identified with a hand lens if not the naked eye. Dolerite is a volcanic rock. As two rocks are not same, it’s fun to compare them. 93 0 obj<>stream In the United States and Canada, the name "diabase" is used for a dark gray to black, fine-grained, intrusive igneous rock that has a composition similar to basalt and gabbro. 0000002025 00000 n An example of an aphanitic rock is basalt. 0000010426 00000 n Dolerite is related to basalt but formed at a medium level in the earths crust. Rocks under the Microscope. Basalt is identical to diabase and gabbro, but is very fine-grained. The crystals that make up dolerite are usually visible to the naked eye, but sometimes porphyritic rocks of basaltic composition with pyroxene and especially plagioclase phenocrysts are also named that way. It is like a granite, Chemistry: None. 0000154256 00000 n In the United States, a syn. 0000067292 00000 n x�b```b``1``e`�gf@ a���#B,�@e���%�|�{�H-��ǔN�r�� r˞700����3U��T��yv�qt���W���U�Jh� W��DOS��2f�C-"��O�M�b��(����'Q�T�:=���#錦�� (�d�L����n�%A�SA�t,�`�~\Adr�T�Q�,O�l�U�4�茆��-s���0� [�P;B�"H1�m�f! 0000009792 00000 n It typically forms slabs and blocks and the varying crystal size and exact chemical make-up determines its roughness. Dolerite, also called diabase, is a dark igneous rock intermediate in grain size between basalt and gabbro. Dolerite is a volcanic rock. is that rockis (uncountable) the naturally occurring aggregate of solid mineral matter that constitutes a significant part of the earth's crust or rockcan be an act of rocking or rockcan be a style of music characterized by … 4b).Furthermore, on the Nb*2–Zr/4–Y diagram (Meschede, 1986) the dolerite dykes plot in the fields of volcanic-arc basalts and N-MORB lavas (Fig. The grain size of diabase is on the smaller side. You can also know more about Gabbro and Diabase Reserves. Granite is an intrusive rock that is formed when magma cools inside the crust. diabase: fine grained intrusive cools below ground) mafic rock. 0 is that rockis (geology) any natural material with a distinctive composition of minerals while doleriteis (geology) a fine-grained basaltic rock. A ��k ���u 0000013186 00000 n Dolerite 1. 0000010538 00000 n It normally occurs as{*filter*}s or sills intruding other rocks. 0000008848 00000 n 0000474100 00000 n 0000490152 00000 n Dolerite features and hazards • Introduction • Mineralogy • Textures • Classification of dolerite • Dolerite dyke • Formation of dolerite • Distribution • Uses • Conclusion 2. It can include microgabbro, basalt, andesite, microdiorite and other rock types. Uses: None. However, not REPORT 1991f22 0000001489 00000 n Diabase is actually a variety of gabbro which consists mainly of labradorite feldspar, augite, magnetite, and olivine. In all these occurrences they are associated with, and pass into, the denser forms of basalt. While similar to basalt, it contains crystals which can be seen with a hand lens.This indicates that it cooled a little more slowly than basalt. 0000001605 00000 n MaryAnn McGarry. H�\�͊�@��WQ��Ecb�s� ���&3`��&*�,r�S_��&���>H���n�w�˿OCs��;u};��p������ٲpm��g���R�YZ{�_�x���!�*��H׮�twO�v8��,�6�q���{��=�?���-�j��x���z�Z_���^�m��������?�ct��|IK3��:�M����j�>+W���*�}���ׂˎ��w=eU���tH�lE��_�%�D��k�Ao�[�C��������@{�G[�tz8�� �M��������{�=�~O�������6�M`�6�M`�6�M`�6�M`�6�M`�6�M`��a�l��V0[�l�U�~�_�W�~�_�W�~�_�W�~�_�W�~�_�Wz��`0��`0��`0��`0��`0� 34��0C� 34��0C��`�a���@�?������@�?������@���s��������w)��w�М���ñ���}�/�m������{ 0000008573 00000 n Dolerite definition, a coarse-grained variety of basalt. Being intruded into country rocks at shallow levels, the magma has more time to cool than if extruded. v�����8�.��7�+� �-� 61 0 obj <> endobj intrudes a type-3 dolerite sill and an early basalt flow of the Etendeka Formation. Prices / Quote. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphanitic chilled margins which may contain tachylite(dark mafic glass). Gabbro is an intrusive igneous rock which is chemically equivalent to plutonic Basalt. Greenschist is a generally used field petrologic term applied to metamorphic or altered basic volcanic rocks like basalt, but also includes dolerite diabase as well. This indicates that it cooled a little more slowly than basalt. While similar to basalt, it contains crystals which can be seen with a hand lens. 4c). Dolerite is a medium-grained (hypabyssal) basalt and forms in shallow intrusions, such as dykes, which cut across the rock strata, and sills, which push between beds of sedimentary rock. When basalt is broken, it leaves very sharp edges. ��u 0��\C3�,F��4 @A���d@�� )fc�k(T These are small vesicles, only a millimeter or so across. Basalt is from a melt that cooled very rapidly- in other words, on the surface of the earth or in the ocean. Diabase is composed of plagioclase feldspar (mostly labradorite) and pyroxene ( augite ). Consisting of plagioclase feldspar and pyroxene, it is a widespread intrusive rock, quarried for crushed and monumental stone (known as "black granite"). It usually occurs as dykes, plugs or sills. 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