Universität zu Köln

Serre, Simon H., van der Meer, Quinten H. A., Waight, Tod E., Scott, James M., Muenker, Carsten, Thomsen, Tonny B. and le Roux, Petrus J. (2020). Petrogenesis of amphibole megacrysts in lamprophyric intraplate magmatism in southern New Zealand. N. Z. J. Geol. Geophys., 63 (4). S. 489 - 510. ABINGDON: TAYLOR & FRANCIS LTD. ISSN 1175-8791

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Abstract

Sr-Nd-Hf-Pb isotopes and major/trace element data are presented for amphibole megacrysts from two separate instances of lamprophyric intraplate magmatism in Zealandia (Cretaceous Westland Dike Swarm and Cenozoic Alpine Dike Swarm). Megacrysts from both regions have comparable geochemical and isotopic signatures (Sr-87/Sr-86((i)) = 0.702754-0.703371, epsilon Nd-(i) = +3.9 to +5.5, epsilon Hf-(i) = +5.0 to +8.2,Pb-206/Pb-204((i)) = 18.909-20.526,Pb-207/Pb-204((i)) = 15.642-15.678,Pb-208/Pb-204((i)) = 38.824-40.271), regardless of them having traversed contrasting crustal terranes at different times and tectonic settings. Several megacryst cores may represent early-crystallised phenocrysts, whereas rims crystallised in equilibrium with amphibole microphenocrysts during final emplacement of host melts. Strontium isotopic offsets between megacrysts and host rocks indicate secondary hydrothermal alteration in some lamprophyres. Correlations between host rock - megacryst geochemistry as well as evidence for amphibole fractionation in Zealandia lamprophyres indicate that megacrysts likely crystallised from melts similar to their hosts. Isotopic (Pb, Nd) and Mg# offsets suggest a non-cognate relationship and reflect interaction between isotopically heterogeneous lamprophyric melts and/or cumulate amphibole in the lower crust. Modelling suggests that most alkaline intraplate magmatism throughout Zealandia may be derived from moderately heterogeneous SCLM sources that experienced localised varying degrees of subduction-related carbonatitic metasomatism between the Jurassic to Middle Cretaceous during Gondwana break-up.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Serre, Simon H. UNSPECIFIED UNSPECIFIED UNSPECIFIED van der Meer, Quinten H. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Waight, Tod E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Scott, James M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED Thomsen, Tonny B. UNSPECIFIED UNSPECIFIED UNSPECIFIED le Roux, Petrus J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-323065
DOI:	10.1080/00288306.2020.1801771
Journal or Publication Title:	N. Z. J. Geol. Geophys.
Volume:	63
Number:	4
Page Range:	S. 489 - 510
Date:	2020
Publisher:	TAYLOR & FRANCIS LTD
Place of Publication:	ABINGDON
ISSN:	1175-8791
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LITHOSPHERIC MANTLE BENEATH; TRACE-ELEMENT ABUNDANCES; ALKALI BASALTS; DEPLETED MANTLE; BREAK-UP; ISOTOPIC SIGNATURES; ULTRAMAFIC XENOLITH; EIFEL GERMANY; HOST BASALTS; DYKE-SWARM Multiple languages Geology; Geosciences, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/32306