66 THE MARQUETTE IRON-BEARING DISTRICT. 



rocks observed iu dike-like masses. Sometimes these latter rocks are 

 believed to have been "formed from the abraded material of the walls of a 

 fault." 



Wiehmaim, Turnebohm, aud Zirkel, according to the author, all agree 

 in regarding many of the greenstones as diorites and diabases of eruptive, 

 and not of metamorphic, origin. Among them they would place also many 

 of the dioritic schists and chloritic diorites. The author, however, still 

 regards them as metamorphic, and so includes them with the metamorphic 

 rocks. 



1878. 



Hunt, T. Sterry. Special report on trap d.ykes and Azoic rocks of south- 

 eastern Pennsylvania. Part I, Historical introduction. 2d Geol. Surv. of I'cnnsyl- 

 vania, E, 1878, 2.")3 pages. 



'Hunt refers to the Marquette rocks as belonging partly in the author's 

 "White Mountain or ]\Iontalban series and partly in his Green i\Iountain or 

 Huronian series. Those belonging to the Montalban are the micaceous and 

 hornblende schists of Brooks's Formation XIX aud the granites associated 

 with them (Formation XX). The Huronian rocks underlie the Montalban. 

 In Michigan they include the greenstones, diorites, serpentines, carbona- 

 ceous argillites, and porphyries. The author agrees with most of the earlier 

 writers on the district in regarding the greenstones as indigenous, that is, 

 as formed in then- present position by the metamorphism of sediments. 



"Wright, Charles E. First annual report of the Commissioner of Mineral 

 Statistics of the State of Michigan for 1887-88 and previous years. Marquette, 1879. 

 229 pages. 



In this report Wright Inietly sketches the geology of the Upper Penin- 

 sula. The author accepts, with st)uie modifications, Brooks's view as to the 

 sequence of rocks in the Marquette district. He believes that there are two 

 metamorphic granites iu the district — one Laurentian and the other occupy- 

 ino' a position in time between the Marquette or Lower Huronian rocks and 

 the members of the copper-bearing or Upj)er Huronian series. The green- 

 stones are believed to exist in beds, and to be represented in some places 



