Page:The Journal of geology (IA journalofgeology11893univers).pdf/109
other dykes containing crystals of feldspar, while both are cut by gray granite, that is in turn cut by red granite.
The Republic formation, commencing with the oldest division, is divided roughly as follows: Conglomerate-breccia and conglomerate-schist; quartzite; dolomite; jaspilite and iron ore; argillite and schist; granite and felsite; diabase; diorite and porodite; porphyrite. At the base of the Republic formation is a series of conglomerates and conglomerate-schists, which pass into hydrous mica-schists. Near Palmer, the coarse conglomerate rests on the gneiss to the south, and is overlaid to the north by quartzite, fragmental jaspilite and quartz-schist. The dip is about 40° northward. The conglomerate contains numerous pebbles of gneiss, as well as some of granite, diorite, schist and quartz veins. Near the Volunteer mine quartzite immediately overlies the basal conglomerate, and in other places reposes directly on the Cascade formation.
The quartzite in the Menominee district, running from Sturgeon river along Pine river to Metropolitan, is thought to belong to the base of the Republic formation, since it is found at various places close to the gneiss and granite, dipping away from them, and is cut by dykes of granite in Sec. 12, T. 41 N., R. 30 W. The dolomite occupies a low horizon, either interbedded with the quartzite or occupying its place. The fundamental ore and jaspilite appears to belong, stratigraphically, to the Republic formation. The most of the jaspilite of the formation is of detrital origin, being originally conglomerates, breccias, sands, muds, which have been subsequently chemically acted upon by percolating waters, since in the Cascade range the jaspilite and ore form layers which are frequently interlaminated with quartzite. The jaspilite of Negaunee and Ishpeming has failed to reveal any evidence that it is sedimentary, although the associated argillite and schist are in part at least clearly sedimentary. The argillite and schists are directly associated with the jaspilite and iron ore. In places they grade up into the fragmental jaspilite, and in other places are interbedded with it. They also succeed the latter rocks and overlie them. These argillites and schists are older than the diorites of the district, and are cut by them.
The Holyoke formation has the following succession, as far as known, commencing with the base: Conglomerate breccia and conglomerate schist; quartzite; dolomite; argillite; graywacke and schist; granite and felsite; diabase, diorite and porodite; peridotite, serpentine and dolomite; melaphyr or picrite; diabase and melaphyr. The conglomerate at the base of the Holyoke contains granitic material, as well as fragments from the jaspilite. In many places the unconformity between the Republic and Holyoke formations is most marked, being seen at many of the mines. In many places, also, the Holyoke formation overlaps the Republic, and is in contact with the granite and gneiss of the Cascade. Associated with the Holyoke conglom-