X-Ray Diffraction Study of Minerals Produced in a Large Volcanic Eruption

By

Junior NkrumahMentor: Dr. Jeff Steiner

CNNanoPhotonics CenterCN

NanoPhotonics Center

The PurposeThe Purpose

To better understand how large To better understand how large igneous rock bodies form by studying igneous rock bodies form by studying the compositional changes of basalt the compositional changes of basalt in the sillin the sill

Large Underground Eruption near Nyack, New York showing Layering

Layers of Basalt in the Palisades Sill, Nyack NY

The Study AreaThe Study Area

What Is a Basalt What Is a Basalt A basalt rock is a common gray to black A basalt rock is a common gray to black

volcanic rock. basalt Is a hard, black volcanic rock. basalt Is a hard, black volcanic rock with Less than about 52 volcanic rock with Less than about 52

weight percent silica so it can flow more weight percent silica so it can flow more easily. Basalt major Minerals Are Pyroxene easily. Basalt major Minerals Are Pyroxene

and Plagioclase.and Plagioclase.

Before After

The minerals under The minerals under investigationinvestigation

A pyroxene is a A pyroxene is a mineral that is found mineral that is found in many igneous rocks in many igneous rocks such as basaltsuch as basalt

This mineral contains This mineral contains high quantities of FE high quantities of FE and Mgand Mg

Plagioclase is a Plagioclase is a mineral in the mineral in the feldspar group which feldspar group which makes up 60% of makes up 60% of earth’s crust.earth’s crust.

Plagioclase is rich in Plagioclase is rich in aluminum and siliconaluminum and silicon

www.proxyene pictures.com

X-ray Diffraction: Identifying X-ray Diffraction: Identifying MineralsMinerals

X-ray diffraction is X-ray diffraction is used to determine used to determine mineral structure.mineral structure.

Once the structure Once the structure is recognized, the is recognized, the mineral is mineral is identifiedidentified

N(lambda)=2(d)sinN(lambda)=2(d)sintheta—The Bragg theta—The Bragg Equation—the Equation—the basis for XRDbasis for XRD

Results Results

0100200300400500600700800900

1000

0 200 400 600

Series1

Series2

Series3

3 3631.527

Alpine 13Alpine 129w 35

•X-ray diffraction patterns for 3 basalt samples•The peaks represent the minerals pyroxene and plagioclase•Notice the difference in minerals present indicated by the labeled peak

2-theta angleintensity