17 Physical and Chemical Processes of Arc Magmatism and Their Impacts on Crustal Evolution

Friday, 14 May 2021
8:30 AM - 12:30 PM
Desert Research Institute Room

PART 1: A HOLISTIC FRAMEWORK FOR STUDYING THE EVOLUTIONS OF TRANSCRUSTAL MAGMATIC SYSTEMS DEFINED BY THE TRAITS OF PLUTON-HOST ROCK SYSTEMS

Paper number: 17-5
Program: Theme Sessions
Time: 9:35 AM – 9:55 AM

Authors

  • Cullen Scheland Presenting Author
    University of Southern California, Los Angeles, CA
  • Scott Paterson
    University of Southern California, Los Angeles, CA
  • Snir Attia
    Geology, Geophysics, and Geochemistry Science Center, Denver, CO

Abstract

Models for transcrustal magmatism are increasingly favored across geologic, geophysical and analytical disciplines. We consider how to compare these diverse datasets for the purpose of characterizing plutonic and host rock material transfer during the formation of transcrustal magmatic systems. The following fundamental traits of magmatic systems are considered: intrusive geometry, pluton and host rock compositions, structures, regional intrusive patterns and tectonism, petro- and thermochronology, and evidence of material transfer in plutons and host rocks.

The traits of pluton-host rock systems can be linked to three components: the intrusive units, host rock units and tectonic setting. All systems have a space-time path defined by the pluton’s shape. We find 14 fundamental shapes in the literature: veins, rods/fingers, phacoids, sheets, dikes, ring dikes, cone dikes, lopoliths, laccoliths, funnels, stocks, elliptical plutons and irregular plutons. These shapes are found repeated and coexisting in intrusive complexes at all tectonic settings. Magma compositions do not appear to be exclusive to specific shapes, although some are more common to specific shapes: elliptical plutons and laccoliths tend to be more felsic, while dikes, ring dikes, and cone dikes tend to be more mafic. Host rock composition also does not preclude specific shapes: similar shapes are found in plutonic, sedimentary, and metamorphic host rocks.

We collate the traits of six migrated intrusive complexes emplaced into diverse host rock compositions (peridotite, felsic plutons, sediments, metamorphic rocks) and tectonic settings (contractional arcs, focusing zone in a migrating arc flare-up, post-arc crustal shearing). We use map areas and geochronology data to normalize the magmatic histories to proportional timelines. Material transfer and chemical differentiation processes recorded in the plutonic and host rock units are placed along the timeline to visualize the stages of magmatism. Our preliminary results show that pluton-host rock systems are defined material transfer in and out of both the plutons and host rocks. The greatest remaining challenge is assessing the material transfer not directly archived in the rock record. These gaps are best drawn out by collating existing data into a common framework such as ours.

Geological Society of America Abstracts with Programs. Vol. 53, No. 4

doi: 10.1130/abs/2021CD-363258

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