GEOLOGICAL AND MINERALOGICAL NOTES, 



NO. 3. 



EL^OLITE-ZIRCON-SYENITES AND ASSOCIATED GRANITIC 



ROCKS IN THE VICINITY OF SALEM, ESSEX COUNTY, 



MASSACHUSETTS. 



BY JOHN H. SEARS. 



THE area covered by the elseolite-zircon-syenite rocks to 

 be described is about eight miles long, extending from 

 Collins cove, Salem neck, along the north shore to Gale's 

 point, Manchester, with long intrusive veins and micro- 

 veins reaching several miles farther in the granite and 

 diorite rocks of the region. The principal outcrops are 

 on Salem neck and Winter island on the west, Peach's 

 point and the Marblehead shore on the south, the Cove 

 village to Gale's point, Manchester, on the east and north, 

 and on all of the small islands and ledges in Salem harbor 

 within the limits included between the extreme points 

 named. These islands are : The Great and Little Haste, 

 Coney island and Coney island ledges, Great Misery 

 island, House island, the Earn islands, Chubb's island, 

 Pride's rock and some others of less importance. The 

 trend of this syenite rock is : east 30 north to south- 

 west, with the dip (N. 30 E.) variable. 



In connection with these syenites are numerous patches 

 of hornblende-granite (granitite of German authors), 

 gabbro-diorite and typical diorite, and remnants of the 

 older metamorphosed crystalline Cambrian sediments. 



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