Melting RocksMelting Rocks

QuestionQuestionDoes a rocks melt like an ice cube, all at the Does a rocks melt like an ice cube, all at the

same time?same time?

Melting RocksMelting Rocks

Rocks melt according to their melting points.Rocks melt according to their melting points. Example: Ice cube with waxExample: Ice cube with wax

Which would melt first ice or wax?Which would melt first ice or wax?

This example is known as This example is known as partial melting.partial melting. Partial Melting: Partial Melting: some minerals melt at lower some minerals melt at lower

temperatures and other minerals remain solidtemperatures and other minerals remain solid Think of “stew”Think of “stew”

Fractional CrystallizationFractional Crystallization

Opposite of Partial MeltingOpposite of Partial MeltingLast to melt are first to solidify (crystallize) Last to melt are first to solidify (crystallize)

Bowen’s Reaction SeriesBowen’s Reaction Series

N.L. BowenN.L. BowenCanadian Canadian 1900’s1900’sStated that “as magma cools, minerals form in Stated that “as magma cools, minerals form in

predictable patterns”predictable patterns”Known as Bowen’s Reaction SeriesKnown as Bowen’s Reaction Series

Bowen’s Reaction SeriesBowen’s Reaction Series

Two BranchesTwo BranchesFeldsparsFeldspars

Continuous, gradual change of mineral Continuous, gradual change of mineral compositionscompositions

Iron-Rich MineralsIron-Rich MineralsAn abrupt change of mineral typeAn abrupt change of mineral type

Bowen’s Reaction SeriesBowen’s Reaction Series

FeldsparsFeldspars

Continuous ChangeContinuous Change First Feldspars are First Feldspars are

rich in Calcium (Ca)rich in Calcium (Ca) Sodium (Na) Sodium (Na)

increases as cooling increases as cooling continuescontinues

Last Feldspars to Last Feldspars to form are Sodium rich form are Sodium rich (Na)(Na)

Iron Rich MineralsIron Rich Minerals Discontinuous ChangeDiscontinuous Change

Magnesium (Mg) cools Magnesium (Mg) cools around 1800around 180000C, when C, when olivine crystallizes, this olivine crystallizes, this continous up to 1557continous up to 155700C. C.

Now Pyroxene begins Now Pyroxene begins to form. All olivine that to form. All olivine that was formed is now was formed is now turned to pyroxene turned to pyroxene

Quartz is the last to Quartz is the last to form, because silica form, because silica and oxygen are the last and oxygen are the last to crystallize to crystallize

Why do we find Olivine?Why do we find Olivine?

•Amongst the common rock forming minerals Felspathoid minerals containing less % of silica are also present which are usually allied with Feldspars

Nepheline(Silicate of sodiumand aluminium=>Albite

Leucite(Silicate of potassiumand aluminium=>Orthoclase