. Bulletin of the British Museum (Natural History), Geology. 84 WILLIAMS, SYMES AND DIN DINAS HEAD. 50 m. Unaltered Slate Adinole and Spilosite I Albite Dolerite Fig. 2 Outline geological map (after Fox, 1895) of Dinas Head indicating locations of traverses A, B, and C for samples analysed. the top of the dolerite intrusion at Mackerel Cove and consists of a mass of small euhedral albite crystals with chlorite, which may represent a chilled margin facies of the dolerite. The dolerite stringers (typically 25-50 cm thick) which cut the adinole sequence usually have been heavily ca
. Bulletin of the British Museum (Natural History), Geology. 84 WILLIAMS, SYMES AND DIN DINAS HEAD. 50 m. Unaltered Slate Adinole and Spilosite I Albite Dolerite Fig. 2 Outline geological map (after Fox, 1895) of Dinas Head indicating locations of traverses A, B, and C for samples analysed. the top of the dolerite intrusion at Mackerel Cove and consists of a mass of small euhedral albite crystals with chlorite, which may represent a chilled margin facies of the dolerite. The dolerite stringers (typically 25-50 cm thick) which cut the adinole sequence usually have been heavily carbonated and chloritised but original textures are better preserved with some remnant pyroxene. (Dolerite mineral analyses shown in Table 2, whole rock in Table 4). Mackerel Cove section The most complete sequence of adinole and spilosite devel- opment occurs above Mackerel Cove. A measured section was sampled from this area as shown in Fig. 2. Heights were recorded from the top of the massive dolerite intrusion found at HWM at intervals dependent upon change of rock lithol- ogy and texture. The intrusive dolerite at the base of the section has an irregular surface from which smaller intrusions penetrate the sedimentary succession (Table 1). The beds of this sedimen- tary sequence dip between 20°-35° to the north and near the dolerite contact they are extensively quartz veined. The whole of this measured section was found to consist of various spilosite or adinole rocks. The distinctive white-weathering adinoles have a simple mineralogy of fine-grained albite and quartz, with minor chlorite, calcite and ankerite occasionally cut by thin carbonate-rich veins. Both calcite and ankerite are present as isolated, late-formed crystals or crystal patches. The carbonate-rich adinoles are often characterised by globu- lar masses of ankerite up to 2 cm in diameter. Above the extensive quartz veining is a somewhat irregular bed which is conglomeratic (or brecciated). Parts of this bed a
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