Geochemistry at DSDP Sites 69-505, 69-504 and 70-504

Deep basement penetration during Legs 69 and 70 at Hole 504B in the Panama Basin allowed the recovery of a 561.5-meter sequence of basaltic pillows, thin flows, and breccias interspersed with thick massive flows. The lavas, which are aphyric to moderately plagioclase-olivine-clinopyroxene phyric, are petrologically indistinguishable from typical mid-ocean-ridge basalts (MORB). Some units are distinctive in that they carry accessory chrome-spinel microphenocrysts or emerald green clinopyroxene phenocrysts. Major and trace element analyses were carried out on 67 samples using X-ray fluorescence techniques. The basalts resemble normal MORB in terms of major elements. However, the trace element analyses show that most of the basalts are characterized by very strong depletion in the more incompatible elements compared with, for instance, normal (N type) MORB from the Atlantic at 22°N. Interdigitated with these units are one or two units that have distinctly higher incompatible element concentrations similar to those in basalts of the transitional (T) type from the Reykjanes Ridge (63°N in the Mid-Atlantic Ridge). All the basalts appear to have undergone some high-level crystal fractionation, although this has not proceeded to the extent of yielding ferrobasalts as it has at the adjacent Galapagos Spreading Center or along the East Pacific Rise. The magnetic anomalies are of lower amplitude than in the latter two regions, which suggests that the absence of ferrobasalts may be a general feature of the ocean crust generated at the Costa Rica Rift. The presence of two distinct magma types, one strongly depleted and the other moderately enriched in incompatible elements, suggests that magma chambers at the spreading center are discontinuous rather than continuous and that there is some chemical heterogeneity in the underlying mantle source. Observed variations in incompatible element ratios of basalts from the more depleted group could, however, reflect mixing between these two magma types. In general it would appear that the mantle feeding the Costa Rica Rift is significantly more depleted in incompatible trace elements than that feeding the Mid-Atlantic Ridge.

1992 University of Michigan Football Team

1993 University of Michigan Football Team

Codium isabelae; Codiaceae

Codium isabelae Taylor

Grinnellia americana; Delesseriaceae

Grinnellia americana var. caribaea (Ag.) Harvey var. caribaea Taylor, determined by Taylor 1939

Leptofauchea rhodymenioides; Faucheaceae

Leptofauchea rhodymenioides Taylor, determined by Taylor 1939

Pub. Virgilii Maronis Bucolicorum, Eclogae X. Georgicorum, Libri IIII. Aeneidos, Libri XII et in ea Mauri Servii Honorati Grammatici Commentarii ex antiquiss. ... ex bibliotheca Petri Danielis ... accessit Fabii Planciadis Fulgentii liber de Continentia Virgiliana ... item Iunii Philargyrii commentariolus in Bucolica & Georgica Virgilii ...

Mode of access: Internet.

Temple of Minevra Sulis, brick channel for the overflow from the sacred spring

Bath, England

University of Michigan Women's Athletics--Rifling

Daybook, image #70

Telephoto x 8 from top hill toward B.H. [Barton Hills] Golf Club House

On verso: Toward Barton Hills Golf Club House, Walser, and Oliphant Residences from top of hill by .... in wood (?) Telephoto x 8. Print: June 1977 from original negative (nitrate)

All of Department of Medicine and Surgery, U of M Class 1895

On verso: Huntington & Clark. Successors to Millard. 224 Woodward Ave., Detroit, Mich. Negatives retained for future orders. Duplicates at any time at reduced rates. We have the 70,000 negatives made by Powelson and Millard. Left to right: Ellen Bradford Murray, Maria Louise Graham, Louisa Terese Black