(1) What metamorphic rock is formed when a limestone is metamorphosed? (2) When the parent rock is a limestone or quartz sandstone, what physical property of the resulting metamorphic rock is used to indicate the intensity of metamorphism? (3) Name three minerals that are stable at the widest range of temperatures and pressures. 1. 2. 3. (4) Briefly explain how a metamorphic rock can recrystallize while remaining in a solid phase. (5) Name 4 examples of non-foliated metamorphic rocks. 1. 2. 3. 4 (6) Related to the previous question, what causes the variations among the non-foliated metamorphic rocks?
The Correct Answer and Explanation is :
Answers:
- What metamorphic rock is formed when a limestone is metamorphosed?
Marble. - When the parent rock is a limestone or quartz sandstone, what physical property of the resulting metamorphic rock is used to indicate the intensity of metamorphism?
The grain size of the resulting metamorphic rock is used to indicate the intensity of metamorphism. - Name three minerals that are stable at the widest range of temperatures and pressures.
- Quartz
- Feldspar
- Garnet
- Briefly explain how a metamorphic rock can recrystallize while remaining in a solid phase.
Recrystallization in metamorphic rocks occurs due to heat and pressure without the rock melting. Under these conditions, the minerals rearrange their atomic structure to form more stable configurations. This process typically involves the growth of new mineral grains or the reorganization of existing grains. Solid-phase recrystallization maintains the rock’s overall solid state while allowing minerals to adjust their size, shape, and orientation. - Name 4 examples of non-foliated metamorphic rocks.
- Marble
- Quartzite
- Hornfels
- Anthracite coal
- What causes the variations among the non-foliated metamorphic rocks?
The variations among non-foliated metamorphic rocks are primarily due to differences in the composition of the parent rock and the metamorphic conditions (temperature and pressure) under which they formed. For example, marble originates from limestone, quartzite from sandstone, and hornfels often forms from shale under high temperatures but low pressures.
Explanation (300 Words):
Metamorphic rocks are formed when pre-existing rocks undergo changes due to heat, pressure, and chemically active fluids. These changes can result in recrystallization, textural transformations, and the formation of new minerals. For example, when limestone is subjected to metamorphism, it recrystallizes into marble, a rock characterized by interlocking calcite crystals. This process enhances its strength and aesthetic appeal.
The intensity of metamorphism affects physical properties like grain size. Under higher temperatures and pressures, grains grow larger, indicating a more intense metamorphic environment. Quartzite, derived from quartz sandstone, shows similar behavior, with larger grains reflecting higher metamorphic grades.
Certain minerals, such as quartz, feldspar, and garnet, are stable across a wide range of metamorphic conditions. These minerals serve as reliable indicators in determining the metamorphic history of rocks.
Recrystallization, a key process in metamorphism, occurs entirely in the solid state. Heat and pressure cause mineral grains to dissolve and redeposit in a more stable arrangement without the rock melting. This process refines the rock’s texture and mineral composition while maintaining its solid framework.
Non-foliated metamorphic rocks, such as marble, quartzite, hornfels, and anthracite coal, lack a layered or banded appearance. Their variations stem from differences in the parent rock composition and the specific metamorphic conditions. For example, marble originates from limestone, while quartzite comes from quartz sandstone. The absence of foliation indicates uniform stress or dominance of recrystallization over deformation during metamorphism.