PART VIII 



REPORT ON THE INCLUSIONS OF THE 



VOLCANIC ROCKS OF THE ROSS 



ARCHIPELAGO 



(With Three Plates and Three Figures in the Text) 



BY 

 J. ALLAN THOMSON, M.A., D.Sc., F.G.S. 



CONTENTS 



PAGE 



I. OLIVINE, PYROXENE, AND GABBROID NODULES IN THE BASIC ROCKS 131 



II. SANIDINITES AND MICROTINITES IN THE TRACHYTES AND KENYTES 134 



Sanidinites and Microtinites in the Trachyte of Mount Cis . . 134 



Sanidinites and Microtinites in the Kenytes ..... 136 



Other Sanidinites .......... 138 



Origin of the Sanidinites and Microtinites ..... 139 



III. HORNBLENDIC INCLUSIONS IN THE TRACHYTES 140 



Origin of the Hornblendic Inclusions of the Trachytes . . . 141 



l\. ORBICULAR AUGITE-SYENITE: PROBABLY AN INCLUSION ... 142 



V. PLAGIOCLASE-PYROXENE INCLUSIONS IN THE TRACHYTE OF MOUNT 



CIS 143 



VI. QUARTZ-BEARING INCLUSIONS 144 



Quartz-Pyroxene Inclusions in the Trachyte of Mount Cis . . 144 



Quartz-bearing Inclusions in the Kenytes ...... 145 



VII. CLASSIFICATION OF THE INCLUSIONS 145 



VIII. SUMMARY AND CONCLUSIONS 147 



Explanation of the Plates .......... 148 



129 



