Petrogenesis and tectonic significance of amphibolites interlayered with metasedimentary gneisses in the Ivrea Zone, Southern Alps, northwest Italy

Constraints on the thermal evolution of the Adriatic margin during Jurassic continental break-up: U–Pb dating of rutile from the Ivrea–Verbano Zone, Italy

“…Green hexagon shows the location of the sample from which rutile was U-Pb dated by Zack et al (2011). Green squares indicate Smye and Stockli's (2014) 2003; Redler et al 2013;Sills and Tarney 1984). Rutile is an accessory mineral in many granulite facies IVZ metapelites, where it formed during high-temperature metamorphism as part of the same reaction that produced garnet and partial melt (Ewing et al 2013;Luvizotto and Zack 2009;Schnetger 1994 The Mafic Complex is a dominantly gabbroic, noritic and dioritic intrusive complex up to 10 km thick that was emplaced into the Kinzigite Formation (Barboza and Bergantz 2000;Sinigoi et al 1991;Voshage et al 1990).…”

Chemical composition and fractionation of the continental crust

“…They represent N-MORB in the NW of the exposed area and E-MORB in the SE (SILLS & TARNEY, 1984;MAZZUCCHELLI & SIENA, 1986) The granulite facies metasediments of the lower part of the continuous profile were named stronalites and the amphibolite-facies rocks in the upper section kinzigites. The lower section of meta-sediments has suffered peak metamorphic temperatures of about 800~ (SILLS, 1984;STRACKENBROCK-GEHR-KE, 1989). Large samples of 62 stronalites and kinzigites have been analyzed by SCHNETGER (1988) for major elements and 34 trace elements.…”

Monazite-(Ce)-huttonite solid solutions in granulite-facies metabasites from the Ivrea-Verbano Zone, Italy

“…Monazite with high concentrations of Th and U, including the huttonitic monazite-(Ce) discussed herein, are probably produced partially or wholly by the breakdown of Th-bearing monazite-(Ce) in the immediate adjacent metasediments (Table 1, analysis 9), with subsequent large-scale, high-grade fluid flow-induced redistribution of the now mobile lanthanide and actinide elements into the metabasites. Significant enrichment in REE, other high field-strength elements and phosphorus in the granulite-facies metabasalts, in comparison with the amphibolite-facies metabasalts, is suggested to be the result of the introduction of elements from external source(s) and does not represent a primary signature as proposed by Sills and Tarney (1984). Thus, current ideas on the nature of the basaltic magmatism in the IVZ, which invoke a different petrogenesis and tectonic position for type 1 and 2 amphibolites (Sills and Tarney, 1984), might require some revision.…”

“…Significant enrichment in REE, other high field-strength elements and phosphorus in the granulite-facies metabasalts, in comparison with the amphibolite-facies metabasalts, is suggested to be the result of the introduction of elements from external source(s) and does not represent a primary signature as proposed by Sills and Tarney (1984). Thus, current ideas on the nature of the basaltic magmatism in the IVZ, which invoke a different petrogenesis and tectonic position for type 1 and 2 amphibolites (Sills and Tarney, 1984), might require some revision.…”

“…These metabasalts (c. 46-50 wt.% SiO2; e.g. Sills and Tarney 1984) are composed of orthopyroxene, clinopyroxene, garnet, plagioclase and quartz with minor K-feldspar, biotite, rutile, ilmenite, zircon, apatite, pyrrhotite and graphite. Monazite is hosted by a variety of major and accessory minerals including garnet, K-feldspar, plagioclase, biotite, quartz, apatite, ilmenite and pyrite and, in general, is distinguished by a large compositional diversity in terms of lanthanide (ZREE203 = 34.5-70.1 wt.%) and ThO2 concentrations (from below the microprobe detection limit to 35 wt.%).…”