JOÜENEYS THROUGH KOREA. 



25 



Korean ridges terminate in headlands in tlie Sonthern Archi- 

 pelago with corresponding incurves of the coast lines. The inlets 

 of Ma-!<an-pho and Cliin-häi are striking examples of these in- 

 dentations ; the narrowing and widening of the channels found there 

 are surely due to the crossing of the equatorial Ilan-san ridges. 

 From Ma-san-pho or Ma-pJw '\ we proceeded towards Chin-hai 



1) Inouyé [loc. cit.) took the left road to Ham-an, find then joined ours at Pan-song. About 

 half way (7 km) to the eiimnäi of Ham-an, a number of gold placers have been and still are at 

 work at Yong-dam. The auriferous region of Yong-daw. comprises an area of about twenty-live 

 square kilometers, lying at the junction of three districts, Ham-an, Chhyang-uon and Chhil-uöu, 

 and is traversed by equatorial and meridional ridges 200 to 30O m high. It is built ujj of a complex 

 of red and black marly shales, and green-banded, indurated, pelitic tufhte of the Upper Kyöng- 

 sang formation, series Xo. 2, and also a i)art of No. 3 (PI. XXXIV. Profile, Traverse I), which 

 is intruded variously by dykes of j)orphyrite, eutectophyre and granite- porphyry (Yong-dang). 

 The whole is capped on the eastern border with sheets of green jjorphyrite. The predominant 

 dyke rocks are diopside-jwrphyrites, some of them containing a little hornblende which has 

 suffered magmatic corrosion. Similar dykes, though much decomjoosed and therefore calcareous, 

 were observed by Inouyé in the same complex on the way from Ham-an to Pan-song. 



Gold occurs in veins and also intermixed with Alluvial sand. Calcareous and quartzose 



veins, usually 2 to 5 in- 



THE YONG-DAM GOLD FIELD 



AFTER IXOUYE 





100,000 



ches thick, run N.N.W. 

 for a distance of 4 km 

 and hade S.W., in con- 

 trast to the country-rocks 

 which dip in the op- 

 j)osite directions and occur 

 in close proximity to 

 the quartzporiDhyry with 

 which the precious metal 

 must have a genetic rela- 

 tion. The quartz vein 

 contains 0.0002 % of gold, 

 but none of silver, though 

 in a concentrate the latter 

 amounts to 0.0022 % and 

 the former rises to 0.0024 

 %. The gold dust is wash- 

 ed at Yong-dam, Mu-i-kol, 

 Tol-pat, Kam-chhol-bahoi, 

 and Yong-dang,in an Allu- 

 vial bed of gravel covered 

 with clay 2 to 3 feet 

 thick. The gold is rich 

 in basal gravel 5 to 10 



