Petrographic & related
Other (UA & related)
My research interests focus on the distribution of materials in the Earth's crust with a particular emphasis on the geologic systems and principles that lead to mineral deposits and related geochemically anomalous rocks. These topics are fundamental to the way that we, as people, interact with and live on the Earth.
The tools (approaches) that my students, colleagues, and I use are diverse, ranging from field work at various scales (particularly outcrop to regional) to a wide spectrum of analytical tools (geochemical, petrological, mineralogical) to theoretical approaches including numerical modeling of energy and mass transfer. I also remain interested in doing experimental studies, although I have not been doing so recently.
Our goals in each project are to produce high quality research results that contribute in a meaningful way to advancing our science while meeting the key objectives for each student's education and, in most cases, apply the science to real world problems.
Direct and indirect funding from all sources over the last 5 years has exceeded $300,000 per year, and has mainly been used for student and post-doctoral support, direct research expenses, and essential institutional support. Support has come from the U.S. Geological Survey, the U.S. National Science Foundation, the mining industry, private donors, and funds raised though teaching Lowell Program short courses. If permitted, approved funding through Science Foundation Arizona and industry partners will substantially increase our scope of activity in Arizona and on challenges of interest to Arizona and organizations involved in mineral resources issues.
There are many opportunities for graduate study and collaborative work on these and related themes. Graduate student projects are typically funded through a mix of industry, federal, and university (TA, scholarship) support. Collaborative work ranges from broad-based research theme (e.g., "Life Cycle of Porphyry Copper Deposits" and "Metallogeny of SW North America") to specific topical studies (e.g., stable isotopic or geochronologic analyses using facilities in Geosciences).
Mineral deposits present a wide array of interesting challenges ranging from characterizing the materials, conditions and evolution of the deposits themselves to the broadest features of metallogenic provinces to the life cycles of deposits beginning with their crustal frameworks and ending with their natural and anthropogenic dispersions. My students and I have worked on ore petrology, ore-forming processes, regional patterns (particularly in the southwestern North America), the broader geologic systems that lead to ore formation, and the life cycles of deposits.
Igneous and Metamorphic Systems
Igneous and metamorphic systems continue to be an area of interest beyond their fundamental role in framing the genesis of many types of deposits. My interests focus around evolution of igneous rocks and intrusive centers in Cordilleran settings, the role(s) of magmatism in metamorphism, and mass transfer in metamorphic systems ranging from subduction zones to shallow plutons.
Tectonics and structure
The physical (thermal and structural) characterstics of ore-forming environments, particularly in Cordilleran settings, is an essential complement to understanding the chemical processes that lead to mineral deposits, as well as their ultimate fates. My interests are principally around understanding the roles that tecotnic (and climatic) processes have in governing the sources for and evolution of hydrothemral systems and the magmatic systems that can be related to them. A related interest is in better understanding the nature of crustal extension which is of particular importance in the Basin and Range Province, both in the generation of some deposits, and in the dismemberment and dispersion of many types of deposits.
Here are brief summaries of current or recent research topics with acknoweldgement of the nature of support over the last few years. All of these projects involve current or former students and many are collaborative with others, particularly with Eric Seedorff.
Porphyry Cu-Mo-Au systems including skarn and replacement deposits
District specific projects in the western US. Synthesis of the Laramide province in SW North America. [industy, USGS, NSF]
Fe-oxide(-Cu-Au) [= "IOCG"] systems and other brine-dominated environments
District specific projects in northern Chile and SW North America. Synthesis of Cordilleran occurrences. Chemical and phyiscal modeling of brine-dominated ore-forming systems. [NSF, industry]
Life cycles of mineralized systems
Natural and anthropogenic life cycles of porphyry copper systems in the Laramide Province of SW North America. [USGS, industry, NSF]
Metallogeny of Southwestern North America
Currently a synthesis and comparison of Jurassic, Laramide, and middle Tertiary magmatism and related mineralization in the Basin and Range Province. [USGS, industry]
Current focus on review, comparison and analysis of Na-Ca-K metasomatism in diverse environments. Field-based analysis of these types in northern Chile and the Jurassic arc of SW North America. [NSF]
Focus on synthesis of Jurassic to mid-Tertiary plutonism in SW North America.Contast and comparison with the central Andes. [USGS, industry]
Gold-rich systems: Carlin-type, alkaline deposits, and others
District specific projects in western US. Synthesis of the Tertiary alkaline province in North America. [industry]
Geology and crustal extension in the Basin and Range Province
Regional mapping and structural reconstruction aimed at mineralized regions and specific districts and better understanding the kinematics of mid-Tertiary extensional tectonics. [USGS, industry]
Mineralogy, petrology and geochemistry of mineralized systems
Current focus is on trace elements in sulfides and silicates, and controls on tourmaline in selected igneous-related hydrothermal systems. [NSF, industry]
Stable isotope lab — silicate extraction lines
As part of the Department-wide geochemical facilities, I maintain and operate two extraction lines for doing oxygen isotope measurements in silicates and refractory minerals. These lines are used by students and post-docs within the Department and for collaborative and contract work with research groups from many areas. One line is a small volume, conventional line, the other is a CO2-based laser line. These data are used in support of many mineral deposit and petrological studies.
Most stable and radiogenic isotopic analyses and geochronology are presently done using other laboratories in the Department of Geosciences and allow a wide range of conventional and novel analytical approaches.
Above: Fluorination lines for extraction of oxygen from silicate, oxide, and refractory minerals.ls.
Petrographic & related facilities in the ore deposits gropu
We share conventional transmitted and reflected light microscopes, conventional and SEM-based cathodoluminescence, and fluid inclusion facilities (heating / freezing stage) with others from the mineral resources, petrology, and geochemistry groups. Extensive sample preparation faclities are collectively maintained under Department supervision.
In addition to the requisite computer work stations and software within our group, a wide range of other preparation, analytical, and experimental facilities are available within the Department and on campus (summarized under each research topic on the Geosciences site). We make greatest use of sample preparation (cutting / polishing), mineral separation, SEM and electron microprobe, stable isotope (H, C, O, S), and radiogenic isotope (Sm-Nd, Rb-Sr, Re-Os, and U-Th-Pb) facilities.
Right: Dates obtained by George Gehrels on a single zircon crystal using the UA multicollector laser ablation system. This zircon is from the Laramide Teacup pluton (illustrated above).
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