Petrographic and chemical characteristics of diabases at DSDP Holes 63-469 and 63-471

Diabasic rocks were recovered at Sites 469 and 471 on IPOD/DSDP Leg 63. The diabasic rocks are composed mainly of Plagioclase, clinopyroxene, and low-temperature alteration products. In addition to these phases, a considerable amount of primary biotite and lesser colorless amphibole are observed in some of the Site 471 diabases. Major and trace element data suggest that these rocks are tholeiitic; however, their highly altered nature obscures their petrologic affinity with the DSDP Leg 63 tholeiitic basalts and others from the nearby Pacific ocean floor. It is likely that the Site 469 and 471 diabasic rocks represent products of off-ridge intrusive activity.

Chemical composition of rocks and minerals from the Doldrums and Arkhangelsky Fracture Zones

The book deals with results of complex geological and geophysical studies in the Doldrums and Arkhangelsky Fracture Zones of the Central Atlantic. Description of the main features of bottom relief, sediments and crustal structure, geomagnetic field, composition of igneous and sedimentary rocks are given in the book. The authors made conclusions on tectonic delamination of the oceanic crust and existence of specific rock complexes forming non-spreading blocks