I giacimenti di Utah . ale le fessure sono tightand relativamente impermeabile; e il minerale-bearingsolutions, salendo fino a che giunsero a stenosi,sono stati costretti a diffondersi e sostituire themore permeabile letti sottostante. Un similarformation dei giacimenti sotto shale bedshas osservato in varie località in theWest. Nella miniera Harrington-Hickory thechemical composizione dei letti è indub-edly influenzato la forma del deposito. Theseries è fatta di calcare interbedded,quarzite, e silicea scisti e calcari.Il minerale principale la deposizione è stata in calce-pietra, silicei
1533 x 1630 px | 26 x 27,6 cm | 10,2 x 10,9 inches | 150dpi
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The ore deposits of Utah . ale the fissures are tightand relatively impervious; and the ore-bearingsolutions, rising till they came to the stricture, were forced to spread out and replace themore permeable underlying beds. A similarformation of ore bodies beneath shale bedshas been noted in several localities in theWest. In the Harrington-Hickory mine thechemical composition of the beds has undoubt-edly influenced the form of the deposit. Theseries is made up of interbedded limestone, quartzite, and siliceous shales and limestones.The main ore deposition has been in the lime-stone, the siliceous beds being very slightlyreplaced. The characteristic alteration of thelimestone adjacent to the fissures is silicifica-tion. The most important metals of thisclass of deposits are lead and silver, thoughsome zinc and copper are present. The de- S. GEOli r „EOLOOICAL SURVEY PROFESSIONAL PAPER 111 PLATE XLIt LONGITUDINAL SECTION SHOWING GENERALIZED OUTLINE OF ORE BODIES ANDAREAS OF MINERALIZED GROUND TRANSVERSE SECTION. LEy£LI6_ i.£V£L /S -^^Zy:- SECTIONS OF THE BORN SILVER ORE BODY. 520 ORE DEPOSITS OF UTAH. fhe fissures may logically be supposed to reachthat rock at depth; in fact it seems highlyprobable that the fissuring was the result ofthe intrusion. These relations, though by nomeans conclusive, certainly suggest a geneticconnection. Such a connection for similar de-posits is also shown in the Marysvale districtto the east. ^ That the solutions affecting the rocks atdifferent points were exactly the same does not, however, seem probable. As the solutionstraverse the rock they are constantly takingup and depositing material; and a solutiondeficient in a particular element at one pointmay be rich in that element at some otherpoint. Differences in the character of the rockand m the temperature and pressure may alsoaffect the solutions by checking or hasteningdeposition. For example, in the contact zonesthe solutions deposited copper and iron sul-phides and only small
