Palaeozoic and Proterozoic zircons from the Mid-Atlantic Ridge

Geochronology and geochemistry of the Hegenshan ophiolitic complex: Implications for late-stage tectonic evolution of the Inner Mongolia-Daxinganling Orogenic Belt, China

“…Zircon inheritance is common in igneous rocks formed on continents (e.g., Pideon and Compston, 1992), but has not been previously reported from ophiolites that are formed in oceanic environments. Pilot et al (1998) reported inherited zircons with ages of $300 Ma and $1.7 Ga in gabbros located on the present-day Mid-Atlantic Ridge, in keeping with the discovery of ancient deposits and continental rocks on the ridge (Bonatti et al, 1996;Beljatsky, 1997). These discoveries suggest that continental materials can be preserved in the vicinity of young mid-ocean ridges and that old zircons with a continental origin can be incorporated in mid-ocean magmas.…”

Sr–Nd isotopes and geochemistry of granite-gneiss complexes from the Meatiq and Hafafit domes, Eastern Desert, Egypt: No evidence for pre-Neoproterozoic crust

“…Regardless of how zircons formed in the crust are introduced into the mantle, they are resilient enough to even survive extensive melting and be carried back to the surface in magmas. This is the simplest explanation for the presence of inherited ancient zircons documented for mid-Atlantic ridge MORB-type gabbros (Pilot et al, 1998;Belyatsky et al, 2008). This is probably the origin of inherited zircons found in some ophiolites (e.g., Whattam et al, 2006), including the Neoproterozoic Thurwah ophiolite of Saudi Arabia (Pallister et al, 1988;Hargrove et al, 2006a).…”

Phase transition of zircon at high P-T conditions

“…Thus, the behavior of the high-pressure phase of ZrSiO 4 may provide significant information 3 regarding the distribution of U and Th among high-pressure phases in Earth's deep interior. Moreover, it has been recognized that the dating of zircon plays an important role in understanding a wide range of processes, including the formation of the oldest crust (Compston and Pidgeon 1986;Bowering et al 1989), material circulation in the mantle (Pilot et al 1998), and the origin of ultrahigh-pressure metamorphic rocks (Katayama et al 2001). Recently, metamorphic high-pressure minerals have been observed as inclusions within zircon grains.…”