MreoME.] ORIGIN OF THE LODE AND STOCK ORES. 133 
i open spaces, to which the solutions had access, and partly as 
splacements of various rocks through metasomatic action. Their 
eposition was accompanied by chemical and mineralogical changes 
1 the immediately adjacent country rock, producing effects which in 
:ie majority of cases diminish rapidly in intensity with increasing 
istance from the fissure walls. As far as is known, the deposition of 
re within the fissures was nol affected by differences in character of 
le wall rock. Il is believed that the facts presented in the descrip- 
ve portions of Ibis report all indicate an initial primary deposition 
y ascending mineralized waters. It is probable, as pointed out by 
bdgren 1 and Van Ilise,- that these waters were originally meteoric 
'aters, which gained their heal and collected their mineral contents 
tiring slow downward ami lateral percolation through the rocks, and 
ere subsequently gathered as ascending currents into the main 
ssures. II is not known from what particular rocks they extracted 
leir metalliferous burden, nor at what depth most of the solution took 
lace. 
Thai the entire process of ore deposition was directly connected 
ith volcanism can scarcely be doubted. The most obvious aspects 
f this connection are threefold : (1) The mechanical formation of the 
ssures; (2) t he accession of heal, whereby the chemical activity of 
nderground water was intensified; and (3) the accumulation of vast 
uisses of igneous rock from which, at some depth, the constituents 
f the ore minerals were probably derived. It is possible that there 
lould be included here also the evolution of carbon dioxide, sui- 
h\ dric acid, and probably other volal ile substances, as active solvent 
jid chemical agents. 
Xciy different views are held by various investigators in regard to 
le extent to which pneumatolytic processes, due to the emanation of 
ighly heated gases and vapors from solidifying igneous rocks, are 
\sponsible for ore deposition. Van Ilise, in his suggestive paper 
ist cited, practically ignores pneumatolysis as a factor in the forma- 
pn of ore bodies. Kemp, 3 on the other hand, considers that meteoric 
aters have little or no efficiency in the original concentration and 
eposition of ores, and that the waters of ore-bea"ing solutions, 
)gether with their dissolved mineral constituents, are of intratelluric 
rigin, and are given off at high temperatures by masses of igneous 
)ck in process of congelation. Various intermediate views are held 
y many European geologists and writers on ore deposits, notabty by 
eck. Yogi, ami Dn Launay. The evident connection between ore 
eposition and volcanism, or at least the products of volcanism, the 
1 The gold-quartz veins of Nevada City and Grass Valley districts, California: Seventeenth 
on. Rept. U. S. Geol. Survey, Pt. II, 1896, p. 176. 
2 Some principles controlling the deposition of ores: Trans. Am. Inst. Min. Eng., Vol. XXX, 
i, p. 47. 
3 The role of the igneous rocks in the formation of veins: Trans. Am. Inst. Mining Eng., Rich- 
ond meeting, 1901. 
