Decoding whole rock, plagioclase, zircon and apatite isotopic and geochemical signatures from variably contaminated dioritic magmas Anna Pietranik a, ⁎, Craig Storey b , Bruno Dhuime c, d , Rafał Tyszka e , Martin Whitehouse f a University of Wroclaw, Institute of Geological Sciences, ul Cybulskiego 30, 50-205 Wrocław, Poland b School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, PO1 3QL, UK c Department of Earth Sciences, University of St. Andrews, North Street, St. Andrews KY16 9AL, UK d Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8, 1RJ, UK e Wrocław University of Environmental And Life Sciences, C.K. Norwida 25/27, 50-375 Wroclaw, Poland f Swedish Museum of Natural History, Laboratory for Isotope Geology, P.O. Box 50007, Stockholm SE-104 05, Sweden abstract article info Article history: Received 29 May 2011 Accepted 3 October 2011 Available online 12 October 2011 Keywords: Magma evolution Quartz diorite Contamination Zircon Apatite Plagioclase Zircon and apatite grains from three types of variably contaminated quartz diorite were analyzed in the Gęsiniec Intrusion (SW Poland). The zircon isotopic compositions (εHf 300 =-5.5–0 and δ 18 O=5.6–9.3‰) are consistent with contamination processes. Zircon is characterized by an increase in U, Th, Pb and REE from the least to the most evolved quartz diorite type. Apatite is characterized by ranges in trace element concentrations and, with the progress of contamination, its composition evolves from those typical for I-type granites toward those typical for S-type. Isotopic and trace element variations in zircon and apatite correlate with Sr isotopic composition of plagioclase ( 87 Sr/ 86 Sr 300 = 0.7069–0.7084; Pietranik and Waight, 2008). However, both Sr isotopic composition of plagioclase and trace element composition of apatite could be homogenized by late-stage resorption, leaving zircon as the only record of contamination processes that predate resorption. Comparison between plagioclase and zircon isotopic composition is consistent with both plagioclase cores and zircons recording similar stages of magma contamination. Comparison between plagioclase and apatite composition indicates that crystallization of apatite was contemporaneous with crystallization of plagioclase rims. The preferred interpretation of isotopic and trace element variations observed in different grains is a two-stage contamination by crustally derived magmas. Early contamination was probably dominated by material typical of the lower crust, i.e. with none or only small amounts of a sedimentary component, as indicated by low δ 18 O in zircon (5.6–6.5‰) in both the least and the most contaminated types. Later contamination was dominated by crustally derived magmas containing more than 20% of a sedimentary component, as the most contaminated sample includes zircon with δ 18 O up to 9.3‰. Partial melts generated from an “S-type granite” source are the most probable contaminant for this second stage contamination, as indicated by apatite trace element composition. In general, isotopic and chemical composition of plagioclase, zircon and apatite provides complementary information on magmatic processes, but records a longer time span than a single mineral only due to their diachronous crystallization histories. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Diorites are usually the least evolved rocks in granitic suites and they occur as enclaves in more felsic hosts or form separate dykes. Granitoids are increasingly regarded as complex intermixtures of melts produced from isotopically distinct sources, both mafic and felsic (Bolhar et al., 2008; Kemp et al., 2007; Yang et al., 2007). Diorites are potentially an important component in granite genesis, recording information on the more mafic end-member. Diorites and quartz diorites are often already contaminated before they are incorporated into the granitic magmas and the contamination processes are observed both in isotopic diversity between rock samples and between individual minerals (Griffin et al., 2002; Kemp et al., 2007; Peytcheva et al., 2008). The challenge is to unpick the information from isotopic and trace element data in different grains to characterize the nature of the contamination. Here, we integrate new isotopic and geochemical data from zircon and apatite with published data from plagioclase (Pietranik and Waight, 2008) to see which processes and contaminants played an important role in the differentiation of dioritic magmas in the Gęsiniec Intrusion, Sudetes, Poland. The contamination in this paper describes the process of the addition of old crustal material to the magma (as crustal melts or fluids) that leads to higher 87 Sr/ 86 Sr and δ 18 O and lower εHf and εNd in the magma. Lithos 127 (2011) 455–467 ⁎ Corresponding author. Tel.: + 48 71 3759296; fax: + 48 71 3759371. E-mail address: anna.pietranik@ing.uni.wroc.pl (A. Pietranik). 0024-4937/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.lithos.2011.10.002 Contents lists available at SciVerse ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos