Geochemistry of a Precambrian Ophiolite from South China

The geochemistry and environment of formation of the Precambrian Fuchuan ophiolite, situated in the eastern part of the southern margin of the Yangtze block in southern Anhui province, China, are discussed. The serpentinized peridotites have high Mg# (94–95) and low CaO and Al2O3 contents, high Cr# (100∗Cr/(Cr + Al)) spinels, and LREE-enriched patterns. The pyroxenites and gabbros exhibit flat to LREE-depleted patterns and positive eNd(T) (+2.1 to +2.6). The spilites have LREE-enriched patterns [(La/Yb)N = 1.5-3.7], positive eNd(T) (+3.2), negative Eu anomalies [(Eu/Eu∗)N = 0.71-0.87], and low ratios of Nb/La(<0.8), Ti/Y (<350), and Ti/V (<30). Both diorites and keratophyres have LREE-enriched patterns and negative Eu anomalies. Seawater alteration is suggested by: (1) negative Ce anomalies exhibited by all samples, (2) large variations in δ18O, and (3) a horizontal trajectory to the higher eSr values in the eNd(T)-eSr (T) diagram. The geochemical data for the Fuchuan ophiolite are consistent with formati...

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