TAG HYDROTHERMAL FIELD 



RIFT VALLEY FLOOR 



HYDROTHERMAL FIELD 

 EAST WALL 



10 



km 5 



MANTLE 



Figure 5. Simplified block diagram showing the geologic setting 

 of subseafloor hydrothermal circulation system at the TAG 

 Hydrothermal Field in the rift valley of the Mid-Atlantic 

 Ridge (Fig. 1; modified by G. Thompson from slide by R.B. 

 Scott). The arrow on the rift valley floor points to a 

 mound the size and shape of the Houston Astrodome where 

 black smokers are venting. The mound is constructed of 

 polymetallic massive sulfides precipitated from the hot 

 springs . 



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