Geocheminar - spring-2017
Graduate student seminars
May 1, 2017
noon - 1 p.m.
3853 Slichter
Presented By:
- Krista Sawchuk - UCLA EPSS
- Allie Schneider - UCLA EPSS
- Bryce Mitsunaga - UCLA EPSS
Subscribe to Calendar
Graduate Student Seminars
Schedule
- 12:00 PM: Krista Sawchuk: A Raman and Infrared Spectroscopic Study of Anglesite at High Pressures
- 12:20 pm: Allie Schneider: Cyclic Geochemical Variation at Sakurajima volcano, Japan"
- 12:40 pm: Bryce Mitsunaga: A reconstruction of temperature, δ18O, and δ13C data at the Last Glacial Maximum using soil and gastropods from the Chinese Loess Plateau
A comparison of oxygen fugacities of S-type granites across the Archean-Proterozoic boundary
May 8, 2017
noon - 1 p.m.
3853 Slichter
Presented By:
- Claire Bucholz - Caltech
Subscribe to Calendar
The partial pressure of oxygen in the atmosphere, and therefore mechanisms of weathering/alteration and redox conditions during sediment deposition and diagenesis, varied over Earth’s history. It might therefore be expected that this would be expressed as secular variations in igneous rocks that contain sediments as source components or contaminants. The largest recognized increase in the partial pressure of atmospheric oxygen occurred circa 2.4 Ga during what is known as the “Great Oxygenation Event” (GOE). The GOE left clear imprints of increased pO2 on the sedimentary rock record, including the appearance of fluvial and nearshore red beds and retention of iron in paleosols, the disappearance of readily oxidized detrital minerals such as pyrite and uraninite from clastic sedimentary rocks, and the appearance of evaporative sulfate mineral deposits. Since they are generated by melting involving such sediments, S-type granites derived from sedimentary rocks deposited on either side of the GOE might have significantly different pO2, mirroring such an abrupt change in the redox state of Fe and S their sedimentary sources. However, it is also possible, despite variations in atmospheric pO2 , the bulk redox state of sedimentary source material depends strongly on the details of its depositional environment and the presence or absence of organic carbon. In this talk, I will develop constraints on the s during crystallization of Archean and Proterozoic S-type granites to determine whether changes in atmospheric pO 2 levels across the GOE are recorded in granites from the continental crust. To isolate the effects of sediment melting or incorporation into igneous rocks and to provide the most direct link between igneous rocks and changing surface conditions, I studied a geographically distributed suite of North American Archean and Proterozoic S-type granites. To place constraints on the s of the S-type granites, I compare Fe(T) /Fe(T) +Mg ratios in biotite and their host rocks, which when examined together and compared among similar rock types, are highly sensitive to the during crystallization. I will discuss our results in light of changes in the sedimentary redox budgets for C, Fe, and S across the GOE.
High-silica Hadean crust
May 15, 2017
noon - 1 p.m.
3853 Slichter
Presented By:
- Patrick Boehnke - University of Chicago
Subscribe to Calendar
Understanding Hadean (>4 Ga) Earth requires knowledge of its crust. The composition of the crust and volatiles migrating through it directly influence the makeup of the atmosphere, the composition of seawater, and nutrient availability. Despite its importance, there is little known and less agreed upon regarding the nature of the Hadean crust. Analyzing the 87Sr/86Sr ratio of apatite inclusions in Archean zircons from Nuvvuagittuq, Canada, using the unique CHILI instrument shows that its protolith had formed a high (>1) Rb/Sr ratio reservoir by ~4.4 Ga. This result implies that the early crust had a broad range of igneous rocks, extending from mafic to highly silicic compositions.
Tracing the deep biosphere methane cycle with fully resolved isotopologues of 13CH3D and 12CH2D2
May 22, 2017
noon - 1 p.m.
3853 Slichter
Presented By:
- Jeanine Ash - UCLA
Subscribe to Calendar
Seminar Description coming soon.
Chemical zonation in and around melt inclusions
June 2, 2017
noon - 1 p.m.
Slichter 3583
Presented By:
- Ed Stolper - Caltech
Subscribe to Calendar
Seminar Description coming soon.
Graduate student seminars
June 5, 2017
noon - 1 p.m.
3853 Slichter
Presented By:
- Heather Kirkpatrick - UCLA
- Jamie Dix - UCLA
- Jeff Osterhout - UCLA
Subscribe to Calendar
Graduate Student Seminars
Schedule
- 12:00 P.M. Heather Kirkpatrick: Fishing on Land: a Mt. Alfred Zircon Expedition.
- 12:20 P.M. Jamie Dix: A multi-proxy approach to relating modern and ancient Arctic CO2, climate, and ice.
- 12:40 P.M. Jeff Osterhout: Isotope geochemistry of an open marine Neoarchean microbial ecosystem: Revealing metabolic diversity in Earth's early oceans