152 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



yielding the greatest amount. In 1912 the production of this belt 

 was about $5,000,000 and for the last decade it has not been less than 

 $4,000,000 in any one year. 



The primary veins from which the placers have been derived are 

 contained in pre-Cambrian schists, diorites, diabases, granites, and 

 granite porphyries. 



The gold belt seems to continue to the southeast beyond the bounda- 

 ries indicated, for it is reported that gold occurs in the Provinces of 



Fig. 2. 



Para, Maranhao, and Ceara, in Brazil, bej'ond the delta of the Ama- 

 zon River. To the south follows a broad, barren interval until we 

 come to the gold deposits of southern Brazil, in the States of Bahia, 

 Minas Geraes, Sao Paulo, Parana, and Eio Grande do Sul. Of these 

 the State of Minas Geraes is by far the most important. Even in the 

 far western part of Brazil, at Cm T aba in Matto Grosso, occur placers 

 said to be derived from older deposits similar to those of Minas 

 Geraes. 



