GABBRO - Intrusive igneous, plutonic to hypabyssal. Close up of the same grain showing 56 and 124 degree cleavages. Prepare a labelled sketch of each selected thin section, being sure to label the sketch with magnification and either CN or PP. In thin section the rock contains strongly cleaved and zoned pyroxene, olivine grains exhibiting cracking and alteration to a combination of chlorite and ilmenite, and bytownite (a calcic plagioclase), which gives the rock its name. This is a thin section of a Diorite, collected from near the Ben Cruachan Dam, (called the Quarry Intrusion) near Loch Awe in Argyll. This is an alkaline olivine gabbro. More research into this rock has suggested it is more accuratly a 'olivine ferromonzodiorite' Take your pick. Photomicrograph of thin section showing large deformed Plagioclase phenocryst embedded in finer matrix of ferromagnesian minerals in gabbro (Haldar and Tišljar, 2014). It can be produced through the metamorphism of mafic igneous rocks such as basalt and gabbro, or from the metamorphism of clay-rich sedimentary rocks such as marl or graywacke.

So, light travels through them in different ways and with different velocities, depending on the direction of travel through a grain. Gabbro near patches is composed of actinolite, hornblende, labradorite, and composite ilmenite–magnetite grains, with minor epidote, albite, quartz, and chlorite. When minerals, rocks, and fossils cannot be accurately identified by macroscopic observation and testing, thin section slides can reveal the composition and structure of the specimens on a microscopic level.Rock specimens are useful for studying textures, grain sizes, and other features altered by pressure, temperature, and other natural forces. This is a good standard for a Diorite, and contains predominantly plagioclase feldspar, An. Available in a range of colours and styles for men, women, and everyone. Orthopyroxene high in Mg is common in gabbro and peridotite groups. Identify the major minerals, and write a concise description of … Norite may be essentially indistinguishable from gabbro without thin section study under the petrographic microscope. Olivine is recognised here by its irregular shaped crystals, with randomly oriented fractures. descriptions of petrographic thin sections of rock samples recovered during ALVIN dives Author: Frieda L Malcolm (scanned and assembled to pdf by William Kidd) Subject: appendix 2 of MS thesis (1979), SUNY Albany Created Date: 3/12/2014 4:53:43 PM The rock is comprised predominately of plagioclase feldspar and pyroxene ( clinopyroxene ) however minor amounts of amphibole and olivine may be present. A gabbro landscape on the main ridge of the Cuillin, Isle of Skye, Scotland. Gabbro is a coarse-grained and usually dark-colored igneous rock.It is an intrusive rock. The island was a volcano, and has been deeply eroded, more deeply than the other volcanoes in the province. See also GCR vol17 chapter 3. The primary magmatic minerals include plagioclase, olivine, augite, biotite, and late brown hornblende. A thin interval of Fe-Ti oxide-rich gabbro (interval 126) is present in Section 179-1105A-27R-1 (139.12-139.56 mbsf). 21.11.2016 - This Pin was discovered by Miloš Gregor. Rocks under the Microscope. Gabbro thin section exhibiting some of the textbook features one would expect from this coarse, mafic igneous rock. This island is part of the Paleogene volcanic province active just before the opening of the Atlantic about 60 million years ago. Gabbro from Huntly, Scotland.