ANALYTICAL ABSTRACTS. 453 



The ore bodies are found in beds of banded lean jasper, which is 

 always an invariable associate of the richer ore, and it may occur anywhere 

 within the jaspery horizon. The rich ore often appears to be a part and par- 

 cel of the general stratification of the lean ore encompassing it. Not infre- 

 quently one finds spots which are apparently in the transition state from the 

 lean jaspery ore, as though the ore body was charged with a solution, which 

 was gradually dissolving out the silica from the adjacent jasper. There is 

 invariably a notable pitch to the ore bodies, and it is generally to the west at 

 an angle of from 30° to 50°. Connected with some of the ore bodies are well 

 defined hanging or foot-walls of so-called soapstone, but often when there are 

 no well-defined walls, the ore body being found in the jasper, the ore is quite 

 sure to carry a minimum of phosphorus, as exemplified at the Millie, Pewabic, 

 Cyclops, Aragon, and S. E. Vulcan mines. The productive portions of the 

 range appear to be located at the points where the formation has been faulted, 

 eroded deeply, or sharply folded. 



Comments. — The sections give additional evidence that in the Menominee 

 district, as in the Marquette, there are two unconformable series. The Chapin, 

 Ludington, and Hamilton appear to belong to the Lower Huronian. The 

 horizon of quartzite, slate and conglomerate is evidently the basal conglomerate 

 of the Upper Huronian. The Mille, Pewabic, and similar ore bodies, are in 

 the Upper Huronian. That the ore bodies occur in disturbed areas, and fre- 

 quently rest upon soapstone or other impervious formations, accords perfectly 

 with what has been previously ascertained as to the manner of concentration 

 of the Lake Superior iron ores. 



Van Hise ' gives the following as the ascending succession in the iron-pro- 

 ducing part of the Marquette district : (i) Basement Complex, consisting of 

 granites, gneisses, schists, and greenstone-conglomerates, the whole intricately 

 intermingled, and the schists intruded by the granites and gneissoid granites ; 

 unconformity : (2) Lower Marquette series, having at its base a conglomerate 

 and quartzite formation, upon which rests an iron-bearing formation ; uncon- 

 formity ; Upper Marquette series, which looked at broadly is a great shale, 

 mica-slate and mica-schist formation, but it often has at its base quartzites and 

 conglomerates, and several hundred or a thousand feet from its base an iron- 

 bearing formation similar to that of the Lower Marquette series. Included 

 within both the Lower and Upper Marquette series are many basic intrusive 

 dikes and bosses of diabase, and also contemporaneous volcanics, which are 

 largely tufaceous 



At the east end of the Marquette district is the Mesnard series, the position 

 of which has not as yet been determined. 



'The Succession in the Marquette Iron District of Michigan, by C. R. Van Hise. 

 Bull. Geol. Soc. of Am., Vol. V., 1893, pp. 5-6. 



