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U-Pb Geochronology

U-Pb Geochronology . Dave Rodriguez Carlos Villa Pat Wagner. Our Area of Exploration. North Central New Mexico. Our Samples. Conglomerate rock samples brought back from New Mexico. Tres Piedras, NM located in the foothills of the Sangre de Cristo Mountains.

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U-Pb Geochronology

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  1. U-Pb Geochronology Dave Rodriguez Carlos Villa Pat Wagner

  2. Our Area of Exploration North Central New Mexico

  3. Our Samples • Conglomerate rock samples brought back from New Mexico. • Tres Piedras, NM located in the foothills of the Sangre de Cristo Mountains. • The Sangre de Cristo Mountains are the longest (350 km), straightest and highest chain of mountains in America. • They were formed about 27 million years ago. • Area was about 60 million years old. • There are ten peaks over 4,200 m high in the range.

  4. Crushing the Rocks • Machine would crush rocks down to pebble sized.

  5. Size Comparison • Pebbles • Original Sample Football Sized Pea Sized

  6. Grinding the Pebbles • Pebbles were then ground into a thin powder.

  7. Using the Super Panner • Side to side motion of panner allows lighter minerals to flow away while heavier minerals sink and are then picked up.

  8. Purifying the Sample • Remaining sample in water filled a 10 ml beaker. • Sample was then dried in an oven. • Dried sample was purified by running a wand magnet over and removing Iron fillings.

  9. Heavy liquids are dense fluids or solutions used to separate materials of different density through their buoyancy. Quartz, feldspar, and mica floated while our zircons sank and were separated. Heavy Liquid Separation

  10. Many minerals have a certain magnetic susceptibility. By varying the magnetic flux (and thus the size of the magnetic field) it is possible to make different fractions. Garnets and Hornblende were separated. Isodynamic Separation

  11. Microscope time consisted of patient sittings separating zircons from other minerals. Picking Zircons

  12. Size Comparison 2 One Millimeter Mineral Field

  13. Size Comparison 2 (cont.) Wire used to separate zircons. One Millimeter Human Hair

  14. Zircon Field Viewing range four millimeters across Zircon field

  15. Zircons are dissolved in several acid solutions. The solution is then baked in an oven for three days. Heat and pressure contribute to dissolving the zircons into an ion solution. Dissolution and Baking

  16. Ion Column Separation • Pb and U ions are separated from the solution and prepared for the spectrometer.

  17. Spectrometer • Sample is placed into mass spectrometer for analysis. • The mass spectrometer will analyze ratio of U and Pb ions. • The ratio will then give us the age of the rock.

  18. Acknowledgments • We’d like to thank Dr. Roy Odom and the Geochemistry department for their help in making this experience possible. • Thanks also go out to Pat Dixon, Karl Hook, and Gina Hickey for supervising the program. • A special thanks to Paula Crone, Gayla Sanders, and Ann Spangler for all their assistance.

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