Deep Sea Drilling Project: Properties of igneous and metamorphic rocks of the oceanic crust

Abstract

The conference was held at a critical time in the development of our knowledge of the oceanic crust as revealed by the Deep Sea Drilling Project (DSDP). The increased drilling capabilities, including a number of new systems such as heave compensation, improved bits and core recovery, and reentry capability, now allow us to explore and sample the deep oceanic crust for the first time. These new capabilities will be applied to a deep hole in basement on leg 37 in December and January 1973–1974. But what have we already learned from the numerous short cores of igneous rocks so far recovered? This conference attempted to pull together workers who had studied these early cores, give a vehicle for rapid publication of their results through the extended abstracts accompanying this summary, and examine the objectives of future drilling. In reviewing the abstracts, it appears premature to reach any but a very few meaningful generalizations. One is that drilling reveals a much greater chemical diversity of igneous rocks than would be expected from our information from dredge samples. How this diversity relates to mantle and crustal processes is so far unknown in detail. The so‐far shallow penetration places the most severe restriction on interpretations of these cores in terms of the broad patterns of earth history. Future deeper drilling may soon remove this restriction.

Partial melting under spreading ridges

“…Second order variations in the chemical composition of mid-oceanic ridge basalts have been reported repeatedly in the literature (Christensen al. 1973;Joron et al 1976).…”

Trace Element Compositions of Leg 24 Basalts and One Diabase

“…The cored basalts may not have flowed out on hard rock surfaces but rather oozed under shallow layers and "burrowed" into sediments (Christensen et al, 1973). In this way, initially extrusive basalts become intrusive bodies, incorporating to some degree the overlying or confining material.…”