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Zorluk: ZorRocks, Minerals, and Soil

A field geologist examines an outcrop exhibiting distinct, alternating light and dark crystalline bands. Laboratory analysis reveals that the mineral grains recrystallized under intense directional pressure and elevated temperatures deep within Earth's crust without melting into liquid magma. Which rock classification and formation mechanism correctly identify this specimen?

  1. A
    Clastic sedimentary rock formed through the sequential deposition, compaction, and cementation of distinct mineral sediments
  2. B
    Extrusive igneous rock formed by the rapid surface cooling and alternating solidification of differentiated lava flows
  3. Foliated metamorphic rock formed by high-grade regional metamorphism causing mineral recrystallization and compositional bandingCevap
  4. D
    Intrusive igneous rock formed by gravity settling and fractional crystallization of minerals in a magma chamber

Cevap

Foliated metamorphic rock formed by high-grade regional metamorphism causing mineral recrystallization and compositional banding
The correct answer accurately identifies the sample as a foliated metamorphic rock. Regional metamorphism subjects preexisting rock to extreme differential stress and high temperatures. In response, minerals recrystallize and migrate into alternating light-colored felsic bands (quartz and feldspar) and dark-colored mafic bands (biotite and amphibole) in the solid state without melting.

Adım Adım Çözüm

1
Analyze the geological conditions and physical characteristics provided in the prompt
The rock exhibits alternating light and dark crystalline bands formed under intense heat and directional pressure deep in the crust without melting.
Identifying that the transformation occurred entirely in the solid state under differential stress is crucial for determining the rock family.
2
Differentiate between igneous, sedimentary, and metamorphic formation pathways
Igneous rocks require liquid magma or lava cooling, sedimentary rocks require surface sediment lithification, while metamorphic rocks form by solid-state alteration under heat and pressure.
Only metamorphism alters mineralogy and texture without melting the parent rock.
3
Determine the specific textural category of the metamorphic rock
The segregation of minerals into parallel light and dark bands represents foliation (specifically gneissic banding) characteristic of high-grade regional metamorphism.
Differential tectonic pressure aligns and separates recrystallizing silicate minerals into visible compositional layers.

Anahtar Kavram

Metamorphic Rock Classification and Gneissic Foliation
Tahmini Süre:1m 15s
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Konular

Rocks, Minerals, and Soil

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