168 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



ported from this region except an auriferous vein worked by the 

 Spaniards near Valdivia, and some auriferous beach sands along the 

 coast, for instance, on Chiloe Island. Not until we reach the Straits 

 of Magellan are there any producing deposits. At Punta Arenas 

 on these straits and on the eastern side of the Andes there are gold- 

 bearing gravels rich enough to justify dredging. Similar placers 

 are found on the south side of the straits in Tierra del Fuego. About 

 1902 a dozen dredges were erected here and for a number of years 

 these gravels have contributed largely to the gold production of 

 Chile, yielding annually up to $100,000. The production has de- 

 creased materially during the last few years, owing, it is said, to 

 difficulties in dredging the bowldery deposits. 



The difference in mineralization is intimately connected with a 

 great change in topographical and geological conditions. 1 From 

 latitude 42° down to Cape Horn the cordillera is invaded by the 

 ocean and by ice. Its westerly margin is cut up into an intricate 

 system of fjords, and its summits are clad in the armor of immense 

 ice fields. A huge batholith of granitic and dioritic rocks occupies the 

 whole western range, probably from Puerto Montt to the tip of the 

 continent. This constitutes a striking analogue to the batholith of 

 British Columbia; it is of greater length and its width in many 

 places reaches 100 kilometers. On the east side the ice fields often 

 cover its margins. On the west side the adjoining sedimentary rocks 

 are largely submerged, but on Wellington and Chiloe Islands these 

 western sediment aries begin to appear as metamorphosed schists of 

 uncertain age. All along the eastern side the batholith is intruded in 

 Mesozoic (Cretaceous and Jurassic) rocks. Along the eastern edge 

 of the latter we find again front ranges of granitic laccoliths, such 

 as Cerro Payne, Cerro Balmaceda, etc., most of them consisting of 

 granitic rocks. There is little doubt that the gold placers of Punta 

 Arenas have derived their metal from the mineralization along the 

 eastern side of the great Chilean batholith. It would be strange if 

 this batholith would not be accompanied by mineral deposits. That 

 no such have been found may in part be accounted for by the ex- 

 tensive present and former glaciation which would destroy most 

 placer deposits and to the fact that the region is extremely inhos- 

 pitable. It would not be surprising if scientific prospecting along 

 the borders of this batholith should lead to the discovery of gold- 

 bearing deposits. 



ARGENTINA. 



The present Argentine production of gold and silver is very small 

 indeed, and the country has never yielded large amounts of these 



metals. 



1 P. D. Quensol : Geologisch-petrographiscbe Studien in der Patagonischen Cordillera 

 (Upsala, 1911). 



