Vol. 6$.~] TITANIFEROT7S BASALTS OF THE MEDITERRANEAN. C9 



5. The Titaniferous Basalts of tlie Western Mediterranean : 

 A Preliminary Notice. By Dr. Henry S. Washington, 

 For.Corr.Geol.Soc. (Read November 7th, 1906.) 



Contents. 



Page 



I. Introduction 69 



II. Petrographical Descriptions 70 



III. Chemical Composition 72 



IV. Classification of the Eocks 77 



V. Extent of the Region 78 • 



I. Introduction. 



In the summer and autumn of 1905 the volcanic districts of 

 Catalonia, Sardinia, Pantelleria, and Linosa were visited by me, 

 and their rocks collected under the auspices of, and with the aid of 

 a grant from, the Carnegie Institution of Washington. During the 

 past year, the abundant and representative material thus brought 

 together has been the object of microscopical and chemical study, 

 which is still in progress. The final results of these investigations 

 are to appear elsewhere, as separate papers dealing with the rocks of 

 the several districts ; but some observations and conclusions of a 

 general character appear to be sufficiently well-established, and of 

 enough interest, to justify their publication in advance of the more 

 detailed descriptions. 



It is the object of the present communication, which I have 

 the honour of laying before the Society, to call the attention of 

 petrologists to the existence, in the Western Mediterranean Basin, 

 of a hitherto unrecognized petrographic province, or comagmatic 

 region, to adopt a term used by me elsewhere, one of the 

 most salient characters of which is the presence of salfemanes 

 (basalts) that contain remarkably-high amounts of titanium. The 

 data available at present are far from complete, as only a small 

 proportion of the numerous rock-types have been analysed : the 

 analyses so far made by me being mostly of basalts (salfemanes), 

 with fewer of the more salic rocks. "Furthermore, there are 

 several gaps in the comagmatic zone, at localities which I was 

 unable to visit, and the rocks of which are still imperfectly known. 



So far as it goes, however, the evidence at hand indicates that 

 the volcanic rocks of Catalonia (including the volcanoes near Olot 

 and Gerona), the extensive basaltic sheets of Tertiary age and 

 those of the two great volcanoes of Monte Ferru and Monte Arci, as 

 well as the lavas of the small recent cones, in Western Sardinia, 

 and the volcanoes of Pantelleria and Linosa (a small islet to the 

 south-east of Pantelleria), possess certain chemical and minera- 

 logical features in common, which point to some genetic relation- 

 ship between them. In other words, the existence is indicated 



