Kurt Hollocher

Kurt Hollocher in the Grand Canyon.

This past year I had one student, Ben Lucas, who did a project and thesis with me in 2016 and into 2017. We collected samples from the Prescott igneous complex, which mostly resides in the Quabbin Reservoir Reservation in Central Massachusetts. He presented his work at the Northeastern GSA meeting in Pittsburgh. The results of his work started out boring, because the rock geochemistry looked so similar to all the other units around it. After some fretting, looking at age dates and some fossil control in some local stratified units, and reworking some previous structural ideas, the result is actually pretty interesting. The felsic part of the Prescott Complex is Taconian, basically identical to the roots of the Taconian volcanic arc, exposed in adjacent gneiss domes. In the new interpretation, the Prescott was transported into its current location along a detachment fault following the Late Ordovician Taconian collision. The much smaller, mafic part of the complex turns out to be the same age, within uncertainty, as nearby Devonian amphibolites (former basalt volcanics), so they are likely magmatically related. There are other tidbits, but you can read the paper. We hope to submit this winter.
This year, Maria Von Nostrand is working with me on amphibolites from the Middle Allochthon in Norway. The unit contains rare eclogites, which have been extensively studied. Not studied are the amphibolites that contain them, though they, too, should once have been eclogites. She is doing petrographic work, SEM imaging, quantitative mineral analyses, and thermodynamic modeling to constrain the conditions of amphibolite formation.
Early in the summer I was given a surprise invite to a two-week rafting trip in the Grand Canyon. I had one week to prepare, which was pretty nerve-wracking, but what a trip! The colors, the geology, the plants, the spiders, and everything else was just amazing. The contrast between the roasting air temperature and freezing river water was shocking, to say the least. There were stunning, narrow slot canyons, Precambrian soft-sediment detachment faults, late brittle faults, lavas, dikes, sills, the “river anticline,” kink bands, partial melting, weirdly river-polished rocks, and huge travertine mounds. We went on lots of boiling-hot hikes, sometimes to cool goof-off places, other times across giant landslide deposits. Quite something.
Lastly, the biggest event of the year was our successful application for a $300,000+ NSF grant for a new ICP-MS instrument, to replace our 17 year old instrument. The new one will be the latest generation of quadrupole mass spectrometers. It will give us much better sensitivity, detection limits, especially for laser ablation, and better interference reduction for many elements. With its sensitivity, and much faster scanning speed, we should be able to do moderate-precision radiometric dating of zircon and other minerals. It will open up several exciting new research avenues. Getting the lab ready is a lot of work. Electrical modifications, a new stainless steel argon line, safety enclosures for certain gasses, and so on. Plus, a steep learning curve for the new software. Ugh. All in all, however, it’s an exciting development.

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