Welcome to GeoUnion, the graduate student body of the Department of Earth, Environmental and Planetary Sciences. GeoUnion strives to supplement the overall graduate student experience at Rice and DEEPS. GeoUnion represents DEEPS in the overall Rice grad student community, acts as a liaison between students and faculty and organizes a number of intra- and inter-departmental events throughout the academic year.
|September 6-8||Overnight Camping at San Marcos|
|September 13||Welcome Barbecue|
|Cancelled because of Imelda||Pre-GSA talk|
|October 12-15||Field Trip to Big Bend|
|October 25||Halloween Kickball Tournament|
|November 26||Multicultural Thanksgiving!|
|Dec 6||Pre-AGU practice session|
Here’s a list of the resources that you would need to use frequently as graduate students at Rice. The websites of the Rice Graduate Student Association (GSA), Office of International Students and Scholars (OISS), Graduate and Postdoctoral Studies (GPS) are platforms which graduate students can use to keep track of upcoming events, funding opportunities, changes in rules and regulations, etc.
Living in a vast city like Houston and exploring a new place can also be challenging, and so we have compiled a list of recommendations for housing and fun things to do in the Space City!
Nature: Scientific Reports: A 5‑km‑thick reservoir with > 380,000 km3 of magma within the ancient Earth’s crust
Rais Latypov, Sofya Chistyakova, Richard A. Hornsey, Gelu Costin & Mauritz van der Merwe
Several recent studies have argued that large, long-lived and molten magma chambers may not occur in the shallow Earth’s crust. Here we present, however, field-based observations from the Bushveld Complex that provide evidence to the contrary. In the eastern part of the complex, the magmatic layering continuously drapes across a ~ 4-km-high sloping step in the chamber floor. Such deposition of magmatic layering implies that the resident melt column was thicker than the stepped relief of the chamber floor. Prolonged internal differentiation within this thick magma column is further supported by evolutionary trends in crystallization sequence and mineral compositions through the sequence. The resident melt column in the Bushveld chamber during this period is estimated at > 5-km in thickness and > 380,000 km3 in volume. This volume of magma is three orders of magnitude larger than any known super-eruption in the Earth’s history and is only comparable to the extrusive volumes of some of Earth’s large igneous provinces. This suggests that super-large, entirely molten, and long-lived magma chambers occur, at least occasionally, in the geological history of our planet. Therefore, the classical view of magma chambers as ‘big magma tanks’ remains a viable research concept for some of Earth’s magmatic provinces.
Latypov, R., Chistyakova, S., Hornsey, R. A. & Costin, G. (2022). A 5 ‑ km ‑ thick reservoir km 3 of magma within the ancient Earth ’ s crust. Scientific Reports. Nature Publishing Group UK 1–12. https://doi.org/10.1038/s41598-022-19915-w
Lithos: Correlations between olivine composition and groundmass mineralogy in Sierra Leone kimberlites provide constraints on craton-specific melt-lithosphere interactions
Anton Viljoen, Geoffrey H. Howarth, Andrea Giuliani, Angus Fitzpayne, Gelu Costin
Sierra Leone contains two Jurassic-aged diamondiferous kimberlite clusters, namely Koidu and Tongo-Tonguma (hereafter referred to as Tongo), consisting of eruptive pipes and NE-SW trending dikes. In this study, a combination of detailed petrography, and phlogopite, spinel, and olivine compositions in hypabyssal samples is presented to classify and constrain the petrogenesis of these kimberlites. Both the Koidu and Tongo rocks are predominantly macrocrystic and highly micaceous with phlogopite abundances, normalised to olivine-free, of 36–65 vol% in the groundmass. These phlogopite contents are comparable to those of some cratonic lamproites and significantly higher than any other kimberlites. Other groundmass minerals include spinel, perovskite, and apatite set in a base of carbonate and serpentine. Phlogopite and spinel have similar compositions in the Koidu and Tongo samples, displaying evolutionary trends consistent with those observed in worldwide kimberlites. Olivine macrocrysts and microcrysts display complex zoning with distinct cores, internal zones, and rims. The core compositions display a range in Mg# (81–95) and are interpreted to be derived from the disaggregation of lithospheric mantle xenoliths and proto-kimberlite-related megacrysts. The Tongo olivine rims, interpreted to be primary magmatic crystallisation products, have similar compositions from various locations within the cluster whereas the Koidu samples display a range in rim compositions (Mg# 87–89) from different locations within the cluster. The average Koidu rim compositions display a strong positive correlation with the average core compositions, consistent with the trend formed by kimberlites worldwide and indicative of a strong control by melt-lithosphere interaction on melt compositions. Previously, it has been shown that the Mg# of olivine rim’s negatively correlates with the abundance of groundmass phlogopite (± oxide minerals) in kimberlites. However, the Koidu and Tongo kimberlites are exceptionally phlogopite-rich given their olivine Mg#, fall outside of the worldwide kimberlite array and have olivine compositions and phlogopite abundances like some cratonic lamproites. This leads us to suggest that Koidu and Tongo represent a rare style of highly micaceous kimberlite magmatism, not previously reported in other cratonic regions, and are genetically linked to the assimilation of K2O-rich, metasomatic mantle lithologies. We further suggest that the K2O content, reflected by groundmass phlogopite abundances, of worldwide kimberlite and cratonic lamproite parent magmas ascending to the surface may be related to assimilation of craton-specific styles of metasomatic lithologies in the SCLM.
Viljoen, A., Howarth, G. H., Giuliani, A., Fitzpayne, A. & Costin, G. (2022). Correlations between olivine composition and groundmass mineralogy in Sierra Leone kimberlites provide constraints on craton-specific melt-lithosphere interactions. LITHOS. Elsevier B.V. 430–431, 106846. https://doi.org/10.1016/j.lithos.2022.106846
Geophysical Research Letters: Autocorrelation R2 on Mars
Sizhuang Deng and Alan Levander
Plain Language Summary
The subsurface structures of Earth are imaged by the detailed analysis of seismic data recorded by thousands of stations deployed on Earth’s surface. The InSight mission landed a seismograph on Mars which was deployed at the end of 2018 to investigate the planet’s interior structure and dynamic evolution. In this study, we preprocessed the continuous vertical-component seismic data, and by autocorrelation retrieved a Rayleigh wave, one class of seismic surface wave, that orbits Mars. Rayleigh wave group velocities between 115 and 200s period were measured from the observed Mars orbiting Rayleigh waves. Synthetic seismograms were calculated using current estimates of the velocity structure of Mars for comparisons to the observation. The spherically symmetric model was updated with a Monte Carlo algorithm, an inversion method that randomly perturbs the velocity model and determines the model that best matches the Mars orbiting surface waves through trial and error. An S-wave low-velocity zone is observed to the depth of ~400km beneath the Martian surface, consistent with other InSight seismic observations and velocity models measured from geophysical modeling and high-pressure laboratory experiments.
Because of COVID-19, the field trip is being postponed to later (date TBD) this year. The seminar will continue via remote meetings through the end of the Spring 2020 semester.
As earth scientists we seek to understand the natural processes that have shaped the world around us through time. The most fundamental requirement to acquiring a deeper understanding of these mechanisms is through observation. EEPS has a strong heritage in field-based research that when combined with analytical excellence, produces skilled scientists with a broad view of Earth as a system. While Rice University is well placed to take advantage of a broad array of research resources, students in Houston do not always have immediate access to nearby geological sites that represent Earth as a system.
A generous gift from Mike Johnson enables EEPS students the opportunity to observe classic and fundamental geologic concepts in the field. Students are in charge of proposing, selecting and managing a field excursion that will benefit everyone in the department. A year-long seminar-based class run by the students prepares them to visit the locality they have selected. Papers are selected, presented and discussed, followed by activities that educate the students on how to run a field-based project. During the field excursion, elected stops will be led and presented by individual students. The knowledge gained before and during the field trip will cumulate into a multi-media field guide that will be made available to the department and public following the trips conclusion.
A significant benefit of a department-wide field excursion is the interaction of students with scientists from various disciplines. Many earth scientists only carry out field work with specialists in their own field. The real discoveries in modern earth science occur when the different disciplines are part of a collective discourse. This trip will have scientists with different backgrounds observe the same outcrops; fostering fruitful discussion that results in the generation of new and unique questions. In addition, this trip may inspire fellowship among EEPS graduate students that will hopefully create life-long collaborations and a cohesive department.
General route starting in Albuquerque, New Mexico
This year, EEPS elected to utilize Mike Johnson’s gift to lead graduate students on a 7 day field expedition to observe some of the most diverse and economically important geologic terrains in the United States.
In early June of 2020, EEPS will travel through New Mexico, Colorado and Utah, which have easily accessible exposures of metamorphic, sedimentary, and igneous rocks. Starting from Albuquerque, New Mexico they will explore the Rio Grande Rift, the San Juan Volcanic field, and the well exposed Mezozoic stratigraphy on the Colorado Plateau. Observing these diverse geologic terrains will give EEPS graduate students a chance to see how their research interests dovetail with what they observe in nature and provide opportunities to create new ideas.
Pre-Trip planning seminars
Fall semester: The graduate student of the winning field trip proposal organizes a weekly reading group focusing on the regional geology of the four corners region and come up with potential stops.
Spring semester: The weekly reading group continues. Students pick the final outcrops that they would like to visit. Each student is assigned to be an expert on 1-3 stops. Before the field trip, each student will submit their description(s) of their stop for the field guide.