Geology: Harker Diagrams and Calcium-Alkaline Series
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Questions and Answers

What are Harker diagrams primarily used for in geology?

Harker diagrams are used to show the relationship between various chemical components of rocks.

What is the main trend observed in Harker diagrams as SiO₂ increases?

The main trend is a decreasing linear relationship as SiO₂ content increases.

Which oxide components are plotted against SiO₂ on the left side of the Harker diagrams?

The oxides plotted are Al₂O₃, FeO, and Na₂O.

What is the X-axis label in Harker diagrams?

<p>The X-axis is labeled as SiO₂ (%).</p> Signup and view all the answers

Describe a feature of the data points in Harker diagrams.

<p>Each plot shows data points that indicate the correlation between a specific oxide and SiO₂ content.</p> Signup and view all the answers

What does the normative composition of the Série Cálcio - Alcalina indicate about silica?

<p>It indicates supersaturation in silica.</p> Signup and view all the answers

How is the magmatism of the Série Cálcio - Alcalina characterized?

<p>It is characterized by arc magmatism.</p> Signup and view all the answers

What occurs with the potassium content in the evolution of Série Cálcio - Alcalina?

<p>There is an increase in potassium content.</p> Signup and view all the answers

In terms of granitic terms, what type of environments are described for Série Cálcio - Alcalina?

<p>They are described as post-collisional environments.</p> Signup and view all the answers

Which study is referenced regarding the environments of Série Cálcio - Alcalina?

<p>The study by Harris et al, 1986 is referenced.</p> Signup and view all the answers

What does the partition coefficient ( $K_d$) represent in mineral and magma interactions?

<p>It represents the distribution of an element between a mineral and magma in equilibrium.</p> Signup and view all the answers

How is the partition coefficient ( $K_d$) calculated?

<p>It is calculated using the formula $K_d = \frac{C_s}{C_l}$, where $C_s$ is the concentration in the solid and $C_l$ is the concentration in the liquid.</p> Signup and view all the answers

What does it mean if a partition coefficient ($K_d$) is greater than 1?

<p>It indicates that the element is <strong>compatible</strong> with the mineral, favoring mineral over magma.</p> Signup and view all the answers

What classification corresponds to a partition coefficient ($K_d$) less than 1?

<p>It is classified as <strong>incompatible</strong>, meaning the element prefers to remain in the magma rather than in the mineral.</p> Signup and view all the answers

Provide an example of information visually represented in relation to partition coefficients.

<p>An illustration showing magma with an element like V³⁺ indicated between the magma and the mineral.</p> Signup and view all the answers

What does the Y-axis of the graph represent in the context of alkaline sub-saturated silica series?

<p>The Y-axis represents the combined weight percentage of Na₂O and K₂O.</p> Signup and view all the answers

Name two rock types classified under the Strongly Alkaline series.

<p>Foidite and Teferito.</p> Signup and view all the answers

How can the Alkaline series rock types be characterized in relation to feldspathoids?

<p>They are characterized by the modal and normative presence of feldspathoids and the absence of quartzite.</p> Signup and view all the answers

What is the significance of the X-axis in the graph provided?

<p>The X-axis represents the weight percentage of SiO₂.</p> Signup and view all the answers

Which rock types are included in the Subalkaline series?

<p>Basalt and Andesite.</p> Signup and view all the answers

What are comparative elements in minerals?

<p>Comparative elements are those that are incorporated into the main minerals, such as Ni²⁺ substituting for Fe-Mg in olivine.</p> Signup and view all the answers

How do incompatible elements behave during fractional crystallization?

<p>Incompatible elements are enriched in the magma as it undergoes fractional crystallization and can form rare minerals.</p> Signup and view all the answers

What is the significance of LIL and HFS in the context of incompatible elements?

<p>LIL and HFS refer to categories of incompatible elements that are enriched during the crystallization process.</p> Signup and view all the answers

Provide an example of an incompatible element and the mineral it forms.

<p>An example of an incompatible element is Zr⁴⁺, which forms the mineral zircon.</p> Signup and view all the answers

What is the relationship between ionic charge and the behavior of compatible and incompatible elements?

<p>The relationship illustrated in the graph shows that elements with specific ionic charges behave differently during crystallization, influencing their compatibility.</p> Signup and view all the answers

What does incompatibility of elements depend on?

<p>Incompatibility depends on the minerals and melts involved.</p> Signup and view all the answers

Why is Sr considered incompatible in certain minerals?

<p>Sr has a high partition coefficient in garnet, indicating it preferentially remains in the melt rather than entering the crystalline structure.</p> Signup and view all the answers

Identify an element that has high compatibility in olivine.

<p>Ni (Nickel) has a partition coefficient of 14.5 in olivine.</p> Signup and view all the answers

What can be inferred about Ba's behavior in amphibole compared to garnet?

<p>Ba has a much higher partition coefficient in amphibole (6.8) compared to garnet (0.923), indicating it prefers to remain in the melt.</p> Signup and view all the answers

How does the partition coefficient of Ce vary across different minerals?

<p>Ce exhibits the highest partition coefficient in garnet (1.45) and lower values in olivine (0.010) and pyroxenes.</p> Signup and view all the answers

Which mineral is considered strongly fractionated in relation to Ni?

<p>Olivine is considered strongly fractionated in relation to Ni.</p> Signup and view all the answers

Which minerals have higher concentrations of Cr and Sc compared to olivine?

<p>Pyroxenes have higher concentrations of Cr and Sc compared to olivine.</p> Signup and view all the answers

What relationship can distinguish the effects of olivine and augite in rocks produced by fractional crystallization?

<p>The ratios Ni/Cr or Ni/Sc can distinguish the effects of olivine and augite.</p> Signup and view all the answers

What are the incompatible elements mentioned that are typically excluded from most minerals?

<p>Sr, Ba, and Rb are the incompatible elements mentioned.</p> Signup and view all the answers

Which minerals are exceptions for the exclusion of Sr, Ba, and Rb?

<p>Plagioclase, alkali feldspar, and micas are exceptions for the exclusion of Sr, Ba, and Rb.</p> Signup and view all the answers

What are the main rock types associated with the toleitic series found in oceanic crust environments?

<p>The main rock types are gabros, tonalitos, and trondhjemitos.</p> Signup and view all the answers

In the QAPF diagram, where do toleitic series from oceanic and continental environments fall?

<p>Oceanic toleitic series are at the base, while continental series are at the top of the subalcaline field.</p> Signup and view all the answers

What geological features are typical of toleitic series?

<p>Toleitic series are typical of oceanic ridges and mid-oceanic chains.</p> Signup and view all the answers

Which diagrams show the trend of toleitic rock types, and how are they classified?

<p>The QAPF and TAS diagrams show the trend, classifying them as subalkaline.</p> Signup and view all the answers

What is the distribution of toleitic series in the TAS diagram?

<p>Toleitic series are distributed at the base for oceanic and at the top for continental in the TAS diagram.</p> Signup and view all the answers

What primarily determines the characteristics of magmatic series rocks?

<p>The characteristics depend mainly on the proportions of Si, Al, Na, and K.</p> Signup and view all the answers

List two classifications within the magmatic series.

<p>Komatítico and Calc-alkalino.</p> Signup and view all the answers

What is the main distinction between máfico and ácido basic rocks?

<p>Máfico rocks are defined by the amount of máfic minerals, while ácido basic rocks are based on the SiO₂ content.</p> Signup and view all the answers

What does the term 'shoshonitic' classify in the context of the magmatic series?

<p>It classifies a type of máfico-felsico rock.</p> Signup and view all the answers

How are the magmatic series classifications primarily established?

<p>They are based on empirical mineralogical studies rather than a systematic approach.</p> Signup and view all the answers

What elements are primarily responsible for the characteristics of magmatic rocks?

<p>The characteristics depend mainly on the proportions of Si, Al, Na, and K.</p> Signup and view all the answers

What is the classification of rocks that are ultramafic to mafic?

<p>They are classified as Komatitico.</p> Signup and view all the answers

Define 'máfico-félmico' in the context of magmatic rock classification.

<p>'Máfico-félmico' is based on the quantity of 'máficos' minerals present.</p> Signup and view all the answers

What are the two bases for classifying rocks as acidic or basic?

<p>They are based on the amount of SiO₂ present.</p> Signup and view all the answers

What type of magmatic series does 'Shoshonítico' belong to?

<p>'Shoshonítico' belongs to the máfico-félfico classification.</p> Signup and view all the answers

Study Notes

Harker Diagrams

  • Harker diagrams are used in geology to show the relationship between various chemical components of rocks.
  • The diagrams typically display the correlation between the specific oxide and SiO₂ content.
  • The trend generally shows a decreasing linear relationship as SiO₂ increases.
  • The x-axis represents SiO₂ (%) and the y-axis represents the corresponding oxide (%).
  • Harker diagrams are used to interpret the chemical composition of igneous rocks and understand their formation processes.

Calcium-Alkaline Series

  • The normative composition of the calcium-alkaline series indicates supersaturation in silica.
  • The series is characteristic of arc magmatism, where its evolution is reflected by an increase in potassium content.
  • Granitic terms of this series are described as being from post-collisional environments (Harris et al, 1986).

Partition Coefficient

  • The partition coefficient (Kd) describes the distribution of an element between a mineral and a magma at equilibrium.
  • Kd = Cs/Cl, where Cs is the concentration in the solid phase and Cl is the concentration in the liquid phase.
  • Elements with Kd > 1 are considered compatible, meaning they are preferentially incorporated into the mineral.
  • Elements with Kd < 1 are considered incompatible, meaning they are preferentially retained in the melt.

Silica-Undersaturated Alkaline Series

  • This series is characterized by the presence of feldspathoids and the absence of quartz.
  • The series is divided into three groups based on Na₂O + K₂O and SiO₂ content:
    • Strongly alkaline series: Foidite, Teferito, Fonolito
    • Alkaline series: Trachite, Trachidandite, Rhyolite
    • Subalkaline series: Basalt, Andesite
  • The series can be classified as potassic or sodic.

Compatible and Incompatible Elements

  • Compatible elements are incorporated into the major minerals, for example, Ni²⁺ in olivine substituting Fe-Mg.
  • Incompatible elements (LIL and HFS) are enriched in the magma during fractional crystallization and can form rare minerals from highly fractionated magma. Examples: Zr⁴⁺ in zircon, REE³⁺ in monazite.

Fractionation of Elements in Rocks

  • Ni is strongly fractionated: olivine > pyroxenes + amphiboles
  • Cr and Sc are fractionated in pyroxenes: pyroxenes > olivine
  • The Ni/Cr or Ni/Sc ratio can distinguish the effects of olivine and augite on a suite of rocks produced by fractional crystallization.

Element Compatibility

  • The compatibility of an element depends on the minerals and melts involved.
  • Elements with lower coefficients of partition in olivine and pyroxene are considered incompatible and are enriched in the magma.
  • Elements with higher coefficients of partition in olivine and pyroxene are considered compatible and are depleted in the magma.

Magmatic Series

  • Magmatic series are defined by mineral and chemical characteristics of magmatic rocks, primarily based on the proportions of Si, Al, Na, and K.
  • The series is classified based on empirical studies and not a systematic approach, and often defined by chemical characteristics.
  • The main series are: komatiitic, tholeiitic, calc-alkaline, shoshonitic, and alkaline.
  • The terms mafic-felsic and acid-basic are used to describe the amount of mafic minerals and SiO₂ content in the rocks.

Tholeiitic Series

  • Tholeiitic series are characterized by rocks like gabbros, tonalites, and trondhjemites, mainly from oceanic crust environments.
  • These rocks define a tonalite trend on the QAPF and TAS diagrams.
  • Tholeiitic series are typical of mid-ocean ridges and ocean floor environments.
  • Tholeiitic series can be divided into oceanic (lower SiO₂ content) and continental (higher SiO₂ content) types.

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Description

Explore the relationships between various chemical components of igneous rocks through Harker diagrams. Understand the calcium-alkaline series and its significance in arc magmatism, along with the concept of partition coefficients in mineral chemistry. This quiz will test your knowledge on these essential geological concepts.

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