Magmatic and Metamorphic Processes: Igneous Petrology, Phase Equilibria, and Geochemistry

Vocabulary practice flashcards covering igneous rock classification, basalt occurrences, mid-ocean ridge geodynamics, magma geochemistry, and binary and ternary phase equilibria.

[Workshop 1: The Classification of Igneous Rocks] Which coarse-grained igneous rock texture is characterized by crystal grain sizes ranging between $5\text{--}50\,\text{mm}$, indicating slow cooling in plutonic (intrusive) settings?

Phaneritic texture (Source: Workshop 1 – The Classification of Igneous Rocks)

[Workshop 1: The Classification of Igneous Rocks] Which fine-grained igneous rock texture features crystal grain sizes smaller than $1\,\text{mm}$, indicating rapid cooling typical of volcanic (extrusive) environments?

Aphanitic texture (Source: Workshop 1 – The Classification of Igneous Rocks)

[Workshop 1: The Classification of Igneous Rocks] Which double-ternary classification scheme established by Le Bas and Streckeisen (1991) classifies igneous rocks with mafic mineral content $M < 90\%$ based on normalized proportions of Quartz, Alkali feldspar, Plagioclase, and Feldspathoid?

QAPF diagram (Source: Workshop 1 – The Classification of Igneous Rocks)

[Workshop 1: The Classification of Igneous Rocks] Which ternary diagram is used to classify ultramafic rocks with mafic mineral content $M > 90\%$, dividing them into peridotites ($> 40\%$ olivine) and pyroxenites ($< 40\%$ olivine)?

Ultramafic rock classification (Ol-Opx-Cpx diagram) (Source: Workshop 1 – The Classification of Igneous Rocks)

[Workshop 1: The Classification of Igneous Rocks] Which ultramafic rock type possesses a mafic mineral content of $M > 90\%$ with olivine abundance exceeding $40\%$, forming the primary rock type of Earth's upper mantle?

Peridotite (Source: Workshop 1 – The Classification of Igneous Rocks)

[Workshop 1: The Classification of Igneous Rocks] Which ultramafic peridotite rock consists of greater than $90\%$ modal olivine?

Dunite (Source: Workshop 1 – The Classification of Igneous Rocks)

[Workshop 3 & 4: Occurrence of Basalt] Which basalt type erupts along the global $60{,}000\,\text{km}$ divergent plate boundary system, generating roughly $20\,\text{km}^3$ of magma annually and forming oceanic crust approximately $7\,\text{km}$ thick?

Mid-Ocean Ridge Basalt (MORB) (Source: Workshop 3 & 4 – Basalt)

[Workshop 3 & 4: Occurrence of Basalt] Which characteristic basaltic texture occurs when clinopyroxene completely encloses plagioclase feldspar laths?

Ophitic texture (Source: Workshop 3 & 4 – Basalt)

[Workshop 3 & 4: Occurrence of Basalt] Which igneous basaltic texture features plagioclase feldspar laths that are larger than pyroxene grains and partially enclose or overgrow them?

Sub-ophitic texture (Source: Workshop 3 & 4 – Basalt)

[Workshop 3 & 4: Occurrence of Basalt] What term describes skeletal crystals characterized by hollow or stepped crystal interiors resulting from rapid crystal growth during quenching?

Hopper crystals (Source: Workshop 3 & 4 – Basalt)

[Workshop 3 & 4: Occurrence of Basalt] What geological designation refers to extensive crustal emplacements of predominantly basaltic magma erupted across continents and ocean basins within short timescales (e.g., Siberian Traps, Deccan, Ontong Java)?

Large Igneous Provinces (LIPs) (Source: Workshop 3 & 4 – Basalt)

[Lecture 1: Mid-ocean Ridges] By what mechanism does asthenospheric mantle rise into the space created by lithospheric thinning beneath mid-ocean ridges, undergoing decompression melting without active thermal plume driving?

Passive upwelling (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] What primary plate-driving force is produced as cold, dense oceanic lithosphere sinks into the asthenosphere, driven further by the metamorphic phase transition of basalt to eclogite?

Slab pull (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] Which secondary plate-driving force results from gravitational potential energy due to the elevated topography of young, hot mid-ocean ridges relative to deeper abyssal plains?

Ridge push (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] Which depleted residual mantle peridotite is left behind after partial melting ($< 25\%$) extracts basaltic melt, consisting of roughly $75\%$ olivine and $25\%$ orthopyroxene?

Harzburgite (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] What geological term denotes an uplifted, preserved slice of oceanic lithosphere obducted onto continental crust during tectonic collisions (e.g., Troodos in Cyprus)?

Ophiolite (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] Which layer of the oceanic crust (Layer 2b) consists of sub-parallel, vertical basaltic dykes displaying one-sided chilled margins?

Sheeted dyke complex (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] Which metalliferous pelagic claystone sediment forms as fallout from hydrothermal smoker plumes and contains hydrated iron(III) oxide ($\text{Fe}_2\text{O}_3\cdot\text{H}_2\text{O}$), manganese oxide ($\text{MnO}_2\cdot n\text{H}_2\text{O}$), and aluminum oxide ($\text{Al}_2\text{O}_3$)?

Umber (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 1: Mid-ocean Ridges] Which type of economic ore deposit forms at submarine hydrothermal vents when superheated ($\sim 400^\circ\text{C}$) fluids mix with cold seawater ($\sim 2^\circ\text{C}$), precipitating sulfides of $\text{Zn}$, $\text{Pb}$, $\text{Cu}$, and $\text{Au}$?

Volcanogenic Massive Sulphide (VMS) deposit (Source: Lecture 1 – Mid-ocean Ridges)

[Lecture 2: Chemistry of Igneous Rocks] Which cosmological rule establishes that chemical elements with even atomic numbers are systematically more stable and abundant than adjacent elements with odd atomic numbers?

Oddo-Harkins effect (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which rule of ionic substitution states that ions of the same charge and similar ionic radii (differing by less than $15\%$) can freely substitute for one another in a crystal lattice?

Goldschmidt's first rule (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which mechanism allows two ions differing by one unit of charge to substitute for other ions simultaneously while maintaining overall electrical neutrality (e.g., $\text{Ca}^{2+}\text{Al}^{3+} \rightleftharpoons \text{Na}^{+}\text{Si}^{4+}$)?

Coupled substitution (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which geochemical modification specifies that ionic substitution is restricted when competing ions have different electronegativities and form bonds of differing ionic versus covalent character?

Ringwood's modification (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] What term designates elements that display a strong affinity for oxygen and silicate phases, concentrating predominantly in the Earth's crust and mantle (e.g., $\text{Si}$, $\text{Al}$, $\text{Na}$, $\text{K}$, $\text{Ca}$)?

Lithophile elements (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] What term designates elements that display a strong affinity for sulfur, concentrating preferentially in sulfide minerals and ore deposits (e.g., $\text{Cu}$, $\text{Zn}$, $\text{Pb}$, $\text{As}$)?

Chalcophile elements (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] What term designates elements that display a strong chemical affinity for metallic iron, concentrating preferentially in planetary metallic cores (e.g., $\text{Fe}$, $\text{Ni}$, $\text{Pt}$, $\text{Ir}$)?

Siderophile elements (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] What phenomenon causes the steady decrease in trivalent ionic radii across the Rare Earth Elements ($\text{La}^{3+}$ to $\text{Lu}^{3+}$) due to poor nuclear charge shielding by 4f electrons?

Lanthanide contraction (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which ratio measures the concentration of a trace element in a solid mineral phase relative to its concentration in the coexisting silicate melt ($D = C_{\text{mineral}} / C_{\text{melt}}$)?

Partition coefficient ($D$) (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which mathematical equation ($C_L / C_0 = 1 / [D + F(1 - D)]$) describes trace element concentrations in a melt fraction $F$ when liquid and solid residue remain in physical and chemical contact?

Equilibrium partial melting equation (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which mathematical equation ($C_L / C_0 = F^{(D-1)}$) models trace element fractionation in a melt fraction $F$ during fractional crystallization when crystals are removed immediately upon crystallization?

Rayleigh distillation equation (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] What term describes the progressive geochemical evolution trajectory of an igneous melt suite driven by crystal fractionation, depleting $\text{MgO}$ while enriching $\text{SiO}_2$?

Liquid line of descent (Source: Lecture 2 – Magma Chemistry)

[Lecture 2: Chemistry of Igneous Rocks] Which geochemical technique normalizes measured trace element concentrations against primitive chondritic meteorites to eliminate Oddo-Harkins zig-zag anomalies?

Chondrite normalization (Source: Lecture 2 – Magma Chemistry)

[Lecture 3: Binary Phase Diagrams] Which thermodynamic principle is expressed by the formula $F + P = C + 2$, relating degrees of freedom ($F$), phase count ($P$), and chemical components ($C$)?

Gibbs phase rule (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What is a region on a phase diagram called where two intensive variables (such as temperature and pressure) can vary independently ($F = 2$) without altering the phase assemblage?

Divariant field (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What is a boundary curve on a phase diagram called where a system has only one degree of freedom ($F = 1$), requiring coupled changes in state variables to maintain equilibrium?

Univariant line (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What designation describes a point on a phase diagram where degrees of freedom equal zero ($F = 0$), fixing the temperature, pressure, and composition of all coexisting phases?

Invariant point (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What is the boundary curve on a phase diagram above which a multicomponent system is entirely liquid and below which crystal precipitation begins?

Liquidus (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What is the boundary line on a phase diagram below which a multicomponent system is entirely solid and above which initial melting begins?

Solidus (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] Which invariant point on a phase diagram marks the minimum temperature at which a liquid can exist, crystallizing into two or more solid phases simultaneously upon cooling?

Eutectic point (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] Which graphical method applied to tie-lines on phase diagrams calculates the relative mass proportions of coexisting equilibrium phases using inverse segment lengths?

Lever rule (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] Which crystal growth feature (such as a calcic anorthite core rimmed by sodic albite) records a failure to maintain chemical equilibrium with the liquid during fractional crystallization?

Compositional zoning (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What melting behavior is characterized by a solid phase transitioning completely into a liquid of identical chemical composition at a constant temperature?

Congruent melting (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What melting behavior occurs when a solid phase decomposes at a constant temperature into a liquid of differing composition and a newly formed solid phase (e.g., enstatite melting to liquid plus forsterite)?

Incongruent melting (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 3: Binary Phase Diagrams] What discontinuous invariant reaction involves an early-formed crystal reacting with residual melt upon cooling to yield a distinct new solid phase ($\text{Liquid} + \text{Forsterite} \rightarrow \text{Enstatite}$)?

Peritectic reaction (Source: Lecture 3 – Binary Phase Diagrams)

[Lecture 4: Ternary Phase Diagrams] Which triangular diagram is used to illustrate equilibrium crystallization, cotectic liquidus surfaces, and liquid lines of descent in three-component chemical systems?

Ternary phase diagram (Source: Lecture 4 – Ternary Phase Diagrams)

[Lecture 4: Ternary Phase Diagrams] What univariant boundary curve on a ternary liquidus projection represents the path along which a liquid coexists with and simultaneously crystallizes two separate solid phases?

Cotectic curve (Source: Lecture 4 – Ternary Phase Diagrams)

[Lecture 4: Ternary Phase Diagrams] What invariant point ($F = 0$) in a three-component system corresponds to the coexistence of a liquid with three crystalline solid phases at the absolute minimum melting temperature?

Ternary eutectic (Source: Lecture 4 – Ternary Phase Diagrams)