New paper on the causes of brittle-to-viscous transition in crustal rocks

Our new paper on “Formation of Nanocrystalline and Amorphous Materials Causes Parallel Brittle‐viscous Flow of Crustal Rocks:Experiments on Quartz – Feldspar Aggregatesbased on experiments from Saleh al Nasser’s second generals project is just published in Journal of Geophysical Research: Solid Earth. Congrats to Saleh!

Fault slip occurs over a vast range of rates and depths in nature. Earthquakes are generated by this fault motion and therefore we need to understand the mechanical properties of fault rocks. To study the mechanism or rock failure at pressures and temperatures corresponding to about 30 km depth, we deformed rocks in the laboratory and analyzed their mechanical behavior. We further studied the samples after deformation using electron microscopy to identify features that are responsible for the measured mechanical behavior. We find that failure occurs due the development of nano‐crystalline to amorphous zones that interconnect upon highest stress and cause sample weakening. Such zones represent a failure mechanism in its own right, distinct from brittle cracks developing at lower pressures and temperatures or crystal‐plastic flow at higher pressures and temperatures. The development of these zones introduces a fluid‐like behavior in small parts of the sample which results in a mixed mechanical behavior: parts of the sample are solid and break and parts of the sample are fluid and flow. This mechanical behavior and its connection to the earthquake cycle is currently only poorly understood and hence is generally not incorporated in models of fault slip

New paper on the development of ultrasound capabilities for our HP-HT deformation apparatus

Our new paper on the development of “An ultrasound probe array for a high-pressure, high-temperature solid medium apparatus” was just published in Review of Scientific Instruments. Hamed has been working on this project very hard and it is great to see the results published! We managed to integrate several piezoelectric sensors along the loading axis in our deformation apparatus. These sensors allow us to record fast, transient deformation episodes known as “acoustic emissions” or AEs. AEs are seen as laboratory analogs to earthquakes occurring in nature. With this new measurement capability we hope to gain further insights into the processes that generate earthquakes especially at elevated pressures and temperatures prevalent at the base of the seismogenic layer.

New paper on reactive melt migration

A new paper co-authored by Matej Pec, Ben Holtzman, Mark Zimmerman and David Kohlstedt on “The Influence of Lithology on Reactive Melt Flow Channelization” is published in GGG. We conducted a series of Darcy-flow type experiments at high pressures and temperatures and observed how feedback between reaction and melt flow lead to the development of high permeability channels. This process is thought to be important for melt extraction from the Earth’s mantle. Check it out! Below is a reconstruction of these channels from 3D tomography images.

12.DTE MITx on-line learning module

This semester we used for the first time an on-line learning module developed in collaboration with MITx and Alejandra Quintanilla Terminel in the class 12.203/205 Mechanics of Earth. This on-line module will serve as a nucleus on which we will build a MOOC focused on rheology and experimental rock deformation in the future. Attached is a short intro video:

Peč Lab at AGU 2019

Come see the Peč Lab’s work on display at this year’s AGU in San Francisco!

Thursday, Dec. 12

8:00 – 12:20 Cailey and Matěj will present a poster, “Deep-crustal Deformation: An Experimental and EBSD-based Study of Amphibole’s Seismic Anisotropy”(S41D-0547)

13:40 – 18:00 Cailey and Matěj will present a poster,  “Experimental investigation of amphibole rheology and deformation mechanisms at deep crustal conditions” (T43D-0457)

13:40 – 18:00 Hamed, Uli, and Matěj will present a poster, “Developing an ultrasound probe array for a high pressure-high temperature solid medium deformation apparatus” (T43D-0456)

17:00 – 17:15: Cailey will present an invited talk, “Seismic Observations of Processes in Collisional Continental Lithosphere: Rheological Changes, Phase Changes, and Deformation” (T44B-05)

 

Friday, Dec. 13

8:00 – 12:20 Cassandra and Matěj will present a poster, “Deformation of Partially Molten Rocks at Lithospheric Temperatures and Pressures,” (MR51B-0045)

8:00 – 12:20 Hongyu and Matěj will present a poster,  “Linear Viscous Flow of Nanocrystalline Fault Rocks at 300 – 500˚C” (MR51B-0048)

13:40 – 18:00 Cailey will present a poster,  “On-Ramps to More Effective Teaching: Quick-Start Guides to Strategies for Actively Engaging Students in The Classroom to Improve Learning”(ED53D-0876)

Visiting ERI Tokyo

Cassandra and Matej are visiting Take Hiraga’s lab at the Earthquake Research Institute in Tokyo. Cassandra is learning how to sinter powders to form textually equilibrated partially molten rocks from Koizumi-san. This visit is generously supported by the MISTI Ulvac-Hyashi fund.

Take demonstrates one of his 1 atm machines
Take’s secret deformation apparatus for research on friction…

New paper on melt segregation!

A new paper co-authored by Alejandra Quintanilla Terminel, Amanda Dillman, Matej Pec, Garrett Diedrich and David Kohlstedt entitled “Radial melt segregation during extrusion of partially molten rocks” just got published . We extruded partially molten rocks through a narrow channel approximating pipe-flow and observed how melt segregates close to the channel wall as predicted by the two-phase flow theory with viscous anisotropy. Check out the results here.

Yuval Boneh from Ben-Gurion University is Visiting

Assistant professor Yuval Boneh from Ben-Gurion University in Israel is visiting our lab to learn more about our tri-axial deformation apparatus and  te perform some experiments on the rheology of the subducting slabs. Yuvals stay is funded through MISTI-Israel awarded to Yuval and Matej. We are looking forward to a fruitful collaboration!