Petrological Abstracts and Reviews 



Campbell, Robert. "Rocks from Gough Island, South Atlantic," 

 Trans. Roy. Soc. Edinburgh, Vol. L (1914), Part II. PL i. 



Describes various igneous rocks collected by the Scottish National 

 Antarctic Expedition, 1902-4. 



Clapp, Charles H. "Geology of the Igneous Rocks of Essex 

 County, Massachusetts," U.S. Geol. Surv., Bull. ^04 (Wash- 

 ington, 192 1). Pp. 132, pis. 18, maps 2. 

 In this report is given a summary of previous work done in this 

 interesting region of alkalic rocks, and considerable new or unpublished 

 data are added. Two groups of rocks are recognized, an older sub- 

 alkaline group consisting of granites, granodiorites, quartz-diorites, 

 gabbro-diorites, and gabbros, and a younger alkaline group consisting of 

 alkali-granites, alkali-syenites, and nephelite-syenites, with some diorite, 

 diabase, and gabbro. There are many varieties of dike rocks, quartz- 

 porphyries, paisanites, solvsbergites, tinguaites, diabases, camptonites, 

 vogesites, kersantites, minettes, fourchites, quartz-keratophyres, etc. 

 The petrographic descriptions are fairly complete, many analyses are 

 given, some of the modes are determined, and the structural relations 

 are described. Of the essexite of Salem Neck, the author says (pp. 1 24-25) : 

 "It is not a differentiate of the alkaline or nephelite syenite but is 

 a contact-metamorphosed gabbro or gabbro-diorite of the Salem type or 

 in some places a metamorphosed olivine-bearing diabase. The schistose 

 varieties and the more siliceous varieties of essexite, such as those con- 

 taining microperthite, considerable nephelite, and large fawn-colored 

 augites, are true hybrid rocks." 



CocKFiELD, W. E. "Sixtymile and Ladue Rivers Area, Yukon," 

 Canadian Geol. Surv., 192 1. Pp. 60, pis. 6. 

 This report, largely stratigraphic and economic, contains general 

 descriptions of various schists, amphibolites, granite-gneisses, pegma- 

 tites, andesites, diabases, rhyolites and granite-porphyries, and various 

 ash beds and sediments. 



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