GEO 215 Minerals & Rocks
Final Exam Review
Metamorphic Rocks
(IGNEOUS-SEDIMENTARY REVIEW SHOULD ALSO BE
CONSULTED)
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Make sure you know the formulas / compositions of common rock-forming
minerals:
Quartz SiO2
Olivine (Mg,Fe)2SiO4
K-spar KAlSi3O8
Plagioclase (Ca,Na)AlSi3O8
Orthopyroxene (Mg,Fe)SiO3
Augite
Hornblende
Biotite
Muscovite
AND, metamorphic minerals… [see attached sheet]
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Be able to classify metamorphic rocks --o Remember: Two classifications: Texture and Composition (bulk X)
o TEXTURE: Foliated: slate – phyllite – schist – gneiss – granulite
and Non-foliated
o COMPOSITION: pelitic (Al-rich) – quartzofeldspathic – mafic
(Fe+Mg-rich) -- calcic – ultramafic (Mg-rich) – iron-rich
What are the AGENTS of metamorphism (T, P, X) and how do they influence
metamorphism and metamorphic rocks?
What are the major TYPES of metamorphism (Regional and Contact)? Are
there others? What is “progressive” metamorphism (and regressive)? What
is meant by “grade”?
Be able to explain the ideas behind ZONES (mappable metamorphic units
defined by equilibrium assemblages). What is an “isograd”? Why does X
have to be constant when mapping zones? What is the difference between
“Barovian zones” and “Buchan zones”?
What are FACIES, and how are they used in a practical sense? What is a
FACIES SERIES, and what do they tell us about thermal-tectonic
environments?
Know simple metamorphic reactions, and why they are significant. How does
schist transform to gneiss in pelitic systems? What is a “cyclic” reaction?
What is involved in “dehydration”?
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Be able to identify “protoliths” of metamorphic rocks, given a mineral
assemblage [e.g., muscovite-staurolite-almandine = pelitic; calcite-diopsidetremolite = calcic (specifically “impure dolostone”); chlorite-actinolite-epidotealbite = mafic, etc.
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Know the Al2SiO5 polymorphs (Andalusite – Kyanite -- Sillimanite) cold! …
and be able to make interpretation of metamorphic conditions on the basis of
their presence in a rock.
What does the Fe/Mg ration in almandine-pyrope garnet tell you about
pressure of formation? What does the Na/Ca ratio tell you about pressure in
feldspar? Which mineral (or “what minerals…are…”) in this group is a high-P
mineral? Pyrope – jadeite – glaucophane – kyanite?
Be able to associate metamorphic rocks and mineral assemblages with major
tectonic environments, i.e., subduction trench, volcanic island arc, arcforeland areas (regional metamorphism), ocean ridges, continental collision
(Alps, Himalayas, Grenville, etc.)…
Be able to associate famous places with their famous rocks or formations.
Examples: Franciscan Formation (what is a “mélange complex”?), Dutchess
Co., NYS, Dalradia, Scotland, Adirondack Mtns., NYS., Precambrian shields
of Minnesota, Michigan, Wisconsin, Canada, (shields on all other major
continents), Rocky Mountains (and other western N.A. mountain belts), etc.
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READING:
Read ALL of Chapter 15. It contains the essentials of what I have discussed in class.
Take special note of:
Fig. 15.1, page 424
Fig. 15.3, page 429
Fig. 15.4, page 430
Chapter 16: Read from 444 to 453; then read “AFM diagram, Reactions…” (p. 460) to
463 (beyond, if you want!). Diagram Fig. 16.10 is worth a look.
Look over section on “Geothermobarometry” (P-T determinations) beginning on page
470 and ending on page 480, just to get an idea of what methods can be used to assess
P and T in metamorphic rocks. This is the “cutting edge” aspects of metamorphic
petrology, and where is gets the most interesting, and practical. Also requires a very
specialized Ph.D. and years of practice!
Check out Fig. 16.25; very useful! Read the Summary, page 487.
For those of you who still do not know what PERIDOTITE is, check out Chapter 17. Of
interest is how minerals change with depth (pressure), and that the mantle rocks must
get very complicated and different with depth. This chapter discusses how we know
these things even though we have no samples from below the upper parts of the Upper
Mantle. We have examples of upper mantle peridotites on display in lab.
Final exam is: 8:30-10:30 Thursday, December 18 in Houghton 112.