Fe-Cu-S rich melts in the subcontinental lithospheric mantle: insight from the Lower Silesian (SW Poland) xenoliths
Authors: Mazurek Hubert , Ciążela Jakub , Matusiak-Małek Magdalena , Puziewicz Jacek , Ntaflos Theodoros 
Published: March 2020

&lt;p&gt;Migration of strategic metals through the lithospheric mantle can be tracked by sulfides in mantle xenoliths. Cenozoic mafic volcanic rocks from the SW Poland (Lower Silesia, Bohemian Massif) host a variety of subcontinental lithospheric mantle (SCLM) xenoliths. To understand metal migration in the SCLM we studied metal budget of peridotites from the Wilcza G&amp;#243;ra basanite and their metasomatic history.&lt;/p&gt;&lt;p&gt;The Wilcza G&amp;#243;ra xenoliths are especially appropriate to study metasomatic processes as they consist of 1) peridotites with Ol&lt;sub&gt;Fo=89.1-91.5 &lt;/sub&gt;representing depleted mantle (group A); 2) peridotites with Ol&lt;sub&gt;Fo=84.2-89.2&lt;/sub&gt; representing melt-metasomatized mantle (group B), as well as 3) hornblende-clinopyroxenites and websterites with Ol&lt;sub&gt;Fo=77.2-82.5&lt;/sub&gt; representing former melt&amp;#160; channels (group C; Matusiak-Ma&amp;#322;ek et al., 2017). The inherent sulfides are either interstitial or enclosed in the silicates. High-temperature exsolutions of pyrrhotite (Po), pentlandite (Pn) and chalcopyrite (Ccp) indicate magmatic origin of the sulfides.&lt;/p&gt;&lt;p&gt;The three peridotitic groups differ by sulfide mode and composition. The sulfide modes are enhanced in group C (0.022-0.963 vol.&amp;#8240;) and group B (&lt;0.028 vol. &amp;#8240;) with respect to group A (&lt;0.002 vol.&amp;#8240;). The sulfides of group C are Ni-poor and Fe-Cu-rich as reflected in their mineral composition (Po&lt;sub&gt;55-74&lt;/sub&gt;Ccp&lt;sub&gt;1-2&lt;/sub&gt;Pn&lt;sub&gt;24-44&lt;/sub&gt; in group A, Po&lt;sub&gt;67-85&lt;/sub&gt;Ccp&lt;sub&gt;1-6&lt;/sub&gt;Pn&lt;sub&gt;14-33&lt;/sub&gt;, in group B and Po&lt;sub&gt;80-97&lt;/sub&gt;Ccp&lt;sub&gt;1-7&lt;/sub&gt;Pn&lt;sub&gt;2-20 &lt;/sub&gt;in group C) and major element chemical composition. Ni/(Ni+Fe) of pentlandite is the lowest in group C (~0.25) and the highest in group A (0.54-0.61). Cu/(Cu+Fe) of chalcopyrite is 0.32-0.49 in group C contrasting to~0.50 in groups A and B.&amp;#160;&lt;/p&gt;&lt;p&gt;The sulfide-rich xenoliths of group C indicate an important role of pyroxenitic veins in transporting Fe-Cu-S-rich melts from the upper mantle to the crust. However, the moderately enhanced sulfide modes in melt-mantle reaction zones represented by xenoliths of group B demonstrate that the upper continental mantle is refertilized with these melts during their ascent. Hence, significant portion of S and metals remains in the mantle never reaching the crust, as has been previously observed in the oceanic lithosphere (Ciazela et al., 2018).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments:&lt;/strong&gt; This study was supported by the NCN project no. UMO-2014/15/B/ST10/00095. The EPMA analyses were funded from the Polish-Austrian project WTZ PL 08/2018.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Ciazela, J., Koepke, J., Dick, H. J. B., Botcharnikov, R., Muszynski, A., Lazarov, M., Schuth, S., Pieterek, B. &amp; Kuhn, T. (2018). Sulfide enrichment at an oceanic crust-mantle transition zone: Kane Megamullion (23 N, MAR). Geochimica et Cosmochimica Acta, 230, 155-189&lt;/p&gt;&lt;p&gt;Matusiak-Ma&amp;#322;ek, M., Puziewicz, J., Ntaflos, T., Gr&amp;#233;goire, M., Kuku&amp;#322;a, A. &amp; Wojtulek P.&amp;#160;&amp;#160; M. (2017). Origin and evolution of rare amphibole-bearing mantle peridotites from Wilcza G&amp;#243;ra (SW Poland), Central Europe. Lithos 286&amp;#8211;287, 302&amp;#8211;323.&lt;/p&gt;