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ESCI-430 Trace-element and isotope geochemistry Cin-Ty Lee Gerald Dickens TA: Zhengxue Li. Grading scheme: 50 % Homework, quizzes, and class participation 25 % Term Paper 25 % Oral presentation of term paper Texts Faure, Isotope: Principles and applications, 3rd edition
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ESCI-430 Trace-element and isotope geochemistry Cin-Ty Lee Gerald Dickens TA: Zhengxue Li
Grading scheme: 50 % Homework, quizzes, and class participation 25 % Term Paper 25 % Oral presentation of term paper Texts Faure, Isotope: Principles and applications, 3rd edition Albarede, Geochemistry: an Introduction Lee, Lecture notes
Guidelines Homework must be turned in on time -25% for late homeworks -100% for homeworks later than 1.5 weeks, i.e. don’t bother Participation will involve reading an assigned paper Each student is responsible for one paper and presenting a 10 minute, concise summary and critique you will be quizzed on the paper so everyone must read the paper Term paper 10 page report on a current topic of your interest Oral presentation Term paper will be followed by a 15 minute oral presentation at the end of the semester NO BULLSHIT
Atmosphere Ocean Continental Crust Mid- ocean Ridge Base of lithosphere Plume Oceanic Crust Mantle Core ? Not to scale
Aerosol Deposition Evaporation Rivers Groundwater Adsorption Precipitation Hydro- thermal Inputs & Outputs Biological Processes Dissolution
Atmosphere Ocean Oceanic Continental Crust Crust Mantle Core We will investigate how various reservoirs interact
We will begin with the origin of the solar system…. Andromeda Galaxy
Trace elements and isotopes as tracers of how Earth was formed and differentiated Evolution of Earth
Major Elements >1 wt. % Minor Elements ~0.1 to 1 wt. % Trace Elements 100 ppm or less
Al 1.41 Ca 1.54 S 2.9 Ni 1.8 Fe 32.1 O 30.1 Si 15.1 Mg 13.9 BULK EARTH
45 Bulk Silicate Earth 40 35 30 25 20 MgO (wt. %) 15 MOR basalt 10 Average Lower Crust Andesite 5 Dacite Rhyolite Average Continental Crust 0 0 10 20 30 40 50 60 70 80 SiO2 (wt. %)
1000 100 10 1 0.1 Cs Rb Ba Th U Nb La Ce Pr Sr Nd Zr Hf Sm Gd Tb Dy Ho Y Er Yb Lu Conc Crust Conc. / Primitive Mantle N-MORB
H 1011 Solar Photosphere Atoms/106 Si atoms (Anders & Grevesse, 1989) He 1010 109 O 108 C Ne 107 Mg Si Fe N 106 Ca 105 Al 104 103 102 Li Pb 10 Ce Ir 1 Be Th 10-1 U 10-2 10-3 0 10 20 30 40 50 60 70 80 90 100 Atomic Number (Z)
1 Seawater Composition Primitive-Mantle Normalized 10-1 10-2 10-3 10-4 10-5 10-6 10-7 Cs Rb Ba Th U Nb La Ce Pr Sr Nd Sm Gd Tb Dy Ho Y Er Yb Lu
ATOMIC STRUCTURE NUCLEUS = PROTONS AND NEUTRONS ELECTRON SHELLS ATOMIC NUMBER = Z NEUTRON NUMBER = N ATOMIC MASS NUMBER = Z + N ELEMENTAL IDENTITY DETERMINED BY Z NEUTRON NUMBER CAN VARY (ISOTOPES)
Z=N Z N Lawrence Berkeley National Laboratory NUCLIDE CHART Valley of stability
A Z+1 N-1 b- A Z N b+ E.C. Z a decay A Z-1 N+1 A-4 Z-2 N-2 N RADIOACTIVE DECAY SCHEMES
Atmosphere Ocean Oceanic Continental Crust Crust Mantle Core Our goal is to look at how the Earth differentiates into its different reservoirs Trace elements can be used to track the process of differentiation Radiogenic isotopes can be used to put constraints on the rates and timing of differentiation processes