Petrology Lecture 2 Classification and Nomenclature of Igneous Rocks GLY 4310 - Spring, 2019 1 Igneous Textures Phaneritic: Crystals are readily visible with the unaided eye.
Aphanitic: Crystals, if present, are too small to be seen with the unaided eye. Fragmental: Composed of pieces of pre-existing, mostly igneous, rock, crystal fragments, and/or glass. These pieces were deposited and later amalgamated into a rock. 2 Porphyritic Size Distribution
Porphyritic - bimodal size distribution, with large grains surrounded by numerous small grains or glass Phenocrysts - Large crystals formed by relatively slow cooling below the earths surface Groundmass - Small crystals or glass, formed by more rapid cooling 3
Composition Felsic: Rocks composed primarily of silica-rich minerals, generally feldspars and silica, from which the term is derived. Common minerals include plagioclase feldspar, alkali feldspar, quartz, and muscovite. The term can be used to modify either a mineral or a rock name. Mafic: Rocks rich in magnesium and iron, and
hence with lower silica contents. Common minerals include olivine, pyroxene, hornblende or other amphiboles, and biotite. The term can be used to modify either a mineral or a rock name. 4 Types of Minerals Essential Minerals which must be present in order for a rock to be classified with a
certain name Accessory Minerals need not be present in a rock, but which may be present in small amounts 5 Chemical Composition Classification
16 Aphanetic Rocks In principle, we follow the same steps for volcanic rocks as we do for intrusive rocks However, the nature of the aphanitic rocks makes determination of the mode difficult, especially in hand specimen
Even in thin section, groundmass material may be too small to recognize, or may be amorphous Phenotypes based on phenocrysts only 17 P Apex Classification Again, rocks near the P apex are troublesome. Andesite may be defined as a plagioclase-rich
rock with SiO2 > 52%, or a color index < 35% Basalt has SiO2 < 52%, or a color index > 35%. 18 IUGS Classification Chemical classification of volcanic rocks 19
Problems with Pyroclastics These rocks present special problems, because they often contain significant impurities (material blasted out by the eruption, or caught in the general updraft) In principle, they can be classified on the basis of a chemical analysis, but the presence of significant impurities argues
against this approach 20 IUGS Classification Pyroclastic rocks Based on type of fragmental material
21 IUGS Classification Pyroclastic rocks Based on fragment size Ash < 2mm Lapilli 2-64 mm
Blocks or bombs >64 mm 22 Web Resource The preceding was a very short outline of igneous rock classification for those students wanting more information, the following is a good
resource: http://www.sepmstrata.org/page.aspx?pageid=593 Includes flow charts designed to aid in igneous rock classification 23
He is the driving force behind magnetic storm research in Canada and works extensively with the Canadian Space Agency. Keramat Ali (UofL) new approaches in dynamics, classical and quantum, to broaden the efficiency & scope of artificial recurrent neural networks....
"Today class, we are going to . take steps . to understanding figurative language " Which sentence identifies what I really mean? A B. We are going to take the steps, like the ones we use to go to lunch,...
Midterm Review Midterm Review (closed book) Phonetics Be able to provide the descriptive terms for both English consonants and vowels (voicing, place of articulation, manner of articulation for Cs - height, backness, rounding, tenseness for Vs)
The Department of Mental Health has been working with MO HealthNet to amend the Medicaid state plan to create the opportunity for CMHCs to be designated as Healthcare Homes for individuals with behavioral health problems, and we appear to be...
Rupert Murdoch, 2006 Overview Confusing technology and media Digital idiocy and Media Studies 2.0 Critical concepts and social media The case of 'fake news' The limits of media literacy Technology or media?
Definition. A "near miss" is an unplanned event that did not result in injury, illness, or damage - but had the potential to do so.. Sometimes called a "near hit" or "close call" - signals a system weakness that, if...