Transactions . Pl^VN Of A Fn)KTI().\ (^FTIIK UKU OMK MINE BIv\( K FfllXS. SOLTH fXVKOTA Showing s Hal -trr body of ronatdvrvbiv huotonial •jn*nifonn^ by iKr roi/ibuird ar Ijon ol «olt>t>on« ^??•\c Ovoafh anuinbrr of cloarly aparrd frai rurr* ByJ D Ir-NnngScaJr LtGC N OUnminrrKiiaed cotvun, V09I1 :;0;j P«»T*ty^ \>rt3C«U I. - Ilall of till lnMili oi llir MiUf. liia South Dnkntji. ^ln)winK thr inanm-r in which the on- is iuotociatcil wit:or < of arrrss uml thf ori-urn-ncf of iHohitcii i-lsirulH of unmii . r i,- itcd 1 •• within thr ore n»jw«. (After Irving, l*. S.
Transactions . Pl^VN Of A Fn)KTI().\ (^FTIIK UKU OMK MINE BIv\( K FfllXS. SOLTH fXVKOTA Showing s Hal -trr body of ronatdvrvbiv huotonial •jn*nifonn^ by iKr roi/ibuird ar Ijon ol «olt>t>on« ^??•\c Ovoafh anuinbrr of cloarly aparrd frai rurr* ByJ D Ir-NnngScaJr LtGC N OUnminrrKiiaed cotvun, V09I1 :;0;j P«»T*ty^ \>rt3C«U I. - Ilall of till lnMili oi llir MiUf. liia South Dnkntji. ^ln)winK thr inanm-r in which the on- is iuotociatcil wit:or < of arrrss uml thf ori-urn-ncf of iHohitcii i-lsirulH of unmii . r i,- itcd 1 •• within thr ore n»jw«. (After Irving, l*. S. (Ii-ol Survry, Ir : pap«T No. 2t). Pint* XIII.) 404 Replacement Ore-Bodies—Irving. Replacement Ore-Bodies—Irving 405 prominent than the replacement mass arisinp^ from it that thereis no possibility of doubt as to opening from which the mineraliza-tion started. When solutions have once gained access to rocks susceptibleto replacement, joint cracks, rock pores, brecciated structures,Btock-works and other smaller and less continuous openings,by affording easy circulation and increasing the availablesurface for chemical action, greatly facilitate and acceleratethe process. Forms due to Single Fissures.—Where replacement has pro-ceeded from a single fissure intersecting a homogeneous rock, theform of the resulting replacement mass usually is tabular. Itsboundary will sometimes be extremely indefinite, the new mineralsbecoming more and more sparsely scattered as one out-ward from the conduit which admitted the solutions until theore passes insensibly into country rock. At other times it willbe extremely sharp, so that the passage from ore to country rockis ab
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Keywords: ., book, bookcentury1800, booksubjectmineralindustries, bookyear1895
