Intractions of mantle and crustal magmas in the southern part of the Ivrea Zone (Italy)

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

“…Contrary to interpretations of early studies (e.g. Fountain 1989;Voshage et al 1990;Sinigoi et al 1991;Quick et al 1994;Schnetger 1994;Henk et al 1997), the now-accepted view is that the intrusion of mafic magmas into the lower crust was not the main cause for HT metamorphism (e.g. Barboza et al 1999;Redler et al 2012).…”

The growth of large mafic intrusions: Comparing Niquelândia and Ivrea igneous complexes

“…However, whereas the Upper Mafic Complex is relatively homogeneous, with εNd values restricted within a narrow range from −3 to −6, igneous rocks interlayered in the Paragneiss Bearing Belt show a markedly larger variation in isotopic ratios, with εNd ranging from +7 to −6 (Sinigoi et al, 2011;Voshage et al, 1990). Noritic gabbros in the Paragneiss Bearing Belt show a clear increase in crustal contamination adjacent to the paragneiss septa, which indicates that at least part of the contamination occurred in situ, by mixing of melts differentiated from the crystallizing mantle magma and anatectic melts delivered from the septa (Sinigoi et al, 1991(Sinigoi et al, , 1996(Sinigoi et al, , 2011. Detailed chemical stratigraphy and SHRIMP zircon ages on a section across the Paragneiss Bearing Belt suggest that norites in the belt with high amounts of crustal component crystallized relatively late, supporting the concept that paragneiss septa remained above the solidus delivering anatectic melts for some millions of years after their incorporation in the mafic body, or re-melted in response of the thermal relaxation during the slow cooling of the complex (Sinigoi et al, 2011).…”

“…Several bands of garnet ±sillimanite-bearing quartzite coexist with noritic gabbro near the village of the Niquel-Tocantins mine. Although the outcrop conditions do not allow these paragneisses to be followed for long distances, their distribution suggests that they are not angular blocks but rather elongated bands with high aspect ratio parallel to the structural pattern of the complex, resembling the paragneiss septa in the Ivrea Mafic Complex (Quick et al, 1994(Quick et al, , 2003Sinigoi et al, 1991Sinigoi et al, , 1995.…”

Sedimentary Crust and Metallogeny of Granitoid Affinity: Implications from the Geotectonic Histories of the Circum‐Japan Sea Region, Central Andes and Southeastern Australia

“…The detailed process of the transformation in the lower crust is not well understood, but exposed lower crustal sections could provide some insight into the process. For example, it is observed in the Ivrea Zone, northern Italy, that the Kinzigite Formation, a metamorphosed accretionary complex was replaced by intrusive and metamorphic complex of basic to intermediate composition, and anatectic felsic magmas formed granitoids in shallower levels and rhyolitic volcanic rocks on the surface (Voshage et al, 1990;Sinigoi et al, 1991;Quick et al, 2009). The Ivrea Zone may represent a time slice view of the transformation process from sedimentary crust to igneous crust.…”

“…Exposure of lower crustal section, although very limited, may provide a useful insight into these processes. For example, geology of the Ivrea Zone in northern Italy suggests that felsic magmas were generated by the underplating of mantle-derived basic magmas beneath the Kinzigite Formation, a metamorphosed accretionary complex (Voshage et al, 1990;Sinigoi et al, 1991;Quick et al, 2009). This formation is still rich in graphite.…”