4()8 KDUARI) STKlDTAfANN 



Koewatin rocks iiicludo acid aiul l)asic oxlrusivcs, some plutonics 

 ias]>iHlic iron format ii)n, I'crro-dolomitcs, anil schists of unknown 

 ori«j;in. 'The lluronian rocks arc chiefly quartzite, graywacke, 

 micaceous schists, and one conglomerate, apparently made up of 

 ignei)us materials. 



Most of the gold ores occur in (|uart/,-bearing veins within 

 nu'taniorphosed igneous rocks of the Keewatin or the lluronian 

 conglomerate. The i|uartz is full of li(]uid inclusions and in places 

 is shattered. Crold occurs between (]uartz veins, included in quartz, 

 in pyrite, and in calcite. 



llore believes that the cues and quartz pyrite gangue were 

 deposited by lu)t alkaline solutions, lie fnids that they resemble 

 the ores of the mother-lode closely and that the same hypothesis of 

 origin is applicable to both. 



The pre-Caml)ria,n successiiui in the Nipissing district according 

 to Hore* is: 



1. Algonkian. 



(/) Keweenawan. Igneous intrusions of quartz (Habase, quartz gabbro 

 with acid differentiation iM-ochicls. Some olivine diabase and diabase 

 porphyrite dikes. Igneous contact. 

 /)) IFuronian. 



(i) An upper series, probably Middle lliui^nian. Cruelly feldspalhie 

 quartzile with some eonglomerate. liarlow's l.orain series. 

 Slight unconformity. 

 (:;) .\ lower series, probably Lower lluronian, graywaeke, shale, eon- 

 glomerate, and feldspalhie (luart/.ite. Miller's C\)ball series, 

 (uvat uneonforniity. 

 11. Arehaean. 



(?) l.aurenlian. (iranites, diorites, syenites, gneisses intrusive into 



Keewatin. 

 /') Keewatin. liasie and aeid extrusives and inlrusives, felsite agglomer- 

 ate, iron formation, slates and green sehist. 



The silver ores occur principally in narrow vertical or nearly 

 vertical I'lssure Ncins cutting Keweenawan diabase, the lower 

 lluronian series, and the Keewatin. i'he veins strike in various 

 ilirections. but are uiu'form in composition, consisting mainly of 

 smaltite, calcite. and silver, tieposited in the order in which they 



» '' ri\o Sil\ er ImoKIs of Nipissing;, Ontario," L\ni. M in. liisl. (JukuI. HiilL. No. 17 

 (lOi i\ pp. Si 105, ,^ pis. 



