The Arkansas carbonatite complexes resemble the Oka, Quebec, complex in indicating derivation from a LIL element-depleted mantle source. The Sr and Nd isotopic compositions of the Magnet Cove carbonate samples are rather uniform and probably reflect the isotopic compositions of the mantle sources. The samples from Potash Sulfur Springs differ from those at Magnet Cove and indicate either derivation from a slightly more enriched mantle source or crustal contamination. The Arkansas carbonate leads have isotopic compositions that plot within the LIL-element-depleted mantle field, as defined by oceanic data in Pb isotope correlation diagrams, and exhibit small variations that are tentatively attributed to mantle-mixing processes. The small differences between the Oka and Arkansas Pb, Sr and Nd ratios probably reflect a degree of mantle heterogeneity between the two localities. Likewise, Arkansas syenites exhibit an affinity to a LIL-element-depleted mantle source. Nd is slightly more radiogenic than the corresponding ratios in the carbonatites from Magnet Cove, whereas Pb has, with two exceptions, similar isotopic compositions in both rock types. Pb in four syenite samples from a single quarry has variable isotopic compositions. Two of the samples contain a large component of lead characteristic of that observed in central Arkansas galenas, that are thought to represent crustal sources. Overall the results show that alkaline complexes can provide information about the geochemical characteristics of the underlying mantle, although careful attention must be given to deciphering the effects of contamination that may alter the mantle signature.-J.M.H.
|Number of pages||8|
|Publication status||Published - 1987 Jan 1|
All Science Journal Classification (ASJC) codes
- Environmental Science(all)
- Earth and Planetary Sciences(all)