Munker, Carsten

Scott, James M.

van der Meer, Quinten

Waight, Tod Earle

English

Copenhagen University Research Information System

u n i ve r s i t y  o f  co pe n h ag e n  Københavns UniversitetFor richer and poorerWaight, Tod Earle; Scott, James M.; van der Meer, Quinten; Munker, CarstenPublication date:2014Document versionPeer reviewed versionCitation for published version (APA):Waight, T. E., Scott, J. M., van der Meer, Q., & Munker, C. (2014). For richer and poorer: depletion andenrichment in sub-continental lithospheric mantle xenoliths from southern Zealandia. Abstract from 31st NordicGeological Winter Meeting, Lund, Sweden.Download date: 03. Feb. 2020For richer and poorer: depletion and enrichment in sub-continental lithospheric mantle xenoliths from southern Zealandia  TOD E. WAIGHT1, JAMES M. SCOTT2, QUINTEN H.A. VAN DER MEER1 and CARSTEN MÜNKER3  New Zealand continental crust has a simple and young history, and the oldest exposed rocks are Cambrian in age. However, xenoliths of the subcontinental lithospheric mantle (SCLM) in Eocene-Miocene intra-plate alkaline volcanics yield Re model ages that indicate ancient depletion and a history that is decoupled from the overlying crust (1).  Laser ablation trace element data and radiogenic isotope compositions have been determined for a suite of clinopyroxene separates from spinel peridotite xenoliths from southern New Zealand. Isotope compositions predominantly overlap with those of the host volcanics, especially with respect to Pb isotopic compositions, suggesting that the HIMU-like signature of the volcanics is also present in the SCLM. However, some samples extend to more depleted compositions and point to a depletion history not evident in the overlying crust. Three groups of xenoliths can be identified. Group 1 has rare earth element (REE) signatures indicative of high degrees of depletion and subsequent metasomatism, i.e. generally depleted patterns but enrichments in the lightest REE. Isotopic compositions of group 1 are consistent with ancient depletion (0.5-2.0 Ga) coupled with relatively ancient metasomatism.  Group 2 has trace element compositions consistent with moderate degrees of depletion and no evidence for subsequent metasomatism. Isotopic compositions for group 2 suggest that depletion is not modern but occurred at some point in the Phanerozoic. Group 3 has REE compositions indicative of moderate to small degrees of depletion and relatively large amounts of subsequent metasomatism. The isotopic signatures of these samples represent either relatively recent depletion and metasomatism, or generally large degrees of metasomatism that swamp potentially ancient depleted signatures and thus preclude distinguishing between ancient or recent depletion and metasomatism. No single metasomatising component can explain the observed REE patterns and some samples are best modeled using a low-degree silicate melt as the metasomatising agent, whereas others require a carbonatitic fluid. 1 Department of Geosciences and Natural  Resource Management, Copenhagen University, Øster Voldgade 10, Copenhagen 1350, Denmark (todw@geo.ku.dk) 2Department of Geology, University of Otago, Dunedin 9054, New Zealand  3Institut für Geologie und Mineralogie, University of Cologne, Cologne 50674, Germany  Reference McCoy-West et al. (2013) Geology 41, 231-234 

For richer and poorer:depletion and enrichment in sub-continental lithospheric mantle xenoliths from southern Zealandia

https://curis.ku.dk/ws/files/100718413/Waight_Lund_2013.pdf

For richer and poorer:depletion and enrichment in sub-continental lithospheric mantle xenoliths from southern Zealandia

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