Geoscience Frontiers 11 (2020) 925-942 ELSEVIER Contents lists available at ScienceDirect Geoscience Frontiers journal homepage: www.elsevier.com/locate/gsf GEOSCIENCE Fl Research Paper Lead isotope evolution of the Central European upper mantle: Constraints (I) from the Bohemian Massif Simona Krmíčkováa'b, Lukáš Krmiček a'b'c'*, Rolf L. Romerd, Jaromír Ulrych1 a Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37, Brno, Czech Republic h Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, CZ-165 02, Prague 6, Czech Republic c Brno University of TechnoU)gy, Faculty of Civil Engineering AdMaS Centre, Veveří 95, CZ-602 00, Brno, Czech Republic d Deutsches GeoForschungsZentrum GFZ, Telegrafenberg D-144 73, Potsdam, Germany ARTICLE INFO ABSTRACT Handling Editor: Christopher J Spencer Keywords: Lead isotopes Lamprophyres Volcanic rocks Mantle components Bohemian massif Variscan orogeny The Pb isotope composition of the upper mantle beneath Central Europe is heterogeneous due to the subduction of regionally contrasting material during the Variscan and Alpine orogenies. Late Variscan to Cenozoic mantle-derived melts allow mapping this heterogeneity on a regional scale for the last ca. 340 Myr. Late Cretaceous and Cenozoic anorogenic magmatic rocks of the Bohemian Massif (lamprophyres, volcanic rocks of basanite/ tephrite and trachyte/phonolite series) concentrate mostly in the Eger Rift. Cretaceous ultramafic lamprophyres yielded the most radiogenic Pb isotope signatures reflecting a maximum contribution from metasomatised lith-ospheric mantle, whereas Tertiary alkaline lamprophyres originated from mantle with less radiogenic 206Pb/204Pb ratios suggesting a more substantial modification of lithospheric source by interaction with asthenospheric-derived melts. Cenozoic volcanic rocks of the basanite/tephrite and trachyte/phonolite series define a linear mixing trend between these components, indicating dilution of the initial lithospheric mantle signature by up-welling asthenosphere during rifting. The Pb isotope composition of Late Cretaceous and Cenozoic magmatic rocks of the Bohemian Massif follows the same Pb growth curve as Variscan orogenic lamprophyres and lamp-roites that formed during the collision between Laurussia, Gondwana, and associated terranes. This implies that the crustal Pb signature in the post-Variscan mantle is repeatedly sampled by younger anorogenic melts. Most Cenozoic mantle-derived rocks of Central Europe show similar Pb isotope ranges as the Bohemian Massif. 1. Introduction Central Europe has been affected by two major extensional events of Permo-Carboniferous and Tertiary age (e.g., Meier et al., 2016). Permo-Carboniferous extension began in Central Europe because of post-collisional changes in the kinematics between the Laurussia and the Gondwana plates (Kroner et al., 2016) and resulted in the formation of the Central European Extensional Province (CEEP) with numerous volcano-sedimentary basins in Europe as well as the Oslo Rift (e.g., Neumann et al., 2004; Wilson et al., 2004). This extension was coeval with the opening of the Palaeo-Tethys Ocean farther to the east and the closure of the remaining Rheic Ocean farther to the west (Kroner and Romer, 2013). Late Cretaceous to Tertiary lithospheric extension was initiated as a response to the tensional reactivation of Variscan Permo-Carboniferous fracture systems by the Alpine collision, eventually resulting in the formation of a vast rift system in Western and Central Europe. The European Cenozoic rift system includes the following individual rifts: Valencia Trough in Spain, the Gulf of Lions, the Saone, Limagne and Bresse grabens in south-eastern France, the Rhine, Ruhr and Leine grabens in Germany, and the Eger Rift in the Bohemian Massif (Ziegler, 1992, Fig. 1). Formation of continental rift systems associated with horizontal movements of plates and subsequent lithosphere thinning is commonly accompanied with magma generation by decompression melting of lithospheric and asthenospheric mantle that is passively upwelling beneath the thinned lithosphere (e.g., Berkesi et al., 2019). Melts generated in rifts by decompression are separated from their residue and ascend from the zone of melting in the upper mantle and are emplaced within the overlying continental crust or are extruded as lava flows. The volume of the produced melts depends on the amount of lithospheric * Corresponding author. Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, CZ-165 02, Prague 6, Czech Republic. E-mail address: lukas.krmicek@gmail.com (L. Krmíček). Peer-review under responsibility of China University of Geosciences (Beijing). https://doi.Org/l 0.1016/j.gsf.2019.09.009 Received 27 April 2019; Received in revised form 2 August 2019; Accepted 25 September 2019 Available online 23 October 2019 1674-9871/© 2019 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND li e (http://creativecommons.o: =s/by-ni>nd/4.0/). S. Knníckovä et al Geoscience Frontiers 11 (2020) 925-942 DHVC Tertiary volcanic rocks: O Basanite A Trachyandesite V Trachyte □ Tephrite O Phonolite O Nephelinite Tertiary alkaline lamprophyres: O Camptonite A Monchiquite T Microsyenite Melilitites: O Cretaceous O Quaternary Cretaceous ultramafic lamprophyres: • Polzenite A Alnöite T Melilitolite Fig. 1. (A) Distribution of major volcanic areas within Central Europe (modified after Blusztajn and Hegner, 2002); EL - Elbe Line, OFZ - Odra Fault Zone. (B) Map of volcanic centres in the Eger Rift with sampling areas (modified after Zacharias et al., 2008). Abbreviations: BRB - Berzdorf Radomierzyce Basin; CDG - Cheb-Domažlice Graben; CSVC - České Stŕedohoŕí Volcanic Complex; DHVC - Doupovské Hory Volcanic Complex; MB - Most Basin; RPVC -Ralská Pahorkatina Volcanic Complex; SB - Sokolov Basin; ZB - Zittau Basin. extension and on the temperature of the asthenosphere. The primary products of volcanic activity in rifts are mainly basaltic. Continental intra-plate rifting produces predominantly olivine/nepheline-bearing alkaline basalts (e.g., White and McKenzie, 1989; Wilson and Downes, 1992; Lustrino and Wilson, 2007; Haase and Renno, 2008). For the Cenozoic rift system of the Central European Volcanic Province (CEVP), there are two end-member type models. Some authors favour asthenospheric melting in response to large-scale upwelling of mantle plumes or small-scale plumelets (e.g., Wilson and Downes, 1991; Hegner et al., 1995). Other studies favour derivation of the intraplate volcanic rocks from the metasomatised lithospheric mantle, either by preferential melting of phlogopite/amphibole-bearing vein assemblages hosted in lherzolitic mantle or by very low degree melting of highly metasomatised domains, resulting in the generation of strongly SiC>2-undersaturated melts (Hegner et al., 1995; Jung et al., 2005; Pfänder et al., 2018). Late Variscan to Cenozoic mantle-derived rocks, such as lamprophyres, lamproites, and alkali-basalts, largely sampled the same mantle on a regional scale and at variable depth during above mentioned extensional events (e.g., Mayer et al., 2014; Krmiček et al., 2016; Ulrych et al., 2018). Although mantle-derived lamprophyres and associated intrusive rocks are relatively rare within the volcanic complexes, these small-volume melts are particularly important for studying processes and geochemical heterogeneities of the upper mantle beneath Central Europe as they preferentially sample the metasomatic component, which was induced during the Variscan orogeny when continental collision brought continental crust to mantle depth (e.g., Kroner and Romer, 2013; Bor-ghini et al., 2018; Pfänder et al., 2018). The Sr, Nd, and Pb isotope composition of mantle-derived rocks may identify contributions from different mantle sources, such as depleted asthenospheric and enriched lithospheric upper mantle and lower mantle, to the generated magmas (e.g., White and McKenzie, 1989; Zou et al., 2000). Isotope constraints on the mantle sources of Mesozoic and Cenozoic volcanic rocks of the Bohemian Massif largely rely on Sr-Nd isotope data (e.g., Alibert et al., 1983, 1987; Blusztajn and Hart, 1989; Bendl et al., 1993; Vokurka, 1997; Ulrych et al., 2002, 2008, 2011, 2013, 2016, 2018; Haase and Renno, 2008; Cajz et al., 2009; Skála et al., 2014, 2015). In contrast, Pb isotope data are rare (Blusztajn and Hart, 1989; 926 S. Knnickovä et al Haase and Renno, 2008; Ulrych et al., 2016). As typical mantle has low Pb Contents, the Pb isotope composition of the mantle is readily affected during metasomatism. Because of the contrasting Pb contents in crust and mantle rocks, small contributions of continental material are more sensitively recorded in the Pb isotope composition than in the Sr and Nd isotope composition (Cohen and O'Nions, 1982; Davies and Macdonald, 1987; Sun and McDonough, 1989; Conticelli et al., 2002). Our paper focuses on Pb isotope data and whole-rock geochemistry of intrusive and extrusive volcanic rocks of the Bohemian Massif that sampled the upper mantle. We pay special attention whether Late Palaeozoic to Quaternary Central European mantle-derived rocks sampled different mantle sources on a local to regional scale and through time. 2. Geological setting The upper mantle beneath Central Europe is heterogeneous, which is largely due to Variscan and Alpine subduction events during which regionally contrasting subducted material of both continental and oceanic crust metasomatically modified the upper mantle (e.g., Witt-Eickschen and Kramm, 1997; Downes, 2001; Ackerman et al., 2009; Kroner and Romer, 2013; Pfänder et al., 2018). Older tectonic structures reactivated during the late Variscan to Alpine events were associated with asthenospheric upwelling and subsequent extension-related mag-matism that sampled this modified mantle (Wilson and Downes, 1991). 2.1. Variscan to post-Variscan development The Variscan orogen is the result of the Devonian-Carboniferous collision of Gondwana with Laurussia that started with the collision of the Armorican Spur, which is part of segmented peri-Gondwana. The collision of the Armorican Spur with Laurussia resulted in the closure of the Rheic Ocean in the area of future Central Europe (Kroner and Romer, 2010, 2013). The subducted material consisted primarily of relative thin lithosphere covered by Palaeozoic volcano-sedimentary rocks (Kroner et al., 2007). In contrast, the unsubductable parts of the peri-Gondwana (Cadomian) magmatic arc (i.e., thick crustal fragments of the Armorican Spur) caused reorganisation within the plate boundary zone (Kroner and Romer, 2013). The Bohemian Massif consists of high- and low-strain domains that behaved differently during the Variscan orogeny. The Teplá-Barrandian Unit and Lusatia (parts of Gondwana) and the Bruno-vistulian Terrane (part of Laurussia) are low-strain domains that collided during the closure of the Rheic ocean (e.g., Kalvoda et al., 2008; Kalvoda and Babek, 2010). The Saxo-Thuringian and Moldanubian Zones are high-strain domains that represent former Gondwana shelf and that were subducted and exhumed during the Variscan orogeny (e.g., Kroner and Romer, 2013; Krmiček et al., 2016; Žák and Sláma, 2018). Plate tectonic processes that may have changed the composition of the upper mantle of the Bohemian Massif include (i) Cadomian subduction followed by Late Neoproterozoic back-arc spreading and early Palaeozoic rifting in northern peri-Gondwana, (ii) intra-oceanic subduction and formation of oceanic arcs that were later accreted to form part of Variscan Europe, (iii) possible subduction beneath the northwards migrating terranes, (iv) subduction and collision at the southern margin of Laurussia, and (v) Carboniferous extension of Central Europe (Wilson et al., 2004; McCann et al., 2006; Pin and Waldhausrová, 2007; Tim-merman, 2008; Abdelfadil et al., 2013; Dostal et al., 2019a,b). Subduction of both oceanic and continental crust peaked at 340 Ma and led to the establishment of isotopically contrasting domains in the meta-somatised lithospheric mantle (Krmiček et al., 2016). During the late stage of the Variscan orogeny, these metasomatised mantle domains underwent partial melting resulting at ca. 340-300 Ma in the intrusion of potassic to ultrapotassic dykes (lamprophyres and lamproites) along deep-fault zones related to initial crustal extension eventually leading to the formation of the CEEP (Awdankiewicz, 2007, 2009; Krmiček et al., 2011, 2014, 2016; Abdelfadil et al., 2013; Hrouda et al., 2016). Geoscience Frontiers 11 (2020) 925-942 Post-Variscan magmatic activity throughout Variscan Europe was associated with the extension of thickened Variscan crust and accompanied by progressively increasing contributions from the asthenospheric mantle (Lorenz and Nicholls, 1984; Timmerman et al., 2009). Permian extension led to the formation of rift basins, such as the North Germany Basin or the Oslo Rift (Benek et al., 1996; McCann et al., 2006). 2.2. Mesozoic to Cenozoic development Within the framework of the African-Eurasian plate collision, the extensive European Cenozoic Rift System (ECRIS) formed in Western and Central Europe stretching from Spain and France through Germany to the Czech Republic and Poland (Prodehl et al., 2006). The ECRIS recorded intermittent sub-volcanic/volcanic activities that started in the Late Cretaceous and have lasted to the present (Lustrino and Wilson, 2007). Episodic volcanism occurred mainly in the Oligocene to Miocene with waning phases of anorogenic volcanic activity reaching to the Plio-Pleistocene (Nowell et al., 2006). Magmatic activity in the ECRIS is concentrated in intrusive complexes and volcanic fields within the gra-bens and their shoulders (Fig. 1A). Rifts formed at reactivated Variscan suture zones separating large different lithospheric segments, indicating structural control on the location of Cenozoic volcanic activity (Dězes et al., 2004). The Bohemian Massif is transected by the nearly 300 km long ENE-WSW trending Eger Rift, by the transverse NW-SE striking Elbe/ Labe-Odra Fault System in the north (Fig. 1A), and by the NW-SE trending Cheb-Domažlice Graben in the west (Špaček et al., 2011). The Eger Rift represents the easternmost part of the Cenozoic rift system of the Central European Volcanic Province (e.g., Ziegler, 1994; Lustrino and Wilson, 2007). The magmatic rocks of the Eger Rift are predominantly Si02-undersaturated alkaline rocks of intra-plate origin (Ulrych et al., 2002, 2011; Lustrino and Wilson, 2007; Dostal et al., 2017). The volcanic activity is a result of reactivation of Variscan structures in the Bohemian Massif during the Alpine orogeny (Babuška and Plomerová, 1992, 2001, 2010). Whether the model of mantle plumes sensu Wilson and Paterson (2001), with Alpine flexure and lithospheric extension followed by adiabatic decompression, decompression melting, and injection of mantle-derived magmas into the crust, played a major role is debated (Wilson and Downes, 1991; Wedepohl et al., 1994; Lustrino and Wilson, 2007; Ulrych et al., 2011) and is reflected in terms like Common Mantle Reservoir (CMR - Lustrino and Wilson, 2007) or European Asthenospheric Reservoir (EAR - Cebriá and Wilson, 1995) used to characterise magmas from a possible sub-lithospheric source region. Ulrych and Pivec (1997) and Ulrych et al. (2011) defined three phases of Cenozoic volcanic activity based on K-Ar dating and palaeostress mapping: (i) a pre-rift period (—80-49 Ma), (ii) a syn-rift period (42-16 Ma) and (iii) a late-rift period (16-0.26 Ma). Ulrych and Pivec (1997) also defined two coeval alkaline series: (i) a volumetrically dominant neph-elinite-basanite-tephrite-phonolite series of strongly to mildly alkaline rocks and (ii) a subordinate and only locally occurring weakly alkaline alkali basalt-trachybasalt-trachyandesite-trachyte-rhyolite series. The Eger Rift comprises several volcanic centres (Fig. IB), namely the České Středohoří Volcanic Complex (CSVC), the Doupovské Hory Volcanic Complex (DHVC; access to volcanic edifice exposures is restricted as they are predominately located in the Doupovské Hory military training zone), the Ralská Pahorkatina Volcanic Complex (RPVC) and a great number of isolated volcanoes in the western part of the Bohemian Cretaceous Basin and in the Cheb-Domažlice Graben (CDG). The youngest volcanoes occur in the Cheb/Eger Basin, a sub-basin of the Eger Rift. The first manifestation of volcanic activity in the Eger Rift is Late Cretaceous ultramafic lamprophyres and related melilitic rocks associated with subsurface intrusion of melilitolite composition that occur near the intersection of the marginal fault of the Eger Rift and the Lusatian Fault within the future RPVC in the northern part of the Bohemian Cretaceous Basin (Ulrych et al., 2014). Most of the Cenozoic volcanic rocks, predominantly of basanitic composition, are concentrated in the 927 S. Knnickovd et al CSVC and DHVC, whereas hypabyssal intrusions spatially associated with alkaline lamprophyre dykes of Cenozoic age are restricted to the CSVC and RPVC (Skala et al., 2014). Sr-Nd-(Pb)-isotope compositions of rocks from the western Eger Rift, i.e., the DHVC and CDG, were recently published by Ulrych et al. (2016) and Haase et al. (2017). For locations of investigated samples and characteristics of sampled areas see Fig. IB and Supplement A. 3. Methods Representative samples of the studied volcanic and subvolcanic rocks are described petrographically using conventional optical microscopy and characterised geochemically by whole-rock and mineral composition using ICP-ES, ICP-MS, and electron microprobe, respectively. Whole-rock chemical analyses from fresh samples lacking signs of alteration or wall-rock assimilation were carried out at Bureau Veritas (former ACME) Analytical Laboratories Ltd. (Vancouver, Canada) using inductively coupled plasma emission spectrometry (ICP-ES; major oxides, Ba, Ni, Cu, Pb, Zn) and inductively coupled plasma mass spectrometry (ICP-MS; Co, Cs, Hf, Nb, Rb, Sr, Ta, Th, U, V, Zr, Y and REE). Loss on ignition (LOI) was determined by weight difference after ignition at 1000 °C. The Pb, U, and Th concentrations are used to recalculate the initial Pb isotope composition. The errors for the Pb, U and Th concentrations correspond to ±0.1 ppm, ± 0.1 ppm, and ±0.2 ppm, respectively. For further analytical details and detection limits see www.acmelab.com. The composition of characteristic dark minerals (amphibole, clinopyr-oxene, and mica) was analysed using a CAMECA SX 100 electron micro-probe (Institute of Geology of the CAS, Prague) operated in wavelength-dispersive mode. Measurements were performed using a 15 keV acceleration voltage, 10 nAbeam current and 2 beam diameter. Both natural and synthetic minerals were used as reference standards. Concentrations of following elements were measured (standard, spectrometer crystals and detection limit for analysed elements are given in parentheses): Si (diopside, LTAP, 222 ppm), Ti (rutile, LPET, 357 ppm), Al (jadeite, LTAP, 272 ppm), Cr (Mn-Cr spinel, LIF, 910 ppm), Fe (haematite, LIF, 1047 ppm), Mn (rhodonite, LIF, 965 ppm), Ni (Ni2Si, LTAP, 1404 ppm), Mg (periclase, LTAP, 422 ppm), Ca (diopside, LPET, 341 ppm), Na (jadeite, LTAP, 262 ppm), K (leucite, LPET, 300 ppm), F (fluorite, PC0,1575 ppm), CI (tugtupite, LPET, 320 ppm), Rb (RbCl, LTAP, 217 ppm) and Ba (barite, LPET, 503 ppm). Counting times on peaks were 10 s for Mg, Al, K, Ca, CI, Ti; 20 s for Na, Si, Rb, Ba, Ni and Mn, Ni; and 30 s for Cr, Ca and Al. The X-phi correction procedure (Merlet, 1992) was used for spectra processing. The Pb isotope compositions were determined at Deutsches Geo-ForschungsZentrum (GFZ), Potsdam, Germany. Powders from representative unaltered samples of volcanic and subvolcanic rocks were dissolved in concentrated HF for four days on a hot plate at 160 °C. Samples were dried, re-dissolved in 2 N HNO3 and dried slowly at 80 °C overnight to convert fluorides to nitrates. Finally, the samples were taken up in 6 N HC1 to convert nitrates to chlorides. Lead was separated in columns using ion exchange resin Bio Rad AG-1-X8. Procedures for the separation and purification of Pb are described in detail by Romer et al. (2005). The ion exchange procedure was repeated to purify Pb elutes. Lead was loaded together with H3PO4 and silica-gel emitter on single Re-filaments. The Pb isotope ratios were measured using a Thermo-Finnigan Scientific TRITON TIMS multi-collector mass-spectrometer operated in static multi-collection mode. The obtained Pb isotope ratios were corrected for instrumental fractionation of 0.1%/a.m.u. as determined from repeated measurement of Pb reference material NBS 981. Total procedural blank is between 15 and 30 pg Pb, thus, negligible. Accuracy of the determined Pb data is better than 0.1% at the 2a level. 4. Results 4.1. Field and petrographic descriptions The studied volcanic rocks were mainly taken from exposures and Geoscience Frontiers 11 (2020) 925-942 quarries (Fig. 2A and B), whereas lamprophyres and related dykes were mostly collected as loose angular blocks in the field (Fig. 2C). Melilitolite sample (OC-12) originates from a 271 m deep Holičský vrch borehole near Osečná (Table 1). Late Cretaceous ultramafic lamprophyres, such as polzenite and alnóite dykes and the melilitolite of the Osečná intrusion, were sampled in the RPVC. Polzenites and alnóites generally have a fine-grained greyish groundmass and microporphyritic textures. They contain abundant partially serpentinised olivine phenocrysts/xenocrysts in a finegrained poikilitic groundmass containing microphenocrysts of phlogo-pite, which may be variably chloritised, flow-oriented melilite laths, feldspathoids, apatite and abundant Ti-rich magnetite (Fig. 2D). Alnóites contain, in contrast to polzenites, also phenocrysts of clinopyroxene. Tertiary basaltic volcanic rocks predominantly have microporphyritic textures with a fine-grained groundmass. Basanite samples are generally dominated by clusters of slightly serpentinised olivine along with elongated brownish, rarely corroded clinopyroxene crystals with oscillatory and/or hour-glass zoning. Twinned clinopyroxene forms isolated crystals or larger glomerophyres. The basanite fine-grained groundmass contains tiny plagioclase laths irregularly distributed together with smaller clinopyroxene columns (Fig. 2E). Most of the tephrite samples are characterised by the presence of both euhedral and partially corroded kaersutite with apatite inclusions. Kaersutite is surrounded by a very fine-grained hypocrystalline groundmass. Tertiary alkaline lamprophyres, such as camptonite, monchiquite and more alkaline leucocratic microsyenite, are especially common in the Roztoky Intrusive Complex of the CSVC. A special form of camptonite to monchiquite dykes occurs in the RPVC. The alkaline lamprophyres typically contain macroscopic amphibole phenocrysts in a fine-grained groundmass. The amphibole phenocrysts typically show corrosion rims comprising Ti-rich magnetite. Clinopyroxene in camptonites forms oscillatory and hour-glass zoned phenocrysts and smaller tabular crystals in a fine-grained plagioclase-rich groundmass. A typical accessory mineral is apatite, which is commonly associated with amphibole and/or clinopyroxene, titanomagnetite and feldspathoids. Zeolites are rare and form vesicular fillings (Fig. 2F). Camptonite to monchiquite samples from RPVC are characterised by amphibole that is rimmed by distinct dark mica, strongly serpentinised olivine and rare oscillatory-zoned clinopyroxene in a glassy matrix. Leucocratic microsyenite samples contain glomerophyres of amphibole and alkaline feldspar in a fine-grained feldspar-rich matrix (Fig. 2G). Amphiboles have inclusions of apatite and ilmenite. The groundmass consists primarily of glass, plagioclase and rare sodalite. Vesicles are filled by hydrothermal calcite. Very finegrained chilled margins of the leucocratic microsyenite dyke show flow-aligned alkali feldspar microphenocrysts (Fig. 2A). Additionally, two areas with nephelinte to melilitite occurrences are included in this study. Cretaceous intrusive melilitite from the Great Devil's Wall in the RPVC is spatially related to ultramafic lamprophyres and forms a spectacular wall with horizontal columnar jointing (Fig. 2H). It contains mildly corroded olivine often forming clusters, and strongly zoned brown Ti-rich clinopyroxene commonly displaying characteristic twinning. Opaque minerals and flow-oriented thin laths of clinopyroxene occur in a melilite-bearing groundmass. In contrast, the Quaternary melilitite effusion from the youngest volcanic field in the Bohemian Massif, i.e., Cheb Basin, is characterised by the mineral association olivine (with thick, corroded rims) and large, kink-banded phlogopite flakes distributed in a vesicular glassy groundmass. For detailed petro-graphical characteristic of individual studied samples see Supplement B. 4.2. Mineral chemistry of amphibole, clinopyroxene and dark mica Chemical compositions of amphibole, clinopyroxene and dark mica from camptonite/monchiquite, leucocratic microsyenite and polzenite samples are listed in Supplement C available in the electronic appendix. Analysed minerals have relatively homogenous compositions without significant variation between cores and rims. 928 S. Knníckovä et al Geoscience Frontiers 11 (2020) 925-942 Fig. 2. Field appearances and petrographic features of intrusive (lamprophyric) and extrusive volcanic rocks from the České Stŕedohoŕí (CSVC) and Ralská Pahorkatina (RPVC) volcanic complexes. (A) Contact of a leucocratic microsyenite dyke in basanite host, characterised by a very fine-grained chilled margin (CSVC). (B) Columnar jointing of sandstone (see Velazquez et al., 2008) at the contact to a camptonite dyke (RPVC). (C) Polzenite with characteristic warty surface (RPVC). (D) Partly serpentinised olivine (Ol) within fine-grained groundmass with slightly chlori-tised phlogopite (Phi), melilite (Mil) and Ti-rich magnetite (Mag) in polzenite (PPL; RPVC). (E) Cluster of olivine (Ol) and clinopyroxene (Cpx) displaying hour-glass zoning in groundmass composed of smaller plagioclase (Pig) laths and tiny clinopyroxene in basanite (PPL; RPVC). (F) Large amphibole (Amp) phenocryst surrounded by corrosion rim with Ti-rich magnetite (Mag) which encloses rounded vesicles filled with zeolite (Zeo) in camptonite (PPL; RPVC). (G) Glomeroporphyritic amphibole (Amp) and plagioclase (Pig) in aphanitic groundmass in leucocratic microsyenite (XPL; CSVC). (H) The Great Devil's Wall melilitite dyke displaying horizontal columnar jointing (RPVC). Amphibole phenocrysts from both camptonite/monchiquite and leucocratic microsyenite samples have relatively uniform contents of CaO (11.6-12.8 wt.%) and Na20 (1.9-2.5 wt.%). Amphibole from leucocratic microsyenite has higher concentrations of FeOtot (13.6-15.3 wt.%) and Ti02 (4.6-5 wt.%) and lower contents of MgO (10-11.2 wt.%) and AI2O3 (12-13.4 wt.%) than those from camptonite/monchiquite samples that have concentrations of MgO = 13-15.2 wt.%, AI2O3 = 13.6-14.6 wt.% and Ti02 = 3.6^1.1 wt.%, except for three analyses that yielded very high Ti02 contents of 6-6.5 wt.%. Concentrations of FeOtot in amphibole from camptonite/monchiquite samples are between 7.4 wt.% and 10.4 wt.%. All analysed amphibole crystals have high Mg/(Mg + Fe) atomic ratios between 0.54 and 0.82 and have —6 Si atoms per formula unit (apfu) and —2 Ca apfu, respectively (Supplement C.l). Analysed amphiboles correspond both to pargasite and kaersutite (Fig. 3A). Clinopyroxene phenocrysts from camptonite/monchiquite and leucocratic microsyenite samples have similar compositions (Supplement C.2). They are Ca-rich with a relatively narrow range of CaO contents (22.4-24.8 wt.%; —1 Caapfu) along with variable concentrations of MgO (7.8-14.2 wt.%), A1203 (4.8-13.1 wt.%), FeOtot (5.6-10.4 wt.%) and Ti02 (1.4-5.1 wt.%). They have only minor MnO (up to 0.4 wt.%) and Na20 (below 1 wt.%) contents. Their Fe/(Fe + Mg) atomic ratios range between 0.19 and 0.43. All analysed clinopyroxene phenocrysts fall in the diopside field (Fig. 3B). Dark mica from the polzenite sample shows a broad variation in MgO (16.8-22.2 wt.%; -1.8-2.4 Mg apfu) and A1203 (11-16.3 wt.%), and plots in two compositional fields (see Fig. 3C). In contrast, dark mica from camptonite/monchiquite is relatively uniform, having MgO and A1203 contents in the ranges of 16.3-17.3 wt.% and 15.9-16.4 wt.%, respectively. The K20 contents are more variable in mica from polzenite 929 S. Knníckovä et al Geoscience Frontiers 11 (2020) 925-942 Table 1 List of mantle-derived rocks of the Bohemian Massif selected for Pb isotope determination, sample location, petrographic types and field characteristics. No. Sample Locality Area Rock type Age (Maj Latitude (NJ Longitude (E) Outcrop characteristic 1 1_1367 Všechlapy CSVC basanite 41.9 50°37.100' 13° 47.767' Quarry 2 4_New Radobýl CSVC basanite 30 50°31.850' 14°05.717' Abandoned quarry 3 5_New Soutěsky CSVC basanite 30 50° 44.883' 14°16.017' Quarry 4 8_1299 Žandov CSVC basanite 25.4 50°42.483' 14°23.817' Quarry 5 12_1295 Radešín CSVC trachybasalt 26.8 50°41.883' 14°03.567' Abandoned quarry 6 14_1358 Valkeřice CSVC trachybasalt 24.7 50°42.117' 14°19.717' Rock exposure 7 15_1359 Chlum CSVC tephrite 26.6 50° 44.817' 14° 13.583' Abandoned quarry 8 17_BM-8 Rýdeč CSVC phonolite 25.8 50°36.433' 14°09.300' Abandoned quarry 9 18_BM-16 Štrbický vrch CSVC phonolite 30 50°33.467' 13° 50.517' Rock exposure 10 19_BM-48 Bořen CSVC phonolite 30 50°31.617' 13° 45.717' Rock exposure 11 20_BM-13 Lhenice CSVC trachyte 30 50°34.500' 13° 52.183' Rock exposure 12 21_BM-51 Milešovský Kloc CSVC trachyte 30 50°32.350' 13° 55.067' Rock exposure 13 23_BM-4 Kalich CSVC trachyandesite 31 50°36.183' 14° 12.567' Abandoned quarry 14 25_BM-60 Borec CSVC trachyandesite 30 50°30.850' 13° 59.267' Rock exposure 15 CS-30 Dobkovice I CSVC monchiquite 30 50°42.633' 14°11.567' Dyke in old quarry 16 CS-31 Dobkovice II CSVC camptonite 30 50°42.640' 14°11.549' Dyke in old quarry 17 CS-43 Leština CSVC camptonite 30 50°39.367' 14° 12.300' Abandoned quarry 18 KK1 Komorní Hůrka CHB melilitite 1 50°06.020' 12° 20.166' Rock exposure 19 KK2 Říp CSVC tephrite 25.6 50°23.230' 14° 17.320' Angular blocks 20 KK3 Panská skála CSVC basanite 29.7 50° 46.146' 14°29.102' Abandoned quarry 21 KK4 Tlustec RPVC basanite 30 50°43.535' 14° 44.649' Angular blocks 22 KK5 Stříbrník RPVC tephrite 30 50°43.936' 14°50.925' Rock exposure 23 KK6 Janův Důl RPVC camptonite/monchiquite 28.7 50°42.102' 14°57.379' Abandoned quarry 24 KK7A Přední Lhota I CSVC leucocratic microsyenite 30 50°42.529' 14°12.03ľ Dyke in quarry - centre 25 KK8 Přední Lhota II CSVC camptonite 30 50°42.557' 14°12.018' Dyke in quarry 26 KK9 Svárov RPVC polzenite 70 50°42.313' 14°53.450' Angular blocks 27 KK10 Velká Čertova zeď RPVC melilitite 70 50° 40.414' 14°56.725' Dyke exposure 28 KK11 Hamerský Špičák I RPVC polzenite 70 50°41.336' 14°50.989' Angular blocks 29 KK12 Ptačí vršek RPVC basanite 70 50° 40.509' 14° 40.782' Dyke in old quarry 30 ME-3/13 Krkavčí skála I CSVC nephelinite 27 50°35.150' 14°04.783' Rock exposure 31 ME-4/13 Krkavčí skála II CSVC basanite 30 50°35.117' 14°04.717' Rock exposure 32 OC-1 Veselí RPVC camptonite/monchiquite 30 50°38.280' 14°38.460' Angular blocks 33 OC-2 Pelousek RPVC polzenite 70 50° 40.680' 14°58.200' Abandoned quarry 34 OC-9 Vesec RPVC polzenite 68.4 50°42.180' 14°58.980' Angular blocks 35 OC-10 Nový Luhov RPVC alnoite 70 50°42.480' 14° 45.000' Angular blocks 36 OC-12 Holičský vrch RPVC melilitolite 70 50° 40.800' 14°53.820' Borehole CSVC - České Středohoří Volcanic Complex; RPVC - Ralská Pahorkatina Volcanic Complex; CHB - Cheb Basin. Ages are taken from Ulrych et al. (1998, 2002, 2013, 2014, 2018), Skala et al. (2014), Ackerman et al. (2015), Dostal et al. (2017). (—8.6-10.8 wt.%; —0.8-1.0 K apfu) than in mica from camptonite/ monchiquite (8.8-9.4 wt.%; —0.8-0.9 K apfu). The latter also contains mica that is relatively poor in BaO (max. 1.8 wt.% BaO). FeOtot concentrations range between 6 wt.% and 10.2 wt.%, except for few dark mica analyses from polzenite that show higher contents of 14.1-15.6 wt.%. Tetrahedral Al ranges between 0.94 and 1.41 apfu along with Mg/ (Mg + Fe) atomic ratio of 0.66-0.88. Dark mica from polzenite falls in the phlogopite and Mg-biotite fields, whereas dark mica from camptonite/ monchiquite samples falls in the phlogopite field (Fig. 3C). Moreover, phlogopite from polzenite with very high Mg/(Mg + Fe) shows an evolutionary trend towards tetra-ferriphlogopite, which is attested by deficient tetrahedral Al in recalculated analyses (Supplement C.3). 4.3. Whole-rock geochemistry 4.3.1. Major elements The SiC>2 and MgO contents of a representative set of 36 samples were recalculated on a volatile-free basis and range from 33 wt.% to 61 wt.% and 0.1 wt.% to 18 wt.%, respectively (Fig. 4, Table 2). The most ultra-basic rocks are Cretaceous ultramafic lamprophyres (SiC>2 —36 wt.%) followed by associated melilitic rocks (SiC>2 —40 wt.%). Tertiary volcanic rocks compositionally range from ultrabasic nephelinite and basic teph-rite/basanite (majority of the samples with SiC>2 —43 wt.%) to more acidic rocks of phonolite composition. Tertiary alkaline lamprophyres are basic (SiC>2 —46 wt.%) with highly variable contents of alkalies. One sample of leucocratic microsyenite plots in the tephriphonolite field (Fig. 4). The various samples define a coherent trend in binary variation diagrams, using Si02 as differentiation index, that may be interpreted as (i) fractionation trend or (ii) mixing/assimilation trend or (iii) superposition of both (Fig. 5). Generally, AI2O3 contents correlate positively, whereas CaO and MgO are negatively correlated. In contrast, Ti02 contents behave differently. Ti02 contents in Cretaceous ultramafic lamprophyres and melilitic rocks are in the range of 2-3 wt.% and correlate positively with Si02. Contrary to that, Ti02 contents in the most primitive members of the Tertiary volcanic rocks and alkaline lamprophyres reach —4 wt.% and correlate negatively with increasing Si02- FeOtot behaves similarly as Ti02 (Fig. 5). K2O contents are —2 wt.% in the majority of ultramafic lamprophyres and associated melilitic rocks. In the most primitive members of Tertiary volcanic samples, K2O contents are below 1.5 wt.% and correlate positively with increasing Si02- An extremely high K2O content of 8.3 wt.% was found in a leucocratic microsyenite (sample KK7A). 4.3.2. Trace elements The samples generally have highly variable transition metal contents and a slightly variable enrichment of large-ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high-field strength elements (HFSE) and heavy rare earth elements (HREE). This is clearly visible both in binary variation diagrams and in primitive mantle normalised trace and chondrite normalised rare earth element abundance plots (Figs. 5 and 6A-F). The highest Cr concentrations (up to 800 ppm) occur in Cretaceous ultramafic lamprophyres and associated melilitic rocks. Chromium correlates negatively with increasing Si02, reaching levels as low as 2 ppm Cr in differentiated trachyte (Fig. 5, Table 2). Cretaceous ultramafic lamprophyres show the highest degree of LREE enrichment. La, Ce and Ce/Yb show a negative correlation with increasing Si02 for ultramafic 930 S. Knníckovä et al Geoscience Frontiers 11 (2020) 925-942 O Camptonite/monchiquite, Ralská Pahorkatina Volcanic Complex W Leucocratic microsyenite, České Středohoří Volcanic Complex • Polzenite, Ralská Pahorkatina Volcanic Complex ® Amphibole classification Ca > 1.50; (Na + K)A > 0.50 Ti < 0.50 Ti > 0.50 1.0 ra 0.5 0.0 1.5 edenite pargasite (."Al > Fe") ^P' Mg-hastingsite ("AI < Fe") Mg-sadanagaite ferro-edenite ferropargasite ("AI i Fe") hastingsite ("Al < Fes*) sadanagaite ferrokaersutite 6.5 5.5 Si 4.5 6.5 5.5 Clinopvroxene classification 1.0- 0.5- 0.0 wollastonite diopside hedenberqite augite pígeonite clinoenstatite clinoferrosilite 0.0 0.2 0.4 0.6 Fe/(Fe + Mg) Dark mica classification 1.0 1.0 siderophyllite ! eastonite (N ! -'ä 1 \ t annite i ' phlogopite i ...........W^i tra-ferriphlogopite 0.4 i 0.6 0.8 1.0 Mg/(Mg + Fe) Fig. 3. Classification of amphibole, clinopyroxene and dark mica from camptonite/monchiquite, leucocratic microsyenite, and polzenite. All chemical elements are given in apfu (atoms per formula unit). (A) Analyses of amphibole phenocrysts from camptonite/monchiquite samples plot in the fields of both pargasite and kaersutite, whereas amphibole in leucocratic microsyenite falls in the kaersutite field of the amphibole classification scheme of Leake (1997). (B) Clinopyroxene from both camptonite/monchiquite and leucocratic microsyenite samples is diopside (Morimoto, 1988), diagram adopted from Rapprich (2005). (C) Dark mica from camptonite/monchiquite and polzenite corresponds to phlogopite. Dark mica from camptonite/monchiquite is compositionally rather homogeneous, whereas dark mica from polzenite falls in two groups ranging from phlogopite to Mg-biotite. Classification diagram after Rieder et al. (1998). lamprophyres towards tephritic and basanitc rocks (Fig. 5). The Cretaceous ultramafic lamprophyres and associated melilitic rocks are characterised by troughs for K and Pb in primitive mantle Fig. 4. Total Alkali-Silica (TAS) diagram showing the chemical composition of analysed samples (after Le Maitre, 2002). normalised trace element plots (Fig. 6A). Tertiary alkaline lamprophyres show slightly negative or even positive anomalies for K along with Pb enrichment and P depletion. The leucocratic microsyenite has the most pronounced anomalies among the analysed alkaline lamprophyres and related rocks (Fig. 6C). Absolute trace element concentrations in Tertiary volcanic samples differ from those of the basanite/tephrite samples and the more evolved trachytic/phonolitic samples. However, they define the same trends in primitive mantle normalised trace element plots. Tertiary volcanic samples show variable Rb depletion, K and Pb depletion or enrichment, as well as troughs for P and Ti that markedly increase from basanite/tephrite to trachyte/phonolite samples (Fig. 6E). There are two geochemical types of phonolite in the representative sample set: type A (Sr-rich) and type B (Sr-poor), first characterised by Ackerman et al. (2015). Whereas the samples of type A phonolite compositionally resemble other types of evolved volcanic rocks, type B phonolite is prominent by extreme depletion of Ba, Sr, P, and Ti along the most pronounced Cs, U, and Pb enrichments among all Tertiary volcanic rocks (Fig. 6E). The samples show variable REE contents and generally lack pronounced Eu anomalies (Fig. 6B, D, F). Cretaceous ultramafic lamprophyres have the highest total REE contents (SREE —500 ppm), whereas Tertiary trachytic/phonolitic samples have the lowest total REE contents of —270 ppm. Ultramafic lamprophyres together with associated melilitic samples are prominent by the highest enrichment in LREE over HREE with CeN/Ybfj of —30 and Lu^ of —7, whereas Tertiary volcanic samples have contrasting enrichment trends in LREE/HREE (Cen/YbN —21 in basanite/tephrite samples, and —31 in more differentiated trachyte/ phonolite samples). Type B phonolite is prominent by its U-shaped REE normalised pattern (Fig. 6F). Ultramafic lamprophyres, associated melilitic rocks, the majority of alkaline lamprophyres and basanite/tephrite volcanic rocks all have Lu^ < 10 indicating the presence of garnet in the mantle source of their parent melts (see Wilson and Downes, 1991). 931 Table 2 Major oxide (wt.%) and trace element compositions (ppm) of mantle-derived rocks of the Bohemian Massif. No. 1 2a 3" 4a 5a 6 7a 8 9a 10" lla 12 13 14 15 16" Sample 1.1367 4_New 5_New 8_1299 12_1295 14.1358 15_1359 17.BM-8 18.BM-16 19.BM-48 20.BM-13 21.BM-51 23.BM-4 25.BM-60 CS-30 CS-31 SiOa 40.2 40.4 42.3 41.6 47.0 45.2 42.2 55.8 55.2 54.2 59.1 56.8 53.9 54.6 45.9 47.8 Ti02 2.65 3.73 3.3 2.8 2.97 3.59 3.92 0.14 0.59 0.28 0.57 0.45 1.27 0.86 3.22 2.13 ai2o3 11.1 12.1 14.7 13.5 15.2 15.5 13.6 21.4 20.3 21.7 19.8 20.2 18.9 19.7 15.0 16.2 Fe2or 12.5 14.0 12.1 11.5 9.6 10.8 1 1.5 2.3 3.63 2.2 3.22 3.11 5.66 4.36 11.1 8.34 MnO 0.19 0.19 0.19 0.19 0.16 0.18 0.33 0.28 0.23 0.26 0.23 0.22 0.2 0.2 0.16 0.16 MgO 12.9 8.91 8.4 9.87 4.57 5.4 6.53 0.08 0.43 0.23 0.21 0.34 1.32 0.67 4.91 2.48 CaO 12.5 12.5 11.8 12.6 9.85 10.6 13.5 0.95 4.15 1.8 3.4 3.59 5.4 4.42 8.79 7.35 Na20 2.73 1.85 2.25 1.84 3.67 3.38 2.61 9.9 6.85 9.1 1 5.0 6.47 6.47 5.94 2.92 3.7 K20 0.66 1.47 1.63 1.31 2.31 1.96 1.38 5.46 5.05 4.73 5.69 5.39 3.84 5.06 4.09 4.07 p2o5 0.79 0.68 0.54 0.54 0.49 0.51 0.65 0.02 0.1 0.03 0.08 0.07 0.35 0.15 0.47 0.52 LOI 2.61 3.2 2.69 2.99 3.62 3.27 4.31 1.79 2.16 5.52 2.47 3.22 2.77 4.51 3.44 6.86 Total 98.8 99.1 99.9 98.7 99.4 100.4 100.5 98.2 98.7 100.1 99.8 99.8 100.1 100.5 99.9 99.6 Mg# 67 56 58 63 49 50 53 6 19 17 11 18 32 23 47 37 Cr 350 210 140 320 50 40 70 10 10 2 2 10 20 10 27 16 Ni 280 170 120 190 10 70 90 10 10 10 10 10 20 10 22 15 Co 51 45 40 44 26 30 34 1 14 4 5 7 14 7 31 17 Sc 26 29 30 32 20 24 30 1 1 1 0 0 4 1 24 10 V 281 336 345 317 336 378 436 23 71 18 60 57 108 100 367 212 Cu 70 60 70 90 40 60 18(1 5 10 5 5 5 10 5 - - Zn 1 1(1 11(1 100 100 90 no 120 150 130 175 1 18 110 130 120 - - Rb 10 36 33 29 144 84 44 371 123 219 184 153 98 121 81 117 Cs 0.5 0.5 0.0 1.7 1.7 1.4 1.2 9.9 1.4 4.78 5.45 2.0 1.70 2.5 0.9 1.5 Ba 643 600 494 700 992 776 752 17 1880 620 1870 1730 1400 1420 781 937 St 981 1260 1290 1000 937 904 1070 21 2070 433 1830 1560 1570 1410 641 1000 Ga 18 19 19 18 20 24 24 53 27 25 41 27 29 26 - - Ta 4.6 7.1 4.5 5.7 4.4 5.5 5.7 2.02 5.5 7.2 8.56 4.1 6.9 5.0 4.84 6.13 Nb 68 70 66 79 70 78 76 138 140 447 198 113 127 1 10 94 123 Hf 5.0 6.2 8.0 5.3 6.7 8.1 7.9 21.2 10.2 22.2 11.1 10.0 13.1 10.4 9.2 12.4 Zr 228 232 211 218 324 329 323 1200 543 1650 634 568 615 562 359 576 Y 23 27 22 22 22 22 24 16 24 24 29 20 27 22 21 25 Pb 4 4 3 4 7 7 7 34 9 12 25 11 15 1 1 6 7 Th 7.5 4.2 5.0 6.5 7.9 8.9 9.0 49.7 14.8 28.8 15.4 15.3 17.9 14.6 8.9 11.8 U 1.9 I.I 1.4 1.6 2.3 3.1 5.7 18.6 3.8 16.6 4.0 3.9 4.1 3.4 2.0 3.4 La 68 46 44 60 58 51 69 139 124 1 15 148 112 108 110 49 77 Ce 124 96.7 87.7 112 112 105 133 146 210 160 216 178 186 181 101 147 Pr 13.7 12.3 10.3 12.3 12.9 12.4 15.4 8.5 19.5 22.0 13.0 15.9 18.7 17.6 11.8 16.4 Nd 50.2 49.2 39.4 43.8 48.2 47.4 57.6 17.3 56.1 45.8 67.3 44.0 60.9 54.4 45.8 59.3 Sm 9.2 10.1 7.5 7.9 8.6 8.5 10.4 1.61 6.8 6.72 8.2 5.6 9.3 7.5 8.58 9.84 Eu 2.92 3.21 2.35 2.5 2.49 2.53 3.08 0.32 2.01 1.34 2.06 1.56 2.71 2.18 2.48 2.89 Gd 7.7 8.4 6.3 6.5 6.5 6.5 8.2 1.13 4.9 3.9 4.4 3.7 6.9 5.4 8.21 9.88 Tb 1.0 1.2 0.9 0.9 0.9 0.9 1.1 0.22 0.7 0.69 0.8 0.5 0.9 0.7 1.03 1.23 Dy 5.1 5.8 4.7 4.8 4.6 4.6 5.3 1.56 3.7 5.3 5.7 3.0 5.0 3.9 4.84 5.62 Ho 0.9 1.0 0.9 0.9 0.8 0.8 0.9 0.41 0.7 0.9 0.9 0.6 0.9 0.8 0.85 1.0 Er 2.3 2.6 2.2 2.3 2.2 2.2 2.3 1.6 2.4 2.8 2.8 2.0 2.7 2.2 2.35 2.88 Tm 0.3 0.34 0.29 0.29 0.29 0.3 0.32 0.34 0.36 0.45 0.52 0.32 0.39 0.33 0.28 0.36 Yb 1.8 1.9 1.9 1.8 1.9 1.8 1.8 2.98 2.4 3.94 2.88 2.3 2.6 2.2 1.81 2.37 Lu 0.25 0.26 0.28 0.27 0.28 0.26 0.26 0.52 0.4 0.61 0.48 0.37 0.41 0.35 0.27 0.34 No. 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31c 32d 33d 341' 35d 36'' Sample CS-43 KK1 KK2 KK3 KK4 KK5 KK6 KK7A KK8 KK9 KK10 KK11 KK12 MK-3/13 ME-4/13 OC-1 OC-2 OC-9 OC-10 OC-12 Si02 42.7 38.2 39.2 42.4 41.7 40.6 44.9 52.8 45.2 33.8 39.9 33.1 41.3 36.8 39.9 38.9 34.0 30.6 34.1 31.5 Ti02 2.97 3.1 3.4 3.17 3.73 3.22 2.62 1.45 3.25 2.62 2.96 2.47 3.08 3.07 2.63 3.43 2.57 2.28 2.1 2.57 A1203 13.8 1 1.5 11.8 13.6 14.5 14.7 13.0 17.8 15.8 7.88 9.99 7.74 14.5 12.6 12.2 13.7 8.96 7.38 8.24 8.65 (continued on next page) Table 2 (conärmed) Xo. 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31c 32d OC-1 33 OC-2 34d OC-9 35d 36d Siimple CS-43 KK1 KK2 KK3 KK4 KK5 KK6 KK7A KK8 KK9 KK10 KK11 KK12 ME-3/13 ME-4/13 OC-10 OC-12 Fe203ot 11.6 13.2 15.6 12.4 12.5 13.3 11.9 5.58 10.4 1 1.7 11.5 10.8 13.0 13.6 12.9 12.3 12.1 11.6 13.7 10.7 MnO 0.19 0.23 0.33 0.18 0.2 0.22 0.23 0.15 0.17 0.2 0.18 0.19 0.21 0.22 0.18 0.16 0.2 0.2 0.2 0.17 MgO 7.88 12.1 7.15 9.15 7.07 8.36 5.94 1.79 4.71 15.3 15.7 16.9 7.90 1 1.4 13.6 11.0 15.1 17.0 16.5 13.4 CaO 10.5 12.4 12.0 12.0 11.8 12.4 1 1.8 4.28 8.07 16.1 13.0 18.6 12.7 14.7 12.1 13.2 14.1 21.1 16.4 17.9 Na20 3.03 3.71 4.39 3.13 3.03 2.92 2.62 3.79 4.03 1.02 2.31 1.59 3.3 3.19 2.02 0.89 2.16 0.52 2.01 0.22 K20 2.15 2.15 1.1 1.57 1.75 1.53 1.67 7.97 4.17 1.72 1.41 1.25 1.33 1.5 0.96 1.9 1.85 0.75 1.66 1.98 P2O5 0.6 0.92 1.41 0.73 0.77 1.09 1.23 0.32 0.52 1.24 0.75 1.30 0.87 1.5 0.63 0.53 1.07 1.12 1.09 0.95 LOJ 4.57 1.8 3.0 1.1 2.3 1.2 3.6 3.7 3.2 7.6 1.4 5.2 1.4 1.8 3.5 5.18 7.4 6.3 4.9 12.0 Total 100.0 99.4 99.3 99.4 99.4 99.5 99.5 99.6 99.5 99.2 99.2 99.2 99.5 100.4 100.6 101.1 99.6 98.8 100.4 100.0 Mg# 57 65 48 59 53 56 50 39 47 72 73 76 55 63 68 64 71 74 71 71 Cr 70 431 27 294 144 130 55 14 34 602 842 746 192 197 486 262 749 810 623 700 Ni 75 147 25 98 41 54 27 5 12 317 339 336 56 132 239 134 327 330 253 216 Co 37 56 37 46 40 43 31 9 28 53 59 60 43 55 60 51 56 59 61 47 Sc 30 29 21 27 26 27 17 5 20 22 30 26 24 27 31 45 33 23 30 22 V 345 304 275 289 348 336 269 141 341 252 308 210 315 378 334 - - 252 - - Cu - 48 38 70 61 47 38 9 46 52 76 48 56 - - - - 30 _ _ Zn - 63 150 90 100 88 91 77 82 86 72 65 84 - - - - 70 _ _ Rb 38 54 21 35 64 37 48 222 118 49 51 47 32 29 35 154 64 26 48 65 Cs 1.3 0.4 1.0 0.4 0.6 0.2 1.2 1.80 1.2 0.9 1.0 0.8 0.4 0.8 0.5 1.89 2.9 0.5 0.93 3.03 Ba 654 965 1030 717 791 591 541 1070 868 737 807 968 726 1470 651 1610 1980 717 1380 754 Sr 920 807 1580 937 1700 940 1230 757 890 866 873 1420 1140 1770 963 854 2000 1800 1780 1280 Ga - 21 25 19 22 20 17 21 21 13 14 12 19 - - - - 18 _ _ Ta 4.9 6.8 10.1 4.5 4.8 5.7 5.7 5.2 5.1 8.5 5.1 6.9 5.3 5.8 4.1 3.49 5.5 10.7 7.80 7.73 Nb 95 122 168 87 78 88 96 107 82 129 84 134 90 141 96 79 188 151 183 125 Ilf 8.1 6.7 14.7 5.8 8.2 6.3 7.0 9.7 8.2 5.5 5.7 4.6 6.1 8.5 7.1 10.2 7.5 5.5 6.3 7.8 Zr 313 299 616 233 351 256 290 461 340 251 224 197 243 333 259 301 357 247 292 345 Y 24 27 42 25 29 28 30 23 23 30 19 24 27 34 21 21 26 29 28 29 Pb 17 2 5 6 4 2 4 15 8 5 3 4 2 10 3 4 6 4 6 4 Th 7.6 11.3 13.8 6.9 6.6 7.1 8.0 18.4 10.0 16.1 6.4 12.7 6.9 17.0 7.0 12.3 15.0 23.0 17.0 10.2 U 2.1 3.1 3.9 1.5 1.8 1.6 2.0 5.2 2.5 3.9 1.6 2.9 1.5 3.7 1.7 1.45 3.9 4.83 4.8 2.49 La 62 89 125 58 63 67 73 80 57 124 52 106 62 165 64 51 103 163 130 84 Ce 128 168 249 110 132 136 144 145 115 248 104 201 125 289 117 104 186 304 235 177 Pr 14.6 18.9 28.7 12.1 15.4 15.4 16.9 14.8 13.0 28.2 11.9 22.2 14.7 28.0 13.0 12.5 21.0 33.8 25.0 19.9 Ncl 56.9 69.3 1 10 46.1 61.5 59.6 61.5 50.4 50.4 106 46.1 84.3 56.9 102 48.0 50.6 79.0 120 90.0 77.2 Sin 10.3 11.4 18.0 8.5 11.0 10.7 10.4 7.69 8.4 17.1 8.61 13.9 9.67 16.0 8.4 9.27 13.0 18.4 14.0 13.4 Eu 3.02 3.33 5.01 2.52 3.3 3.1 1 3.13 2.06 2.42 4.73 2.56 3.92 3.07 4.5 2.5 2.74 3.6 5.13 3.9 3.85 Gd 9.74 9.34 14.2 7.51 9.39 8.98 9.05 6.11 6.97 12.7 7.06 10.6 8.29 15.0 8.1 8.61 10.0 12.9 13.0 13.9 Tb 1.22 1.16 1.75 0.98 1.2 1.1 1 1.16 0.83 0.9 1.52 0.86 1.23 1.08 1.7 1.0 1.03 1.30 1.53 1.5 1.62 Dy 5.51 5.88 8.98 5.13 6.31 6.35 6.50 4.58 4.93 7.69 4.28 6.03 5.88 7.6 4.8 4.77 6.6 7.08 6.3 6.28 Ho 0.96 0.95 1.52 0.88 1.02 1.04 1.07 0.75 0.84 1.12 0.67 0.91 0.94 1.3 0.85 0.82 1.10 1.11 1.0 0.97 Er 2.72 2.46 3.93 2.29 2.83 2.86 2.83 2.31 2.28 2.66 1.67 2.18 2.53 3.6 2.3 2.19 2.6 2.61 2.6 2.87 Tm 0.33 0.31 0.56 0.28 0.35 0.38 0.37 0.32 0.31 0.32 0.19 0.25 0.33 0.42 0.27 0.26 0.33 0.3 0.3 0.29 Yb 2.05 1.89 3.33 1.89 2.16 2.15 2.46 2.30 1.94 1.84 1.26 1.49 1.92 2.6 1.7 1.92 1.9 1.63 1.8 1.82 Lu 0.29 0.26 0.49 0.25 0.33 0.34 0.35 0.33 0.3 0.25 0.16 0.19 0.29 0.36 0.23 0.22 0.25 0.21 0.23 0.25 LOI - loss on ignition; Mg# = 100 x Mg/(Mg + Fetot). a Analyses adopted from Dostal et al. (2017). b Analyses adopted from Skala et al. (2014). c Analyses adopted from Skala et al. (2015). d Analyses adopted from Ulrych et al. (2014). S. Knnickovd et al Geoscience Frontiers 11 (2020) 925-942 q 5, o 30 35 40 45 50 55 60 Si02 (wt.%) "i-1—<5-1-1-1-r & □ o AO J_I_I_I_I_I_l_ 30 35 40 45 50 55 60 SiO,(wt.%) 30 35 40 45 50 55 60 Si02(wt.%) Tertiary volcanic rocks: O Basanite A Trachyandesite V Trachyte □ Tephrite O Phonolite O Nephelinite o O O 30 35 40 45 50 55 60 Si02(wt.%) i i - * ▲ o VA 1 1 1 1 1 o 30 35 40 45 50 55 60 Si02(wt.% 1 1 1 1 1 1 1 \ i o _ % V o o V 1 1 o u 30 35 40 45 50 55 60 Si02(wt.%) Tertiary alkaline lamprophyres: © Camptonite A Monchiquite V Microsyenite Melilitites: O Cretaceous O Quaternary 30 35 40 45 50 55 60 Si02(wt.%) 30 35 40 45 50 55 60 SiQ2(wt.%) 30 35 40 45 50 55 60 Si02(wt.%) Cretaceous ultramafic lamprophyres: • Polzenite ▲ Alnoite T Melilitolite 4.4. Lead isotope composition The initial lead isotope composition of Cretaceous ultramafic lamprophyres, Tertiary basaltic volcanic samples as well as alkaline lamprophyres, related leucocratic microsyenite and Cretaceous and Quaternary melilitite rocks defines a scattered linear trend between two end-members (schematically marked by red asterisks A and B in Figs. 7, 9 and 10). In the 207Pb/204Pb vs. 206Pb/204Pb diagram, most data fall above the Northern Hemisphere Reference Line (NHRL; Hart, 1984), whereas in the 208Pb/204Pb vs. 206Pb/204Pb diagram, the Pb trend intersects the NHRL, as it is slightly flatter than the NHRL (Fig. 7). Fig. 5. Si02 vs. selected major and trace element contents of analysed samples. The Cretaceous ultramafic lamprophyres and melilitolite sample of the RPVC sampled a more radiogenic mantle component (206Pb/204Pb = 19.62-20.01, 207Pb/204Pb = 15.61-15.64, 208Pb/204Pb = 39.29-39.77) than the Tertiary alkaline lamprophyres and associated leucocratic microsyenite (206Pb/204Pb = 19.05-19.35, 207Pb/204Pb = 15.60-15.61, 208pb/204pb = 38.91-39.14; Table 3). The Cenozoic volcanic samples have a very heterogeneous Pb isotope composition (206Pb/204Pb = 18.98-19.96, 207Pb/204Pb = 15.59-15.65, 208Pb/204Pb = 38.80-39.62). Data points plot along a linear array extending from the least radiogenic Pb isotope compositions of the alkaline lamprophyres to the most radiogenic compositions of the ultramafic lamprophyres (Fig. 7). 934 S. Knnickovä et al Geoscience Frontiers 11 (2020) 925-942 - Rb Th Nb Sample/Primitive mantle Ultramafic lamprophyres '(this study and Ulrych et al., 2014) Cs Ba U K Ce Pr P Zr Eu Dy Yb —'-1-'-1-'-1-'-1-'-1-'-1-'-1-'-1-'- La Pb Sr Nid Sm Sample/Primitive mantle Y Lu Alkaline lamprophyres (this study, Skala et al., 2014; Ulrych et al., 2014) Cs Ba U K Ce Pr Zr Eu Dy Yb \Rb Th M Nb La Pb Sr Nd Sm Sample/Primitive mantle ^E) Volcanic rocks of /trachytic/phonolitic composition (this study, Dostaletal.,2017) Cs Ba Volcanic rocks of basanitic/tephritic composition (this study, Skalaetal., 2015; Dostaletal.,2017 Type B phonolite ......(Dostalotal, 201V)----- U K Ce Pr P Zr Eu M Dy Sample/REE chondrite Ultramafic lamprophyres ''(this study and Ulrych et al., 2014) h|o Tpn Ce Nd Sm Gd Ďy Sample/REE chondrite Yb Alkaline lamprophyres (this study, "Skala et al., 2014; Ulrych et al., 2014) ..Leucacratic.microsyenite (this study) 3L Hp Trn Ce Nd Sm Gd Dy Er Sample/REE chondrite __Volcanic rocks of trachytic/phonoiitic composition (this study, Dostal et at, 2017) Yb © - Volcanic rocks of basanitic/tephritic composition (this study, Skala etat, 2015; □ostal etat, 2017 Pr Type B phonolite (Dostal etat, 2017) Prn Eu Tb Ho Rb Th Nb La Pb Sr Nd Sm TÍ Nd Sm Dy Yb Fig. 6. Abundances of trace elements and rare earth elements (REE) in the analysed samples normalised to primitive mantle values (McDonough and Sun, 1995) and chondritic abundances (Boynton, 1984), respectively. Intrusive and effusive melilitite samples, which are of Cretaceous and Quaternary age, respectively, have essentially identical Pb isotope compositions (206Pb/204Pb = 19.30-19.36, 207Pb/204Pb = 15.60, 208pb/204pb = 39.09-39.10). Among the ultramafic lamprophyres, alnoite OC-10 with a 206Pb/204Pb ratio of 20.01 is the most radiogenic sample and melili-tolite OC-12 with 206Pb/204Pb ratio of 19.62 is the least radiogenic sample. The Pb isotope compositions of polzenite samples fall between these two values (Fig. 7). The monchiquites from the CSVC as well as the camptonite to monchiquite sample OC-1 are among the least radiogenic samples from the Bohemian Massif. They have 206Pb/204Pb ratios of 19.05-19.10. Similarly, the Pb isotope signature of the leu-cocratic microsyenite is very unradiogenic and points to derivation from the same mantle source as the less fractionated camptonites and monchiquites. 5. Discussion 5.1. Chemically contrasting mantle sources in the Bohemian Massif Common K-bearing silicate phases such as phlogopite or K-amphibole are not stable in the asthenospheric (convective) mantle (Class and Goldstein, 1997). Negative K anomalies observed in intraplate mantle-derived rocks indicate that these phases were stable during the petrogenesis of these rocks, and, thus, are considered as geochemical evidence for the involvement of lithospheric mantle sources (e.g., Wilson and Downes, 1992; Melluso et al., 2011; Pfänder et al., 2018). Variations in the whole-rock composition of Late Cretaceous to Quaternary undifferentiated magmatic rocks from the Bohemian Massif point to contributions from two geochemically distinct mantle sources. The Cretaceous ultramafic lamprophyres show strong LREE over HREE enrichment (Fig. 6B) in combination with high K2O and low TiC>2 at given SiC>2 (Fig. 5) and significant troughs in K and Pb in primitive mantle 935 S. Krmickovä et al Geoscience Fronders 11 (2020) 925-942 19.0 19.2 19.4 19.6 19.8 20.0 20.2 6PbrPb(il Cretaceous ultramafic lamprophyres: • Polzenite A Alnöite ▼ Melilitolite Tertiary alkaline lamprophyres: • Camptonite A Monchiquite T Microsyenite Tertiary volcanic rocks: O Basanite A Trachyandesite v Trachyte □ Tephrite O Phonolite O Nephelinite Melilitites: O Cretaceous O Quaternary Fig. 7. Initial Pb isotope composition of individual samples from the Bohemian Massif. Melilitite samples of different age (Cretaceous and Quaternary) are plotted separately as their Pb isotope composition is relatively uniform but different from other melilitic rocks (i.e., ultramafic lamprophyres). NHRL: Northern Hemisphere Reference Line (Hart, 1984). Abbreviations and references for other volcanic fields from the Bohemian Massif: WB - Western Bohemia (Ulrych et al., 2016); LSB - Lower Silesian Basin (Blusztajn and Hart, 1989); EG - Erzgebirge, ESG - Elbsandsteingebirge, LL - Lower Lusatia (Haase and Renno, 2008). normalised trace element plots (Fig. 6A), indicating that they originated by low degrees of partial melting of a metasomatised lithospheric mantle source containing a stable K-bearing residual phase (e.g., Ulrych et al., 2008, 2014; Skala et al., 2015). Such a lithospheric mantle formed during Variscan subduction of continental crust. This process led to stabilization of metasomatised parts containing inclusions of granitic composition within the mantle rocks beneath the Saxothuringian and Moldanubian zones of the Bohemian Massif (Borghini et al., 2018; Ferrero et al., 2018 and references therein). This is in line with the composition of phlogopite in ultramafic lamprophyres that shows high MgO and elevated K2O and BaO contents, coupled with a compositional affinity towards the tetra-ferriphlogopite end-member (cf. Skala et al., 2015). Moreover, K-rich sulphides of rasvumite (KFe2Ss) type, identified by Ulrych et al. (2008), occur locally in association with phlogopite in melilitolites. Such a K-rich sulphide may be a primary phase that crystallised from metasomatised lithospheric mantle-derived ultramafic melts (e.g., Sharygin et al., 2008). Compared with the source of Cretaceous ultramafic lamprophyres, the second mantle source is characterised by significant TiÜ2 enrichment and K2O depletion. This resulted in relatively flat OIB-like primitive mantle normalised trace element patterns for the majority of the Tertiary alkaline lamprophyres (characterised by the presence of Ti02-rich amphibole - kaersutite with up to 0.74 apfu Ti) and basanite/tephrite volcanic rocks (Fig. 6C, E). Their mantle source was significantly influenced by interaction with asthenospheric (convective) mantle depleted in large-ion lithophile elements (Rock, 1991). This is in line with rift-related passive asthenospheric upwelling that resulted in the generation of large volumes of Tertiary mantle-derived magmas in the Eger Rift (e.g., Ulrych et al., 2011). Both mantle sources are distinguishable: undifferentiated Cretaceous ultramafic lamprophyres show a trend with relatively large variations in Nb/Ta and narrow variation in Lu/Hf, whereas Tertiary alkaline lamprophyres and basanite/tephrite volcanic rocks show a narrow range of Nb/Ta values as also known from OIB's (Fig. 8A). The higher and more variable Nb/Ta ratios in the Cretaceous ultramafic lamprophyres likely indicate a higher contribution from the lithospheric mantle and a more heterogeneous source than for the Tertiary alkaline lamprophyres and the basanite/tephrite volcanic rocks (cf. Pfänder et al., 2012). The Cretaceous ultramafic lamprophyres and undifferentiated Cenozoic volcanic rocks show a comparable range in Nb/La ratios at different (Ce/Yb)N (Fig. 8B). The Nb/La ratios fall between the values for depleted MORB mantle source and for the lithospheric mantle source metasomatised by continental crust (Fig. 8B). The narrow range of Nb/La ratios may be indicative for a similarly enriched mantle source, whereas different (Ce/Yb)N may reflect contrasting degrees of partial melting (cf. Haase and Renno, 2008). The Cretaceous ultramafic lamprophyres and undifferentiated Cenozoic volcanic rocks show different trends in the Ba/La vs. (Ce/Yb)N diagram (Fig. 8C), which may indicate involvement of different mantle sources. For instance, the high and variable (Ce/Ybj^ and relatively constant Ba/La ratios of Cretaceous ultramafic lamprophyres may reflect different degrees of partial melting of highly metasomatised domains of the lithospheric mantle, producing such SiC>2-undersaturated melts (cf. Hegneret al., 1995; Blusztajn and Hegner, 2002). In contrast, Cenozoic volcanic rocks with relatively constant (Ce/Yb)N and highly variable Ba/La may reflect a carbonatite component (Haase et al., 2017), which may be indicative for a mantle source that was affected by interaction with the convective mantle. Significant CO2 release from the asthenosphere in a continental rifting environment is also indicated by metasomatised mantle xenoliths from the lithospheric mantle beneath the Bohemian Massif (Ackerman et al., 2013). Besides these compositional differences related to different degrees of partial melting of heterogeneously metasomatised mantle sources, fractional crystallisation also affected the chemical composition of the rocks (Dostal et al., 2017). Fractional crystallisation in particular affected the composition of Tertiary trachytic to phonolitic volcanic rocks and the leuco-cratic microsyenite of the CSVC and is reflected in linear enrichment trends for Si02, A1203 and K20 and depletion trends for CaO, MgO, FeOtot, Cr203, P205 or TiQ2 (Figs. 5 and 6). 5.2. Lead isotope compositions of the samples lithospheric mantle components asthenospheric vs. The lead isotope data define a relatively narrow two-component mixing trend ranging from moderately high 206Pb/204Pb ratios (—19.0) to more radiogenic values (up to 20.0), suggesting a mixture between a mantle source showing geochemical characteristics of modification by interaction with convective mantle and metasomatically enriched lithospheric mantle (cf. Blusztajn and Hart, 1989; Stracke et al., 2005; Ulrych et al., 2016 and section 5.1 in this paper). The suggested two-component 936 S. Krmicková et al Geoscience Frontiers 11 (2020) 925-942 Table 3 Whole-rock Pb isotope data of the mantle-derived rocks of the Bohemian Massif. No. Sample Area Rock type Age (MaJ 206pb/204pb 207pb/204pb 208pb/204pb 206pb/204pb m 207pb/204pb m 208pb/204pb m 1 1_1367 CSVC basanite 41.9 19.752 15.620 39.489 19.55 15.61 39.23 2 4_New CSVC basanite 30 19.218 15.604 38.983 19.14 15.60 38.88 3 5_New CSVC basanite 30 20.001 15.647 39.619 19.86 15.64 39.45 4 8_1299 CSVC basanite 25.4 19.902 15.644 39.652 19.80 15.64 39.51 5 12_1295 CSVC trachybasalt 26.8 19.222 15.599 39.060 19.13 15.59 38.96 6 14_1358 CSVC trachybasalt 24.7 19.280 15.610 39.127 19.17 15.60 39.02 7 15_1359 CSVC tephrite 26.6 19.781 15.650 39.356 19.56 15.64 39.24 8 17_BM-8 CSVC phonolite 25.8 19.577 15.652 39.343 19.43 15.65 39.22 9 18_BM-16 CSVC phonolite 30 19.763 15.645 39.510 19.63 15.64 39.34 10 19_BM-48 CSVC phonolite 30 20.021 15.655 39.551 19.83 15.65 39.44 11 20_BM-13 CSVC trachyte 30 19.426 15.623 39.270 19.36 15.62 39.18 12 21_BM-51 CSVC trachyte 30 19.756 15.639 39.497 19.65 15.63 39.36 13 23_BM-4 CSVC trachyandesite 31 19.237 15.607 39.164 19.15 15.60 39.04 14 25_BM-60 CSVC trachyandesite 30 19.509 15.620 39.324 19.41 15.62 39.19 15 CS-30 CSVC monchiquite 30 19.201 15.601 39.187 19.10 15.60 39.04 16 CS-31 CSVC camptonite 30 19.345 15.618 39.216 19.20 15.61 39.05 17 CS-43 CSVC camptonite 30 19.389 15.600 39.190 19.35 15.60 39.14 18 KK1 CHB melilitite 1 19.323 15.605 39.119 19.30 15.60 39.10 19 KK2 CSVC tephrite 25.6 20.178 15.655 39.873 19.97 15.65 39.63 20 KK3 CSVC bazanite 29.7 19.057 15.604 38.908 18.98 15.60 38.79 21 KK4 RPVC bazanite 30 19.542 15.603 39.259 19.41 15.60 39.10 22 KK5 RPVC tephrite 30 20.041 15.625 39.665 19.79 15.61 39.31 23 KK6 RPVC camptonite 28.7 19.493 15.622 39.244 19.35 15.62 39.05 24 KK7A CSVC microsyenite 30 19.161 15.608 39.039 19.06 15.60 38.92 25 KK8 CSVC camptonite 30 19.193 15.603 39.088 19.10 15.60 38.97 26 KK9 RPVC polzenite 70 20.309 15.667 40.152 19.73 15.64 39.37 27 KK10 RPVC melilitite 70 19.756 15.622 39.613 19.36 15.60 39.09 28 KK11 RPVC polzenite 70 20.422 15.644 40.173 19.82 15.61 39.30 29 KK12 RPVC basanite 70 19.988 15.644 39.634 19.74 15.63 39.29 30 ME-3/13 CSVC nephelinite 27 19.720 15.625 39.536 19.62 15.62 39.38 31 ME-4/13 CSVC basanite 30 19.743 15.626 39.481 19.59 15.62 39.27 32 OC-1 RPVC camptonite 30 19.164 15.606 39.067 19.05 15.60 38.91 33 OC-2 RPVC polzenite 70 20.491 15.656 40.210 19.92 15.63 39.56 34 OC-9 RPVC polzenite 68.4 20.849 15.678 41.135 19.97 15.64 39.77 35 OC-10 RPVC alnoite 70 20.567 15.655 40.233 20.01 15.63 39.55 36 OC-12 RPVC melilitolite 70 19.951 15.638 39.816 19.62 15.62 39.38 T - Lead isotope data recalculated for their published age using the constants recommended by IUGS (>.232Th = 4.9475E-lly~1, >.235U = 9.8485E-10y_1, >.238U = 1.55125E-10y_1), and Pb, U and Th concentrations listed in Table 2. Ages are taken from Ulrych et al. (1998, 2002, 2013, 2014, 2018), Skala et al. (2014), Ackerman et al. (2015), Dostal et al. (2017). mixing trend crosses the NHRL of Hart (1984) and most samples have higher 207pb/204 Pb at given 206Pb/204Pb than the NHRL (Fig. 7). There is 9H7 9H4 no correlation between SÍO2 and Pb/ Pb. The absence of crustal xenoliths excludes substantial crustal contamination of the mantle-derived magmas during fractionation of the more acidic rocks en route (cf. Blusztajn and Hart, 1989; Ulrych et al., 2016). Late Cretaceous ultramafic lamprophyres, including polzenite, alnóite and related melilitolite cluster at the radiogenic end of the Pb array (Fig. 7), suggesting that their parent magma resulted from decompression melting of metasomatically enriched lithospheric mantle beneath the Bohemian Massif (cf. Embey-Isztin et al., 1993a; Riley et al., 2003; Kroner et al., 2010; Rudnick and Gao, 2014; Krmiček et al., 2016). Tertiary alkaline lamprophyres, comprising camptonite, monchiquite and related leucocratic microsyenite, which is a more felsic equivalent of alkaline lamprophyre, fall near the low-206Pb/204Pb end-member of the mixing trend (Fig. 7). This suggests that they were produced via subsequent interaction of the lithospheric mantle with asthenosphere-derived material during the extensional phase of the Eger Rift opening (cf. Gallagher and Hawkesworth, 1992; Wilson, 1993; Harangi and Lenkey, 2007; Aghazadeh et al., 2015; Dostal et al., 2019a). Other Tertiary volcanic samples of the Bohemian Massif are distributed between above two end-members. The variations in 206Pb/204Pb do not depend on petro-graphic rock type or on the degree of fractionation, but instead, reflect various contributions from contrasting mantle sources during melting. Cretaceous (pre-rift) intrusive and Quaternary (late-rift) effusive melilitites have Pb isotope compositions very similar to those of alkaline lamprophyres (Fig. 7). The Pb isotope data demonstrate that the Cretaceous melilitites (e.g., the Great Devil's Wall) did not originate from the same mantle source as the polzenites, despite emplacement in a similar tectonic stress field (Ulrych et al., 2014). The source of the melilitites was more primitive, which may have been a direct consequence of higher degree of melting (compared to the LREE enriched ultramafic lamprophyres), different melting depths, or a combination of both (cf. Hof-mann, 1988; Sun and McDonough, 1989; Melluso et al., 2011). 5.3. Regionally contrasting Pb isotope signatures in mantLe-derived rocks in the Bohemian Massif On the scale of the Bohemian Massif, most mantle-derived rocks 9H7 904 follow the same orogenic Pb growth curve in the "u'Pb/z,"Pb vs. 206Pb/204Pb diagram (Figs. 7 and 9). As the metasomatised lithospheric mantle has higher Pb contents than the asthenospheric mantle, small or moderate contributions from other reservoirs than the lithospheric mantle may not significantly affect the Pb isotope composition of the various melts and the character of the lithospheric mantle did not change over time. The oldest mantle-derived dyke rocks emplaced during the extensional phase after the final collision of Laurussia, Gondwana and Gondwana-derived terranes are orogenic lamprophyres and lamproites (e.g., Krmiček, 2010; Krmiček et al., 2011). The orogenic Pb isotope signature as sampled by mantle-derived rocks of the Bohemian Massif since ca. 340 Myr predominantly originates from a metasomatised lithospheric mantle source affected by subduction of oceanic and continental crust during the Variscan orogeny (Krmiček et al., 2016; Dostal et al., 2019a). The lower Pb isotope ratios of Variscan lamproites and lamprophyres from the Bohemian Massif (Abdelfadil et al., 2013; Krmiček et al., 2016) do not reflect a different source than the Cretaceous to 937 S. Krmíčková et al Geoscience Frontiers 11 (2020) 925-942 40 35 30 25 20 15 10 5 0 (A) i-1-1-1-1-1-r chondritic ratio (19.9 ±0.6) O A O-A------v--cr------»-o------------------ average OIB (15.9 ±0.6) J_I_I_I_I_I_L 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06 Lu/Hf 2.5 2.0 1.5 ■1.0 0.5 25 20 15 LMMCC i i i i i i A • I Aril ^ - o • average depleted MORB mantle ........ I 10 15 20 25 30 35 40 45 50 (Ce/Yb)N CO CQ 10 © I I I I I • - 2 and Ba/La and distinct troughs for K and Pb in primitive mantle normalised trace element plots (Figs. 5, 6A and 8). The high-radiogenic mantle component A is also prominent in the source of some off-rift volcanic areas (e.g., Blusztajn and Hart, 1989; Haase and Renno, 2008). Alpine extension within the Variscan massifs of Central Europe in the Tertiary eventually resulted in the Cenozoic rift system with widespread and voluminous volcanism in the Rhine, Ruhr Valley, and Leine grabens in Germany, and in the Eger Rift in the Bohemian Massif (Ziegler, 1992). During these events, Variscan metasomatised lithospheric mantle (component A) below the rifts was refertilised by upwelling material from the asthenosphere (Dostal et al., 2019a), which is reflected by rocks with less radiogenic 206Pb/204Pb values (Fig. 9). This mixed mantle (mantle component B) is the major source for the majority of rift-related Tertiary and Quaternary volcanic rocks of Central Europe, e.g., Vogelsberg, Siebengebirge, Schwäbische Alb, Westerwald, Kaiserstuhl, Rhön, Hegau, Heldburg as well as for volcanic rocks from the Eger Rift. Mantle-derived rocks from the Carpathian-Pannonian region have 207Pb/204Pb values that resemble those of Siebengebirge, Kaiserstuhl, Westerwald, Siebengebirge-Westerwald transition zone and Rhön, and are slightly higher than those of corresponding rocks from the Bohemian Massif (Fig. 9). Additionally, several samples from the Carpathian- 907 904 Pannonian area are characterised by Pb/ Pb values as high as 15.75 (Trua et al., 2006; Harangi and Lenkey, 2007). These high values reflect variable contributions from old crust. Most volcanic rocks of CEVP fall on a two-component mixing trend in 143Nd/144Nd vs. 206Pb/204Pb diagram (Fig. 10). Although the Nd isotope values more or less positively correlate with the Pb isotope signature, the subtle differences in composition of the upper mantle sampled by Mesozoic and Cenozoic rocks are not so clearly documented by Nd isotopes as by Pb isotopes. Dostal et al. (2019a) demonstrated the evolution of Nd isotope composition of the upper mantle beneath Central and Western Europe from very unradiogenic values induced by the Variscan orogeny to more radiogenic values that developed during the Mesozoic rifting of the Atlantic Basin. The Nd isotope composition of Central European upper mantle was not further significantly affected since ca. 100 Ma, which is supported by studied samples. The Mesozoic to Cenozoic mantle-derived rocks are distinctly radiogenic (Ulrych et al., 2008; Skála et al., 2014; Dostal et al., 2017) compared to those of the Variscan age (Krmiček et al., 2016). Studied mantle-derived rocks are neither overlapping, nor trending to the FOZO mantle component (Fig. 10) that isotopically overlaps with a low-velocity component (cf. Hoernle et al., 1995). This excludes an involvement of the mantle plume in their magma evolution, which is in line with seismic data from the mantle beneath the Bohemian Massif (Plomerová et al., 2007; Hrubcova et al., 2017). 6. Conclusions Based on our Pb isotope study of mantle-derived rocks from the Bohemian Massif and their comparison with other volcanic provinces in Central Europe, we make the following conclusions: (1) Upper Palaeozoic mantle-derived rocks demonstrate that the lithospheric mantle beneath the Bohemian Massif was metasomatised during the Variscan orogeny and received its Pb iso-topic signature from subducted crustal material. Cretaceous, Tertiary and Quaternary mantle-derived rocks of the Bohemian Massif have been extracted from this mantle and, therefore, share the same crustal signature. (2) The Pb isotope data define a two-component mixing trend. The Cretaceous ultramafic lamprophyres represent a high radiogenic end-member characterised by 206Pb/204Pb ratios up to 20.0 (Variscan metasomatised lithospheric mantle), whereas the Tertiary alkaline lamprophyres and Cretaceous and Quaternary melilitites originated from the mantle with 206Pb/204Pb ratios below 19.4 (lithospheric mantle substantially modified via interaction with the convective mantle). The Pb isotope composition of the Tertiary volcanic samples falls between these two components. 939 S. Krmíčková et ai Geoscience Frontiers 11 (2020) 925-942 (3) Generally, off-rift volcanic/subvolcanic rocks are derived from a mantle source with higher 206Pb/204Pb than corresponding rocks from axial parts of the rift, possibly indicating that the low 206Pb/204Pb component is derived from the mantle source influenced by asthenosphere upwelling. (4) The majority of Cenozoic mantle-derived rocks of Central Europe show similar Pb isotope variations as those of the Bohemian Massif. Acknowledgments This research was financially supported by the institutional project RVO 67985831 of the Institute of Geology of the Czech Academy of Sciences, as well as by the Brno University of Technology project LO1408 "AdMaS UP - Advanced Materials, Structures and Technologies", supported by the Ministry of Education, Youth and Sports of the Czech Republic under the "National Sustainability Programme I". S.K., L.K. and J.U. thank Jaroslav Dostal (Saint Mary's University, Canada) and Martin J. Timmerman (University of Potsdam, Germany) for discussion. The authors greatly appreciate an anonymous reviewer and Dr. C. Spencer for their very constructive and helpful comments and suggestions. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.gsf.2019.09.009. References Abdelfadil, K.M., Romer, R.L., Seifert, T., Lobst, R., 2013. 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