X-Ray Diffraction Study of Minerals Produced in a Large Volcanic Eruption By Junior Nkrumah Mentor: Dr. Jeff Steiner

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

Large Underground Eruption near Nyack, New York showing Layering Layers of Basalt in the Palisades Sill, Nyack NY The Study Area

What Is a Basalt A basalt rock is a common gray to black volcanic rock. basalt Is a hard, black volcanic rock with Less than about 52 weight percent silica so it can flow more easily. Basalt major Minerals Are Pyroxene and Plagioclase. BeforeAfter

The minerals under investigation A pyroxene is a mineral that is found in many igneous rocks such as basalt A pyroxene is a mineral that is found in many igneous rocks such as basalt This mineral contains high quantities of FE and Mg This mineral contains high quantities of FE and Mg Plagioclase is a mineral in the feldspar group which makes up 60% of earth’s crust. Plagioclase is a mineral in the feldspar group which makes up 60% of earth’s crust. Plagioclase is rich in aluminum and silicon Plagioclase is rich in aluminum and silicon pictures.com

X-ray Diffraction: Identifying Minerals X-ray diffraction is used to determine mineral structure. X-ray diffraction is used to determine mineral structure. Once the structure is recognized, the mineral is identified Once the structure is recognized, the mineral is identified N(lambda)=2(d)sin theta—The Bragg Equation—the basis for XRD N(lambda)=2(d)sin theta—The Bragg Equation—the basis for XRD

Results 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 angle intensity