NATS 1750 A (Winter 2017): Assignment 3, Version 1.0 – February 20, 2017 Due: March 15, 2017 by 11 pm EDT via Moodle (Late Penalty: 25% per day – including weekends. Strictly enforced.) Instructions:
● You are expected to provide answers for every question. You are encouraged to show all of your work so that marks can be awarded for partially correct answers.
● Although you are encouraged to collaborate with your classmates, each of you is expected to submit a separate and distinct assignment – a point that will require acknowledgement upon submission.
1. Using Google Maps (or a similar mapping capability):
a. Provide the latitude and longitude for a feature of your choosing on Mount Royal. [2 marks]
b. Using your map, or some other source, provide an estimate for the altitude of Mount Royal. (Be certain to cite your source of this estimate.) [1 mark]
c. Using your map, or some other source, provide an estimate for the altitude of area around Mount Royal. (Be certain to cite your source of this estimate.) [1 mark]
d. Using your map, provide a three-dimensional picture of Mount Royal that illustrates its relief relative to the surrounding area. Based on your answers 1(b) and 1(c), provide a quantitative estimate for the relief of Mount Royal. [4 marks]
e. Based on your answer to 1(d), estimate the minimum depth of rock that the Mount Royal would have required for intrusion (as an igneous pluton – i.e., assume Mount Royal intruded into a preexisting strata of sedimentary rocks.) [2 marks]
f. Through use of a sketch, provide a geological reconstruction for Mount Royal around the time at which the intrusion took place. Add sketches that provide before and after illustrations. [3 marks each = 9 marks; add 3 bonus marks for 3D block diagrams]
g. Provide a geologically sound narrative to account for Mount Royal’s evolution through use of your sketches – from the past, through to how it appears today. [3 marks]
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2. Locate a geological map of Mount Royal (e.g., Plandowski’s or Eby’s Figure 3). a. Prepare a geological cross section that trends East-West. Your cross section
should be to scale, and intersect with the thin Utica shale lithology that is present at the easternmost edge of Mount Royal. Label each lithology on your cross section, and indicate which fundamental rock type it represents. In addition to your cross section, provide an annotated version of the geological map you used to indicate the location of your cross section in map view. [10 marks]
b. According to your cross section, which lithology (or lithologies) has the Mount Royal pluton intruded into? [2 marks]
c. From your geological section, estimate the thickness of the Utica shale lithology at the easternmost edge of the pluton. [3 marks]
d. According to Bodycomb (2001), the metamorphic aureole extended for about 800 m. Indicate this on your cross section by extending an 800 m thick region from the edge of the last igneous lithology into a sedimentary one. [4 marks]
3. According to Eby: “…the intrusion is in contact with Ordovician shales (Utica formation)
and limestones (Trenton formation) that have been metamorphosed to the pyroxene hornfels facies.” And, according to Bodycomb, maximum temperatures were estimated at ~500 ℃, while pressures would have been relatively low (less than 2 kbars).
a. Given this context, which polymorph of Al2SiO5 might you expect to find in a sample of the hornfels rock from this location? Using the Phase Change animation for Al2SiO5, locate this polymorph on the pressure-temperature graph provided. Obtain a screenshot of your graphical interpretation that includes a representation of its crystalline shape. [2 marks]
b. Suppose that during an earlier stage of contact metamorphism temperatures were above 725 ℃, and pressures were higher. Using the Phase Change animation for Al2SiO5, locate this polymorph on the pressure-temperature graph provided. Obtain a screenshot of your graphical interpretation that includes a representation of its crystalline shape. [2 marks]
c. Suppose that at some time in the distant future, a sample of the mineral produced in Question 3(a) is buried to a pressure in excess of 4.0 kbars, without a change in temperature. Using the Phase Change animation for Al2SiO5, locate this polymorph on the pressure-temperature graph provided. Obtain a screenshot of your graphical interpretation that includes a representation of its crystalline shape. [2 marks]
d. Provide a process-flow diagram that makes use of The Rock Cycle to account for the scenario described in Question 3(c). [3 marks]
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4. Age relationships. a. The sedimentary rocks, that Mount Royal has intruded into, date back to the
Ordovician. Estimate their youngest-possible age, and add this information to your sketches. [5 marks]
b. Eby provides ages for the igneous rocks that comprise Mount Royal. Estimate this age and add it to your sketches. Knowing that the of the hornfels facies rocks (Question 3) are the byproduct of contact metamorphism, what is their age most likely to be? Explain. [8 marks]
c. Are these relative ages, i.e., your answers to questions 4(a) and 4(b), consistent with the intrusion hypothesis? Explain. [2 marks]
5. The origin of Mount Royal remains a matter of some debate.
a. According to Tourisme Montreal, what is the myth surrounding this prominent feature of the city? [2 marks]
b. Other sources suggest that the Monteregian Hills have an origin that is analogous to the Hawaiian islands and seamounts.
i. Identify the island/seamount chain that the Monteregian Hills (including Mount Royal) are deemed to be a part of. [1 mark]
ii. Briefly described the Plate Tectonic setting required for the island/seamount chain origin. [2 marks]
iii. Based on the island/seamount interpretation for the origin of the Monteregian Hills, describe plate motion and ages in relative terms. [4 marks]
c. Does Eby’s grain-size data, for this feature’s igneous rocks, encourage or discourage belief in this myth? Explain. [3 marks]
d. Eby claims that a failed aulacogen allows for an interpretation that is more consistent with the geological/geochronological evidence.
i. Define this term and provide a sketch of its Plate Tectonic context. [4 marks]
ii. In stating “… note the approximately 120° angle between the [Monteregian Hills] and younger [White Mountain] plutons …” draws our attention to the spatial appearance of these intrusions. By annotating Eby’s Figure 1, are you able to confirm the angular relationship between these series of plutons? [3 marks]
iii. Is this interpretation consistent with the Tourisme Montreal myth? Explain. [3 marks]
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[Marking: ● 1: 22 marks (+3 bonus) ● 2: 19 marks ● 3: 9 marks ● 4: 15 marks ● 5: 22 marks ● Total: 87 marks]
Resources Bodycomb, V., FIELD TRIP 2: THE IGNEOUS, SEDIMENTARY AND METAMORPHIC HISTORY OF MOUNT ROYAL, http://transsexy.geophys.mcgill.ca/~olivia/UPE/Field_trips/trip2.html#geology, 2001. (Plandowski’s geological map is referenced in this resource.) Available from: Nelson Eby, Sep 15, 2015 https://www.researchgate.net/publication/281784303_GEOLOGY_AND_PETROLOGY_OF_THE_MONT_ROYAL_PLUT ON_MONTREAL_QUEBEC, DOI: 10.13140/RG.2.1.5022.8884 ·
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