Precisely dating Paleozoic kimberlites in the North China Craton and Hf isotopic constraints on the evolution of the subcontinental lithospheric mantle

Linking continental deep subduction with destruction of a cratonic margin: strongly reworked North China SCLM intruded in the Triassic Sulu UHP belt

“…The CCSD-pp1 and the Raobazhai peridotites were interpreted as the NCC mantle wedge metasomatized by fluids/melts released from the subducted Yangtze continental crust (Zheng et al , 2008a. Most depleted mantle model ages (*1.3 Ga) of these peridotitic zircons are identical to those of baddeleyite xenocrysts in the Mengyin and Fuxian kimberlites (Li et al 2011), suggesting that these Type A peridotites experienced a history similar to that of the SCLM beneath the eastern part of the North China craton. Some zircons with high T DM and T crust (i.e., [2.5 Ga) can be found not only in the Xugou and Yangkou peridotites, but also in the Hujialing samples.…”

“…1a) and Fuxian (FX) kimberlites (inset of Fig. 1a) in the Middle Ordovician (*470 Ma; Lu et al 1998;Yang et al 2009;Li et al 2011). Peridotite xenoliths from the kimberlites represent samples of an ancient refractory mantle lithosphere that was thick (ca 200 km) and cold (geotherm of ca 40 mW/m 2 ), while xenoliths from basalts erupted at B100 Ma show a thin (\90 km) and hot (mean geotherm 80 mW/m 2 ) lithosphere .…”

“…At the same time in the Early Paleozoic, the quiescent North China craton began to be active, resulting in the eruption of Mengyin and Fuxian kimberlites at *470 Ma Yang et al 2009;Li et al 2011), and this sort of magmatic activity was synchronous with lithospheric subduction along the margins of the craton . Therefore, we interpret the Early Paleozoic zircons from the Sulu peridotitic bodies as probably formed by mantle metasomatism, related to a strong tectonothermal event accompanied by kimberlite eruption at *470 Ma.…”

Uranium-Lead, Rubidium-Strontium, Kimberlite

“…Although groundmass perovskite and mantle zircon are the most common minerals used in dating kimberlites by the U-Pb method, there have been attempts to utilize other less common U-bearing minerals, such as baddeleyite (ZrO 2 ; Schärer et al 1997;Heaman and LeCheminant 2000;Li et al 2011), ilmenite (FeTiO 3 ; Noyes et al 2011), and rutile (TiO 2 ; Cooper et al 2008). There has been some success using other U-bearing minerals to date kimberlite emplacement but there is always a challenge to prove that the dates obtained reflect the time of kimberlite emplacement and not the age of mantle or crustal xenocrysts, potentially recording dates that significantly predate kimberlite eruption.…”

Formation of mafic magmas through lower crustal AFC processes — An example from the Jinan gabbroic intrusion in the North China Block

“…The occurrence of Ordovician (~480 Ma, Li et al, 2011) diamond-hosted kimberlites Lithos 179 (2013) [157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172][173][174] and associated mantle xenoliths suggests the survival of an Archean lithospheric keel that extended into the diamond stability field (180-200 km) before the early Paleozoic. In contrast, the Cenozoic upper mantle beneath the NCB is mainly composed of geochemically fertile but isotopically depleted peridotites at 70-80 km depths with similar characteristics to those of oceanic basins and tectonically mobile belts (e.g., Fan and Menzies, 1992;Fan et al, 2000;Menzies et al, 1993Menzies et al, , 2007Zheng et al, 2001Zheng et al, , 2006.…”