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At the outset, we planned to add our trace element analyses and petrographic descriptions to the major element analyses of the same rocks presented by Dmitriev (this volume). However, C. Engel was unable to reproduce the values on several elements obtained by Soviet Laboratories on identical samples. Such discrepancies are, in our experience, almost the rule rather than the exception and prompted us to request that the JOIDES Advisory Panel on Igneous and Metamorphic Petrology select several hundred grams of basalt from one DSDP core, preferably from Leg 24, because of the large amount of basalt obtained, to be split and used as one "standard" or reference sample in petrochemical studies of oceanic basalts. Interlaboratory standardization is a prerequisite to meaningful interpretations and evaluation of the proliferating DSDP analytical data. In May 1974, the panel rejected our request for a core reference sample, but agreed to consider preparing a large quantity of a low-K dredged basalt. A slightly oxidized and hydrated, low-potassium basalt reference sample is essential for workers and laboratories involved in the Deep Sea Drilling Project. The U.S. Geological Survey "standard" rocks do not include a basalt which is low in potassium, barium, and related elements. The basalt BCR-1 is an alkali-rich basalt which does not approach the composition of oceanic basalts. The supply of the older standard, W-l, is exhausted. W-l was similar in some ways to oceanic basalts, but the amount of Ba in W-l is higher by an order of magnitude than the Ba content of oceanic basalts, and K2O in W-l is about 0.63 weight percent compared to an average K2O of about 0.22 in oceanic basalts. There are also major discrepancies in concentrations and ratios of many other elements. Until use of appropriate oceanic-type standards becomes commonplace, there can be no rigorous comparisons between basalts cored and dredged in the world oceans, whether from mid-ocean ridges, scarps, basins, trenches, or other major tectonic features. Emission spectrographic analyses for selected trace elements and for Ti and Mn were carried out by Elisabeth Bingham at the California Institute of Technology on portions of basaltic rocks cored at five sites: one well within the Gulf of Aden, one just outside the gulf, and three in the western Indian Ocean. In addition, brief petrographic descriptions are given for each sample analyzed. Finally, we have attempted to relate the trace element composition of these basalts to emission spectrographic analyses of dredged basalts. The drilled localities of Leg 24 where basaltic rocks were encountered and sampled are shown in Figure 1, abstracted from a much more detailed map prepared by Fisher prior to Leg 24. Figure 1 includes the north-south-trending Central Indian Ridge, north to Carlsberg Ridge and west to the African coast. The deep, sedimented Somali Basin forms a broad depression between the mid-oceanic ridges and Somali/Kenya. Our interest in the igneous rocks of the western Indian Ocean dates back to publications commencing in 1965, and work continues on the rocks from the Central and Southwest Indian Ridges (Engel et al., 1965; Fisher et al., 1968; Engel and Fisher, 1969; Fisher and Engel, 1970; Fisher et al., 1973; Engel and Fisher, in preparation).

Trace Element Compositions of Leg 24 Basalts and One Diabase