Day: February 28, 2020

First, that you research an interesting
and often controversial issue as a topic. In so doing, you provide an outline, explaining how you
will address the issue. In an outline you should have something similar to that given in the
example below that I made (you cant do this question, sorry!):
EXAMPLE
Why are highly siderophile elements enriched in Earths mantle?
Introduction (1-2 paragraphs/400 words): 1) Explain what a highly siderophile element is. 2) Point
out that highly siderophile elements are enriched in Earths mantle relative to what we would
predict from low-pressure experiments between metal and silicate and how they are enriched
(i.e., in chondritic relative abundances). 3) Explain briefly the controversy. (I will make a figure
here, to show the abundances of HSE in Earths mantle versus that predicted from 1 Atm
experiments)
Main text (3-4 paragraphs/800-1000 words): Possible hypotheses to explain the relative
enrichment in HSE in Earths mantle, with strengths and weaknesses (I will make a figure here,
to summarize the main competing hypotheses)
Hypothesis 1 high-pressure high-temperature experiments explain what it is and why its a
possibility (good for single elements, but all elements?)
Hypothesis 2 inefficient core formation explain what it is and why its a possibility (good for
some HSE, but what about Fe in Earths mantle?)
Hypothesis 3 Late accretion of chondritic impactors explain what it is and why its a
possibility (explains abundances well, but is this true for all planets???)
Conclusions (200-400 words): Overall summary of strengths and weaknesses are and which
hypothesis has fewest flaws (Hypothesis 3). Future of the field (diamond anvil cell to reach very
high pressures, metal-silicate mixing experiments for inefficient core formation, examine more
planetary bodies to see if late accretion matches all predictions). Summary sentence explaining
important of research
Primary references that I will use in my Term Paper (in alphabetical order) to make my case (I
plan to use more, but these are the basis, I would have between 5-10 references in total):
Chou, C.L., 1978. Fractionation of siderophile elements in the Earth’s upper mantle. In Lunar
and Planetary Science Conference Proceedings (Vol. 9). (Original late accretion idea)
Day, J.M., Pearson, D.G. and Taylor, L.A., 2007. Highly siderophile element constraints on
accretion and differentiation of the Earth-Moon system. Science, 315(5809), pp.217-219.
(Evidence for late accretion to both Earth and the Moon)
Jones, J.H. and Drake, M.J., 1986. Geochemical constraints on core formation in the Earth.
Nature, 322(6076), pp.221-228. (Inefficient core formation)
Mann, U., Frost, D.J., Rubie, D.C., Becker, H. and Audtat, A., 2012. Partitioning of Ru, Rh, Pd,
Re, Ir and Pt between liquid metal and silicate at high pressures and high temperaturesImplications for the origin of highly siderophile element concentrations in the Earths
mantle. Geochimica et Cosmochimica Acta, 84, pp.593-613. (High pressure-high temp
experiments)
Walker, R.J., 2009. Highly siderophile elements in the Earth, Moon and Mars: update and
implications for planetary accretion and differentiation. Geochemistry, 69(2), pp.101-125.
(Summarizes planetary compositions)
Second, at the end of the quarter, you present us with a completed term paper. As you can see
from the outline, you simply need to flesh out the outline properly to achieve this in my
example, I note the length of the sections and also where the figures will be placed. Please
provide the term in a clear way to read, as my outline suggests it would be.
Potential Topics for Papers
Consider the likelihood of habitability of exoplanets around stars. What basic conditions are
required for the star and for the planet?
Are the distribution of p-, s- and r-process nuclides homogeneous or heterogeneous within
Earth and other planetary bodies and what does this reveal about the formation of our Solar
System?
How well do we know the age of the Earth?
When was the onset of continental crust formation?
The continental crust formed exclusively by subduction processes. Discuss.
Examine the evidence for how partial melting on Mars to form Olympus Mons and other
volcanoes takes place.
No water, no granites No oceans, no continents. Discuss.
What are the main lines of evidence for the formation of Earths ocean?
Ocean sediments contain evidence for major extraterrestrial impacts. What geochemical
tracers are most suitable for determining extraterrestrial impacts, and how and why would
sediments affected by such processes differ in their chemistry to normal sediments?
What are the controls on weathering and their relative importance over time?
Is the Mg cycle of seawater closed? If not what is needed to close it?
How do snow Snowball Earth conditions begin and end?
How was the Paleocene-Eocene Thermal Event discovered and what are the main documented
characteristics of the event, and their competing interpretations?
Discuss the Phanerozoic history of seawater 18O, and the main arguments for the constancy of
seawater 18O with time versus its evolution with time. Which is (or are) the most convincing to
you?
What are the main geologic and geochemical observations used as key evidence for the
evolution of atmospheric O2?
What is the significance of the seawater Sr isotope curve using a case study to elaborate?
Why are geochemists interested in the history of seawater chemistry, and how do they obtain
the evidence for a constant or changing chemistry? Briefly provide a case study.
What is the evidence for changing atmospheric chemistry during glacial and interglacial
periods? Discuss two to three major findings and their significance.
There have been multiple strategies proposed to remove – to sequester – atmospheric CO2 to
curb rising global temperatures. Discuss the efficacy of two of the main strategies proposed
using chemical principles and supporting literature, suggest which is the most promising
method and why. What solution might you explore?
What are the origin and sources of diamonds in Earth and how do we know?
Explain the evidence for the little Ice Age and how it affected the hydrological cycle.
Explain how we know the long-term record of climate change over 500 kyr and what it might
reveal about the future.
Discuss the formation of Earths Moon.