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QFL diagram

QFL diagram is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand QFL diagram rather than just read about it. In short: A QFL diagram or QFL triangle is a type of ternary diagram that shows compositional data from sandstones and modern sands, point counted using the Gazzi-Dickinson method. The abbreviations used are as follows: Q – quartz F – feldspar L – lithic fragments In general, the most contentious item counted is chert, which is usually counted as a lithic fragment, but is sometimes better suited in the Q pole.

QFL diagram — main illustration
QFL diagram — illustration

Key takeaways

  • QFL diagram belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect QFL diagram to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of QFL diagram from memory before moving on to harder problems.

Reference excerpt

A QFL diagram or QFL triangle is a type of ternary diagram that shows compositional data from sandstones and modern sands, point counted using the Gazzi-Dickinson method. The abbreviations used are as follows:

Q – quartz F – feldspar L – lithic fragments In general, the most contentious item counted is chert, which is usually counted as a lithic fragment, but is sometimes better suited in the Q pole. When this happens, the pole is renamed 'Qt' instead of Q.

The importance of a QFL triangle is mainly demonstrated in tectonic exercises. As first demonstrated in the 1979 paper by Bill Dickinson and Chris Suczek, the composition and provenance of a sandstone is directly related to its tectonic environment of formation.

Craton sands are clustered near the Q pole. As sandstones, these are known as quartz arenites. Transitional continental sands are along the QF line. As sandstones, these are known as arkoses. Basement uplift sands are near the F pole. This includes "thick-skinned tectonics." As sandstones, these are known as arkoses. Recycled orogen sands plot near the Q pole, but with significant F and L components. This includes "thin-skinned tectonics" common in subduction back-arc thrusting. As sandstones, these are known as lithic sandstones. Arc sands plot along the F and L line, with sometimes significant Q components. Clustering near the F pole indicates a dissected arc, and clustering near the L pole indicates an undissected, or new arc. As sandstones, these are known as arkoses and/or lithic sandstones.

See also Folk classification

References

Illustrations

QFL diagram: Ternary diagram showing the relative abundance of quartz, feldspar, and lithic grains and views of what selected compositions would look like.
Ternary diagram showing the relative abundance of quartz, feldspar, and lithic grains and views of what selected compositions would look like.
QFL diagram: QFL triangle showing schematic plots of common sand compositions
QFL triangle showing schematic plots of common sand compositions

Worked examples

Example 1 — a first encounter with QFL diagram

Start with the simplest possible case. Write down what QFL diagram claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to QFL diagram before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about QFL diagram ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of QFL diagram

In research
QFL diagram appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses QFL diagram in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
QFL diagram is common in secondary-school and first-year university syllabi. It links to neighbouring topics Petrology, Petrology stubs, Sandstone, so understanding it makes those chapters shorter.
In everyday life
Look for QFL diagram outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study QFL diagram in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what QFL diagram means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain QFL diagram out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is QFL diagram in simple terms?

A QFL diagram or QFL triangle is a type of ternary diagram that shows compositional data from sandstones and modern sands, point counted using the Gazzi-Dickinson method. The abbreviations used are as follows: Q – quartz F – feldspar L – lithic fragments In general, the most contentious item counte…

Why does QFL diagram matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study QFL diagram?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on QFL diagram.

Tags

  • Petrology
  • Petrology stubs
  • Sandstone

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