describe the olivine structure as pressure increases at 10km, 450km, and 700km.

Question

describe the olivine structure as pressure increases at 10km, 450km, and 700km. use illustrations as necessary Systematic Mineralogy of the Earth's Mantle: Neso- and Inosilicates This homework is designed to focus on the composition, physical characteristics, and Purpose: structures of minerals that comprise a large portion of Earth's mantle. The following ques will facilitate your comprehension of these minerals and their diagnostic properties. tions Note: Use your book and lecture notes to assist in answering the questions 1. Describe the olivine structure as pressure increases at 10 km, 450 km, and 700 km. Use illustrations as necessary

Explanation / Answer

Olivines are magnesium iron sulphates found in the mantle layer of earth. They are most stable at upper mantle, i.e. at shallow depth of 10km from the earths surface. Its structure at this depth is (Mg+2, Fe+2)2SiO4

At the high temperatures and pressures found at depth within the Earth the olivine structure is no longer stable.

At 450 km: below this depth, olivine undergoes an exothermic phase transition to the sorosilicate, wadsleyite

At 700km: At this depth it decomposes into silicate perovskite ((Mg,Fe)SiO3) and ferropericlase((Mg,Fe)O) in an endothermic reaction. These phase transitions lead to a discontinuous increase in the density of the Earth's mantle that can be observed by seismic methods.

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