April 1, 2020 at 3:45 pm

CANCELED | Geology Colloquium | Petrogenesis and Significance of Lawsonite-bearing Hybrid Rocks, April 3

Katherine Fornash, portrait

Dr. Katherine Fornash

Note: This event has been canceled.

The Geological Sciences Colloquium series presents Dr. Katherine Fornash discussing “Petrogenesis and Significance of Lawsonite-bearing Hybrid Rocks” on Friday, April 3, at 2 p.m. in Clippinger 205.

Fornash is an Assistant Professor at Ohio University in the Department of Geological Sciences.

Abstract:  Hybrid rocks, which have bulk rock compositions that do not correspond to any known sedimentary or igneous protolith, are found in paleosubduction zones worldwide, where they have been interpreted as forming as a result of tectonic mixing and/or metasomatic interactions between mafic, ultramafic, and sedimentary rocks of the subducted slab. The formation and progressive metamorphism of these unique bulk compositions results in hydrous, low density, mechanically weak rocks that consist almost entirely of sheet silicates and trace element-rich accessory phases. As a result of these physical and chemical properties, hybrid rocks have been proposed to play an important role in subduction zone dynamics, including influencing the strength of the slab-mantle interface and contributing to arc magma genesis. In most paleosubduction zones, chlorite ± talc ± amphibole rocks are the most volumetrically significant hybrid rock. However, in the Tavsanli Zone, lawsonite + chlorite rocks are the most common hybrid rock and chlorite ± talc ± amphibole rocks are less common. This talk will address the petrogenesis and metamorphic evolution of lawsonite + chlorite rocks, which may represent the dominant hybrid rock in subduction zones with normal to cool geothermal gradients, using an integrated field, petrologic and geochemical dataset.

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