Island arc and continent-building magmatism - A review of petrogenic models based on experimental petrology and geochemistry

T. H. Green*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

181 Citations (Scopus)

Abstract

Detailed geochemical and petrological studies of igneous rock suites in island arc and continental marginal environments have revealed the complexity of magmatism in these regions. Rocks once collectively termed the orogenic calc-alkaline suite are now recognized as forming a continuum between tholeiitic, calc-alkaline and alkaline suites. Although this diversity of rock types has inspired varied and overlapping hypotheses of origin, the application of experimental and geochemical data do limit the appropriate choice of a genetic hypothesis for individual magma suites in convergent plate regions. Also a number of hypotheses of origin may be linked to give an integrated model of the growth of island arcs and continental crust and certain geochemical parameters are distinctive in tracingthisprogressive development. Minor phases such as titanochondrodite, titanoclinohumite and sphene have a critical bearing on key geochemical parameters. Water plays a key role in the integrated model for generation of magmas in convergent plate regions. In the first stage, release of water through dehydration of phases in subducted material controls large-scale melting processes in the mantle, forming the early and most "primitive" tholeiitic magmas in the island arc suite (c.f. Ringwood, 1974), where olivine plays a dominating fractionating role. These magmas form a modified and thickened crust in plate collision regimes. Once this thickened crust has developed, subsequent calc-alkaline magmatism becomes more complex, involving a number of possible sources or processes, including (a) silicic melt from eclogite in the subduction zone, (b) melts from "contaminated" peridotite and (c) relatively shallow level, hydrous, often amphibole-dominated fractionation in the thickened crust. Key trace element abundances can constrain the involvement of these sources or processes. Further magmatic activity in island arcs is related to deeper and low degrees melting, with mica breakdown making an important contribution and jadeitic clinopyroxene remaining.as a residual mantle phase. This produces high-K calc-alkaline rocks transitional into the alkaline suite. Finally, in both "mature" island arcs and continental margins where crustal thicknesses exceed 35 km, continued access of water from the subduction zone and/or underplating of the crust by mantle- or subduction zone-derived magmas, causes partial melting of the crust. The resultant magmas are dominantly silicic and plutonic or ignimbritic. An increasing amount of experimental, geochemical and mineralogical evidence indicates a prominent role for "mature" sedimentary material being involved in melting at depth and the generation of volcanic and plutonic magmas in evolved island arc or continental marginal environments. REE provide useful additional constraints on the genesis of these rocks, as they do for other rocks in the island arc suite.

Original languageEnglish
Pages (from-to)367-385
Number of pages19
JournalTectonophysics
Volume63
Issue number1-4
DOIs
Publication statusPublished - 10 Mar 1980

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