205 



Bulk composition 



Five greenstones which are representative of some of the main types were selected 

 for analysis. Table V gives modes on the analyzed greenstones, and Table VI, the 

 analyses and norms. 



An ACF plot of these analyses allows comparison of the modes with bulk 

 composition (Fig.5). The approximate range in chlorite and actinolite compositions 

 given in the plot are based on microprobe analyses in which all iron again was assu- 

 med to be as FeO. Specimens 3-2 and 3-7, which are essentially free of chlorite, 

 plot on the actinolite-epidote join, as should be the case. However, greenstones 2-5 and 



TABLE V 



ESTIMATED MODES OF ANALYZED METABASALTS 



1 Explanation: 2-5 = unsheared metabasalt; 3-2 = brecciated metadolerite. Abundant euhedral 

 crystals in albite veins; earlier generation of epidote in sheared monominerallic aggregates; 3-3 = 

 brecciated metabasalt. Shears in part later than crystallization of epidote: brecciated coarse-grained 

 aggregates of epidote. Relicts of labradorite; 3-6 = brecciated metabasalt; 3-7 = brecciated meta- 

 basalt. Abundant albitized plagioclase phenocrysts. 



2 Includes unalbitized calcic plagioclase. 



EPIDOTE 



Fig.5. ACF diagram for five 22°N greenstones, two fresh basalts from 22'N, dredge 2 (specimens 

 2-1 and 2-2), and the average of 15 Mid-Atlantic Ridge abyssal basalts (/). 



