REMINDER. MOVIE: Rocks that Originate Underground 5:41 to 12:40

Transcription

1 REMINDER 2 chapters covered next week Sedimentary Rocks Soils and Weathering (first half) Learn vocabulary for both! Turn to Neighbor: Without using your book or notes, try to remember which te mineral is made of : Independent tetrahedra? Single-chains? Double-chains? Sheets? 3-D Framework? Which of the above has the most Silica? Least? What are these large minerals from the Museum of Natural History, NY? (About 4 feet tall!) MOVIE: Rocks that Originate Underground 5:41 to 12:40 Texture Composition Aphanitic (glassy & vesicular) Pyroclastic or fragmental Basalt Scoria Intermediate Andesite Felsic Rhyolite Igneous Rocks are classified by.. Pegmatitic of Porphyritic of Aphanitic 1

2 Composition < 45% 45 55% 55 65% > 65% Name Mineral composition Mostly Olivine Minor Pyroxene Minor Plagioclase Pyroxene Ca-rich Plagioclase Minor Olivine Minor Hornblende Interme- Hornblende diate Biotite Na-rich Plagioclase Minor Pyroxene Felsic Quartz K-Feldspar Muscovite Minor Biotite Minor Hornblende Minor Na-rich Plagiocl. Intrusive rock names Extrusive rock names 45 55% 55 65% > 65% Name Felsic Mineral composition Mostly Olivine Minor Pyroxene Minor Plagioclase Pyroxene Ca-rich Plagioclase Minor Olivine Minor Hornblende Hornblende Biotite Na-rich Plagioclase Minor Pyroxene Quartz K-Feldspar Muscovite Minor Biotite Minor Hornblende Minor Na-rich Plagiocl. Intrusive rock names Extrusive rock names NONE EXIST ON PLANET EARTH Basalt, Scoria Andesite,, Tuff Rhyolite,, Tuff, Intermediate Composition Intermediate Composition < 45% Felsic Pegmatitic of Aphanitic Basalt Andesite Rhyolite Porphyritic of Aphanitic Texture (glassy & vesicular) Scoria Pyroclastic or fragmental 2

3 Aphanitic Pyroclastic Pyroclastic 3

4 PUMICE FLOATING MOVIE Tongariro National Park Mt. Ngauruhoe Texture Composition Aphanitic (glassy & vesicular) Pyroclastic or fragmental Basalt Scoria Intermediate Andesite Felsic Rhyolite Pegmatitic of Porphyritic of Aphanitic 4

5 Turn to Neighbor: Come up with a good definition (no books or notebooks) of VISCOSITY. Which is more viscous: Water or Honey? Hot syrup or cold syrup? DEMO: Oil Viscosity Highly Viscous Felsic Lava Low-Viscosity Lava Mineral Growth ANIMATION Museum of Natural History, NY. Rare minerals from Pegmatites As molten granite crystallizes, the melt that remains becoems enriched in water and rare elements such as B, Ta, and Nb. These elements concentrate in the melt because they are not taken up by the minerals crystallizing from it. Eventually, enough water builds up that steam forms. Gem and ore minerals containing rare elements form in the pockets of steam-and water-rich melt. In the presence of water, minerals can grow to enormous sizes. 5

6 Pegmatite Vein Filled In Sierra Nevada Mountains Grand Canyon Pegmatite (at the bottom!) Tourmaline Mine Pegmatite San Diego 6

7 Texture Composition Aphanitic (glassy & vesicular) Pyroclastic or fragmental Basalt Scoria Intermediate Andesite Felsic Rhyolite Pegmatitic of Porphyritic of Aphanitic Assimilation Sierra Nevada Mountains Desolation Wilderness 7

8 Silicate structure Single Si-O tetrahedron connected to other tetrahedron by ionic Single chains connected to other chains by ionic Double chains connected to other chains by ionic Sheets connected to other sheets by ionic Three dimensional framework of Si-O tetrahedrons with ionic bonds filling holes within. Cleavage type None 2 planes at 90 (square columns) or hairs/fibers 2 planes at 60 and 120 (sheared columns) or hairs/fibers 1 plane 2 planes at 90 (square tablets) Examples Olivine Pyroxene Hornblende Micas Feldspars Si:O ratio 1:4 1:3 1:2.75 1:2.5 1:2 Three dimensional framework of Si-O tetrahedrons with no ionic None Quartz 1:2 Temperature Si, K, Na content Fe, Mg, Ca content Viscosity Water content Quartz content Olivine content Plagioclase content Moves from Carich to Na-rich 8

9 Silicate structure Single Si-O tetrahedron connected to other tetrahedron by ionic Single chains connected to other chains by ionic Double chains connected to other chains by ionic Sheets connected to other sheets by ionic Three dimensional framework of Si-O tetrahedrons with ionic bonds filling holes within. Cleavage type None 2 planes at 90 (square columns) or hairs/fibers 2 planes at 60 and 120 (sheared columns) or hairs/fibers 1 plane 2 planes at 90 (square tablets) Examples Olivine Pyroxene Hornblende Micas Feldspars Si:O ratio 1:4 1:3 1:2.75 1:2.5 1:2 Three dimensional framework of Si-O tetrahedrons with no ionic None Quartz 1:2 Turn to Neighbor: Intermediate Composition Felsic Aphanitic Basalt Andesite Rhyolite Texture (glassy & vesicular) Scoria Pyroclastic or fragmental Brainstorm all igneous rock textures, names, characteristics, etc. that are associated with Extrusive rocks only Intrusive rocks only (Make two columns on paper and decide where to place each thing so far discussed or read) Pegmatitic of Porphyritic of Aphanitic Definition Textures and features Rock names Extrusive or volcanic Lava erupted and cooled at surface Vesicles Aphanitic Porphyritic Pyroclastic Scoria Basalt Andesite Rhyolite Intrusive or plutonic Magma that remains underground where it cools Pegmatitic 9

10 Pluton Formation ANIMATION Parallel to surrounding bedding (concordant) or cross-cutting (discordant) Sill Parallel Dike Cross-cutting Batholith Cross-cutting Shape: tabular or massive Tabular Tabular Massive Size 5-30 m thick m thick 100s of km wide Basalt Sills Glacier National Park Basalt Dike Mt. Moran Grand Tetons 10

11 Shiprock Peak in New Mexico Shiprock Peak in New Mexico 11

12 Magma Mixing and Cabo San Lucas, Mexico We have now completed this week s question sheet. On your own, review each question again. I recommend that you write out your answers (synthesize your thoughts and notes and put the answers into your own words). If something doesn t make sense or to just get some feedback, come see the tutors or me during my office hours. Rock ID Activity Recommend setting samples up into 5 texture columns and 4 compositional rows, just like on naming table. ALSO set up the Bowens Reaction Series minerals alongside the rocks, so you can see how they match. There are some duplicate names in the boxes. Remember: half of next week s quiz will contain any question from the question sheet. 12