Active Research

Eruption Timescales

This project uses a new method that I have developed, called magnetic geothermometry. The method can determine the amount of time that an intrusion or magmatic conduit was actively supplied with magma (dike, sill, pluton, etc.). The method uses a combination of paleomagnetic data, geochemical data, and thermal modeling. Since it does not rely on radioactive decay or chemical diffusion, it can be applied equally to young (<1 Ma, or active) and old (>2 Ga) magmatic systems.

I’m applying this technique to shallow dikes of the Columbia River Basalts, in order to determine their eruption timescales. A paper currently in review shows that no dike in the CRB was active for more than 10 years, and eruption rates were 0.6-6 km3/day during eruptions.

Superior Province Metasediments

This project focuses on the numerous Archean S-type granitoids found in Northern Ontario, and the metasediments from which they are derived. In some cases (such as at the Ghost Lake Batholith near Dryden, ON) the melting process that forms S-type granitoids has been preserved in-situ. As you walk from the edge of the batholith into the surrounding metasediments, you also walk progressively down-grade from granulite facies to lowest greenschist facies. This project focuses on the hydrothermal systems hosted in these metasediments, the mass balance between wall-rock and partial melt, and the origin of S-type granitoids. Some of these results have been published in an EPSL paper with Dr. Bucholz.

Aeromagnetic Volcano Monitoring

Current volcano monitoring techniques typically have high operating costs or produce ambiguous data (or both). This project illustrates how aeromagnetic data might be usable for real-time, low-cost volcano monitoring. This is modeled using reconstructions of the 2015 eruption of Axial Seamount and the 2014-15 Bárðarbunga eruption in Iceland. The technique that I’ve developed shows potential for widespread applicability and can be modified for use in remote locations. A paper on these results is currently in preparation. Going forward, I plan to implement magnetic monitoring strategies at active volcanoes as a proof-of-concept study.

Mafic Terranes of Northern Alaska

Interior and northern Alaska is host to abundant mafic and ultramafic rocks. These units collectively cover 38,000 km3, the same area as Switzerland or Maine. However, very few geochemical analyses exist for these rocks, despite their prevalence.

This project aims to geochemically characterize these rocks, in order to better inform tectonic models of the region. Results suggest that portions of these terranes are remnants of a mafic arc/forearc, while the remainder are MORB-related. A few OIB/hotspot massifs are also present. One paper on this topic has already been published, another is in prep.

Cascade Volcanics

This project focuses the Goat Rocks volcanic complex, located between Mt. Adams and Mt. Rainier. This complex hosts several extinct volcanic centers which together provide most of the volcanic complexity that the Cascades have to offer (polygenetic to monogenetic, explosive to effusive, basaltic to rhyolitic). Within these volcanic sequences, several geomagnetic reversals and excursions are preserved. This project focuses on documenting these events and precisely dating them using paleomagnetism and 40Ar/39Ar geochronology. Results from this study will allow for more accurate dating of Quaternary rocks, sediments, and archeological artifacts throughout the world.

Oregon Coast Range Rotation

The Coast Range of Oregon is thought to have rotated ~60 degrees into its current position since the Eocene. This is largely based on paleomagnetic data gathered in the 1960s and 70s.

However, a reexamination of these data found that they are not up to modern standards (only NRMs reported in many cases), and should not be relied on for any tectonic interpretations.

The goal of this project is to re-sample the Eocene Tyee formation of the Oregon Coast Range, to test the rotation hypothesis. A paper currently in preparation shows that these sediments do not pass the fold test, and therefore do no preserve a primary remanence.

Baffin Flood Basalt Eruption Tempo

The flood basalts of southeastern Baffin Island (North Atlantic Igneous Province) are famous among isotope geochemists for their high 3He/4He ratios. However, these rocks are too primitive to date via 40Ar/39Ar or any other means yet developed. Therefore the age of these basalts is very poorly constrained. In addition, very little paleomagnetic data exists from this unit.
A paper currently in preparation presents an expanded paleomagnetic, geochemical, and stratigraphic dataset for these basalts. Furthermore, I demonstrate that the entire sequence erupted in ~15 kyr and eruption rates were typical of other flood basalt provinces.

40Ar/39Ar Geochronology of Altered Basalts

The Columbia River Basalts have been extensively dated by 40Ar/39Ar geochronology, and more recently by U-Pb Zircon geochronology from interbedded ash deposits. These two methods disagree significantly, and the U-Pb results are now widely accepted as ‘correct’.
In this project, I geochemically and magnetically characterized CRB basalts of varying degrees of alteration. These same samples were then dated via 40Ar/39Ar to determine the link between alteration and age, and to determine which geochemical or magnetic indicators will show that a sample can yield a ‘correct’ age. Preliminary results suggest that rock-magnetic properties can predict if a sample will yield and anomalously young age, and this routine can be easily implemented in most Argon geochronology labs.

Uplift of Steens Mountain

Steens Mountain is a very large and prominent topographic feature in southeastern Oregon. You should drive to the top if you’re ever in the area, the view cannot be overstated. This is the source region of the Steens Basalts, the oldest member of the Columbia River flood basalts. The eastern face of the mountain was created by a prominent basin and range normal fault. However, the timing of fault activation and topographic uplift is not known.

This project uses thermochronologic, structural, stratigraphic, and paleomagnetic data to determine the uplift history of Steens Mountain. Preliminary data suggests that uplift was already underway by 15 Ma but significant uplift did not occur until after 10 Ma.

Antarctic Peninsula Paleomagnetism

The history of the geomagnetic field over Antarctica is poorly constrained. This is due to a lack of samples, which is obviously due to the remote location.
This project uses hundreds of cores from the Antarctic peninsula to better characterize the declination, inclination, and intensity of the magnetic field in this area over the last ~5 Ma.

In addition, a paper currently in preparation also uses magnetic and geochemical data to refine the volcanostratigraphy and magma supply rates of the James Ross Island Volcanic Group.

Contact:
biasi@caltech.edu

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