386 
VADOSE ORE DEPOSITION 
and fracturing of brittle rocks due to tortional strains, by local 
pressure-lines without notable dislocation, by faulting, by shear¬ 
ing, or by volcanic outbursts, brecciated beds or belts constituting 
ore-masses of vadose deposition have the ore-matter disseminated 
in thin films or sheets between the broken rock-fragments. 
Rarely does the ore penetrate the latter. 
Although brecciation of calcareous rocks arises in various 
ways, the most prevalent cause is the irregular contraction which 
such beds undergo during the process of dolomitization. The 
Hurst iron deposits of Wythe county, Virginia, is an illustration, 
especially noted by Benton and is one of the best known. 
Close-patterned jointing and fracturing of brittle rocks, mainly 
due to tortional strains during mountain-making movements, 
produce open structure whereby metallic salts tend to accumulate 
extensively in the intermolar spaces thus formed. This is par¬ 
ticularly true in arid lands. Usually the rock-mass is a rhyolite, 
monzonite, or quartzite^ The Santa Rita copper-deposits in 
southwestern New Mexico, are widely known examples. Bingham, 
Morenci, and Ely in this country, Cananea in Sonora, Spassky 
in Siberia, and Braden in Chile, seem to be first representatives 
of the large class of ores known as the porphyry-coppers. 
Restricted breccias along lines of jointing often contain con¬ 
siderable precipitations of metallic salts. Many of the gold 
prospects of the Tuertos and Ortiz mountains, in central New 
Mexico, quite fully described by Yung and McCaffety are of 
this sub-type. 
Brecciated belts bordering fault-planes are especially notable 
for their mineral content, which is commonly a strictly intermolar 
deposition. In the desert, deposits of this character and of 
strictly vadose origin often extend unchanged to depths of 1000 
to 1500 feet, or until groundwater-level is reached. Large num¬ 
bers of such “veins” have no connection with deep-seated mag¬ 
mas. The Tres Amigos gold-veins, in the Oro Blanco mining 
district of southern Arizona, present clearly these conditions; 
as do, many of the gold deposits around Animas Peak, northeast 
of Hillsboro, in New Mexico. 
Sheared belts, in metamorphic and eruptive rocks especially, 
19 U. S. Tenth Census, Vol. XV, p. 275, 1883. 
20 Trans. American Inst. Mining E)ng., Vol. XXXIII, p. 358, 1903. 
