Nd, Sr and O Isotopic Study on Spilite-Keratophyre in Xiqiu,,Zhejiang Province, China

Nd, Sr and O isotopic study on the spilite-keratophyre sequence in Xiqiu shows that its ∈_(Nd) values are inthe range of 4.02-5.26, and its ∈_(Sr) values, +1.4-2.6. According to the points of these data in the ∈_(Nd)-T,∈_(Sr)-T and ∈_(Nd)-∈_(Sr) diagrams, the spilite-keratophyre is interpreted as being slightly contaminated by crustalmaterials. Its δ~(18)O values are 3.9-5.0‰. The depletion of ~(18)O in the rocks resulted from the influence ofseawater hydrothermal alteration during or soon after the rock formation. Based on the isotopic characteristicsand available geochemical data, it is believed that the spilite-keratophyre was formed in the well-developedisland-arc environment during the Late Proterozoic subduction of the palaeo-Pacific plate beneath thesoutheastern margin of the Yangtze massif.

Nd,Sr and O Isotopic Study on Spilite-Keratophyre in Xiqiu,Zhejiang Province,China

Abstract Nd, Sr and O isotopic study on the spilite-keratophyre sequence in Xiqiu shows that its ?_Nd values are in the range of 4.02–5.26, and its ? _sr values, +1.4-2.6. According to the points of these data in the ? _Nd-T, ? _Sr-T and ? _Nd-? _Sr diagrams, the spilite-keratophyre is interpreted as being slightly contaminated by crustal materials. Its δ¹⁸O values are 3.9-5.0%₀. The depletion of ¹⁸O in the rocks resulted from the influence of seawater hydro thermal alteration during or soon after the rock formation. Based on the isotopic characteristics and available geochemical data, it is believed that the spilite-keratophyre was formed in the well-developed island- arc environment during the Late Proterozoic subduction of the palaeo- Pacific plate beneath the southeastern margin of the Yangtze massif.