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Modeling chemical geodynamics of subduction zones using the Arc Basalt Simulator version 5

Jun-Ichi Kimura
Modeling chemical geodynamics of subduction zones using the Arc Basalt Simulator version 5
Geosphere (Boulder, CO) (June 2017) 13 (4): 992-1025

Abstract

Arc Basalt Simulator version 5 (ABS5) is a forward geochemical and petrological model that can be used to examine the element mass balance in primary arc magmas including the source and nature of slab materials and flux melting of the mantle-wedge peridotite. The inverse problem approach using ABS5 allows the estimation of intensive and extensive geophysical variables in arc magma genesis. The intensive variables are slab dehydration depth (P (sub SS) ) and temperature (T (sub SS) ) and mantle melting pressure (P (sub perid) ) and temperature (T (sub perid) ). The extensive variables are the amount of slab liquid added to the mantle (F (sub slab liq) ) and the degree of melting of the mantle (F (sub perid) ) along with the amounts of water in the slab liquid (XH (sub 2) O (sub slab liq) ), mantle (XH (sub 2) O (sub perid) ), and magma (XH (sub 2) O (sub melt) ). Subordinate geochemical variables that also can be estimated using ABS5 include the degree of chemical reaction between slab liquids and the solid slab (%R); slab liquid fractions derived from igneous oceanic crust [F (sub liq) (AOC)], sediment [F (sub liq) (SED)], and metasomatized mantle peridotite layers [F (sub liq) (DMM)]; and the degree of depletion of the mantle wedge (%MORB (sub ext) ). The mass balances for 26 incompatible elements, six major elements including H (sub 2) O and Sr, Nd, Hf, and Pb isotopes are calculated based on the same scheme. Monte Carlo calculations are used to estimate the aforementioned variables by fitting the calculated magma composition to observed values. This paper describes the ABS5 calculation scheme and presents examples of its successful use. The geophysical variables determined for these example cases are compared with those estimated by other methods. The spatial variations of the magma productivity and implications for the location of the volcanic front are also discussed.


EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 13
Serial Issue: 4
Title: Modeling chemical geodynamics of subduction zones using the Arc Basalt Simulator version 5
Author(s): Kimura, Jun-Ichi
Affiliation: Japan Agency for Marine-Earth Science and Technology, Department of Solid Earth Geochemistry, Yokosuka, Japan
Pages: 992-1025
Published: 20170620
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 140
Accession Number: 2017-056589
Categories: Geochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201730
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