Aug 20, 2024 | No Comments
Dear Nancy, Hello, I have attended GRC meetings for over a decade, and am very grateful for the many ways they have benefited the scientific community I participate in (rock deformation) as well as my personal career path. I’m writing to request a change in GRC policy because I care deeply about the meetings. This month I served as co-chair for the Power Hour. One of the questions we asked the participants to discuss was what topics felt important for future Power Hour discussions. The most common response (from nearly half the groups) was work-life balance. As you’re aware, lack of work-life balance is a major block for achieving equity in science—many women I’ve spoken to simply aren’t willing to make the dual sacrifices of (generally) minimal pay and a stressful, workaholic academic culture. This brings me to the GRC. It was noted by participants in the Power Hour, that the GRC meeting itself—a nearly-continuous, multi-day blast of science and networking at all waking hours—is not a model of work-life balance. I’m not requesting a change in the schedule; I’m writing to simply ask for the flexibility for our meeting to make a choice that would improve work-life balance at the GRC. We would like the flexibility to hold Power Hour during the morning or evening session rather than during afternoon “free time.” We are already using free time to attend field trips, hike, swim, network, take a nap, or do other activities that are purposeful, community-building, rejuvenating, and otherwise meaningful and essential activities in line with the goals of the GRC. Most of the issues discussed at Power...
Oct 02, 2017 | No Comments
I’m excited about some xenoliths I’ve been looking at from beneath the Alpine Fault… come to my AGU talk to hear more: A few spinel peridotite xenoliths found near the Alpine Fault, New Zealand, exhibit a mylonitic texture and, locally, an extremely fine ~30 micron grain size. The harzburgite xenoliths were emplaced in a ~200 km-long elongate dike zone interpreted as a gigantic tension fracture or Reidel shear associated with Alpine Fault initiation ~25 Ma. The presence of thin (~1 mm) ultramylonite zones with px-ol phase mixing and fine grain sizes, minimal crustal-scale strain associated with the dike swarm, and the absence of mylonites at four of the five xenolith localities associated with the dike swarm indicate that upper mantle deformation was highly localized. Strings of small, recrystallized grains (planes in 3D) are found in the interiors of olivine porphyroclasts. In some cases, bands 1-2 grains thick are traced from the edges of olivine grains and terminate in their interiors. Thicker zones of recrystallized grains are also observed crossing olivine porphyroclasts without apparent offset of the unrecrystallized remnants of the porphyroclasts. We suggest a brittle-plastic origin for these features since the traditional recrystallization mechanisms associated with dislocation creep require much more strain than occurred within these porphyroclasts. Analogous microstructures in quartz and feldspar in mid-crust deformation zones are attributed to brittle-plastic processes. We hypothesize that such fine-grained zones were the precursors of the observed, higher-strain ultramylonite zones. Given the size of the new grains preserved in the porphyroclasts (~100 micron) and a moho temperature >~650°C, grain growth calculations indicate that the observed brittle-plastic deformation occurred <10,000 yrs. prior to eruption. It...
Jul 06, 2016 | No Comments
Excited about a session I proposed at AGU this fall, New insights on igneous and metamorphic processes from non-traditional thermobarometers and geospeedometers. Co-conveners are Matt Kohn, Jay Thomas, And William Nachlas. Mark Ghiorso is an invited speaker. Consider submitting an abstract! “Within the last decade, a variety of new techniques have emerged to better constrain the formation history of minerals and rocks from the shallow crust to the mantle. These approaches utilize experimentally- and empirically-determined thermodynamic, kinetic, and physical properties to retrieve information on the conditions and rates of igneous and metamorphic processes. The introduction of new techniques has necessitated a re-evaluation of results from conventional approaches and also opens the possibility to add new insights to previously-studied problems. We welcome presentations on the development and application of emerging techniques for quantifying the pressure, temperature, and/or temporal history of geologic events. Presentations on the development of such non-traditional thermobarometers and geospeedometers, and comparisons of results with more established techniques in both nature and experiment are especially...
May 02, 2015 | 2 Comments
Some photos from the EAS 227 field trip last week to Catskill, New York Devonian Becraft Limestone comprising mainly grainstone with some greenish shale beds The distinctive brachiopod Gypidula Coeymenensis (pencil for scale in bottom left) Class...
Apr 03, 2015 | No Comments
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Aug 12, 2014 | No Comments
Interesting post by Stuart Wright on estimating grains sizes using a weighted area average approach:...
