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Six samples of gray shale were analyzed from Leg 41, Site 367, Cores 17, 18, 21, and 22 drilled in the Cape Verde Basin southeast of the Cape Verde Islands. According to the Initial Core Descriptions, Cores 17, 18, and 21 are Cenomanian and Core 22 is Albian in age. The four Cenomanian aged samples are darker and more fissile than the clay from Core 22. The chemical composition of Core 22, Section 3 approaches that of a normal noncarbonaceous shale. The analytical methods employed with relative standard deviation in square brackets are: coulometry (CW((, CO) 5 [2%], AASflame (Fe, K, Na, Mn, Cu, Ni, Zn, Cr, Ba) [<10%], yspectrometry (U, Th) [25]%, optical emission spectrography (V, Mo) [20%], and AAS-flameless after separation (Cd, Pb, Tl, Bi, Hg) (Heinrichs and Lange (1973; Heinrichs (1975a)) [15%]. Systematic errors have been excluded by the use of several sets of international standard reference rocks. Our analytical results are compiled in Table 1. The content of Corβ of the Cenomanian samples is high compared with black shale from other than oceanic occurrences. Several elements are well correlated with the concentration of Corg and are far beyond the ranges in which these elements often occur in black shales (V, Mo, Ba, U). The elements Zn, Cd, Cu, Ni, and Tl are also correlated with C w . Their concentrations are less pronounced than those of the above-mentioned constituents. A correlation of Tl with COT has not been reported before. No correlation with C m could be observed for the following minor elements: Cr, Pb, Th, Hg, and Bi. The concentrations of Cr and Th in our samples are higher than in noncarbonaceous shales however. Vine and Tourtelot (1970) have compiled data on 21 minor elements in 20 sets of 779 individual black shales from North America. We have included their median values in our Table 1 for comparison. Wedepohl (1964) published a similar compilation of European black shales considering a smaller number of elements. He demonstrated that black shales often contain about 1000 ppm V and 100 ppm Mo. Both compilations mention manganese as the only element being lower in typical black shale than in shale and clay with subordinate concentrations of COT. Diagenetic mobilization of manganese after reduction of Mn can explain the low concentrations in the reducing environment.

Notes About the Specific Chemical Composition of "Black Shales" from Site 367 (Leg 41)