The importance of talc and chlorite ‘‘hybrid’’ rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction melange of New Caledonia
Spandler, Carl, Hermann, Joerg, Faure, Kevin, Mavrogenes, John A., and Arculus, Richard J. (2008) The importance of talc and chlorite ‘‘hybrid’’ rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction melange of New Caledonia. Contributions to Mineralogy and Petrology, 155 (2). pp. 181-198.
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The transfer of fluid and trace elements from the slab to the mantle wedge cannot be adequately explained by simple models of slab devolatilization. The eclogite-facies melange belt of northern New Caledonia represents previously subducted oceanic crust and contains a significant proportion of talc and chlorite schists associated with serpentinite. These rocks host large quantities of H2O and CO2 and may transport volatiles to deep levels in subduction zones. The bulk-rock and stable isotope compositions of talc and chlorite schist and serpentinite indicate that the serpentinite was formed by seawater alteration of oceanic lithosphere prior to subduction, whereas the talc and chlorite schists were formed by fluid-induced metasomatism of a melange of mafic, ultramafic and metasedimentary rocks during subduction. In subduction zones, dehydration of talc and chlorite schists should occur at subarc depths and at significantly higher temperatures (* 800C) than other lithologies (400–650C). Fluids released under these conditions could carry high trace element contents and may trigger partial melting of adjacent pelitic and mafic rocks, and hence may be vital for transferring volatile and trace elements to the source regions of arc magmas. In contrast, these hybrid rocks are unlikely to undergo significant decarbonation during subduction and so may be important for recycling carbon into the deep mantle.
|Item Type:||Article (Refereed Research - C1)|
|Date Deposited:||10 Mar 2010 05:03|
|FoR Codes:||04 EARTH SCIENCES > 0403 Geology > 040304 Igneous and Metamorphic Petrology @ 100%|
|SEO Codes:||97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%|