Note on the Occurrence of Native Copper in Tertiary Nannofossil Oozes from the Goban Spur (Hole 550)

Анотація

In the course of examining the Tertiary cores from Hole 550 for volcanic ash layers, we observed minor amounts of a bright blue green mineral at three horizons (Fig. 1). When separated from the enclosing sediment, the blue green material proved to be coating a dark brown core of metallic copper. In two of the occurrences the copper is associated with carbonate ooze host sediment: nannofossil ooze in Sam-ple 550-29-2, 66.5-67.5 cm and somewhat coarser grained turbiditic siltstone laminae in Sample 550-29-4, 138-140 cm. In the latter sample, the copper is clearly acting as a cementing agent for quartz silt and forami-niferal grains. In the third occurrence (Sample 550-36-2, 41-43 cm), the copper lies along fractures within a soft chert concretion, indicating that the copper is again of secondary origin and proving that its precipitation fol-lowed the formation of the concretionary silica. Detailed chemical analysis has not been carried out on the copper, but an electron-microprobe analysis of one particle indicated that the copper was almost pure; the only other elements detected were trace amounts of Si and Al, indicating slight contamination by detrital impurities. Native copper has previously been reported from sev-eral other DSDP sites. In some the copper is associated with the basaltic basement (Site 282: Ovenshine et al.,

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