GEO 105 Nova Southeastern University Geography Lab Report
PurposeThe purpose of this lab is to give you a chance to study closely a variety of igneous rocks. This lab is also a good review for the Final Exam!DirectionsOpen the Igneous Rock Sample Set web site (Links to an external site.) in a new window or tab to view GigaPan Images of some samples (lettered samples). You'll be bearing in mind some of the lessons of the Minerals lab here, and establishing competence in rock identification, building a foundation for the collaborative Rock Identification and Interpretation assignment at the end of Module 08.To complete these lab questions, use the Igneous Rock Sample Set web site rock illustrations, the Igneous Rocks Classification Key.pdf, Igneous I and II PPTs, your course workbook and Igneous chapters in your online textbook.https://opentextbc.ca/geology/part/chapter-3-intrusive-igneous-rocks/ https://opentextbc.ca/geology/part/chapter-4-volcanism/GradingThis part of lab exercise is required and worth 35 points. Each question is multiple choice. Choose your answer and either highlight it, circle it, make it a different font color or create a numbered list with the correct term. Do not use letters as it is not always clear which letter goes with which term.Lab Questions1) Zoom in on Sample A. You will see that this hand sample is composed of a very dark (black) rock that forms the "matrix" or "groundmass." Embedded within the black rock are beautiful green crystals. The green crystals are referred to as "phenocrysts." What is the overall texture of this igneous rock?fine-grained (aphanitic) coarse-grained (phaneritic) porphyritic pyroclastic or fragmental2) Looking at Sample A, how would you classify this igneous rock based on its composition? felsic intermediate mafic3) Zoom in on Sample A and investigate the beautiful green mineral phenocrysts. Identify the phenocryst mineral.olivine quartz potassium feldspar biotite4)Compare Sample A to Sample B.Both Sample A and Sample B are fine-grained (aphanitic) in texture however Sample B has an overall ultramafic composition.Both Sample A and Sample B are porphyritic in texture however Sample B appears to be intermediate in composition.Both Sample A and Sample B are coarse-grained (phaneritic) in texture however Sample A has an overall mafic composition.Both Sample A and Sample B are pyroclastic (fragmental) in texture and as such, their composition cannot be determined by hand sample investigation.5) Sample B displays large plagioclase phenocrysts that are composed of an even amount of both calcium and sodium in their crystalline structure. Thinking of Bowen's Reaction Series (Refer to lab book or Igneous PPT), this would indicate that the overall composition of the rock sample would be _________________________. ultramafic mafic intermediate felsic6) Move on to Sample C. Look at the overall texture, color and the fact that this sample contains "a rock in a rock"! The black, rectangular shaped rock exists as an inclusion in the lighter rock and is referred to as a/anphenocryst porphyrite pegmatite xenolith7) The texture of Sample C is indicative of two stages of cooling. Both light and dark crystals occur as phenocrysts. If the light mineral crystals are composed of a sodium-rich plagioclase, according to Bowen's Reaction Series, the dark crystals would most likely beolivine pyroxene (augite) amphibole (hornblende) calcite8) Sample D is an example of a "contact" between two different types of igneous rock. Compare the two rocks. The texture of the dark rock is ________________________; the texture of the light rock is __________________________.fine-grained (aphanitic); glassy fine-grained (aphanitic); coarse-grained (phaneritic)porphyritic; pyroclastic coarse-grained (phaneritic); fine-grained (aphanitic)fine-grained (aphanitic); coarse-grained (phaneritic)9) Sample D is an example of a "contact" between two different types of igneous rock. Compare the two rocks. The compostion of the dark rock is ________________; the composition of the light rock is __________________.ultramafic; mafic mafic; felsic felsic; mafic intermediate; felsic10) Sample D is an example of a "contact" between two different types of igneous rock. Compare the two rocks. Based on texture and composition, the name given to the black rock is _____ while the name given to the light rock is _______.basalt; granite gabbro; rhyolite andesite; diorite calcite; dolomite11) Sample E is referred to as a "xenobomb." (Like a xenolith but ejected as a lava blob that cooled later.) The green rock is encased in a black rock. Compare the composition of the two rocks. The green rock is composed almost entirely of one mineral. Identify that mineral.quartz plagioclase pyroxene (augite) olivine12) Based on your identification of the green mineral in Sample E, the overall composition of the green rock would _______.be high in silica and low in iron and magnesiumbe low in silica and high in iron and magnesiumhave approximately equal amounts of silica, iron, and magnesiumcontain calcium carbonate and no silica13) Based on the overall composition of the green rock in sample E, it would be safe to assume that the green rock originated in _____________________________.outer space the continental crust the upper mantle core14) Zoom in and look at Sample F in detail. This igneous rock contains at least 50% of a dark greenish grey mineral that has been identified as calcium rich plagioclase. There is also about an equal amount of a dark greenish black mineral that forms a texture of interlocking crystals with the plagioclase. Thinking of Bowen's Reaction Series, the dark greenish black mineral would most likely be ___________.pyroxene (augite) amphibole (hornblende) biotite muscovite15) Zoom in and look at Sample F in detail. This igneous rock contains at least 50% of a dark greenish grey mineral that has been identified as calcium rich plagioclase. There is also about an equal amount of a dark greenish black mineral that forms a texture of interlocking crystals with the plagioclase. This overall texture of this sample is _______________________.coarse-grained (phaneritic) porphyritic fine-grained (aphanitic) pegmatitic16) Based on your answers to the previous two questions, Sample F can be identified as ______________________.peridotite gabbro basalt andesite17) Take a look at sample G. Look at the architecture peeking out to the right in the picture. Cool! Where do you think this picture was taken? Zoom in closely to this sample. It is dominated by three minerals: one pink, one clear and one black. Based on the overall comparison of dark to light minerals, what general composition would you apply to this rock?ultramafic mafic intermediate felsic18) Continue examining sample G. What would be the most likely identification given to the peach-colored or pink mineral?plagioclase potassium feldspar muscovite quartz19) Continue your examination of Sample G. This overall texture of this sample is _______________________.coarse-grained (phaneritic) porphyritic fine-grained (aphanitic) pegmatitic20) Based on your answers to the previous three questions, Sample G can be identified as _______________________.peridotite gabbro granite rhyolite21) Holy cow! Look at this outcrop of igneous rock seen in Sample H. The layered grey to tan/pinkish colored rock is volcanic tuff. The texture of this rock would be _______________________________.aorphyritic glassy pyroclastic/fragmental pegmatitic22) Let's keep examining Sample H. The black, rectangular rock is a piece of the pre-existing volcanic rock prior to the eruption. Looking at the scale provided in the photo, what is the specific size/shape classification given to this pyroclastic chunk of black rock? It may be useful to skip ahead and consult the Igneous PPT slide on the types of pyroclastic materials. ash lapilli block bomb23) Zoom in closely on the black rock in Sample H. In particular, look at the bottom left corner of the rock. It contains quite a few "holes." What is the specific name given to these "holes"?pyroclasts phenocrysts porphyroblasts vesicles24) Sample IA and IB tell an interesting story of the cooling history of lava. Sample IB is composed of basalt. Sample IA was originally basalt but has since been lightly metamorphosed during the formation of the Appalachian Mountains, however, still retains some of its original igneous structure. These rocks originally would have been classified as ________.intrusive extrusive plutonic pegmatitic25) The distinctive structure seen in these Samples IA and IB (from two different angles) is/are _____________________ and is caused by ______________________.columnar jointing; cooling and contraction of the freshly crystallized volcanic rocklava tubes; quick cooling of lava forming a pipe-like conduit for the still molten rock materialpillow lavas; lava erupting underwaterpahoehoe lava; cooling of low viscosity lava with a "ropey" texture26) Be a field geologist! Approach the Sample J outcrop with our hand lens. Zoom in on the rock to determine its overall texture and composition. The occurrence of the pink potassium feldspar coupled with the observed texture would most likely indicate that the rock is ________________________.diorite andesite granite rhyolite27) Sample K is an interesting rock with a varied cooling history. Zoom around and check out phenocrysts of quartz, potassium feldspar and a dark mineral that is most likely hornblende. There are also a few small, angular pink fragments that are pieces of pre-existing rock. Based on the overall color and identification of the phenocryst minerals, what would be composition of this rock? ultramafic mafic intermediate felsic28) Now evaluate the texture of sample K. What is the texture of this igneous rock?fine-grained (aphanitic) coarse-grained (phaneritic) porphyritic pyroclastic /fragmental29) The best name for sample K, which erupted 760,000 years ago in eastern California, would be...granite rhyolite welded tuff lapilli30) Examine Sample M. What could I say about this sample based on its observable characteristics?I could say that it is volcanic in origin and felsic in composition.I could say that it is plutonic in origin and felsic in composition.I could say that it is volcanic in origin and intermediate in composition.I could say that it is plutonic in origin and intermediate in composition.31) Compare Sample N with Samples L1 and L2. All of these samples represent an environment of formation classified as _______________________________.volcanic plutonic intrusive under water32) Sample N is an example of a/an __________. It may be useful to consult the Igneous PPT slide or other resources on the types of pyroclastic materials.andesite volcanic bomb ashfall volcanic block33) Sample O's texture indicate that it is ____________________________.volcanic in origin plutonic in origin extrusive in origin pyroclastic in origin 34) Sample P contains quite a few holes. These holes indicate that as the lava was cooling, exsolved gas (gas that comes out of the liquid lava) became trapped and formed air pockets called _______________________.pyroclasts vesicles glass lava bubbles35) Examine Sample S and spend some time examining some of its larger clasts. What type of texture characterizes this sample?porphyritic pyroclastic coarse-grained (phaneritic) fine-grained (aphanitic)