198 



TABLE I 



IGNEOUS AND METAMORPHIC ROCKS SO FAR NOTED IN DREDGE SAMPLES FROM THE MID-ATLANTIC RIDGE 



References 



Basalts Correns (1930); Shand (1949); Quon and Ehlers (1963); 



MuiR et al. (1964); Nicholls et al. (1964); Engel and 

 Engel(1964); present study 



Gabbros (includes all medium to Correns (1930); Shand (1949); Quon and Ehlers (1963); 



coarse-grained basaltic rocks) Muir et al. (1964); present study 



Serpentinite Shand (1949); Quon and Ehlers (1963); Nicholls et al. 



(1964) 



Quartz-epidote rock after basalt Quon and Ehlers (1963) 



Greenstones present study 



on the Mid-Atlantic Ridge has been pointed out by several authors (Muir et al., 1964; 

 Engel and Engel, 1964; Nicholls et al., 1964; Engel et al., 1965; and Nicholls, 

 1965). 



The widest variety of rocks described from the Mid-Atlantic Ridge is that 

 dredged by the Atlantis I during the summers of 1947 and 1948 (Shand, 1949; Quon 

 and Ehlers, 1963). Unfortunately, few of these rocks have been adequately described. 

 Of particular interest is the quartz-epidote rock dredged from 49°16'W 30^04'N by 

 the Atlantis I. Quon and Ehlers (1963) point out that it was derived perhaps from 

 a basalt. Although it lacks albite, actinolite, and chlorite, minerals which characterize 

 greenschist facies metabasalts and the 22^N greenstones, the epidote-quartz rock 

 suggests that greenschist facies rocks may be among the remaining undescribed 

 Atlantis I samples. 



Greenstones were first reported from the deep-sea floor by Mathews et al. 

 (1965) from the Carlsberg Ridge, Indian Ocean. However, detailed data on these 

 are not available to the writers at present, and thus a comparison with those of the 

 present study is not possible. 



Present study 



Greenschist facies rocks, and unmetamorphosed basaltic rocks were dredged between 

 22° and 23° N latitude on the Mid-Atlantic Ridge by the R. V. "Chain" of the Woods 

 Hole Oceanographic Institution during October, 1964 (Van Andel et al., 1965). 

 These are the first recorded albite-chlorite-epidote-actinolite rocks from the Mid- 

 Atlantic Ridge and their detailed description is the main subject of this paper. The 

 results of a preliminary study of these rocks have been summarized previously 

 (Melson et al., 1966). 



The greenstones were found with fresh basalts and dolerites in two dredges 



