Question

The silicate mineral(s) that commonly occur(s) in regionally metamorphosed siliceous dolomitic limestone is/are

• A. Diopside
• B. Cordierite
• C. Tremolite
• D. Wollastonite

Hint:

In regional metamorphism of dolomitic limestone, diopside and tremolite are the common minerals, while cordierite and wollastonite are less common in this setting.

Answer 1

The Correct Option is A, C, D

Regionally metamorphosed siliceous dolomitic limestone undergoes significant changes in mineral composition due to high pressure and temperature. This process, known as regional metamorphism, produces a variety of silicate minerals. The silicate minerals commonly found in such metamorphosed rocks depend on the mineral composition of the original limestone and the metamorphic conditions.
- Diopside: Diopside is a clinopyroxene mineral that commonly forms in metamorphosed rocks under moderate to high-temperature conditions. It is one of the primary minerals found in siliceous dolomitic limestone that has undergone regional metamorphism. The mineral diopside forms due to the chemical reactions between the calcite and silicate components in the limestone during metamorphism.
- Tremolite: Tremolite is an amphibole mineral that can also form in metamorphosed limestones, particularly in more silica-rich conditions. It forms in the presence of water and high-pressure conditions, but it is less abundant than diopside in dolomitic limestone.
- Cordierite: While cordierite is a typical mineral in certain metamorphic environments, it is not commonly found in siliceous dolomitic limestone. It tends to form under conditions of high-temperature and low-pressure, often in the presence of aluminum-rich materials.
- Wollastonite: Wollastonite is a mineral that forms in the presence of calcium and silica, but it is not typically associated with dolomitic limestone metamorphism. It is more common in other metamorphic settings, such as marble and skarn.
Step 1: Understanding Regional Metamorphism
Regional metamorphism occurs when rocks are subjected to high pressures and temperatures over large areas, often due to tectonic forces. This process leads to the recrystallization of minerals and the formation of new minerals. In the case of siliceous dolomitic limestone, the minerals typically present after metamorphism include pyroxenes like diopside and amphiboles like tremolite, as well as other minerals depending on the exact chemical composition of the rock.
Step 2: Analyzing the Minerals
- Diopside: Diopside is one of the most common minerals found in metamorphosed dolomitic limestone due to its formation under the specific conditions of regional metamorphism.
- Tremolite: While tremolite is present in some metamorphic rocks, it is less characteristic of dolomitic limestone compared to diopside.
- Cordierite and Wollastonite: Both of these minerals form under different conditions and are not as commonly associated with siliceous dolomitic limestone.
Thus, the correct answer is (A) Diopside.