Question

The most commonly available minerals in the oceanic crust are:

• A. clinopyroxene, orthopyroxene, olivine
• B. quartz, feldspar, mica
• C. clinopyroxene, quartz, feldspar, mica
• D. orthopyroxene, feldspar, mica

Hint:

Oceanic crust = mafic minerals → olivine + pyroxenes dominate.

Answer 1

The Correct Option is A

To determine the most common minerals in the oceanic crust, we need to understand its composition and how it differs from continental crust.

1. Composition of Oceanic Crust:
Oceanic crust is primarily composed of mafic rocks (rich in magnesium and iron) that form from rapidly cooling magma at mid-ocean ridges. The most abundant minerals are:

• Clinopyroxene (calcium-rich pyroxene)
• Orthopyroxene (magnesium-rich pyroxene)
• Olivine (magnesium-iron silicate)

2. Key Differences from Continental Crust:
Unlike continental crust which contains felsic minerals like quartz and feldspar, oceanic crust is dominated by:

• Basalt (extrusive) and gabbro (intrusive) as primary rock types
• Higher density minerals rich in Fe and Mg
• No significant quartz content

3. Mineral Formation Process:
These minerals crystallize from mantle-derived magma in this order:
1. Olivine first
2. Pyroxenes (both clino- and ortho- varieties)
3. Calcium-rich plagioclase feldspar (though less abundant than in continental crust)

4. Scientific Evidence:
Studies of:
- Ophiolite sequences (exposed oceanic crust)
- Deep sea drilling samples
- Mid-ocean ridge basalt (MORB) analysis
all confirm this mineralogical composition

Final Answer:
The most common minerals in oceanic crust are $\boxed{\text{clinopyroxene, orthopyroxene, olivine}}$.