Editing Lower Old Red Sandstone volcanism, Caledonian magmatism, Grampian Highlands

Jump to navigation Jump to search

Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.

The edit can be undone. Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.

This page supports semantic in-text annotations (e.g. "[[Is specified as::World Heritage Site]]") to build structured and queryable content provided by Semantic MediaWiki. For a comprehensive description on how to use annotations or the #ask parser function, please have a look at the getting started, in-text annotation, or inline queries help pages.

Latest revision Your text
Line 9: Line 9:
  
 
The lavas are of potassic calc-alkaline type and show chemical similarities with the nearby lamprophyre intrusions; certain flows are anomalously rich in Mg, Ni and Cr. The lavas as a whole are richer in Sr, Ba, K, P and light rare-earth elements (LREE) than the equivalent age lavas of the Midland Valley and Southern Uplands, and the magmas are thought to be largely mantle-derived, with some contamination by crustal material, possibly of mafic granulite composition (Groome and Hall, 1974; Thirlwall, 1981; 1982). Clayburn et al. (1983) obtained a Rb/Sr isochron age of 400 ± 5 Ma (Early Devonian) for the Lorne Plateau lavas, very similar to the 401 ± 6 and 396 ± 12 Ma obtained from the probably geneticallyrelated Etive granites. The initial <sup>87</sup>Sr/<sup>86</sup>Sr ratio (0.7045–0.7050) of the lavas is also similar to that of the Etive granites (0.7055–0.7058). However, Thirlwall (1988) has suggested, on the basis of argon isotope work, that the Lorn Plateau lavas may be as old as 421 to 413 Ma, and that the Rb/Sr systematics of the lavas have been reset by the plutonic intrusions.
 
The lavas are of potassic calc-alkaline type and show chemical similarities with the nearby lamprophyre intrusions; certain flows are anomalously rich in Mg, Ni and Cr. The lavas as a whole are richer in Sr, Ba, K, P and light rare-earth elements (LREE) than the equivalent age lavas of the Midland Valley and Southern Uplands, and the magmas are thought to be largely mantle-derived, with some contamination by crustal material, possibly of mafic granulite composition (Groome and Hall, 1974; Thirlwall, 1981; 1982). Clayburn et al. (1983) obtained a Rb/Sr isochron age of 400 ± 5 Ma (Early Devonian) for the Lorne Plateau lavas, very similar to the 401 ± 6 and 396 ± 12 Ma obtained from the probably geneticallyrelated Etive granites. The initial <sup>87</sup>Sr/<sup>86</sup>Sr ratio (0.7045–0.7050) of the lavas is also similar to that of the Etive granites (0.7055–0.7058). However, Thirlwall (1988) has suggested, on the basis of argon isotope work, that the Lorn Plateau lavas may be as old as 421 to 413 Ma, and that the Rb/Sr systematics of the lavas have been reset by the plutonic intrusions.
[[File:P915437.png|thumbnail|Volcanic evolution of the Glencoe cauldron (after Roberts, 1974). ]]
+
[[File:P915437.png|thumbnail|P915437]]
[[File:P220488.jpg|thumbnail|Granite tors on Mither Tap, Bennachie, Aberdeenshire, with well-marked horizontal and subvertical joints (D 4523). P220488. P220488.]]
+
[[File:P220488.jpg|thumbnail|P220488]]
[[File:P002751.jpg|thumbnail|Glencoe Boundary Fault, Stob Mhic Mhartuin, Lochaber. The fault separates the main Glen Coe Fault Intrusion (top left), from bedded quartzites (bottom right).  P002751.]]
+
[[File:P002751.jpg|thumbnail|P002751]]
 
Glencoe and Ben Nevis are two of the best-exposed examples of cauldron subsidence (Bailey, 1960). The volcanic sequence in '''''Glencoe''''' (109<nowiki>;</nowiki>  
 
Glencoe and Ben Nevis are two of the best-exposed examples of cauldron subsidence (Bailey, 1960). The volcanic sequence in '''''Glencoe''''' (109<nowiki>;</nowiki>  
 
[[Media:P915437.png|(P915437)]]<nowiki>;</nowiki> [[Media:P220488.jpg|(P220488)]] and [[Media:P002751.jpg|(P002751)]]) is preserved in a downfaulted block within the elliptical ring fracture. Roberts (1974) has postulated the following sequence of events and products in the Glencoe cauldron:
 
[[Media:P915437.png|(P915437)]]<nowiki>;</nowiki> [[Media:P220488.jpg|(P220488)]] and [[Media:P002751.jpg|(P002751)]]) is preserved in a downfaulted block within the elliptical ring fracture. Roberts (1974) has postulated the following sequence of events and products in the Glencoe cauldron:

Please note that all contributions to Earthwise may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here.
You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Earthwise:Copyrights for details). Do not submit copyrighted work without permission!

Cancel Editing help (opens in new window)

  [] · [[]] · [[|]] · {{}} · · “” ‘’ «» ‹› „“ ‚‘ · ~ | ° &nbsp; · ± × ÷ ² ³ ½ · §
[[Category:]] · [[:File:]] · <code></code> · <syntaxhighlight></syntaxhighlight> · <includeonly></includeonly> · <noinclude></noinclude> · #REDIRECT[[]] · <translate></translate> · <languages/> · ==References== · {{reflist}} · ==Footnote== · {{reflist|group=note}} · <ref group=note> · __notoc__ · {{DEFAULTSORT:}} <div class="someclass noprint"></div> {{clear}} <br>

Template used on this page: