272 ABSTRACTS : GEOLOGY 



masses of schist melted; and elsewhere granitic material forced itself 

 between the layers of the schists and formed injection gneisses. 



The iron ores are chiefly magnetite or mixtures of magnetite with 

 hematite. The magnetite deposits typically conform with the layering 

 of the enclosing schistose rocks, notably in the case of the leaner ore 

 bodies. 



The geologic history of the Llano ores is as follows: (1) Deposition 

 of iron as oxide, carbonate, etc., with the sediments, either in extended 

 basins or along borders of the sea; (2) Burial, followed by intrusion of 

 dikes and sills of a diabasic type with possible local introduction of soda 

 and perhaps granitic intrusions; (3) Deeper burial with subsequent 

 folding and metamorphism and a second intrusion of basic types; (4) 

 Intrusion by granite with great Focal disruption; (5) Elevation and 

 erosion. H. D. McCaskey. 



ECONOMIC GEOLOGY.— Copper deposits of the Appalachian States. 



Walter Harvey Weed. Bulletin U. S. Geological Survey No. 



455. Pp. 166, with 5 plates and 32 sections. 1911. 

 Throughout the Appalachian province the copper ores are confined 

 to (1) crystalline schists; (2) altered basalts; (3) Triassic rocks close to 

 trap intrusions; and (4) Devonian rocks, in which they are generally 

 insignificant. No two deposits are precisely alike, yet if their general 

 characteristics be considered they all fall into six types, as follows: 



(1) Ducktown type. Pyrite lenses and veins in crystalline schists. 

 (2) Copper quartz-vein type. Quartz veins containing metallic sul- 

 phides: (a) Virgilina variety; quartz veins with glance and bornite. 

 (b) Gold Hill variety; silicified schists, containing chalcopyrite and 

 pyrite, with ore shoots of quartz and chalcopyrite. (c) Seminole variety; 

 zone of pyritized schists, carrying local shoots of high-grade ores. (3) 

 Carolinian type. Bands of amphibolite traversing mica schists and 

 carrying chalcopyrite and pyrite disseminated through the rock or 

 gathered in bunches or, more commonly, deposited in the gray gneiss 

 alongside. (4) New Jersey type. Impregnated shale and sandstone 

 adjacent to trap masses; in part in the trap. (5) Pahaquarry type. 

 Devonian sandstones impregnated with copper ores; and shales, etc., of 

 Coal Measure regions with occasional ore; not rare, but insignificant in 

 amount. (6) Blue Ridge (Catoctin) type. Bunches and joint fillings in 

 the surficial portions of the basaltic rocks (Catoctin schist) of the Blue 

 Ridge region. F. L. Ransome. 



