|
CEOLOCY.
<br />y, incor_
<br />ital stook
<br />Lue, ~l
<br />There is a good geological survey of the district by Cross &
<br />Emmons, compiled from field work made during the latter part o3 1'
<br />i
<br />1894, and publiehgd by the U, S. Geological Survey some time
<br />later, and contained in part ascend of the 16th Annual Report.
<br /> Pulesa. I.indghran & Randaome, are at the present time engaged
<br />^ado,
<br />in Further work for the survey, their especial attention being
<br /> given to the underground geology of the district, results of
<br /> whioh have not reached the press up to the present time.
<br />.ngs, Colo, The granitio area whioh surrounds the entire Cripple Creek
<br /> 1141ning District, occupies the southern border of the Portland
<br />" property, the contaot with the andeaitic breocia orosaing the
<br />' Black Diamond and Queen of the Hills claims.
<br /> The surface of the porphyritic area is covered with such an
<br /> amount of detrital mesa in a decomposed condition, that it is
<br /> hard to distinguish the different verities on the surface.
<br />nuary, Tdasaive andesite forms most of .the northern and easterm
<br />took portions of the property, while the typioal andesitic brecoia and
<br />!10 of
<br /> tuff, fills the intervening apaoe.
<br />:ir The whole mountain, regardless of the charaoter of the country
<br />peen rook, is intersected by a mast intricate system of dykes and veins,
<br />id the dykes being andesite, phonolite and basalt, varying in
<br />prominenoe, width from a fevr inches to several feet, having a general north
<br /> westerly and south easterly course, and being practically vertical,
<br /> The veins which carry the high gold values, sometimes fol-
<br /> low the walla oP the dyke, (example, Soranton) sometimes are
<br /> mineralizations of the whole dyke, (example, Portland in places)
<br /> and sometimes are entirely independent of any dyke, and oooupying
<br />and their own fissures, oithor in the granite, or the ad~aaent vol-
<br />3ed hill, oanio rock, or both, (example, Bobtail). It may he noted that
<br />The the general strike of the veins, ie much the same ae that of the
<br />has dyke, that ie, between N. 66o W. on the one hand, and North on
<br />con- '
<br />the other,
<br />rfaoe Thero are many veins out and developed by tho underground
<br /> workings, known ae "blind" veins, that is, they do not apex on
<br /> the surface.
<br />
|