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������{ It is like a granite, of diabase Ref: AGI 0000004169 00000 n 0000008573 00000 n 0000010538 00000 n The results are considered to be representative of the general quality of dolerite currently quarried. 0000474100 00000 n 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). 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. Ophitic texture (randomly oriented plagioclase laths enclosed by pyroxene grains) is a characteristic feature of … This basalt sample is so full of vesicles that it is more hole than basalt. Because it cools quickly, basalt is often found in formations where granite is not. 0000003118 00000 n Diabase or dolerite or microgabbro is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. 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. An example of an aphanitic rock is basalt. The greenish brown crystals are olivine. H�\��j�0F���l/�{4J��N��6�pl%k��Fq.����_��#��{T4��>�-~��;�ٞ�اpo���C4���C7i�g��9�lWv��}8����N��K�������0ߟr̿��)�ry^ӥ�p��.�6���W����-_[b�ߺlv. 0000192896 00000 n 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. basalt: fine grained extrusive (cools above ground) mafic rock. Dolerite has better polished stone values and skid resistance properties. 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. Huge collection, amazing choice, 100+ million high quality, affordable RF and RM images. Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. 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. Comparative testing of basalt and dolerite indicates that dolerite has better properties for road seals. Dolerite features and hazards Basalt Igneous rock Composition Mafic: plagioclase, amphibole, and pyroxene, sometimes feldspathoids, or olivine. Basalt is from a melt that cooled very rapidly- in other words, on the surface of the earth or in the ocean. endstream endobj 69 0 obj<> endobj 70 0 obj<> endobj 71 0 obj<>stream For example, Slemish in County Antrim is a dolerite plug. It typically forms slabs and blocks and the varying crystal size and exact chemical make-up determines its roughness. 4c). Dolerite is a volcanic rock. There are also an area with a lot of dolerite in County Tyrone. 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). This slow cooling gives time for crystals to grow, making it more coarsely grained than an extrusive rock. Metabasalt - Sequence of conformably layered volcanic rocks of fine-grained to aphanitic, greenish-gray, retrogressively metamorphosed greenstone, greenschist, and basalt. 0000010426 00000 n 61 33 However, not REPORT 1991f22 0000000956 00000 n 0000153923 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! You can also know more about Gabbro and Diabase Reserves. Dolerite is a volcanic rock. 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. 0000004441 00000 n 0000001605 00000 n 0000004059 00000 n Basalt is a mafic extrusive igneous rock formed from the rapid cooling of lava rich in magnesium and iron exposed at or very near the surface of a terrestrial planet or a moon. startxref It normally occurs as{*filter*}s or sills intruding other rocks. It is amazing to me how much dissolved water and gas a molten rock can hold. ��:�‚��p�� Lh��� VJ8^���AăH��"X�0� �.040,`|�0ˁi���+��7�81�:0O ��t`L`U�5Q�0�9�����`�b����� 0��10�`g�W�ŵ���tp�bp b� However, on the logarithmic Zr/TiO 2 *10 −4 vs. Nd/Y diagram (Winchester and Floyd, 1977) the dolerite dykes have an apparent sub-alkaline basalt composition (Fig. These are small vesicles, only a millimeter or so across. 0000013186 00000 n The grain size of diabase is on the smaller side. xref i. 0000000016 00000 n 0000004959 00000 n 0000001489 00000 n Diabase and gabbro have the same general mineral composition as basalt, but they have a larger grain size. • Introduction • Mineralogy • Textures • Classification of dolerite • Dolerite dyke • Formation of dolerite • Distribution • Uses • Conclusion 2. 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. While similar to basalt, it contains crystals which can be seen with a hand lens. • A dolerite is the medium-grained equivalent of a basalt - a basic rock dominated by plagioclase and pyroxene. As nouns the difference between rockand dolerite. 0000003418 00000 n %PDF-1.4 %���� Basalt, on the other hand, has a smooth texture from rapid cooling, usually by water. Characteristics of rocks include texture, appearance, color, fracture, streak, hardness etc. 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. MaryAnn McGarry. Gabbro vs Diabase Information. 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… The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. While granite often takes the form of monoliths or boulders, basalt is often found in roughly hexago… Typically it is found in volcanic plugs which channeled the basalt to the surface. 0000490152 00000 n Y�B�n��e`� Basalt is identical to diabase and gabbro, but is very fine-grained. Granite is an intrusive rock that is formed when magma cools inside the crust. 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. 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