210 THE MARQUETTE lliON-BEARmG DISTRICT. 



places they are crossed by zones of crushed rock. In the same area occur 

 the Palmer gneisses. These are highly schistose, light-gray, pink, or 

 yellowish rocks, forming- a narrow belt between the undoubted gneissoid 

 granites to the south and the Algoukian sediments to the north. Many 

 phenomena indicate that these rocks are but very much squeezed granites, 

 in which case their foliation is probably due to the fact that they exist 

 along the plane of contact between the crystalline rocks of the Basement 

 Complex and the sedimentary beds of the Algonkian series, a zone of great 

 accommodation during the folding of the Marquette rocks. 



Microscopical. — Uudcr tlic uiicroscopc the principal components of the 

 granites are seen to be orthoclase, albite and other plagioclases, microcline, 

 quartz, occasionally a little biotite, and the alteration products of the feld- 

 spars. All these minerals have the same properties as they do in the northern 

 granites. The feldspars are a little more altered, but their decomposition 

 products are the same as those in the northern rocks. The orthoclase and 

 microcline have given rise to kaolin and sericite, and the plagioclases have 

 yielded chlorite, kaolin, and small flakes of some micaceous mineral. In 

 extreme cases these alteration products are so abundant that they entirely 

 obscure the outlines of the grains by ^^■hose decomposition they were pro- 

 duced. The quartz grains always exhibit undulatory extinction, they are 

 almost always surrounded by granulated borders, and very frequently they 

 are filled with little liquid inclosures containing movable bubbles. The 

 biotite is present in very small quantity, and its flakes are nearly always 

 partially changed to chlorite. A few zircons, a little magnetite, some 

 limonite, and, very rarely, plates of hematite, are the only other minerals 

 noted in the rock. 



In the most massive phases of the granite the typical granitic structure 

 can still be seen, though the abundance of alteration products scattered 

 through most of the sections obscures it more or less. The structure of the 

 schistose phases presents the same features as does that of the gneissoid gran- 

 ites of the Northern Complex. Their quartzes are granulated and crushed, 

 and their feldspathic components fractured. Between the larger grains is 

 a mosaic composed of the finer fragments of both quartz and feldspar, and 

 scattered through this are muscovite flakes winding in and out between 



