RESEARCH

PUBLICATIONS

FIELD PHOTOS

PEOPLE

LABORATORY

COURSES

CLAIRE BUCHOLZ

Assistant Professor of Geology

cbucholz[at]caltech.edu

Curriculum Vitae

BARBARA RATSCHBACHER

Postdoctoral Scholar in Geology

ratschba[at]gps.caltech.edu

research website

My broader research interest is to understand the structural and geochemical architecture of arc crustal columns. In particular, I am interested in the importance of differentiation processes (fractional crystallization, mixing and assimilation) at various crustal depths (surface to Moho), their tempos and links between deformational regime, magma ascent, and storage in the crustal column. I further use isostatic mass balance modeling to understand the behavior of the arc crust during arc activity and subsequent solid-state deformation.


To answer my research questions, I study exposed arc crustal section, which offer a unique possible to study depth-dependent, crustal generating processes. I use a combination of field mapping, structural and geochemical tools, geochronology, geochemical and thermal modeling.


For my postdoc at CalTech working with Claire Bucholz, I will focus on better understanding the oxidation state of arc crustal columns and the role crustal differentiation in affecting the oxidation state of magmas as various crustal depths. We are also interested in using amphibole, beside more traditional redox proxies, as a potential proxy for the melt chemistry is crystallized from.


MADELINE (MADDIE) LEWIS

Graduate Student in Geochemistry

mjlewis[at]caltech.edu

research website

My research with the Bucholz lab combines fieldwork, geochemistry, and geochronology to investigate the role of upper crustal mafic intrusions in the Sierra Nevada batholith, a paleo-continental arc. These mafic plutons are opportune locations to study both lower and upper crustal processes, because the parental melts to these mafic magmas were presumably produced in the mantle, and then had to ascend through the arc crust to their current level, recording both lower and upper crustal processes along the way. My geochemical modeling shows that polybaric fractionation can generate the observed non-peraluminous mafic and felsic compositions in the upper crust of the Sierra Nevada batholith. We have determined that all of the granitic and gabbroic intrusions that we have studied thus far are Cretaceous in age, so the system was contemporaneously producing both end member compositions.



I am co-advised by Dr. Bucholz and Dr. Asimow at Caltech, so I am working on two additional projects with Dr. Asimow: petrology of large explosive eruptions from mid-ocean ridges and the rare earth element budget of banded iron formations.

JOE BIASI

Graduate Student in Geochemistry

biasi[at]caltech.edu

I’m PhD student in the Bucholz lab, with a diverse set of research interests. Due to this broad range of interests, I’m best described as a geologist as opposed to a true igneous petrologist. My current interests and projects include pluton source/emplacement processes, chemostratigraphy of ophiolites, Arctic/Antarctic tectonics, use of paleomagnetics as thermochronometric technique, long-term behavior of the geodynamo, and magnetic determination of magmatic fO2.

 

To tackle these problems I combine fieldwork, labwork, and a variety of methods that are often more common in other fields. By staying at the intersection between multiple areas of geoscience, I can tackle a variety of problems that are not addressed by more specialized geoscientists.

 

For the Bucholz lab I am working on the generation and emplacement processes of S-type granites. More specifically, do S-type granites faithfully record any elemental and isotopic signatures of the sediments that they’re derived from? And how do S-type granites stand up to subsequent metamorphism compared to their sedimentary protoliths?

EMMA SOSA

Graduate Student in Geology

esosa[at]caltech.edu

I am interested in the chemical evolution of magmas produced in subduction zones, and how magmatism in these complex geological settings has varied through space and time. Constraining the petrologic properties of primary magmas is of particular interest to me, and I want to understand how changes in pressure, temperature, source rock lithology, fO2, and the composition of liquids and melts fluxed from the subducting slab influence their chemical properties and subsequent evolution. I aim to address these questions by using major and trace element mineral chemistry, stable isotope geochemistry, and other laboratory-based techniques to study intrusive rock suites and draw inferences about their formation and the properties of the magmas from which they crystalized. My current work seeks to use mineral chemistry to constrain the crystallization conditions of cumulate xenoliths from Adak Island in the Aleutians. These mid-to-lower crustal xenoliths represent the first crystallization products of primitive primary to basaltic magmas that have not been modified by supracrustal processes, providing a window to study this enigmatic and inaccessible portion of the crust.

FORMER LAB MEMBERS

Matt Barickman (SURF Student - 2017) - now graduate student at Washington University St. Louis

Sam Newall (SURF Student - 2018)

JULIET RYAN-DAVIS

Graduate Student in Geology

jrd[at]caltech.edu

My research focuses on understanding differentiation of arc magmas through field-based study of mafic plutons in the Sierra Nevada batholith. These upper-crustal mafic bodies are scattered and smaller in exposed area than the major felsic plutons that build most of the batholith. However, they represent drivers of differentiation: parental mafic magmas that have transited the crustal column, likely sourced from primitive subduction-zone melts after some amount of deep-crustal processing. Field, geochemical and petrologic study to determine their chemical and physical characteristics and relationships to coexisting felsic plutons will elucidate what characteristics may have allowed these mafic melts to ascend to the upper crust,  and what role they may play in building continental crust.


JAMES (JAMIE) WORTHINGTON

Postdoctoral Scholar in Geology

jamesworthington[at]caltech.edu

I am a field- and lab-based tectonicists interested in Cordilleran-style and collisional orogenic systems, especially the Alpine-Himalayan and Central Asian orogenic belt. My research integrates geologic mapping, structural analysis, geo-thermochronology, petrology, and geochemistry to interrogate the structural, petrologic, and sedimentologic features that Earth manufactures in its lithosphere as dynamic symptoms of interaction between tectonic plates. I implement integrated datasets to assess the timing and rate of tectonic processes and petro-tectonic origins of rocks as they pertain to testable end-member models of orogenesis.

     My postdoc research with Claire Bucholz at Caltech explores the Neoproterozoic petro-tectonic evolution of the ophiolitic Bayankhongor suture zone in central Mongolia. The Bayankhongor ophiolite has been suggested to have formed in a handful of tectonic settings including a forearc, backarc, mid-ocean ridge, mantle plume, or continental margin; knowledge of its petrogenesis is imperative for understanding the broader suturing dynamics. Another question to this end is similarity or lack thereof between the sutured terranes--does the Bayaknhongor suture zone unite Siberia- and (peri)Gondwana-derived crustal terranes? Our geologic mapping and petrography, integrated with analytical tools including whole-rock geochemistry, mineral chemistry and zircon U/Pb geochronology, will elucidate the tectonics of the Bayankhongor suture. As a component of a broader geopuzzle, this knowledge may be applied to improve regional tectonic models for the amalgamation of the Central Asian orogenic belt.