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Gabbro specimen Photomicrograph of a thin section of gabbro. Gabbro (/ ˈ ɡ æ b r oʊ / GAB-roh) is a phaneritic (coarse-grained and magnesium- and iron-rich), mafic intrusive igneous rock formed from the slow cooling magma into a holocrystalline mass deep beneath the Earth's surface.
The complex is mainly composed of gabbro and syenite and is of the Silurian-Devonian age. [1] The Concord Gabbro-Syenite Complex is a part of a larger suite of twenty plutons that form a chain extending almost 500 km, which lie within the Charlotte Metamorphic belt. [2]
Diabase (/ ˈ d aɪ. ə ˌ b eɪ s /), also called dolerite (/ ˈ d ɒ l. ə ˌ r aɪ t /) or microgabbro, [1] is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grained to aphanitic chilled margins which may ...
The Sandy Group Gabbro is a member of the Roosevelt Gabbros that forms blobby irregular sills which are like small plutons. These intrusive blobs are internally differentiated, with the composition becoming increasingly more felsic upwards approaching the overlying Mount Scott Granite.
The Famrinto Gabbro has two gabbronorites that are slightly different in mineralogy and texture. [1] One rock type is a olivine, pyroxene, hornblende while the other has clinopyroxene, olivine, and plagioclase gabbronorite with cumulus texture. [1] The hornblende gabbronorite is a dark grey to grey-green with a fine to medium grained texture. [5]
Baltimore Gabbro Complex is a hypersthene gabbro with subordinate amounts of olivine gabbro, norite, anorthositic gabbro, and pyroxenite. Igneous minerals and textures are well preserved in some rocks, and other rocks exhibit varying degrees of alteration and recrystallization with a new metamorphic mineral assemblage.
Examples of phaneritic igneous rocks are gabbro, diorite, and granite. Porphyritic textures develop when conditions during the cooling of magma change relatively quickly. The earlier formed minerals will have formed slowly and remain as large crystals, whereas, sudden cooling causes the rapid crystallization of the remainder of the melt into a ...
The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...