. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. SOUTH SHETLAND ISLANDS 49 The 'conspicuous lava flow' north of the Headland is a doleritic type of andesite characterized by an exceedingly coarse intergranular texture. The rock is mainly composed of laths of plagioclase (AbjAnj), pale brown augite, and serpentinous patches which may represent vanished olivine or hypersthene or both. The ferromagnesian minerals form clots as is common in this lava series. A sparingly developed earlier generation of feldspars, slightly larger than the laths, is
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. SOUTH SHETLAND ISLANDS 49 The 'conspicuous lava flow' north of the Headland is a doleritic type of andesite characterized by an exceedingly coarse intergranular texture. The rock is mainly composed of laths of plagioclase (AbjAnj), pale brown augite, and serpentinous patches which may represent vanished olivine or hypersthene or both. The ferromagnesian minerals form clots as is common in this lava series. A sparingly developed earlier generation of feldspars, slightly larger than the laths, is highly zonal, both chemically and mechanically, and gives rhomboidal cross-sections. Four specimens of the boulders in the great conglomerate erratics consist of typical augite-andesites differing among themselves only in the texture of their ground-masses. The numerous large pheno- crysts consist of plagioclase (mainly about AbaAug), and pale brown augite. Many of the feldspars show strong chemical and mechanical zoning. They are often full of inclusions except for a narrow zone of oligoclase on the margins. Nevertheless, many of the feldspars are quite free from inclusions. In fact the cloudy feldspars look rather like xenocrysts, especially when thev^occur in juxtaposition to perfectly clear crystals. The facts that these rocks carry the bluish apatites, and occur in a hard HARMONY cove., NELSON STI^-, SOUTH SHETLPiNDS V;.n» ^oU«.i^ +.1 iS, 67MI0N 1465 ISi-ftMO STl?>Mr. N A M. F'g- 5- coarse conglomerate of well-rounded boulders indicating a long period of erosion, suggest that, notwithstanding their freshness, they belong to the older series of lavas. Examination of a series of pebbles from the agglomerate in the vicinity of Martin's Head and Lion's Rump shows that the majority consist of hornblende-augite-andesite lavas and their tuffs. In addition, there is an altered doleritic andesite somewhat similar to that described above, a highly epidotized andesite obviously
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