Talk:Petrology/Archive 1

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Archive 1

Lithology & Petrography

It is completely useless to link the word lithology to this article without any explanation. As someone who came without any idea what the word means trying to find out, this article does nothing. —The preceding unsigned comment was added by 168.216.125.251 (talk • contribs) 17:21, November 28, 2005 (UTC)

I agree, some reference to lithology should be made. Tnek46 01:51, 10 October 2006 (UTC)

well i don't think it is right--168.216.125.251

You are correct. Lithology is a term I saw in later 20th Century map legends only, where one describes the 'lithological' properties that help the geologist identify a geological formation in the field. I thought it obsolete. Petrography is the proper description of all kinds of rocks, sedimentary, metamorphic, & igneous: it is not limited to microscopic properties. Petrography is a subdivision of petrology, necessary before studying a rock's origin. Below I offer an illustration of this. Geologist (talk) 06:07, 7 December 2008 (UTC)

What is Petrology?

This page has like no info!!! —The preceding unsigned comment was added by 66.66.170.22 (talk • contribs) 00:01, 5 June 2006 (UTC)

Well, little. It was just begun, apparently by a petroleum geologist.

Petrology is divided artificially into sediments (the subject of sedimentology), sedimentary rocks, metamorphic rocks, and igneous rocks. Here is an imaginary cycle that might help the beginning student. You can study actual, local geological history as deviations from it. Because it is cyclic, heat & work (energy) sum to zero, and the (specific) net heat released is a measure if its efficiency. These latter statements are quite a surprise.

Granite (along alpine mountains, following a convergent crustal margin), is eroded & weathered. It makes its way to the ocean: sand on the shelf, silt & clay farther out on the continental ridge. As this ridge is buried, it become a mudstone, then indurated (hardened) mudstone. (Breathe on it, and you can smell clay; taste it and your tongue will stick.) Sandstone is on the shelf.

Buried deeper, chemical reactions and pressure differences force larger chemical substances (H2O, SiO2, & K2O) upward, usually in dykes. When the above smell & taste tests fail, clays have become converted to microscopic, Si-rich micas (sericite) in phyllite. Deeper, the visible, white & dark micas (muscovite & biotite) form microscopically, sometimes foliated; though not especially parallel to the plane of deposition (as preserved in shale's foliation or mudstone's color banding). Buried deeper, the micas grow to visible size in foliated schists.

Deeper, the K-rich feldspar becomes more Na-rich in the feldspar plagioclase, and the K- and H2O-rich micas become less rich in the dark amphibole hornblende, within banded gneisses. It is here the dykes become not milky (water-rich) quartz, but rich in K-rich orthoclase and K- & H20-rich micas: granitic. Metamorphism, by definition, began at an arbitrary stage during the early reactions (sometimes when a zeolite disappears). Igneous activity, more naturally, begins when fluids cause bodies of rock to move. Dark basalts, not part of this cycle, are igneous rocks thought to have arisen from not the crust, but the deeper, upper-mantle of the Earth.

The depth of amphibolites is the nursery for granite and other plutons, which may remain stationary (metamorphic, showing ghost banding), or rise, as a teaspoon of light-oil rises through molasses. Fluid-rich plutons may shatter rocks in their paths, creating soaked regions of ore deposits; or rise to the surface, creating volcanoes. Surfaces raised may erode into alpine mountains, following a convergent crustal margin, the minerals weather, and the process starts anew.

This picture is a simple image that unites sedimentary, metamorphic, & igneous petrology. One can see that petrology, the science of rocks' origins, draws upon both chemistry & physics (particularly, and the mechanics of solids and liquids; and even, more recently, ballistics). Geologist (talk) 06:07, 7 December 2008 (UTC)

Massive stub

Well, now it's a stub with really deep roots. I'll add the images when I finish chopping them up. I made only minor changes to the text from 1911 although I saw quite a few things that need updating, so it's easy to find something to improve. (SEWilco 08:59, 24 December 2006 (UTC))

I cut the massive 1911 text dump and created User:Vsmith/1911 Petrology as a working copy. Most of this would go in various petrologic subtopics rather than the general article. Please don't just dump stuff into the article for something to improve - rather add copy as it is improved/updated. Vsmith 16:14, 24 December 2006 (UTC)

The 1911 text seems to have a lot of info not here now, and there are a number of articles with text from the same source. Should the 1911 notice be at the top of the page to better advise readers? User:Vsmith page reinserted in article. (SEWilco 17:41, 24 December 2006 (UTC))

I have removed the 1911 stuff again. Much of it was duplicated (or more?) by recent edits. The information is available (see above) - please add only relevant and non-obsolete material to the article. Much has transpired in the field of petrology in the past 90+ years and the 1911 bit is more than a little dated. The added material made the page excessively looong (see WP:SIZE) especially when duplicated as it was. Again the article is for reading - information for editors should not be included on the page itself - and the 1911 stuff was presented for editorial use (as such it is still available). Please keep the article concise, readable and up to date. Much better sources exist in the form of modern petrology texts - of course that means real writing, summarizing and editing - much easier to just copy/paste some antiquated out of copyright text. Vsmith 02:42, 25 December 2006 (UTC)

Sorry, boys and girls, Vsmith has decreed you can't use all sources. You'll have to craft your own cathedrals instead of sharing all that is available. (SEWilco 03:56, 25 December 2006 (UTC))

Editors: note that some of the outdated material may have information which would be useful for a "History of the field" section. I have a 1771 source which seems to not mention petrology but does have a lot of mineral study classified as part of "Chemistry". (SEWilco 17:41, 24 December 2006 (UTC))

The 1911 material does include historical information for a History of petrology section. Other sources exist - for example the book Mind Over Magma by Davis Young (2003) is an excellent reference for igneous petrology history. A history section is a great idea, but please, not just a copy/paste addition of 1911 text or other older sources. Vsmith 02:42, 25 December 2006 (UTC)

Section 6 looks useful, but the rest is of limited relevance to this article: maybe for igneous rocks, sedimentary rocks, metamorphic rocks.Babakathy (talk) 23:34, 25 October 2008 (UTC)

Geology Project. Please Help

If you are interested, please sign up to help establish the Geology Project. See Wikipedia:WikiProject Council/Proposals#Geology. Solarapex 21:41, 15 April 2007 (UTC)

Ouch

Thought this page was short as it linked to full articles on igneous, sed and met petrology. So I made {{main|}} links only to find they were just redirects. Am trying to start igneous petrology... Babakathy (talk) 22:55, 25 October 2008 (UTC)

Have started structure etc on a temporary page, so if anyone is interested? Babakathy (talk) 23:00, 25 October 2008 (UTC)

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