Geology 203, Fall 2023 (1)
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/. Geology 203, Fall 2023 Name: AVW /l’f ner” Blackwell, UO Main Campus Lab day/time:TLv(sé? 1-3:50 GB _lan Lab 1 — Introduction to Minerals and Rocks (Assignments) Lab Portion Assignment: (86 points total) i i amples. On the Canvas site you will find the file To be completed during the In-person Lab using the hand samp A . 3 “Lab1- lr}:troduction to Minerals and Rocks - Lab Sample Photos for Lab Questions 'ASSI l‘lm:nt 2023f if you want to look at a preview of the lab materials. You will also need your l,al.) 1 Reading Han o'ut to refer back to various diagrams, tables, etc when answering some of the questions on the samples. Minerals: The basic building materials of most rocks are minerals. Since silicon and oxygen are the two most common elements in the Earth’s crust, silicate minerals make up 92% of all the minerals in the crust. Of the silicate minerals, only 8 are common (see figure below). 3% 8% xdure - Other Nonsilicates . ;;1( silicates ,,,,lemu} - pran 1€ (oters chery Cowe — (s celisblay al\iu(fif:*)" size clats 5% Micas 39% Plagioclase feldsper 5% Amphiholes ‘T 11% Pyroxenes Look at the samples of some of the common minerals and answer the following questions. A-2 & A-12 - Feldspar (Alkali Feldspar & Plagioclase Feldspar) Feldspars make up 51% of the Earth’s crustal minerals. Alkali feldspar (A-2) is commonly shades of pink & red, while plagioclase feldspar (A-12) is generally shades of gray to white. They have similar crystal structures that provide both with similar physical properties that allow for their recognition. These two feldspars are unstable at the Earth’s surface and chemically weather into a variety of clay minerals (5% of the minerals of the crust). Therefore after long periods of chemical weathering many feldspars have weathered to clay. Look at the feldspar samples. The smaller A-2 samples are typical shapes of what a feldspar crystal commonly looks like. The larger A-2 and A-12 samples are pieces of feldspar crystals that have been broken from crystals that might have had a similar shape. Describe the shape of the feldspar crystal: i/ t/uulfl( [ b« s £l (1pt)
‘ ’:——' A-3 - Quartz W a variety of colors but gray is Quartz makes up roughly 12% of the minerals of the Earth’s crust. It Cnfl; uf;ax;flke it very resistant 0 chemic fairly typical. The crystal structure and bonding of elements in lh.l‘S mi £ i) woallering of silicate rock decomposition at the Earth’s surface. As such after prolonged periods o quartz is one of few remaining original minerals left over from the process. | 4 . (o/df h ang whifp Briefly give a description of the quartz: ,b‘;lc ‘/M'/}/f‘l (;”5 s L k 1pt) ,1]2 G 2!,1;.1 {,/J(ll( t(,\,,’—frfl/\w,fl,“} % Smue}( l(,{l[//(_ dp Vit (T v ¥ A-9 - Pyroxene Pyroxene is a group name for a n sample you are observing is the crystal shape in a rock it is ofte color due to the higher ercent that is chemically unstable at t (hematite). umber of related specific pyroxene minerals (11% Of E"’r, th’s cru 2 0. The % variety augite, common in many igneous rocks. If this mineral displays a n n short and stubby prismatic crystals (small crystals in the trays). It has a gaLk age of iron and magnesium elements within this mineral. This is anqlhcr mineral he Earth’s surface. When it weathers it oxidizes to form a reddish mineral Briefly give a description of the pyroxene: dflk fiunML (fl“r s W,// ’Wu CKOU'W( wil !‘”’Vém("'_‘g lé ([S;‘u( ninerale et in rawL Fexpct / A-25 - Amphibole (1pt) as). Like pyroxene group it has a dark color due to the higher percentage in this sili ineral. This is another mineral that is chemically unstable at the Earth’s surface, Brieflygiveadescn'ptionoftheamptfibole:_@/4 black cflr,flfi/{ with 4 f/‘%* SV, £ 400l vl -L ,7!%?} Ll fi(/_/ “uh //lt&fi} lushe ¢ A-7 and A-11 - Mica (I'pt) Mica is group name for a number of related specific mica minerals (5% of Earth’s crust). The samples in the photos you are observing are A-7 (muscovite) and A-11 (biotite) that are common in many igneous rocks and metamorphic rocks. What feature, which is observable in both of in these two mica minerals, is common to the mica group? glassy sk an aloest glytt Emithe vory lagacy 40} Lk, 75 12 Jd 7 7 (1'pt) Which of the two micas has a higher iron and magnesium content and why? biotite (4-1 /) })4! a hishic iron anb m; adion condod du bo i oxfiled ’1 Jivre (1py)
r I ¥ \-26 - Clay “lay is group name for a number of related specific clay minerals (5% of Earth’s crust). The sample you are sbserving is Kaolinite. Clays are a bi-product of the chemical weathering of the feldspar group minerals. They are a common mineral in the sedimentary rocks. The clay minerals have a similar cryst_al structure to that of the mica group minerals. As such they have a similar flat, platy shape to their individual minerals. The sample you are observing is a massive piece containing millions of individual clay minerals that are 00 small to see (each one is < 1/256 mm in size). , T > Briefly give a description of the kaolinite clay sample: 27160 th ,/r it/‘f ex + r . iZ’” (I'py) For the pictures of silicate igneous rocks (below), identify the minerals (based upon the previous silicate mineral descriptions): Granite Andesite Porphyry ____ . e T Tl e R.7 L0 R e e k. : ' A g A Kkl «CtUgflf B pbmflw Lllger C pyactz. (note the 9B labeled in 2 pictur is same mineral) The black mineral is probably: A’r\'yik]bolc (1 ;;t each, 4 pts total) A-17 - Hematite Hematite is not a silicate mineral. It is an iron oxide mineral that is the product of chemical weathering of many iron-bearing silicate minerals. It is commonly observed as coatings on the weathered surfaces of rock and minerals. It may also be found as cement that binds sediment grains together. Briefly give a description of the hematite: [ow]q y ced, pon ‘_SL\irw Y ) l &r s/vyj”' (1pt) Of the silicate minerals you have just observed, which ones might be chemically weathered to hematite? Augie 1 pt — (1py) e
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A-6 - Calcite i i d : 4CO3). This is a common Calcite is not a silicate mineral. It is a carbonate mineral Fcalmum carpo'r};xlc, g:IC - :!de B mineral of the sedimentary rock, limestone. The mineral is both chep]lca % 5; p and/or biochemically precipitated by many marine organisms secreting a SHeil. n the acid wi aper towel after Use the acid bottle and place one drop of acid on a sample. (Wipe off the acid with the paper o observation, 1 4Hle) servation.) ((,alh ol saokeh & What happens? !Mtl of LJLH?Y Deafan ob' aeil losf H f/l,rrv(,,y:L(lpl) 7 Igneous Rocks ¢ J"‘:" N g B et " A= ‘\//_\i"." A;!.“'B“':,' akle Divergent /,f\ St tta: ] 5 I gt B ??;\.Q %3 % Sy - et Ae) Asthenosphere l\ ceat Lroats of am¢ (plestic flowing mantle) cruf I T,.,.:.»p*l" Igneous rocks are associated with divergent and convergent plate boundaries of the tectonic cycle (see diagram above) (and also associated with the hot spot cycle, not illustrated above). Oceanic crust is composed of mafic igneous rock (i.c. basalt) that is the result of the partial melting of ultramafic rock (peridotite) of the mantle beneath oceanic/oceanic divergent plate boundaries. Continental crust has a wide variety igneous compositions [mafic, intermediate (andesites in continental volcanic arcs), and felsic (granite in the roots of the mountain ranges and pyroclastic tuffs in continental volcanic arcs)]. The variety of compositions are produced by complicated partial melting processes at oceanic/continental convergent plate boundaries. Observe the igneous rocks in the lab (or by using the photos on Canvas). _The Lab 1 Reading Handout will assist you in determining the interpretation of formation or cooling history, Some questions will be easier to answer if you look at the diagrams and reading provided in this lab portion handout (such as the labeled tectonic diagram above and its reading). Sample B-16. Basalt What is the texture of the rock? (1 point) Texture: V0N ',A:(mfw.i !45“V(y \/";L((, do e n«ktéyL Based upon the texture of the rock how was the rock formed? (refer to the texture portion of the igneous reading, p. 3 and 4 of the Lab 1 Reading Handout) (2 points) FA(A tob‘"/\} d s %nl“fi Mt 1y or neas Jhe Sorlue This rock would be a common component of what part of the Earth (mantle, continental crust or oceanic crust) (1pt) (refer to reading and plate tectonic diagram above) Ocenic cowt WSSl |
rv—i ample B-30. Granite What is the texture of the rock? (1 point) \ " ik exture: /190 fa\,..q&, ]A,“ \/L(r/—(cw;( (o b ¥l Sasec-l upon the texture of the rock how was the rock formed? (refer to the texture portion of the igneous reading, p. 3 and 4 of the Lab 1 Reading Handout) (2 points) Show M\y mé cgs’m?z,«ov% wcceleratey b/ Iag(, wiomb ob wat4r in the r"\yma This rock would be a common component of what part of the Earth (mantle, continental crust or oceanic crust) (Ipt) (refer to reading and plate tectonic diagram above) Leusk Sample B-11. Peridotite What is the texture of the rock? (1 point) Texture: \om ‘L' x'(,lab Nerios copla el 7 2 + Based upon the texture of the rock how was the rock formed? (refer to the texture portion of the igneous reading, p. 3 and 4 of the Lab 1 Reading Handout) (2 points) slow coliy of Mignn b dophh wihn e oarth This rock would be a common component of what part of the Earth (mantle, continental crust or oceanic crust) (Ipt) (refer to reading and plate tectonic diagram above) MflA“’IC Sample B-3. Andesite Porphyry What s the texture of the rock? (1 point) Texture:f\Df\‘«L”w’%’}"A rwyl» emall, vithle Based upon the texture of the rock how was the rock formed? (refer to the texture portion of the igneous reading, p. 3 and 4 of the Lab 1 Reading Handout) (2 points) This rock would be a common component of what part of the Earth (mantle, continental crust or oceanic crust) (I'pt) (refer to reading and plate tectonic diagram above) Continantl_coush —
i ——— et A A A e WW}/\'\/\:\ o Ty 30 g 145 - .,: z o /(1’('/ (y, - T > A = [ 7 s = L Pailiia 5 - L G @ g g T [ i i £Iv z jj E/ 5:“"{3"‘1 from .Lruré;V< co)avn : » ',\ (el 2 288 A unweldid g g Depesit 2 AAO DA arctr L "\ = = r < 22 waldaol Ash Flow = soaa b 'Dcf""t- Besides quiescent eruptions of lava from volcanoes, explosive pyroclastic eruptions can also occur. These eruptions commonly occur in two types: Air/Ash Fall eruptions and Ash Flow eruptions. Ash fall eruptions jettison tiny ash and larger pumice fragments into the atmosphere where the winds can blow them over very long distances. As they move the particles of ash and pumice cool down and settle out of the air according to their density. This produces an ash fall deposit or layer of ash and pumice that may be preserved in the rock record, especially if the particles settle out into a lake or ocean basin. These rock layers of ash are wonderful marker beds to work out the geologic history as they are dateable and deposited almost instantaneous! (geologically speaking). The ash flow eruptions are dense clouds of ash, pumice and rock fragments that rapidly flow down the slope. These dense clouds do not travel as far and come to rest hot. The mass, heat, and escaping gases in the deposit cause the material fuse together into a dense welded mass. Samples B-1 Pumice Lapilli Ash Tuff (friable) What is the texture of these rocks? (1 point) Texture: Sl m;?h agtall pon-Loliakes Based upon the texture of the rock how was the rock formed? (refer to the texture portion of the igneous reading, p. 3 and 4 of the Lab 1 Reading Handout) (2 points) r@fvé L.»ly ok 4n ynwb mdéjm mxg; at or neac surdiie Why is this pyroclastic deposit so useful in deciphering the geologic history of a region? (1pt) (reading above) (J{';c‘fl_('ll (,lefajr&’? 4re uxifv‘ in crfll"flé”? Hhe /zo Iy i }myt? i a reyim becqure /%a luJ.o o! nxL wre Jahaut- A/IL Atfo:‘/"'k alpesd m‘MJ‘* ewf/. Sedimentary Rocks Platte River Sand to Pebble Sediment Sample Photo of sediment collected from the North Platte River near the town of Cozad in central Nebraska. The North Platte River erodes and drains from the Laramide Mountains of Wyoming where 2.5 billion year old Precambrian granites and metamorphic rock of the continental basement are exposed. This river sediment was deposited in the stream after approximately 450 miles of transport from its source. Many of the fragments are
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r— - rock fragments of pink granite and the minerals of that compose the granite (pink to pinkish gray alkali feldspar; gray, often transparent to translucent quartz; gray, dull and shiny grains, many still with somewhat rectangular shape of plagioclase feldspar; and some dark minerals of biotite mica and hornblende amphibole). There are also some other dark colored metamorphic rock fragments and associated mineral fragments from those rocks. ——— Use the Figures 4, 6 and 7 in the Lab 1 Reading Handout to describe the angularity/rounding, size & sorting of the grains (note there is a metric ruler with the samples to assist in describing the size of particles, a centimeter scale is the provided in the photo file on Canvas). (4 pts) L SiZe i Hhe selimpb yeciet wildly ,,/U(/,(n/,, lpm & &vl)u)k ok ducd (site) 4cD.Lem 7 ihéj ne m,‘(fw,\ cerndaddi. sl deifiibibe sorted on e saller end- Sedimentary Rocks of Siliciclatic Dominated Systems Sedimentary rocks are formed from the weathering of rocks to form sediment that is then transported by water, wind or ice, to accumulate as sediment layers in a depositional basin. Many of the depositional systems/basins are dominated with siliciclastic sediment (fragments of silicate minerals and rocks) derived from the mechanical and chemical weathering of silicate rocks. Some siliciclastic depositional systems have very long river systems allowing for greater compositional and textural maturity to develop as the fragments are being transported (see “Long System” left side of figure below). These are more characteristic of passive continental margins (think Gulf of Mexico). (Note: the sediment sample that you just examined from Nebraska would have been located approximately where the “B” of “Braided River” is found on the figure below.) Some siliciclastic depositional systems have short river systems allowing for far less compositional and textural maturity to develop in the fragments being transported (see “Short System™ top right side of figure below). These are more characteristic of active continental margins (think Oregon) and oceanic volcanic arcs. Siliciclastic Dominated Systems AIASAT? /e 2| GRAVEL BEACH LSF.- 1991 Not to Seale (from Fichter and Poche, 1997)
R \ Observe the sedimentary rock samples in the lab (or use the photos file on Canvas). l.’.s.(' the Lab 1 Reading Handout to assist you in determining texture and the interpretation of d(-pnsmmml. ; environments. Some questions will be easier to answer il you look at the diagrams and reading providec in the lab portion handout (such as the diagram above). Sample C-2. Shale What is the texture of the rock (include size of particles)? What structure is observable in the rock? (2 points) Texture: Foli 4}-4, 5410% Structure: §~}ra"'\ri(afldq Using Figure 15 (Lab 1 Reading Handout), what depositional environments might the sediment of this rock have been deposited in? (2 points) Ao’ fl\?y'y-! glein cond, bl WA Pir lasan cotng Howd gl 7 T 7 7 ¥; I Sample C-4. Graywacke Sandstone What is the texture of the rock (include size of particles)? Texture: Jolialel, ; \cmc‘/qm'mé (1 point) Using Figure 15 (Lab 1 Reading Handout), what depositional environments might the sediment of this rock have been deposited in? (2 points) Tochiddy concent On the Fichter and Poche (1997) Siliciclastic “short system” diagram (previous page), write the sample # on the location where you believe the sediment of this rock might have been deposited. (1pt) Sample C-10. Quartz Sandstone ~ What is the texture of the rock (include size of particles)? (1 point) Texture: Lne 'aqrmub Using Figure 15 (Lab 1 Reading Handout), what depositional environments might the sediment of this rock have been deposited in? (2 points) b{uL AM On the Fichter and Poche (1997) Siliciclastic “long system” diagram (previous page), write the sample # on the location where you believe the sediment of this rock might have been deposited. (1 pt) Sample C-12. Arkose Sandstone ~ What is the texture of the rock (include size of particles)? (1 point) Texture: f1h 'fi’ {f‘tjf‘é 5 E’"/t\ Ine-4/a nek ”WJ“\Mf,fl/ui Using Figure 15 (Lab 1 Reading Handout), what depositional environments might the sediment of this rock have been deposited in? (2 points) citte_channdl, allovial dom On the Fichter and Poche (1997) Siliciclastic “long system” diagram (previous page), write the sample # on the location where you believe the sediment of this rock might have been deposited. (1 pt)
r Sample C-8. Conglomerate What is the texture of the rock (include size of particles)? (1 point) Texture: J{uy&o N;L qtf(lflp"\b ot r\'Ck Using Figure 15 (Lab 1 Reading Handout), what depositional environments might the sediment of this rock have been deposited in? (2 points) hesd wa‘}m/, ovnduing On the Fichter and Poche (1997) Siliciclastic “long system” diagram (previous page), write the sample # on the location where you believe the sediment of this rock might have been deposited. (1 pt) Sample C-6. Rock Salt What is the texture of the rock? (1 point) 2t e Texture: oo lN-;i‘/ (249['4(5 Q/lOQfJ\(xég 5 Referring back to the sedimentary texture in the Lab 1 Reading Handout, what depositional environments might the sediment of this rock have been deposited in? (2 points) On the Fichter and Poche (1997) Siliciclastic “long system” diagram (previous page), write the sample # on the location where you believe the sediment of this rock might have been deposited. (1 pt) Carbonate Dominated Systems In regions where there is very little input of siliciclastic sediment to a region, carbonate (calcite) biochemical and chemical deposition may become dominant. The illustration below displays carbonate environments of deposition in a shoreline to shallow shelf and a shoreline to deep shelf environment. The shallow shelf environment of this diagram would correspond to the “neritic” environment of Figure 15 in the Lab 1 reading. Carbonate Dominated Systems SHALLOW SHELF BARRIER REEF DEEP SHELF LSF .91 (from Fichter and Poche, 1997)
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P — Sample C-13.Fossilifer0us Limestone What is the texture of the rock? What structure is observable in the rock? (2 points) Texture: ) J;[ Structure: faft ‘ Usipg Figure 15 (Lab I Reading Handout), and assuming the fossils are marine, what depositional environments might the sediment of this rock have been deposited in? (2 points) @,m waim e wite, |imp mvd €24,uing On the Fichte.r and Poche (1997) Carbonate diagram (previous page), write the sample # on the location where you believe the sediment of this rock might have been deposited. (1 pt) Metamorphic Rocks i Continental Crust MeBI:;:ge Oceanic Crust % ccretional rism Dynamothermal Middle Grade |/ High Grade}, " A N continental crast Partial Melting Proc Generate Magmas ECLOGITE —y (from Fichter and Poche, 1997) Most metamorphic rocks are created by regional dynamothermal metamorphism in convergent plate boundaries with subduction zones (see figure above). In the overriding continental plate where magmas are injecting into the growing mountain range, pressures and temperatures are increasing from low P &T (near surface conditions) to high P and T at great depths. This produces the generalized sequence of metamorphic rocks from slate to schist to gneiss to migmatite with increasing depth. In the accretionary prism and cold subducting plate portions of the convergent plate boundary the pressure increases rapidly, but temperature only slowly. This produces rocks that form under low T and High P and progress to moderate T and very high P conditions. This type of metamorphism produces the blueschist and eclogite rocks. This metamorphism makes the rock of the subducting oceanic crust very dense and helps to pull the subducting oceanic lithospheric plate down into the plastic asthenosphere. The subducting oceanic crust (black layer on the diagram) starts out as igneous mafic magma when it erupts at the ocean ridge to harden into basalt lava. While at the oceanic ridge large quantities of hydrothermal fluids circulate the basalt to metamorphose the igneous basalt into metamorphic greenstone.
rfv “he rocl_( of the ocean crust that subducts is therefore greenstone that is then metamorphosed again into slueschist and then eclogite as the plate sinks deeper into the mantle. Ohse_l‘Ve the metamorphic rock samples in the lab (or use the photos file on Canvas). Use the rock names provided and Figures 21A and B of the Lab 1 Reading Hand i lout o assist you in identifying the textures. Fl;:ur.c;s 21A and B of the Lab 1 Reading Handout will assist you in determining the protoliths and conditions & types of metamorphism. Sample D-4. Slate Texlure:jMM,"l M z\‘}' ! What is the texture of the rock? (1 point) Based upon the rock name and texture, what was the possible protolith of the rock (refer to Figure 21A)7 (1 pt) chele §/oc ciltchme Based upon the rock name and texture, what were the conditions the rock was met Figure 21A)? (1 point) amorphosed under (refer to | (oy MO [ d/»"‘\rm "Yl]l,(m" con &1 103 Sample D-13. Garnet-Mica (Pelitic) Schist What is the texture of the rock? (1 point) Texture: [‘D\);L Am—/mrnb& 5/ecks ofi 4!&(55 (,,(Jn(g f 7 7 (24 Based upon the rock name and texture, what was the possible protolith of the rock (using Figure 21A of Lab 1 Reading Handout)? (1 pt) S }mh A/«f ‘,\ ermc Based upon the rock name and texture, what were the conditions the rock was metamorphosed under (using Figure 21A of Reading Handout)? (1 point) cgrongd dunome el oadihmc g a Sample D-3. Gneiss What is the texture of the rock? (1 point) Texture: J\D\'\A“Cb (quh Based upon the rock name and texture, what was the possible protolith of the rock (using Figure 21A of Lab 1 Reading Handout)? (1 pt) \(\‘)L())p Lleé S|N1|(, s;u)‘w ‘t\ Gnd fl/ J'”“': Based upon the rock name and texture, what were the conditions the rock was metamorphosed under (using Figure 21A of Reading Handout)? (1 point) [L)l(,“.( Z\/,qvfla“lu'\t[ C ‘r)/‘wtw’/ Jd J
Migmatite — Large Sample in Front of Classroom (photo in photo file on Canvas) Migmatites are formed when metamorphic rocks are transitioning into partial melting rocks, Give a brief description of the migmatite rock. (1 point) ccb\;f«\c} rgy[\ égg vinble (Q/il"’s Sample D-8. Greenstone What is the texture of the rock? (1 point) Texture: fOUsh, &+ 4 wep Based upon the rock name and texture, what was the possible protolith of the rock (using Figure 21B of Lab 1 Reading Handout)? (1 pt) L_) 154 | l/ Based upon the rock name and texture, what were the conditions the rock was metamorphosed under (using Figure 21B of Reading Handout)? (1 point) (L.cfww, (l.mzm(i,muLfl L 1!&""4" [ can)) Tions / / 0 Sample D-11. Blueschist What s the texture of the rock? (1 point) Texture: _rovih #ine “4/eine Based upon the rock nfame and texture, what was the possible protolith of the rock (using Figure 21A of Lab 1 Reading Handout)? (1 pt) [O hoq H/ Based upon the rock name and texture, what were the conditions the rock was metamorphosed under (using Figure 21A of Reading Handout)? (1 point) } riv.;“‘»’.l Du,r",n")kv[{mq( Sample D-17. Eclogite What is the texture of the rock? (1 point) Texture: (m:;’), vichle feehce ,Q\luhg Based upon the rock name and texture, what was the possible protolith of the rock (using Figure 21B of Lab1 Reading Handout)? (1 pt) 175 ’;’H’ Based upon the rock name and texture, what were the conditions the rock was metamorphosed under (using Figure 21B of Reading Handout)? (1 point) (g2 i““b\l (iu. nAMQ J/,: mel n 2| ! on( 7 d
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