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Published June 1989 | Published
Journal Article Open

Nd and Sr isotopic evidence for the origin of tektite material from DSDP site 612 off the New Jersey coast


Late Eocene tektite material from DSDP site 612 is composed of angular to spherical tektites and microtektites containing abundant vesicles and a few unmelted to partially melted mineral inclusions. The major element compositions of the 612-tektites are generally comparable to those of North American tektites, but the physical features suggest that the DSDP-612 tektites were formed by less severe shock melting. The ^(87)Sr/^(86)Sr and ^(143)Nd/^(144)Nd compositions of 612-tektites: a) show much wider ranges than the tightly constrained group of North American tektites and microtektites, and b) are significantly different from those of other groups of tektites. The existence of large isotopic variations in tektites from DSDP site 612 requires that they were formed from a chemically and isotopically heterogeneous material in a regime that is distinctive from that of other groups of tektites. T^(ND)_(CHUR) and T^(Sr)_(UR) model ages of the 612-tektites indicate that they were formed from a crustal source of late Precambrian mean age (800–1000 Ma) which in middle Palaeozoic time (≅400 Ma) was further enriched in Rb/Sr during sedimentary processes. These source characteristics suggest that the impact which produced the 612-tektites occurred in rocks of the Appalachian orogeny or sediments derived from this orogenic belt. Potential source materials for both 612-tektites and North American tektites are present on the eastern and southeastern part of the North American continent and its adjacent shelf. The distinct isotopic differences between 612-tektites and North American tektites indicate that the two groups of tektites were either formed by the impact of more than one bolide in the same general area, or by a single impact event that sampled different layers.

Additional Information

© 1989 Meteoritical Society. Received 8 September 1988; accepted in revised form 20 April 1989. We are indebted to the work of G. Keller and her willingness to provide us with well documented samples for this study. We thank V. E. Barnes for the samples of bediasites. Meticulous and diligent sample preparation by L. M. Hedges is acknowledged as is expert assistance by J. T. Armstrong and J. Sheng with the SEM and microprobe analyses. This work was supported by NASA, under grant NAG 9-43. Division contribution No. 4679 (638). Editorial handling: C. J. Allegre and J. T. Wasson.

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