Igneous Structures and Field Relations-CH4

Image source winter 2010 40 intrusive plutonic

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Unformatted text preview: postis of minerals foreign to host rock developed within fractures developed within fractures Hyrdothermal veins - irregular pencil or sheet-shaped Image source: Barb Dutrow intrusions rich in water usually from igneous plutons - importants sources for Au Ag Cu Ni Schematic section through a hydrothermal system developed above a magma chamber in a silicic volcanic terrane image source: Winter (2010) 41 Intrusive (plutonic) processes and bodies completely foreign 2. non tabular intrusive bodies pluton - large igneous body crystallized at depth batholiths stocks Sierra Nevada batholith - granitic rocks are light and metamorphic roof rocks are dark. image source: Hamblin and Christiansen (2001) 42 14 8/27/2012 Intrusive (plutonic) processes and bodies contact effects depend on 3. Contact relations with plutons composition (mafic magmas are hotter) type of country rock depth of intrusion size of intrusion fluids in igneous body 43 Intrusive (plutonic) processes and bodies injected relation - border zone may be strictly 3. Contact relations with plutons mechanical in character with country rocks being image source: Winter (2010) intruded by magmas in apophyses These grade to agmatite zones (network of spaced injected dikes) and then xenoliths (country rock 44 Intrusive (plutonic) processes and bodies floating in pluton) 1. epizone - shallow (<10km) with cool country rock 4. Intrusion depth of plutons (<300 C) with brittle behavior sharp, discordant contacts Image source: Winter (2001) image source: Winter (2010) 45 15 8/27/2012 Intrusive (plutonic) processes and bodies 2. Mesozone - intermediate depth (5-20km) with 4. Intrusion depth of plutons country rock temps of 300-500C 3. Catazone - deepest (>10km) - country rock temps of 450-600 C image source: Winter (2010) 46 Intrusive (plutonic) processes and bodies 5. Common multiple intrusions Developmental sequence of intrusions composing the Tuolumne Intrusive Series (Yosemite) Image source: Winter (2010) 47 Intrusive (plutonic) processes and bodies 6. pluton rise and emplacement melts are gennerally less dense than surroundings 48 16 8/27/2012 Intrusive (plutonic) processes and bodies 5. Lateral wall rock displacement - ballooning Sketches of diapirs in soft putty models created in a centrifuge 6. emplacement in extension environments Diagrammatic cross section of the Boulder Batholith, Montana, prior to exposure image source: Winter (2010) 49 Intrusive (plutonic) processes and bodies 6. Pluton rise and emplacement For magmas to rise they must overcome "room problem" 1. Lift roof by folding or block elevation (upper 2-3km) 2. Assimilation of wall rock by melting (limited 3. Stoping - dislodged blocks are dense and sink image source: Winter (2010) 50 4. Ductile wall rock deformation 17...
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