Geocheminar - fall-2016

Sept. 27, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

• Edwin Schauble - UCLA

Seminar Description coming soon.

Oct. 11, 2016
noon - 1 p.m.
3853 Slichter

Presented By:

• Paul Warren - UCLA

Secondary alterations in lunar ferroan anorthosites: Implications for the magma ocean hypothesis

Age data, surprisingly far younger than 4.50 Ga, from lunar ferroan anorthosites have been interpreted as key constraints on the hypothesis that the Moon's crust formed mainly by plagioclase flotation over a primordial, global magma ocean. However, various features of apparent secondary origin, such as reverse zoning and Na-poor plagioclase compositions associated with clouds of pyroxene inclusions, imply that the age results should not be directly identified with original igneous crystallization. The magma ocean hypothesis remains viable.

Oct. 18, 2016
noon - 12:50 p.m.
3853 Slichter

Presented By:

• Ming-Chang Liu - UCLA

The initial 41Ca/40Ca ratios in two Type A Ca-Al-rich Inclusions: Implications for the origin of short-lived 41Ca

In this talk, I will present new 41Ca-41K isotopic data from two Type A CAIs, NWA 3118 #1Nb (compact Type A) and Vigarano 3138 F8 (Fluffy Type A), from reduced CV3 chondrites. The NWA CAI is found to have carried live 41Ca at the level of (4.6±1.9)×10?9, consistent with the proposed Solar System initial 41Ca/40Ca = 4.2 × 10?9 by Liu et al. (2012). On the other hand, the Vigarano CAI does not have resolvable radiogenic 41K excesses that can be attributed to the decay of 41Ca. Combined with the 26Al data that have been reported for these two CAIs, we infer that the 41Ca distribution was not homogeneous when 26Al was widespread at the canonical level of 26Al/27Al = 5.2 × 10?5. Such a 41Ca heterogeneity can be understood under two astrophysical contexts: in- situ charged particle irradiation by the protoSun in the solar nebula that had inherited some baseline 10Be abundance from the molecular cloud, and Solar System formation in a molecular cloud enriched in 26Al and 41Ca contaminated by massive star winds. That said, more high quality 41Ca data are still needed to better understand the origin of this radionuclide.

Oct. 25, 2016
noon - 12:50 p.m.
3853 Slichter

Presented By:

• Jessica Hinojosa - Caltect

Developing New Zealand records of Southern Hemisphere westerly wind shifts during the last deglaciation

Nov. 1, 2016
noon - 12:50 p.m.
3853 Slichter

Presented By:

• Laura Wasylenki - Indiana U

Tungsten stable isotopes: can they help us monitor and predict tungsten contaminant migration?

Nov. 15, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

• Beth Ann Bell - UCLA

Seminar Description coming soon.

Nov. 29, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

• Abby Kavner - UCLA

Chalk talk: a new model for the anharmonic oscillator