Peridotites from the southern Mariana forearc were sampled on the landward trench slope of the Izu-Bonin-Mariana (IBM) subduction zone by dredging.These mantle wedge peridotites underwent hydration by fluid derived fr...Peridotites from the southern Mariana forearc were sampled on the landward trench slope of the Izu-Bonin-Mariana (IBM) subduction zone by dredging.These mantle wedge peridotites underwent hydration by fluid derived from a dehydrated descending slab,and later interacted with seawater after emplacement at or near the seafloor.This study investigates how these two different rock-fluid interaction processes influenced trace element distribution in the southern Mariana forearc peridotites.We measured trace element concentrations of peridotites from the southern Mariana forearc.The southern Mariana forearc peridotites are characterized by a distinct seawater-like REE pattern with an obvious negative Ce anomaly,and La shows good correlation with other REEs (except Ce).In addition,there is a great enrichment of U,Pb,Sr and Li elements,which show a distinct positive anomaly relative to adjacent elements in the multi-element diagram.For the seawater-like REE pattern,we infer that REEs are mainly influenced by seawater during peridotite-seawater interactions after their emplacement at or near the seafloor,by serpentinization or by marine weathering.Furthermore,the anomalous behavior of Ce,compared with other rare earth elements in these samples,may indicate that they have undergone reactions involving Ce (IV) when the peridotites interacted with seawater.Positive U,Pb,Sr and Li anomalies are inferred to be related to seawater and/or fluids released during dehydration of the subducting slab.展开更多
The article presents the results of study of composition, structure and properties of three genetic types of serpentinite, developed by chromite-bearing ultrabasic rocks, by metamorphic zones of carbonate rocks and wi...The article presents the results of study of composition, structure and properties of three genetic types of serpentinite, developed by chromite-bearing ultrabasic rocks, by metamorphic zones of carbonate rocks and within the zone of weathering of ultrabasic rocks. The samples were selected from deposits, located along the Main Ural Fault-the Paleozoic subduction zone （named GUR）. Peculiarities of microstructure, chemical composition and properties of serpentinites formed in different geological conditions were investigated and their comparative study was held. They were devided three groups of serpentinites with oriented and non-oriented structure which formed by different protholites： mantle, lithosphere and crust.展开更多
基金Supported by the Pilot Project of Knowledge Innovation Project,Chinese Academy of Sciences (Nos.KZCX2-YW-211, KZCX3-SW-223)the National Natural Science Foundation of China (No.40830849)the Special Foundation for the Eleventh Five-Year Plan of COMRA (No.DYXM-115-02-1-03)
文摘Peridotites from the southern Mariana forearc were sampled on the landward trench slope of the Izu-Bonin-Mariana (IBM) subduction zone by dredging.These mantle wedge peridotites underwent hydration by fluid derived from a dehydrated descending slab,and later interacted with seawater after emplacement at or near the seafloor.This study investigates how these two different rock-fluid interaction processes influenced trace element distribution in the southern Mariana forearc peridotites.We measured trace element concentrations of peridotites from the southern Mariana forearc.The southern Mariana forearc peridotites are characterized by a distinct seawater-like REE pattern with an obvious negative Ce anomaly,and La shows good correlation with other REEs (except Ce).In addition,there is a great enrichment of U,Pb,Sr and Li elements,which show a distinct positive anomaly relative to adjacent elements in the multi-element diagram.For the seawater-like REE pattern,we infer that REEs are mainly influenced by seawater during peridotite-seawater interactions after their emplacement at or near the seafloor,by serpentinization or by marine weathering.Furthermore,the anomalous behavior of Ce,compared with other rare earth elements in these samples,may indicate that they have undergone reactions involving Ce (IV) when the peridotites interacted with seawater.Positive U,Pb,Sr and Li anomalies are inferred to be related to seawater and/or fluids released during dehydration of the subducting slab.
文摘The article presents the results of study of composition, structure and properties of three genetic types of serpentinite, developed by chromite-bearing ultrabasic rocks, by metamorphic zones of carbonate rocks and within the zone of weathering of ultrabasic rocks. The samples were selected from deposits, located along the Main Ural Fault-the Paleozoic subduction zone （named GUR）. Peculiarities of microstructure, chemical composition and properties of serpentinites formed in different geological conditions were investigated and their comparative study was held. They were devided three groups of serpentinites with oriented and non-oriented structure which formed by different protholites： mantle, lithosphere and crust.
