Abstract Details
(2020) Early Cretaceous Lamprophyre Dykes in Jiaodong Peninsula, China and Implications for Subduction-Related Mantle Metasomatism
Wang X, Wang Z, Cheng H, Foley S & Xiong L
https://doi.org/10.46427/gold2020.2776
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03g: Room 1, Thursday 25th June 08:15 - 08:18
Xiang Wang
View all 2 abstracts at Goldschmidt2020
Zaicong Wang View all 6 abstracts at Goldschmidt2020 View abstracts at 11 conferences in series
Huai Cheng View all 3 abstracts at Goldschmidt2020 View abstracts at 4 conferences in series
Stephen Foley View all 4 abstracts at Goldschmidt2020
Le Xiong View all 2 abstracts at Goldschmidt2020
Zaicong Wang View all 6 abstracts at Goldschmidt2020 View abstracts at 11 conferences in series
Huai Cheng View all 3 abstracts at Goldschmidt2020 View abstracts at 4 conferences in series
Stephen Foley View all 4 abstracts at Goldschmidt2020
Le Xiong View all 2 abstracts at Goldschmidt2020
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Submitted by Jingao Liu on Monday 22nd June 05:44
Hi Xiang, good work. Nice data and finding. From your work and many previous studies, the metasomatism from the continental subduction did not add water which was later added by the flat or low-angle suduction of the Paleo-Pacific plate. The slab roll-back led to the melting of hydrated metasomatised lithopsheric mantle, i.e., Arc-like mafic magmatism. Thus, relativley dry metasomatism that is common in cratonic peridotites did not trigger lithosphere destruction, but water attenuated the lithosphere followed by slab roll-back. It is kind of strange to me that why the water addition did not affect the trace element systems in these lamprophye rocks. Do you think the formation of these rocks occurred prior to the slab roll-back by adding only water-rich fluids from the flat-slab beneath the lithosphere? Thanks, Jingao
Thank you for your good questions. I favour that the lamprophyres formed during the slab roll-back of Paleo-Pacific plate, and the subsequent extension-induced thinning of SCLM and upwelling of the asthenospheric mantle triggered melting of the enriched SCLM. The question provided here is mainly about the elemental and isotopic contribution from the subducted Paleo-Pacific plate to their source in addition to water. However, to be honest, it is difficult to quantitatively discriminate such contributions in this study. Both subduction of continental crust and oceanic crust could result in arc-like trace element patterns in SCLM-derived rocks, whereas the continental crust-like Sr-Nd isotopic composition of the lamprophyres more likely from the melts of subducted Yangtze crust. Given the SCLM were previously enriched by fertile materials from subducted continental crust during the Triassic (as shown in those Late Triassic mafic rocks), the subsequent fluids released from the subducted Paleo-Pacific plate may bring amounts of fluid-mobile elements but seems not strongly change the trace element patterns (arc-like) in those Early Cretaceous mafic rocks. However, those Early Cretaceous mafic rocks in the eastern NCC show discriminable Nb/U, Ba/Th and Th/Nb ratio variations to those Late Triassic counterparts, and 87Sr/86Sr(t) of them seemingly decrease from the southeastern (~0.710) to northwestern (~0.706) NCC. All these observations may reflect heterogeneous reworking by input from the subducted Paleo-Pacific plate. Best regards, Xiang.
Hi Xiang, good work. Nice data and finding. From your work and many previous studies, the metasomatism from the continental subduction did not add water which was later added by the flat or low-angle suduction of the Paleo-Pacific plate. The slab roll-back led to the melting of hydrated metasomatised lithopsheric mantle, i.e., Arc-like mafic magmatism. Thus, relativley dry metasomatism that is common in cratonic peridotites did not trigger lithosphere destruction, but water attenuated the lithosphere followed by slab roll-back. It is kind of strange to me that why the water addition did not affect the trace element systems in these lamprophye rocks. Do you think the formation of these rocks occurred prior to the slab roll-back by adding only water-rich fluids from the flat-slab beneath the lithosphere? Thanks, Jingao
Thank you for your good questions. I favour that the lamprophyres formed during the slab roll-back of Paleo-Pacific plate, and the subsequent extension-induced thinning of SCLM and upwelling of the asthenospheric mantle triggered melting of the enriched SCLM. The question provided here is mainly about the elemental and isotopic contribution from the subducted Paleo-Pacific plate to their source in addition to water. However, to be honest, it is difficult to quantitatively discriminate such contributions in this study. Both subduction of continental crust and oceanic crust could result in arc-like trace element patterns in SCLM-derived rocks, whereas the continental crust-like Sr-Nd isotopic composition of the lamprophyres more likely from the melts of subducted Yangtze crust. Given the SCLM were previously enriched by fertile materials from subducted continental crust during the Triassic (as shown in those Late Triassic mafic rocks), the subsequent fluids released from the subducted Paleo-Pacific plate may bring amounts of fluid-mobile elements but seems not strongly change the trace element patterns (arc-like) in those Early Cretaceous mafic rocks. However, those Early Cretaceous mafic rocks in the eastern NCC show discriminable Nb/U, Ba/Th and Th/Nb ratio variations to those Late Triassic counterparts, and 87Sr/86Sr(t) of them seemingly decrease from the southeastern (~0.710) to northwestern (~0.706) NCC. All these observations may reflect heterogeneous reworking by input from the subducted Paleo-Pacific plate. Best regards, Xiang.
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