Are the regional variations in Central American arc lavas due t

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• journal_title：Geology
• Contributor：Lars H. Rüpke ; Jason Phipps Morgan ; Matthias Hort ; James A.D. Connolly
• Publisher：Geological Society of America
• Date：2002-
• Format：text/html
• Language：en
• Identifier：10.1130/0091-7613(2002)030<1035:ATRVIC>2.0.CO;2
• journal_abbrev：Geology
• issn：0091-7613
• volume：30
• issue：11
• firstpage：1035

摘要

<p id="p-1">Central American arc volcanism shows strong regional trends in lava chemistry that result from differing slab contributions to arc melting. However, the mechanism that transfers slab-derived trace elements into the mantle wedge remains largely unknown. By using a dynamic model for mantle flow and fluid release, we model the fate of three different slab-fluid sources: sediment, ocean crust, and serpentinized mantle. In the open subarc system, sediments lose almost all their highly fluid mobile elements by ∼50 km depth, so other fluid sources are necessary to explain the slab signal in arc-lava compositions. The well-documented transition from lavas with a strong geochemical slab signature (i.e., high Ba/La ratios) found in Nicaragua to lavas with a weaker slab signature (i.e., low Ba/La ratios) erupted in Costa Rica seems easiest to produce by a higher fraction of serpentine-hosted fluids released from the deeply faulted, highly serpentinized lithosphere subducting beneath Nicaragua than from the less deeply faulted, thicker, amphibolitic oceanic-crust and oceanic-plateau lithosphere subducting beneath Costa Rica. p>